|Abu-Tabak, N., Auloge, J. & Auriol, P.||Dynamic Stability and Optimal Control of a Multi-Machine Power Networks Modeling and Simulation (abstract)||Damping of small oscillations, linear optimal control, and dynamic stability||Session 5 - System Dynamics, SSR Studies|
|Abstract: In electrical power networks small oscillations appear from time to time. These oscillations concern the quantities determining the equilibrium point of the system, and following which, system stability and system behaviors are influenced. To improve system behaviors and dynamic stability it is necessary to minimize these transient states. The objective of our study is, first, showing the importance of good choice of state variables of a multimachine power system because controllability and observability of the system depend on this choice. On the other hand, we want to increase the damping of the small oscillation by adding of additional signals on excitation systems. The results of simulation approve the utility of the method used in this paper to choice the weighting matrices. These matrices are used to obtain the optimal control which minimizes a quadratic index. The problem of immeasurable states is noted but not discussed in detail.|
|Ahmad, A. S. & Aka-Ngnui, T.||Lightning Induced Voltage on Telephone Cables and Power Systems (abstract)||telephone cable, lightning protection system, modeling, transient analysis, lightning induced voltages, cable parameters, EMTP, overvoltage||Session 23 - Lightning Surges|
|Abstract: Several times, the lightning damaged the electronics components of a real station of communication. Consequently, this work relates to a study on the interaction of lightning with the lightning protective system, telephone cables, and power system in order to analyze lightning induced voltages. A topology of a communication station is described and the structural lightning protection, telecommunication station, earthing network, power system is well realized. The cable parameters are calculated and it is represented as transmission line model TLM. The others system elements are modeled by equivalent circuits. The global model is introduced in EMTP (ElectroMagnetic Transient Program) allowing to study various configurations of telephone cable and power systems. Discussions of results and comparisons with other methods are presented. The results show the influence of topology configuration (power system/telecommunication sites), on induced overvoltages and confirm, for the case studied, which is a factor important.|
|Alves, F. R. & Regis Jr., 0.||A Comparison of the Performance of a Conventional Transmission Line and Expanded Bundle Regarding Transient Overvoltages (abstract)||Transient Overvoltages; Transmission Line; HSIL Lines; Expanded Bundle; Energization; Three Phase Reclosing; Load Rejection; No-Load Line Switching||Session 16 - Switching Transients, Lines and Cables|
|Abstract: This paper presents a comparative analysis of switching overvoltages concerning line energization, transformer energization, load rejection and three phase reclosing of a 500kV system, with three series stretches of transmission lines, under recovery conditions and considering two bundle configurations meant to be, standard dimension and expanded one. It is verified that, in general, the use of expanded bundle in these lines leads to the consequent need for a higher compensation amount of shunt reactors, and the occurrence of higher overvoltages in the phenomena analyzed, when compared with the alternative of standard bundle.|
|Ametani, A. & Hosakawa, Y.||EMTP Simulations and Theoretical Formulation of Induced Voltages to Pipelines from Power Lines (abstract)||induced voltage, pipeline, power line, EMTP, theoretical formulation||Session 20 - Transmission Lines and Cables|
|Abstract: This paper has investigated induced voltage characteristics on a pipeline system from an overhead line based on EMTP simulation results and theoretical formulation developed by the authors. The induced voltages are significantly dependent on the configuration of the power line. A horizontal line induces the largest voltage to the pipeline, and an induced voltage by a vertical twin-circuit line is smaller by about 20% than that by a vertical single-circuit line. The simulation result shows a reasonable agreement with a field test result. The basic characteristic of the induced voltages and the effect of the power line currents are explained by applying the theoretical formulation, which is very useful to explain simulation results from the physical viewpoint.|
|Ametani, A., Matsuoka, K., Omura, H. & Nagai, Y.||Surge Voltages and Currents into a Customer due to Nearby Lightning (abstract)||lightning surge, grounding, distribution line, home appliance, EMTP||Session 12 - Lightning Surges|
|Abstract: This paper has carried out EMTP simulations of lightning surges incoming into a customer due to lightning to an antenna of the customer, a pole and a ground nearby the customer based on experimental results. The ground voltage rise is represented by a mutual resistance between grounding electrodes. EMTP simulation results have been observed to agree qualitatively with the measured results.|
|Avendaño, A., Chiesa, N., Mork, B. A., Høidalen, H. K., Ishchenko, D., Gonzalez, F. & Kunze, A. P.||Transformer Short-Circuit Representation: Investigation of Phase-To-Phase Coupling (abstract)||EMTP, Leakage Representation, Short-Circuit, Transformer Models||Session 11 - Transformers|
|Abstract: Transformer short-circuit behavior is typically represented in electromagnetic transient simulation programs by the inverse of the leakage inductance matrix, also known as the A-matrix or [A].
The terms of [A] represent the magnetic coupling (flux linkages) between windings, i.e. between coils on the same core leg. In addition to the representation of coupling between windings of the same phase, intra-phase coupling effects can also be included.
This paper investigates the sensitivities of results of EMTP-type simulation to intra-phase entries of [A]. A method for obtaining [A] that includes intra-phase coupling is developed and verified by comparing simulation results with laboratory measurements. The percent error between measured and simulated short-circuit currents that result from implementing a full and simplified [A] was quantified. A correlation of the size of the elements representing intra-phase coupling in [A] with transformer MVA size is investigated and valuable conclusions and recommendations are made.
|de Azevedo, A. C., Delaiba, A. C., de Oliveira, J. C., Carvalho, B. C. & de S. Bronzeado, H.||Transformer Mechanical Stress Caused by External Short-Circuit: A Time Domain Approach (abstract)||Electromagnetic force, finite element method, short-circuit currents, transformer modeling, time domain||Session 27 - Transformers|
|Abstract: This paper presents the results of an investigation carried out on the field of short circuit effects upon transformers electromechanical forces calculation. A time domain transformer model based on magnetomotive forces and reluctances is used. This model allows for simulating the transformer transient and steady state behaviors regarding electric, magnetic and mechanical variables. The methodology is applied to a typical power transformer operating under nominal and short circuit conditions. For comparison purposes a due to the lack of accepted performance values, a finite element program is utilized for similar studies and the results are compared to the time domain ones.|
|Baba, Y. & Rakov, V. A.||A Study of Current Waves Propagating Along Vertical Conductors and Their Associated Electromagnetic Fields (abstract)||Current attenuation, electromagnetic field structure, FDTD method, grounding impedance, lightning, transmission-line tower, traveling waves||Session 7 - Lightning Surges|
|Abstract: Using the finite-difference time-domain (FDTD) method, we have analyzed current waves propagating along vertical conductors of different type, including a cone, an inverted cone, and a parallelepiped (uniform-thickness conductor), each located above ground and excited at one of its ends by a lumped current source, as well as their associated electric and magnetic fields. A current wave suffers neither attenuation nor dispersion in propagating from the apex of cone to its base, and the resultant field structure is transverse electromagnetic (TEM), as expected from the theory. On the other hand, a current wave suffers significant attenuation and dispersion in propagating from the base of cone to its apex, and the resultant field structure is non-TEM. In propagating along a parallelepiped, a current wave suffers attenuation and dispersion particularly near the source region, which become more pronounced as the thickness of parallelepiped increases. The resultant field structure away from the source region is close to TEM. Further, we have shown that the field structure around a vertical phased current source array, which simulates unattenuated propagation of current wave at the speed of light, is TEM. In the case of vertical in-phase current source array placed between two horizontal perfectly conducting planes, a cylindrically expanding TEM wave is formed, and the input impedance seen from the terminals of the array varies with time as 60ln(h/ct), where h is the separation between the planes, and c is the speed of light.|
|Bak, C. L., Wiechowski, W., Søgaard, K. & Mikkelsen, S. D.||Analysis and Simulation of Switching Surge Generation when Disconnecting a Combined 400 kV Cable/Overhead Line with Shunt Reactor (abstract)||400 kV cable, disconnection, switching overvoltage, resonance, mutual coupling||Session 16 - Switching Transients, Lines and Cables|
|Abstract: This paper demonstrates the results from a detailed study of the dynamic behavior of a shunt reactor compensated 400 kV combined cable/overhead line. This is accomplished by means of theoretical considerations, simulations and measurements. The work presented here is based on a real-life operating 400 kV power system and initiated by Danish TSO Energinet.dk after having measured the voltage of the cable/overhead line after disconnection. A particular decaying dynamic phase voltage containing voltages higher than the voltage before disconnection appeared. A simulation model for the entire system consisting of overhead lines, crossbonded cable sections and shunt reactor has been created in PSCAD/EMTDC and verified against measurements with good results. Main focus has been put on the generation of switching overvoltages. It is shown that the generation of switching overvoltages is caused by slightly different resonant frequencies of the three phases which are reflected between the phases by mutual couplings in such a way that a low-frequent modulation appears in the phase voltages.|
|Borghetti, A., Bosetti, M., Di Silvestro, M., Nucci, C. A. & Paolone, M.||Continuous-Wavelet Transform for Fault Location in Distribution Power Networks: Definition of Mother Wavelets Inferred from Fault Originated Transients (abstract)||Fault location, power quality, distribution network, continuous wavelet transform, mother wavelet||Session 22 - System Protection and Fault Location|
|Abstract: The paper presents a fault location algorithm for distribution networks based on wavelet analysis of the voltage waveforms of the traveling waves recorded at a bus during the fault. In particular, the proposed procedure implements the continuous wavelet transform combined with the use of mother wavelets inferred from the fault-originated transient waveforms. The performance of the proposed algorithm are analyzed for the case of the IEEE 34-bus test distribution system and compared with those achieved by using the Morlet mother wavelet.|
|Bui-Van, Q., Lecompte, A., Leblanc, N. & Larivière, P.||Control of Switching Overvoltages and Transient Recovery Voltages for Hydro-Québec 735-kV Series-Compensated Transmission System (abstract)||Fault Transients, Switching Overvoltages (SOV), Transient Recovery Voltages (TRV), Circuit Breakers (CB), Series Compensation (SC), Series-Capacitor Banks (SCB), Substation Surge Arresters (SA), Line-end Surge Arresters (LSA), Metal-Oxide Varistors (MOV)||Session 13 - Switching Transients|
|Abstract: This paper summarizes results of transient simulation studies assessing transmission line insulation coordination and the performance of line circuit breakers that are to be used in the Hydro-Québec 735-kV series-compensated system. The effectiveness of permanently connected surge arresters at line ends to control switching overvoltages along 735-kV lines has been confirmed. The characteristics of transient recovery voltages during a line fault clearing, a line charging current breaking as well as an out-of-phase current interruption were thoroughly analyzed. Finally, the effects of mitigation measures on transient recovery voltages such as fast by-passing of series-capacitor banks, metal-oxide varistors across circuit breaker terminals, were also investigated in order to optimize performance requirements for 735-kV line circuit breakers.|
|Bukh, B., Gudmundsdottir, U. S., Holst, P. B., Jensen, K. B., Jensen, L. C. & Bak, C. L.||Advantages in Using Kalman Phasor Estimation in Numerical Differential Protective Relaying Compared to the Fourier Estimation Method (abstract)||Numerical differential protection, Protective relaying, Kalman phasor estimation, Differential protection||Session 6 - System Protection Analysis and Models|
|Abstract: This paper demonstrates the results obtained from detailed studies of Kalman phasor estimation used in numerical differential protective relaying of a power transformer. The accuracy and expeditiousness of a current estimate in the numerical differential protection is critical for correct and not unnecessary activation of the breakers by the protecting relay, and the objective of the study was to utilize the capability of Kalman phasor estimation in a signal model representing the expected current signal from the current transformers of the power transformer. The used signal model included the fundamental frequency, an exponentially decaying current, the 2nd and the 5th harmonic to the fundamental frequency.|
|Calzolari, G. & Saldaña, C.||ATP Simulation of the Out-of-Step Phenomenon in the Batlle Thermal Power Plant (abstract)||Session 6 - System Protection Analysis and Models|
|Abstract: Due to a fault in the 500 kV network, a unit in the Batlle thermal power plant was tripped by an out-of-step relay. From a preliminary analysis of this disturbance, it was concluded that the thermal unit did not lose synchronism. This fact led to an evaluation of the present settings of the out-of-step relay in order to determine if they were correct or not. This paper focuses on the most important aspects of the issues: a) the relaying principle, its settings and ATP (Alternative Transients Program) modeling b) the main conclusions resulting from the simulation of the sequence of events which led to the trip of the thermal generator c) the evaluation of the out-of-step relaying performance during electromechanical oscillations. They were simulated with ATP program.|
|Carrasco, G.||Electromagnetic Interference in the Substation Jose up 400/115 kV (abstract)||ATP, cables control, disconnect switch, electromagnetic
noise, Induction, Interference.
|Session 13 - Switching Transients|
|Abstract: In the Jose substation the presence of transient electromagnetic interference was dete cted in control and instrumentation cables. This interference arises during the operation of a 400 kV disconnect switch affecting the remote measurement temperature transducer and the tap changer voltage regulator (MK30) of Autotransformer #3 (AT3), located in control house #2, which is used for data acquisition (DAH-2), and is near the disconnect switch. In this study have presented the results obtained by simulations carried out with the Alternative Transients Program (ATP) about the interferences in weak currents in control and instrumentation cables due to transient or permanent electromagnetic fields that cause false trips to the equipment.|
|Chandrasena, W., Bisewski, B. & Carrara, J.||Effects of Phase-Shifting Transformers, and Synchronous Condensers on Breaker Transient Recovery Voltages (abstract)||circuit breakers, electromagnetic transients, phase-shifting transformer, switched capacitors, synchronous machines||Session 14 - Switching Transients, Circuit Breakers|
|Abstract: This paper describes several system configurations that could lead to very high TRV/RRRV in the presence of a phase shifting transformer, and synchronous condensers. The special considerations involved in determining the most limiting TRV and RRRV are presented. Mitigation measures required for 15 kV and 115 kV breakers that are applied in the above system configurations are also presented.|
|Charalambous, C., Wang, Z. D., Li, J., Osborne, M. & Jarman, P.||Validation of a Power Transformer Model for Ferroresonance with System Tests on a 400 kV Circuit (abstract)||ATP, Ferroresonance, Power Transformer, Simulation Model, Field Tests||Session 8 - Ferroresonance|
|Abstract: National Grid has performed in the past a number of switching tests on a circuit configuration which was known to exhibit ferroresonance. The aim of the tests was to establish the likelihood of ferroresonance and quantify the effect on switchgear due to the de-energisation of a power transformer attached to a long over head line circuit. This paper, describes and compares the modeling work carried out in ATP (commercially available software) with the field ferroresonance test recordings. The accomplishment of a suitable simulation model will allow sensitivity studies to be carried out to determine the degree of influence of different components and parameters on the ferroresonance phenomenon.|
|Chavez, J. J., Ramirez, A. & Naredo, J. L.||Dynamic Harmonic Domain Transmission Line Modeling for Transients (abstract)||Dynamic harmonic domain, electromagnetic transients, harmonics, switching maneuvers, transmission line, time-varying systems||Session 19 - Transmission Lines and Cables|
|Abstract: Harmonics have become a relevant topic as the number of nonlinear elements and electronic devices connected to power systems is increasing constantly. This paper presents a methodology for the modeling of single-phase transmission lines interfaced with nonlinear loads. It is intended for transient analysis and special emphasis is put on the harmonic content of the propagating waveforms through the dynamic harmonic domain (DHD) technique.|
|Cheriyan, E. P. & Kulkarni, A. M.||Determination of Study Zone for Sub-Synchronous Oscillation Analysis in Large Power Systems (abstract)||SSR, Torsional Interaction, Series Compensation, Selective Generalized Eigen Analysis||Session 5 - System Dynamics, SSR Studies|
|Abstract: In this paper, we address the issue of identification of a reduced study zone to carry out torsional interaction studies. The generators which could be adversely affected by interaction with a series compensated network, are selected based on approximate damping torque analysis. This does not require complete frequency scanning of damping torque, but evaluates only the residues corresponding to the sub-synchronous network modes. We formulate a differential algebraic model of the network for SSR analysis for this purpose. This formulation is easy to implement and is suitable for selective generalized eigen analysis using widely available tools. A case study on a large power system, with multiple series compensated lines is presented to illustrate the methodology.|
|Chiesa, N., Avendaño, A., Høidalen, H. K., Mork, B. A., Ishchenko, D. & Kunze, A. P.||On the Ringdown Transients of Transformers (abstract)||Power transformer, inrush current, ringdown transient, residual flux, shunt capacitance||Session 11 - Transformers|
|Abstract: This paper details the analysis of transformer ringdown transients that determine the residual fluxes. A novel energy approach is used to analyze the causes of transformer saturation during de-energization. Coupling configuration, circuit breaker and shunt capacitor influence on residual flux have been studied. Flux-linked initialization suggestions are given at the end of the paper.|
|Cogo, J. R. & Dommel, H. W.||Overvoltage Problems of Small-Scale Generators Connected to Large Systems (abstract)||Independent power producer (IPP); protection; sustained overvoltages; protection relays||Session 6 - System Protection Analysis and Models|
|Abstract: Electric utility companies and/or government agencies, as well as professional organizations such as IEEE, are formulating interconnection requirements for connecting small distributed or dispersed-resource generation to large utility systems. “Small” typically implies generators up to 30 MW. If the small generator is connected to the distribution system, as is normally the case, then the distribution system will no longer be radial, which requires changes to the protection.
Some of the protection-related problems are inadequate coordination, energization with generators out of synchronism, transfer tripping, protection against formation of unintentional islands, overvoltages, etc.
This paper discusses transient studies made for the connection of an Independent Power Producer (IPP) to a 138 kV connection point. The results show the overvoltages that can result from out-of- step reclosing after a line-to-line fault with ground connection on the transmission line. Solutions are suggested to prevent sustained overvoltages with revised under- and overvoltage settings. The proper choice of surge arresters is discussed as well.
If the IPP is connected to a distribution system of 13.8 kV, 25 kV or 34.5 kV, the grounding of the neutral of the transformer at the connection point (point of common coupling) will influence the current distribution between the utility and IPP. This will affect the sensitivity of the neutral protection relays.
|Colla, L., Gatta, F. M., Geri, A. & Lauria, S.||Lightning overvoltages in HV-EHV “mixed” overhead-cable lines (abstract)||backflashover, extra-high voltage lines, lightning, mixed-lines, overvoltages, shielding failure||Session 12 - Lightning Surges|
|Abstract: In this paper the authors analyze the lightning behaviour of extra-high voltage unconventional transmission lines, named mixed-lines, consisting of a XLPE-insulated cable line (CL) solidly series-connected to conventional overhead line (OHL). ATP-EMTP time-domain simulations have been carried out to analyze overvoltage levels achieved in a 380 kV-50Hz mixed-line in Europe varying the CL length. Attention is focused on the effects both of shielding failure and of direct lightning strokes to OHL sections, in particular to cable-overhead transition tower. The ATP-EMTP model of the affected portion of mixed line includes frequency dependent modeling both of CL and of OHL, a CIGRE leader progression model (LPM) of line insulation, and a detailed circuit-based model of tower grounding system, taking into account soil ionization. Numerical results show a good lightning performance of the line under study: shielding failures do not endanger the main CL insulation, probability of backflashover is extremely low and stresses on outer sheath insulation are effectively contained.|
|Colla, L., Lauria, S. & Gatta, F. M.||Temporary Overvoltages due to Harmonic Resonance in Long EHV Cables (abstract)||EHV AC cables, resonance, overvoltages, harmonics, ATP, EMTP||Session 16 - Switching Transients, Lines and Cables|
|Abstract: With the increasing recourse to cables in EHV networks the likelihood of low-order harmonic resonance is becoming of even more concern.
The scope of this paper is to analyze the overvoltages due to harmonic resonance at the no-load energization of a prospective 400kV-50Hz double circuit submarine cable line. ATP-EMTP analyses are carried out to predict the possibility of occurrence of low-order harmonic resonance; a phenomenon more liable to happen in case of EHV cables connected to low short circuit power networks.
The occurrence of resonances is sought for in the frequency domain and overvoltages are calculated in the time domain for the no-load energization of the EHV double circuit cable line. A sensitivity analysis is carried out varying the switching instants of line circuit breakers and the network short circuit power, while load and operating configurations are taken as a parameter. The effect of shunt reactor saturation voltage on the harmonic overvoltages is also investigated.
Operational and design countermeasure are proposed.
|Costa, F. B., Silva, K. M., Dantas, K. M. C., Souza, B. A. & Brito, N. S. D.||A Wavelet-Based Algorithm for Disturbances Detection Using Oscillographic Data (abstract)||Disturbance detection, transmission lines, wavelet transform.||Session 16 - Switching Transients, Lines and Cables|
|Abstract: This paper presents a discrete wavelet transform approach to disturbance detection by the analysis of electromagnetic transients in transmission lines using oscillographic data. The detection is carried out by the analysis of the detail coefficients energy of the phase currents. The performance of the method was evaluated for actual oscillographic data and excellent results were obtained.|
|De Silva, H. M. J., Gole, A. M. & Wedepohl, L. M.||Accurate Electromagnetic Transient Simulations of HVDC Cables and Overhead Transmission Lines (abstract)||Electromagnetic transients, rational function approximation, direct phase domain model, constrained least squares||Session 19 - Transmission Lines and Cables|
|Abstract: This paper introduces three different procedures for improvements in the accuracy at very low frequencies of time domain simulation models for overhead lines and underground cables. In the first two methods, a suitable modification is introduced to the functional form of the rational function approximated in the curve fitting procedure for the phasedomain model, such that the model is perfectly accurate at dc frequency. By comparing with analytical results, the paper also quantifies the errors made in simulation when the fitting at very low frequencies is inaccurate. These procedures are numerically efficient and robust. These two methods are also compared against a third less accurate method which simply adds a series dc resistor in the model to correct the dc response. Simulation results are presented for underground cable systems. The modifications introduced in the paper are expected to be useful in the simulation of High Voltage Direct Current (HVDC) transmission systems.|
|De Tommasi, L. & Gustavsen, B.||Accurate Transmission Line Modeling Through Optimal Time Delay Identification (abstract)||Magnitude fitting, minimum phase shift function, transmission line model, rational approximation, method of characteristics, time delay identification, vector fitting||Session 20 - Transmission Lines and Cables|
|Abstract: Frequency dependent transmission line modeling by the Method of Characteristics requires to calculate a rational approximation of the characteristic admittance Yc and the propagation function, H. Most models rely on fitting the modal components of H in order to handle the delay terms of the line. This paper compares various techniques for delay extraction and fitting with emphasis on accuracy and computational efficiency. The comparison includes asymptotic magnitude fitting, phase reconstruction from magnitude data followed by vector fitting (VF), and VF with time delay included in the optimization. The latter approach is shown to be the most accurate, at the cost of longer computation times. The alternative fitting strategies are applied to one example of transient overvoltage calculation on an underground cable system.|
|Dehkordi, A. B., Gole, A. M. & Maguire, T. L.||Real Time Simulation of Internal Faults in Synchronous Machines (abstract)||Internal fault, synchronous machine, real-time simulation, electromagnetic transient simulation, winding distribution||Session 24 - Real-Time Simulation|
|Abstract: This paper presents the development of a real-time digital simulator model for the simulation of arbitrary internal faults in synchronous machines. The model is an extension of the embedded phase-domain model of the synchronous machine . To represent a fault, the winding or windings involved in the fault are considered as a set of split windings[2,3,4,5] with their terminal nodes connected by a suitable fault impedance (or short circuit), which is switched in when the fault is applied. From the machine and winding geometry, values are calculated for the resulting set of mutually coupled inductances for this new winding arrangement.
The proposed method takes into account the actual geometry of the slots and the number of turns in each coil and uses an offline procedure to obtain the magneto-motive force (MMF) distribution due to each winding for a unit injection of current. This MMF along with the air-gap geometry information is used to calculate the flux linkages, and hence the self and mutual inductances of the windings. Thus in contrast with earlier approaches, it is able to calculate the inductances of the machine when the windings are arbitrary distributed.
Since this model is developed for real-time digital simulator, it has the unique feature of being a tool to test the relays designed to protect the synchronous machines from internal faults.
|Dennetière, S., Guillot, Y., Mahseredjian, J. & Rioual, M.||A Link Between EMTP-RV and FLUX3D for Transformer Energization Studies (abstract)||EMTP, FLUX3D, interface, switching transients, transformer transients||Session 2 - New Tools and New Techniques|
|Abstract: This paper presents a programmed link between the electromagnetic transients program EMTP-RV and the finite element field solver FLUX3D. The model created in FLUX3D is driven from simulation designs in EMTP-RV. The test cases presented in this paper demonstrate that the coupling method is numerically robust and with sufficient accuracy. This approach benefits from EMTP advantages in modeling large scale networks and from field solver advantages for detailed representation of power transformer iron cores.|
|Desjardine, M., Forsyth, P. & Mackiewicz, R.||Real Time Simulation Testing Using IEC 61850 (abstract)||IEC 61850, GOOSE, GSSE, closed-loop testing, real time, power system simulation||Session 26 - Real Time Simulation|
|Abstract: As IEC 61850 becomes more widely accepted in the electrical engineering community, it is important that the testing tools keep pace with this development. IEC 61850 presents new challenges to real time simulation and closed-loop testing of protective relays. Electrical interfaces used for binary signaling and voltage/current amplifiers must be replaced by an Ethernet connection and an IEC 61850 protocol stack. The electrical interfaces of a real time simulator are engineered to provide low latency and deterministic performance appropriate for a real time simulation. Similar attention must be given to IEC 61850 interfaces. Latency must be minimized so that the IEC 61850 interface does not add unacceptable delays to the operation of the simulator. Also, protocol processing must be deterministic to allow real time simulations to be repeatable and dependable. In addition, IEC 61850 specifies new configuration parameters and a new method for configuration called the Substation Configuration Language (SCL). These must be implemented in such a way that they fit within the typical modes of operation of the simulator.
The paper presents a successful hardware implementation for IEC 61850 messaging on a real time simulator and discusses the key design criteria. The software required to configure the IEC 61850 will also be addressed along with the advantages in using the IEC 61850 protocol. One of the biggest advantages is brought about by the realization of the IEC 61850-9-2 sampled values, removing the need for amplifiers as the standard interface to protection devices. Sampled values of the voltage and current signals can be sent via Ethernet, making it even more practical to perform testing on a protective relaying scheme rather than just individual devices.
|Dufour, C., Paquin, J., Lapointe, V., Bélanger, J. & Schoen, L.||PC-Cluster-Based Real-Time Simulation of an 8-Synchronous Machine Network with HVDC Link using RT-LAB and TestDrive (abstract)||real-time simulator, power system stability, HVDC link, FACTS devices, FPGA-based I/O, SimPowerSystems, Xilinx System Generator||Session 24 - Real-Time Simulation|
|Abstract: In this paper, we detail the real-time simulation results of a medium-sized network composed of 8 synchronous machines and an HVDC link. The model is composed of two Kundur-like 4 machines networks connected together with a 12-pulse HVDC link.
The complete network is modeled with SimPowerSystems with ARTEMIS real-time plug-in and is simulated in real-time on a RT-LAB InfiniBand PC-cluster composed of 3 dual-CPU dual-core Opteron PCs.
The network model includes the HVDC control and protection systems as well as the synchronous machine regulators and power stabilizers. It also includes typical fault simulation capability like HVDC DC faults, thyristor misfires and AC faults. This model is excellent to study the complex interactions between an HVDC link and AC network under normal and transient conditions.
The real-time simulation is controlled and monitored with a TestDrive interface from Opal-RT. This interface, based on LabView, permits easy monitoring and control of the complete system and enables Python-based scripting for automated tests. The proposed simulator can be interfaced with external equipments and controllers by direct reconfiguration of a FPGA I/O card with Xilinx System Generator blockset.
|Elguera, A. V., Tavares, M. C. & Portela, C. M.||Evaluating the Importance of Properly Representing Actual Transmission Line Transposition for Electromagnetic Transient Studies (abstract)||Electrical Parameters, Electromagnetic Transients, Frequency Dependence, Line Transposition||Session 20 - Transmission Lines and Cables|
|Abstract: In this paper transmission line transposition is analyzed focusing electromagnetic transient phenomena in the range up to 10 kHz. Line transposition is implemented to decrease phase unbalances at fundamental frequency. In the present paper it will be analyzed the error of treating transmission line as ideally transposed for all frequency ranges, specifically when dealing with switching transients up to 10 kHz. A theoretical analysis is performed identifying the unbalances between the phases considering the transmission line ideally transposed and considering the line with actual transposition sections. The difference between both line representations under transient was analyzed. The frequency dependence of transmission line parameters was properly represented.|
|Elkalashy, N. I., Lehtonen, M., Darwish, H. A., Taalab, A. I. & Izzularab, M. A.||DWT-Based Detection and Transient Power Direction-Based Location of High Impedance Faults Due to Leaning Trees in Unearthed MV Networks (abstract)||Arc model, DWT, initial transients, residual current and voltage, wireless sensors||Session 22 - System Protection and Fault Location|
|Abstract: Electrical faults due to leaning trees are common in Nordic Countries. This fault type has been studied in  and it was found that the initial transients in the electrical network due to the associated arc reignitions are behavioral traits. In this paper, these features are extracted using the discrete wavelet transform (DWT) to localize this fault event. Wireless sensors are considered for processing the DWTs on a residual voltage of different measuring nodes that are distributed in the network. Therefore, the fault detection is confirmed by numerous DWT processors over a wide area of the network. The detection security is also enhanced because the DWT is responded to a periodicity of the initial transients. The term for locating the faulty section is based on the polarity of a specific frequency band-power computed by multiplying the DWT detail coefficient of the residual current and voltage at each measuring node. The fault due to a leaning tree occurring at different locations in an unearthed 20 kV network is simulated by ATP/EMTP and the arc model is implemented using the universal arc representation. Test cases provide evidence of the efficacy of the proposed technique.|
|Fayet, P., Auriol, P. & Clerc, G.||Sensitivity Studies for AC Railway Networks Design (abstract)||Conductivity, grounding, impedance matrix, power cables, power system simulation, rail transportation, simulation software||Session 15 - Solution methods and modeling techniques|
|Abstract: AC Railway networks design is a particular application field which requires specific simulation tools. These networks include moving loads, different catenary types, and some connections between line conductors may exist, implying a specific research on line models.
The results presented were obtained with a new simulation tool which was specifically build for railway networks design. This development was lead in parallel by CEGELY and SEMALY.
This tool is composed of three modules:
- Mechanical calculations. Speed, position and mechanical power vs. time are calculated,
- Electrical calculations. Single or dual AT-feeding systems can be simulated. Contact wire to rail and rail to earth potential and currents in each conductor and at the pantograph of a train are calculated. Some other data such as power factor at the substation are also available.
- Thermal calculations. The temperature of the contact wire is calculated.
The work presented here deals with the electrical aspect and is divided into two parts. In the first part, three different line models are compared. The goal of this part is to quantify the error made on the calculated currents and voltages using one of the three models (Carson, Dubanton, Escane). In the second part, the influence of different parameters is studied in order to quantify the results sensitivity to input data variations.
Parameters such as earth resistivity, rail to earth impedance value (along the line or at the substation) and rail to earth conductance are studied. These studies were made on the 1x25 KV single power supply system. A special attention is given to the rail to earth potential calculation, which must not exceed 50 Volts. This work has also been validated with dual power supply (2x25 Autotransformers system)
|Filomena, A. D., Salim, R. H., Resener, M. & Bretas, A. S.||Fault Resistance Influence on Faulted Power Systems with Distributed Generation (abstract)||Protective relaying, fault resistance, distributed generation, fault location||Session 4 - System Protection Analysis and Models|
|Abstract: Fault resistance (RF) is a critical component in power systems protection schemes and fault locations algorithms. It introduces an error that if not taken into account for, may cause misoperation of ground distance relays and fault locators. The presence of distributed generation (DG) is becoming common in power systems, and new fault location methods and power system protection schemes are being developed to consider it. This paper proposes an analysis of the RF influence in power system relaying and fault location algorithms with and without DG, allowing future research for fault resistance compensation.|
|Fulczyk, M., Balcerek, P., Izykowski, J., Rosolowski, E. & Saha, M. M.||ATP-EMTP Investigation of a New Fault Location Method for Multi-Terminal Power Lines (abstract)||ATP-EMTP, current differential relay, fault location, simulation, multi-terminal line||Session 3 - System Protection and Fault Location|
|Abstract: This paper presents a new method for locating faults on multi-terminal power lines. Estimation of a distance to fault and indication of a faulted section is performed using three-phase current from all (n) terminals and additionally three-phasevoltage from the terminal at which a fault locator is installed. The fault location algorithm consists of (2n-3) subroutines designated for locating faults within particular line sections and a procedure for indicating the faulted line section. Testing and evaluation of the algorithm has been performed with fault data obtained from comprehensive ATP-EMTP simulations. Sample results of the evaluation are reported and discussed.|
|Ghiani, E., Pilo, F., Soma, G. G. & Celli, G.||Power Quality Measurements Performed on a Large Wind Park at Low and Medium Voltage Level (abstract)||Wind power, Power quality measurements||Session 17 - Wind Turbine Transients and Harmonics|
|Abstract: The integration of wind parks into the power system may cause power quality concerns. Thus, an important issue is the evaluation of how much the power quality would be affected by fluctuant power production and by the connection of the wind turbines to the power system.
This work investigates the impact of wind parks on the distribution network power quality. The field measurement results give important indications about the real effects of the integration of large interruptible renewable energy sources within the power system.
|Grasselli, U. & Di Erasmo, D.||Time Labelling for Fast Transients (abstract)||Transient, Wavelet transform, Travelling wave, Fault, Power quality||Session 15 - Solution methods and modeling techniques|
|Abstract: Among the different PQ disturbances voltage sags and interruptions are the most frequent. Those disturbances typically involve even high costs for customers, mainly due to the various damages on equipment, services un-availability, product losses, recovery time, and re-start procedures. It is possible, in actual PQ monitoring applications, to utilize as timing reference in multi-location monitoring activities GNSS (Global Navigation Satellite Systems) reference. A novel wavelet technique is proposed for detecting fault in power systems.
This paper presents the characterization of transients resulting from faults in power systems using the Discrete Wavelet Transform (DWT). This characterization will aid in the development of a method for localize and find faults in a power system. The analyzed case study is obtained by simulations of different fault locations.
|Gustavsen, B. & Mo, O.||Interfacing Convolution Based Linear Models to an Electromagnetic Transients Program (abstract)||state space model, convolution, electromagnetic transients, PSCAD, vector fitting||Session 18 - Solution methods and modeling techniques|
|Abstract: This paper describes a convolution based terminal equivalent for the PSCAD/EMTDC simulation environment, implemented as a user-defined component. This frequency dependent terminal equivalent (FDTE) reproduces the terminal behavior of a multi-port linear system given as a phase domain state-space model. The model can be identified using available software. A user-written PSCAD component reads the state space parameters from file and includes the model in the simulation via a companion model and trapezoidal based convolution. In addition is implemented a frequency dependent transfer function model (FDTF) that calculates the transfer between a set of inputs and outputs. The accuracy of the FDTE/FDTF components is validated by numerical examples. Also is shown an example from network equivalencing where large savings in computation time is achieved, compared to a traditional modeling procedure.|
|Gérin-Lajoie, L.||A MHO Distance Relay Device in EMTPWorks (abstract)||MHO distance relay, EMTP-RV, protection||Session 6 - System Protection Analysis and Models|
|Abstract: Distance relays are widely used for protection of transmission lines. Usually, the nonlinear nature of an arcing fault requires that a time model should be implemented to know if the relay detects or not this faulted condition. Moreover, the mutual effect of line conductors for single or multiphase faults requires that all three phases of the relay be modeled. This paper describes in detail a first generic MHO distance relay in EMTPWorks based on three separate single phase impedance vectors. Cosine-sine filters are used to perform the phasor representation of the fundamental current and voltage computed over a 60 Hz sliding time window. Validation of the measured impedance function of the model is compared with the real apparent impedance of the network. This paper also discusses logical operations to initiate the opening of line breakers.|
|Gérin-Lajoie, L. & Kamwa, I.||High-Frequency Impedance Estimation and Equivalent with N4SID (abstract)||Harmonic impedance, frequency scan, EMTP, state-space identification, N4SID, spectrum analysis||Session 18 - Solution methods and modeling techniques|
|Abstract: This paper describes a Multiple Input Multiple Output (MIMO) System Identification technique for high- frequency impedance and admittance measurement. This technique uses a current or voltage white-noise source in the time domain and a generated linear state-space matrix in MATLAB™ environment. Part I of this paper presents a N4SID impedance validation with the classical frequency scan option in EMTP. This will be very useful when the user has FACTS models in his network and when FS cannot be used directly. In Part II, the admittance matrixes are calculated and the new state-space admittance power part is used in the time domain connected like a Norton Equivalent for a multiphase frequency-dependent network equivalent.|
|Gómez, P., Arellano, P. & Mota, R. O.||Frequency Domain Transient Analysis Applied to Transmission System Restoration Studies (abstract)||Frequency domain analysis, restoration, switching transients||Session 2 - New Tools and New Techniques|
|Abstract: In this work, a frequency domain method to evaluate transient overvoltages produced in the restoration process of transmission systems is described. During this process, long simulation times are necessary given that several switching operations are performed to interconnect different parts of the network. The method is applied to analyze a particular transmission system, for which maximum overvoltages derived from the sequential energization of transmission lines at different restoration stages are evaluated. For the frequency domain analysis, the Numerical Laplace Transform (NLT) is applied, comparing its results with those obtained directly in time domain using the ATP-EMTP.|
|Heidari, M., Filizadeh, S. & Gole, A. M.||Computer-Aided Sensitivity Analysis for Optimal Systems (abstract)||Sensitivity analysis, transient simulation, selective harmonic elimination, STATCOM||Session 15 - Solution methods and modeling techniques|
|Abstract: In this paper, a computer-aided sensitivity analysis tool is developed for analyzing nonlinear optimum systems. To enable sensitivity analysis around the optimum points, the concept of second-order sensitivity analysis is introduced. The developed tool not only provides the conventional sensitivity indices (which are useful for non-optimal solutions), but also provides the second-order sensitivity indices. The proposed method have been exemplified using Selective Harmonic Elimination (SHE) switching scheme for voltage sourced converters.|
|Henriksen, T. & Petterteig, A.||Detection of Earth Fault in a Medium Voltage Distribution Network (abstract)||Arc suppression coil, ground fault, measurements, fault detection, non-symmetrical conditions||Session 10 - System Protection and Fault Locati|
|Abstract: The application of sophisticated computational models are frequently limited by the available input data. This paper presents results from measurements where a single phase to ground fault was introduced in a distribution network grounded by an arc suppression coil. The non-symmetrical conditions prior to the fault limit the possibility of the detecting a high impedance fault when using phasor variables. These non-symmetrical conditions depend on parameters that are normally not known with sufficient accuracy but the performed measurements give the relevant information for the actual network. The time domain measured signals have been converted into time variable phasors and it is shown how the phasors are influenced by the transients due to the fault initiation and the disconnection of the faulty feeder. Most of the tests where made by introducing a permanent fault, but a series spark gap was introduced in some measurements. The gap caused multiple extinctions and re-ignitions of the fault current that became substantially distorted.
The fault initiation causes current spikes that can be used to detect the fault and identify the faulty feeder. The spikes are reduced by the fault resistance and the measurements indicates 1 kΩ as an upper limit for detecting the fault, while the phasor analysis indicates 5 kΩ as an upper limit.
|Hosseini, S. M. H., Vakilian, M. & Gharehpetian, G. B.||An Improved MTL Modeling of Transformer Winding (abstract)||Transformer winding, Fast transient, Multiconductor transmission line, Loss factor||Session 27 - Transformers|
|Abstract: This paper presents a new approach for modeling of the windings using Multiconductor Transmission Line (MTL) theory. In this model loss factor coefficient (tan δ) and dielectric constant (ε) have been considered as frequency dependent parameters. The improved multiconductor transmission line (MTL) theory has been employed to model a 900 MVA, 500 kV transformer windings. It is shown that the simulation result of model with frequency dependent loss factor has a good agreement with measurements results.|
|Huang, W. & Kaczmarek, R.||Wave Propagation Regime to Point to the Faulted Feeder in Mixed Cable-and-Lines Distribution Systems with Single-Line-to-Ground Fault (abstract)||Traveling waves, fault detection, distribution systems||Session 3 - System Protection and Fault Location|
|Abstract: In radial distribution network with no discontinuities in feeders’ impedances the shape of traveling wave induced by a single line to ground (SLG) fault inception is modeled by multiple refractions and reflections from busbar, fault and loads. Only initial propagation zone presents a rigorous polarity disposition of residual currents, with sound residuals having the same polarity. We can determine the minimal sampling frequency necessary to get in that zone the current data indicating faulted feeder. The initial polarity length does not depend on the fault position, its resistance value or on the soil resistivity, and if scrutinized on all feeders it can point out from busbar to faulted feeder in systems with laterals.
The propagating waves can thus be involved in directional procedures in lines or in cables. Under certain conditions the faulted feeder detection can be assumed also in mixed networks, built up partly of cables and partly of lines.
|Huang, W. & Kaczmarek, R.||Transient Regime to Support Steady State Directional Function in Presence of Strong Capacitive Currents in Compensated MV Systems (abstract)||fault detection, distribution systems, compensated systems||Session 3 - System Protection and Fault Location|
|Abstract: A Single Line to Ground (SLG) fault location task in systems grounded with Petersen Coil can be out of reach of steady state methods, based on detection of active component in faulted currents. Efficiency of these methods may not be assured when strong capacitive currents on faulted feeder squeeze the phase shift between the faulted and the sound zero sequence currents below actual acquisition limits.
Then the way to assure the directional decision is to exploit data recorded in transient regime, where an apparent phase difference is more important than actual phase difference in steady state. This is a consequence of the way the transient regime develops, beginning just after the fault inception with phase opposition between the faulted and the sound current residuals and finishing in steady state with a slight phase advance of the faulted residual over all the sound ones.
|Huang, W. & Kaczmarek, R.||Symmetrical Components for Transient Regime Applications in MV Systems (abstract)||power distribution lines, power cables, fault diagnosis, fault location, equivalent circuits||Session 3 - System Protection and Fault Location|
|Abstract: In order to apply advantageously the symmetrical components theory to Single Line to Ground (SLG) fault transients in distribution systems we take profit of similitude of transient components in faulted phase current and in zero sequence current on faulted feeder. Then we are able to take into account the load current contribution within voltage drop account of zero sequence equivalent circuit. The result is an Extended Zero Sequence circuit, of better accuracy comparing to Traditional Zero Sequence circuit or Full Sequence 0-p-n circuit. It reproduces the overall response of distribution system to an SLG fault inception, whereas traditional equivalent circuits assume only one frequency analysis. Consequently, the new zero sequence circuit is more adapted for evaluation of amplitudes of actual transients or for fault location tasks.|
|Høidalen, H. K., Mork, B. A., Gonzalez, F., Ishchenko, D. & Chiesa, N.||Implementation and Verification of the Hybrid Transformer Model in ATPDraw (abstract)||Transformer modeling, saturation, leakage inductance, winding resistance, capacitance, topologically correct core||Session 11 - Transformers|
|Abstract: The paper documents a new transformer model in ATPDraw called XFMR. This model handles 3-phase transformers with two or three windings. Autotransformers and all Wye and Delta couplings are supported. The model includes an inverse inductance matrix for the leakage description, optional frequency dependent winding resistance, capacitive coupling, and a topologically correct core model (3- and 5-legged) with individual saturation and losses in legs and yokes. Three different sources of data are supported; typical values, standard test reports, and design information. The hybrid model XFMR is compared to the UMEC model in PSCAD showing good agreement at rated, stationary operation, but considerable differences in transient situations. Both models need development to reproduce all switching transient behaviors properly.|
|Ikuta, M., Asakawa, A., Yokoyama, S. & Soeda, M.||Customer Indoor Surge Phenomena due to Lightning Strike on the Joint Pole of Power Line and Telecommunication Line (abstract)||Lightning, Lightning protection, Low-voltage line, Surge protective device, Telecommunication line||Session 12 - Lightning Surges|
|Abstract: Abstract--This paper describes an experimental study to examine how surge phenomena emerge when a lightning surge enters a customer’s premises via a power line and a telecommunication line. In the test, the authors simulated various cases in which lightning strikes a pole on which a high-voltage distribution line, a low-voltage distribution line and a telecommunication line are jointly mounted. The variation of customer indoor surge phenomena resulting from differences in the installation conditions of a power drop wire and a telecommunication drop wire, and that of a surge protective device (SPD) and a bonding wire, was clarified. Further, it was found that the current passing through the telecommunication equipment was suppressed by connecting the grounding wire of the SPD, which is installed at the customer’s incoming port of the power line, with the grounding wire of the surge arrester installed in the incoming port of the telecommunication line.|
|Jithin Sundar, S. V. N. & Vaishnavi, G.||Performance Study of a Continuously Controlled Shunt Reactor for Bus Voltage Management in EHV Systems (abstract)||High impedance transformer, shunt reactor, reactive power, compensation, EHV systems, voltage control, thyristors||Session 9 - Power Electronics Applications|
|Abstract: In EHV substations, it is a common practice to use breaker switched bus reactors to maintain the bus voltage within permissible limits under varying load conditions. With the development of Controlled Shunt Reactor (CSR) which is a thyristor controlled high impedance transformer, a stable bus voltage can be maintained by providing variable reactive power based on the bus voltage deviations due to the load variations. The high impedance transformer which is also known as reactor transformer (RT) can be made to any size without any limitation unlike gapped core shunt reactors. As a single CSR of large capacity can be realized with suitable control mechanism, this approach proves to be technically superior and economical compared to the existing practice of breaker switched bus reactors.
A CSR with a detailed control system is modeled along with a typical EHV system in PSCAD/EMTDC environment. The study includes the effectiveness of filters introduced in the tertiary of the reactor transformer in controlling the harmonics generated during partial conduction of thyristors. The transient and steady state performance of the CSR system for varying system conditions is studied and the same is compared with the conventional practice. The paper presents and discusses the results of the study.
|Kang, Y., Lee, B., Lee, M., Jang, S. & Kim, Y.||Real-Time Estimation of a Delta Winding Current in a Wye-Wye-Delta Transformer (abstract)||Circulating component, Delta winding current, Estimation, wye-wye-delta transformer||Session 24 - Real-Time Simulation|
|Abstract: This paper proposes an algorithm for estimating a delta winding current for a wye-wye-delta transformer in realtime. The primary induced voltages of the three phases are calculated from the primary currents and voltages. The induced voltages are referred into the tertiary side i.e. the delta-winding considering the turns ratio of the transformer. Applying the Kirchhoff’s voltage law on the delta winding gives a first-order differential equation in terms of the delta winding currents. The delta winding currents is estimated by solving the equation. The performance of the proposed algorithm is investigated under various conditions including magnetic inrush and over-excitation from the EMTP generated data. The algorithm can estimate the winding currents very accurately even under magnetic inrush and over-excitation. This paper concludes by implementing the algorithm into the digital signal processor based prototype testbed.|
|Kang, Y., Zheng, T., Kim, Y., Jang, S. & Kim, Y.||Compensation of the Secondary Voltage of a CCVT Considering Hysteresis Characteristics of the Core in Time Domain (abstract)||CCVT, compensation, hysteresis, time domain||Session 10 - System Protection and Fault Location|
|Abstract: This paper proposes an algorithm for compensating the distorted secondary voltage of a coupling capacitor voltage transformer (CCVT) in the time domain considering the hysteresis characteristics of a core. The voltage across the capacitor and the tuning reactor is the error between the correct primary voltage and the measured primary voltage. The proposed algorithm estimates and adds the voltage across the capacitor and the reactor to the measured primary voltage to obtain the correct voltage considering the effect of the hysteresis characteristics of the core. The algorithm reduces the errors significantly both in the steady state and during the fault. The performance of the algorithm is verified under the various fault conditions by varying the fault distance, the fault inception angle and the fault impedance with the EMTP generated data. Test results clearly indicate that the algorithm can increase the accuracy of a CCVT significantly under the fault conditions as well as in the steady state. The algorithm may improve the performance of a relay or a metering device.|
|Kezunovic, M., Luo, X., Zhang, N. & Song, H.||Testing and Evaluating New Software Solutions for Automated Analysis of Protective Relay Operations (abstract)||test, software solution, automated analysis, protective relay||Session 6 - System Protection Analysis and Models|
|Abstract: This paper presents the test and evaluation environments for three new software solutions for automated analysis of protective relay operations. For each environment, the test requirements, test solution and benefits are discussed. A comprehensive modeling and simulation environment serving as the common test and evaluation platform for all the three software solutions is proposed.|
|Khaburi, D. A. & Tootoonchian, F.||Using average DC-Pulse Response of Stator Current for Identification of Single-Phase Rotary Transformer Parameters (abstract)||Rotary Transformer, Parameter Identification, Resolver||Session 25 - Transformers|
|Abstract: Because or temperature independence, highest resolution andnoi seless outputs, rotary transformer together with brushless resolvers are widely used in high precision control systems. To apply efficient rotor position information to control algorithm, without any brushes noise, it is necessary to use rotary transformer. This paper is presented for parameter identification or rotary transformer that eliminates or reduces classic method disadvantages. It presents a DC-Pulse method based on a simple configuration, which increase estimated parameters accuracy and reduce time or test. On the other hand the classic method needs three or two tests to estimate parameters but proposed method needs just one test. Finally electrical parameters are estimated by comparing the average DC-Pulse current with current response function or mathematical curve fitting. Validation or the method and estimated parameters accuracy is performed by comparing experimental current test with simulation results.|
|Kizilcay, M. & Neumann, C.||Backflashover Analysis for 110-kV Lines at Multi-Circuit Overhead Line Towers (abstract)||flashover, back-flashover, lightning stroke, lightning surge, transmission tower, EMTP||Session 23 - Lightning Surges|
|Abstract: An increase of back-flashovers in a 110-kV system has been observed along an overhead line route that consists of multi-circuit transmission towers of voltage levels 380-kV, 220- kV and 110-kV at the same tower. The height of multi-circuit towers varies in the range of 55 m – 88 m. The 110-kV doublecircuit line is positioned at the lowest cross-arm of the tower. Influence of the various factors on the back-flashover of the 110-kV insulator strings has been studied by means of EMTP-ATP simulations. Different current waveforms of the lightning stroke have been used to represent the first stroke and subsequent strokes. Available flashover analysis methods like leader development method by Pigini et al and by Motoyama, as well as the voltage-time integration method by Kind have been implemented using a simulation language and the performance of flashover models has been compared.
The purpose of this study was to identify those towers at which back-flashover is more likely to occur than at other towers along the line route. Replacement of one insulator string of a 110-kV duplex insulator by a surge arrester is shown to be a successful mitigation technique to reduce the back-flashover rate of those 110-kV lines.
|Kizilcay, M., Teichmann, K., Agdemir, A. & Kaflowski, G.||Flashovers at a 33-kV Filter Reactor during Energization (abstract)||temporary overvoltages, flashover, magnetic saturation, temporary ferroresonance, energization, star point displacement, harmonic filter, reactor switching, EMTP||Session 13 - Switching Transients|
|Abstract: For an extrusion plant 33-kV filter circuits are installed to absorb harmonics of the 5th and 11th order in the electric power supply. During the system start-up of the filters flashovers occurred between the two coil parts of the reactor belonging to the filter for the 5th order harmonic in two of the three phases.
This paper shows how overvoltages can be produced during energization of the filter, which may cause flashovers at the filter reactor by means of digital simulations of switching transients. The system components including the filter circuit are represented in detail using ATP-EMTP. Both filters are fed by a relatively long 33-kV cable. The saturation characteristic of the filter reactors plays an important role in initiating repetitive high transient voltages. The neutral point of the filters is isolated, since the neutral of the feeding 33-kV system is not grounded.
The overvoltages across the reactor obtained by a statistical analysis of switching surges are far higher than the amplitude of the withstand test voltage performed at the factory. Severe overvoltage stress of the filter reactor may also happen, when the filter will be re-energized shortly after it has been switched off, so that the filter capacitors remain charged. In this case, the highest overvoltage of 83.9 kV is expected across the filter reactor.
|Kocis, L.||Ferroresonances during Black Starts - Criterion for Feasibility of Scenarios (abstract)||Ferroresonance, magnetizing curve, blackstart scenarios, temporary overvoltage, transient phenomenon||Session 8 - Ferroresonance|
|Abstract: After large black-out events in the USA and Europe, there is a great interest to have power systems able to restart as quickly as possible, systems with reasonable number of potential starting sources and sufficient variety of blackstart scenarios.
Typically, recovery of a system operation starts from small generator(s), which power should be given to a remote larger power plant to start up it. During this process, various nonstandard combinations of sources, lines and transformers can occur, that can be unstable and exhibit very high level of transient temporary overvoltages. The main cause of that is a ferroresonant oscillation between source, line capacity and switched power transformers with saturation. The transient behaviour with temporary overvoltages can endanger hv equipment and it was considered that surge arresters are the most sensitive. Therefore a criterion of satisfactorily low and permissible thermal stressing of surge arresters was established as the criterion for acceptability of a given step of black-start process.
The problem is in the paper demonstrated on the real event - black-start experiment realized in czech power system. The ferroresonance was predict by EMTP simulation during preparation of the test and it really occured.
The authors analysed various configurations of sources, lines and transformers by EMTP simulations on appropriate EMTP models and prooved them for transient ferroresonance - its magnitude and duration. They looked for some rules for appearing of resonances and temporary overvoltages and found some regularity, which will be presented in the paper. Then the authors created models of real network configurations for blackstarts and prooved them by simulation. Permissible black-start scenarios were specified on basis of the criterion of acceptable energy absorption of surge arresters then verified as feasible and implemented to plans of system recovery.
|Larivière, P. & Racine, M.||Integration of a Hydraulic Production Plant in a Weak Power System on a Long Radial Line (abstract)||Transmission lines, Electric Machines and Drives Temporary Overvoltages, Control Systems||Session 5 - System Dynamics, SSR Studies|
|Abstract: Integrating power plants on long lines and weak power systems requires some care. To this effect, a study was conducted to determine if severe disturbances could result when a hydraulic production plant is integrated along a very long radial transmission line. Frequency responses were evaluated to identify possible resonant system operating conditions. Many events such as faults, transformer energizing and line opening were investigated. All power plant synchronous machines were represented including exciter and governor regulators. Impact of dynamic modeling of the load was examined. The study demonstrates that the overall protective strategy implemented will limit worst overvoltage constraints imposed to equipment and load within an acceptable level.|
|Larsson, T., Hasler, J., Forsyth, P. & Maguire, T.||Voltage Source Converter Modeled in RTDS - Experiences and Comparison with Field Results (abstract)||Power electronics, Power system simulation, Pulse Width Modulation, Real time simulator, Static VAR compensators||Session 24 - Real-Time Simulation|
|Abstract: For the first time it has been possible to model a three-level Voltage Source Converter (VSC) and test the physical firing pulse controls using a Real Time Digital Simulator (RTDS®). The new RTDS model is more flexible and comprehensive than both earlier digital versions and analogue TNA models. This allows more tests to be conducted in a shorter time and provides a more detailed power system representation for the tests. Using the new system to test the controls also simplifies the recording of results since all signals can now be gathered by the RTDS Simulator.
For the case of Electric Arc Furnace (EAF) compensation, the new real time digital simulation has made it convenient and easy to demonstrate the flicker improvement factor provided by the actual VSC controls under realistic system conditions.
The paper compares results from off-line and real time RTDS simulations, as well as from field measurements taken at a full scale ABB SVC Light® installation. The good correlation between simulation results and field measurements give confidence to the digital modeling.
|Lee, H., Lee, C., Lee, H., Jang, G. & Chang, S.||A Novel Fault Location Scheme on Korean Electric Railway System Using the 9-Conductor Representation (abstract)||Fault analysis, Boost wire, Korean AC electric railway system, Fault current ratio||Session 22 - System Protection and Fault Location|
|Abstract: This paper presents a novel fault location scheme on Korean AC electric railway systems. On AC railway system, because there is a long distance, 40 km or longer, between two railway substations, a fault location technique is very important. Since the fault current flows through the catenary system, the catenary system must be modeled exactly to analyze fault current magnitude and fault location. In this paper, before suggestion for the novel scheme of fault location, a 9-conductor modeling technique that includes boost wires and impedance bonds is introduced, based on the characteristics of Korean AC electric railway. After obtaining a 9-conductor modeling, the railway system is constructed for computer simulation by using PSCAD/EMTDC. By case studies, we can verify superiority of a new fault location scheme and suggest a powerful model for fault analysis on electric railway systems.|
|Legrand, X., Xémard, A., Auriol, P., Nucci, C. A. & Mouychard, C.||Modeling of Substation Grounding for Fast Front Overvoltage Studies (abstract)||Grounding, Substation insulation, Maxwell equations, Lightning||Session 7 - Lightning Surges|
|Abstract: When performing insulation coordination studies, grounding electrodes of substations are frequently represented as as lumped resistances, in some cases even when extended grounding grids are dealt with. This paper presents an analysis of the approximations deriving from such a practice when studying fast transient phenomena, for several cases in term of grid geometry and soil electric resistivity. The influences of two models are compared for the grounding system: a very simple model that consists only of a resistor, and a model based on the more rigorous application of Maxwell’s equations. The limits of applicability of these models are investigated and discussed by means of a comparative study. We conclude that depending on the type of engineering problem that one has to tackle, the adoption of one model instead of the other can lead to significant differences. For insulation coordination, lightning fast front overvoltages in the substation could be still computed in a first approximation using a simple resistor to model the grounding grid. Regarding EMC studies, the simplest model can lead to a certain underestimation of the potential rise of the grid, which means that, in general, the application of the Maxwell’s equations-based model is recommended.|
|Lima, A. C. S., Gustavsen, B. & Fernandes, A. B.||Inaccuracies in Network Realization of Rational Models Due to Finite Precision of RLC Branches (abstract)||System identification, Vector fitting, Frequency dependence, Network synthesization, Rational approximation||Session 18 - Solution methods and modeling techniques|
|Abstract: One of the most challenging points in the simulation of power system transients is the modeling of frequency dependent impedances or admittances and their inclusion in the simulation environment. Highly accurate models can be identified via rational function approximations in the frequency domain, for instance by Vector Fitting. One way of including the obtained model in a time domain simulation is via an equivalent electrical circuit. This paper shows a case where the modeling via an equivalent circuit in ATP gives an inaccurate representation of the rational model. It is shown that the finite precision of the branch cards causes a catastrophic cancellation error in the representation of an RLCG branch. The sensitivity to the output format is investigated.|
|Lin, X., Gole, A. M. & Yu, M.||A Wide Band Multi Port Equivalencing Method for Real Time Digital Simulators (abstract)||Power System Simulation, Real Time Digital Simulator, Dynamic Equivalent, Frequency Dependent Network Equivalent, Electromagnetic Transient, Transient Stability||Session 26 - Real Time Simulation|
|Abstract: This paper proposes a wideband multi-port equivalent for real time digital simulators, which permits the simulation of a large power system in real time with reduced hardware cost. The proposed equivalent includes a Frequency Dependent Network Equivalent (FDNE) for the high frequency electromagnetic transients and a Transient Stability Analysis (TSA) type solution block for the electromechanical transients. The FDNE equivalent is obtained using Vector Fitting techniques. A method for approximating the frequency dependent characteristics of large power networks is also presented. The conventional TSA algorithm is shown to be unsuitable for realtime application; and a modification suitable for implementation on real-time platforms is proposed. The validity and efficiency of the proposed equivalencing method are demonstrated using examples that include: i) a large ac network and ii) a multi-infeed HVDC system based network.|
|Lira, G. R. S., Jr., D. F. & Costa, E. G.||Computation of Energy Absorption and Residual Voltage in Metal Oxide Surge Arrester from Digital Models and Lab Tests: A Comparative Study (abstract)||EMTP, energy absorption, surge arrester, surge arrester models, transient simulations||Session 7 - Lightning Surges|
|Abstract: In this work, analysis of some Metal Oxide Surge Arresters (MOSA) models, proposed in literature, were carried out to compare the absorbed energy computed by digital simulations with the energy obtained from laboratory measurements. The residual voltage was compared as well. In digital simulations, it was used the conventional model (nonlinear resistor from ATP), and two frequency-dependent models (IEEE model and the simplified model proposed by Pinceti). In the lab tests, the varistor blocks were submitted to voltage at power frequency, lightning current impulses (8/20 μs waveform) and fast transients. The voltage and current signals applied to the varistor were recorded and used as the input sources to obtain the digital simulations. As a result, all the models presented good agreement between peak values of voltages for digital simulations and lab. With respect to energy absorption, the models have also shown good agreement results for lightning current impulses. The frequency-dependent models have shown reasonable agreement for fast transients.|
|Mademlis, C. & Kioskeridis, I.||Smooth Transition between Optimal Control Modes in Switched Reluctance Motoring and Generating Operation (abstract)||Reluctance motor drives, reluctance generators, variable speed drives, optimal control, optimization methods||Session 9 - Power Electronics Applications|
|Abstract: This paper presents the design and implementation of a control system for switched reluctance machines applicable over the entire speed range, for motoring and generating operation. The suggested control system achieves high performance and smooth transition between PWM-control to single-pulse control modes. The proposed controller on-line determines the optimal firing angles for all operating modes. The optimal condition of one operating mode is derived from the optimal condition of the other operating mode and thus smooth transition between the control modes is provided. The parameters of the optimal controller and the model of the test switched reluctance machine are determined experimentally. Simulation results under various operating conditions are presented to demonstrate the effectiveness of the proposed control scheme.|
|Martinez-Velasco, J. A. & Castro-Aranda, F.||Assessment of the Lightning Flashover Rate of a Shielded Transmission Line Protected by Surge Arresters (abstract)||Surge Arresters, Overvoltages, Modeling, Monte Carlo Method, Power System Lightning Effects||Session 12 - Lightning Surges|
|Abstract: Surge arresters are installed to improve the lightning performance of overhead lines with a poor shielding or with very high tower footing impedances. The flashover rate of a shielded transmission line protected by surge arresters can be negligible when arresters are installed at all phases and all towers, but even if arresters are not installed at all phases, some improvement is achieved. However, arresters must be selected taking into account energy discharge stresses since failures can be caused when the energy discharged exceeds the maximum absorption capacity. This paper is aimed at analyzing the lightning performance improvement of a shielded transmission line that is achieved after installing surge arresters.|
|Martinez-Velasco, J. A. & Martin-Arnedo, J.||EMTP Model for Analysis of Distributed Generation Impact on Voltage Sags (abstract)||Distributed Generation, Power Quality, Voltage Sag, Modeling, Simulation||Session 21 - Power Quality and Harmonics|
|Abstract: Small generation units connected to distribution systems can improve end-user power quality; e.g. by providing voltage support. However, the presence of distributed generation (DG) changes the radial nature of distribution systems and affects the performance of the protection system. DG can also affect during- and post-fault voltages; in addition, voltage sags are highly influenced by the type of protective devices and the coordination between them. This paper is aimed at exploring the impact that DG can have on voltage sags characteristics at distribution levels when the main cause of voltage sags can be either at a transmission or a distribution network.|
|Marzinotto, M. & Mazzetti, C.||Propagation of Transients in Extruded MV and HV Cables Considering Typical Thickness and Resistivity Values of Commercial Semiconductive Compounds (abstract)||cable line, semiconductive compounds, frequency dependent cable line model, transients on cable line||Session 7 - Lightning Surges|
|Abstract: The effect of the semiconductive layers on the propagation of transients along a cable line has been considered in the light of the cable line model recently introduced by metani et al.. The analysis has been addressed on different cable line lengths and considering the cable line installed in a typical layout between an overhead line and a transformer. Fast and slow front voltage shapes impinging the cable line, simulated via the Heidler function with selected parameters, has been considered coming from the overhead line. Actual cable formations of typical 20 kV and 150 kV cable ratings have been adopted. The characteristics of the semiconductive compounds in terms of dielectric constant, resistivity and thickness values have been selected from commercial compounds.
The results obtained using an accurate cable line model that takes into account the semiconductive layers in the cable formation and a less accurate one that disregards such layers are compared and discussed. Although the analysis shows that the differences in the propagation of transients using the mentioned models are not strong, the advanced models is in any case to prefer in order to avoid possible misleading results.
|Matar, M. & Iravani, R.||An FPGA-Based Real-Time Digital Simulator for Power Electronic Systems (abstract)||Real-time simulation, Switching, Modeling, Field Programmable Gate Array (FPGA)||Session 24 - Real-Time Simulation|
|Abstract: Testing digital controllers for power electronic systems in real-time using a real-time digital simulator presents a problem, due to the discrete nature of the controller outputs which are not necessarily in synchronism with the time-step of the simulator. Reducing the simulation time-step resolves the issues resulting from the lack of synchronism between the digital simulator and the hardware controller under test. The simulation time can be reduced by distributing the computational burden among a number of parallel processors. However, the reduction in time is not directly proportional to the number of processors due to the interprocessors communication overhead.
However, the simulation time can be greatly reduced if the simulator's hardware is custom configured. This paper is an effort to introduce and develop a reconfigurable hardware simulator using FPGAs to simulate power systems that contains power electronic switching elements. The simulation time-step for this simulator is less than 100ns. A new time domain model for power electronic switching elements is also presented in this paper. The new model is very convenient for real-time simulation purposes due to its simplicity and the elimination of numerical oscillations associated with other models.
|Matsuura, S., Noda, T., Asakawa, A. & Yokoyama, S.||EMTP Modeling of a Distribution Line for Lightning Overvoltage Studies (abstract)||concrete pole, direct lightning stroke, distribution lines, EMTP modeling, FDTD method, ground wire, lightning channel, lightning overvoltages, and phase wires||Session 19 - Transmission Lines and Cables|
|Abstract: Recently, the focus of lightning protection measures for distribution lines has moved to the direct lightning stroke. Studies of such countermeasures are generally carried out by digital simulation using the EMTP (Electro-Magnetic Transients Program). This paper first shows the surge response of a distribution line obtained by pulse tests using a reduced-scale distribution line model. The results of the pulse tests are simulated using the FDTD (Finite Difference Time Domain) method, and comparisons show that FDTD simulations give sufficiently accurate results. Finally, EMTP models of the distribution pole and wires, which can reproduce the transient overvoltages at the insulators, are proposed. The parameter values of the proposed models can be determined based on the pulse test or the FDTD simulation results.|
|Mehrizi-Sani, A., Filizadeh, S. & Wilson, P. L.||Harmonic and Loss Analysis of Space-Vector Modulated Converters (abstract)||Harmonic analysis, space-vector modulation, switching losses, transient simulation, voltage-sourced converter||Session 21 - Power Quality and Harmonics|
|Abstract: Space Vector Modulation (SVM) is an alternative method to the conventional, sinusoidal PWM for control of highpower converters. It is known for its higher utilization of the dcbus voltage as well as being readily available for digital implementation. This paper presents the SVM method and a number of its variations, which are implemented in a digital transient simulation program (PSCAD/EMTDC). The developed model is used to study the performance of SVM in terms of its harmonic spectrum and associated losses. These factors are compared against different SVM implementations as well as the sinusoidal PWM strategy. The suitability of the model is hence ascertained.|
|Mestas, P. & Tavares, M. C.||Comparative Analysis of Control Switching Transient Techniques in Transmission Lines Energization Maneuver (abstract)||Synchronized switching, metal oxide surge arrester, pre-insertion resistor, PSCAD||Session 16 - Switching Transients, Lines and Cables|
|Abstract: The long transmission line energization can cause high overvoltage stresses mainly along the transmission line, but also in the supply network. A traditional method of limiting switching overvoltages to acceptable levels is to use circuit breakers equipped with pre-insertion resistors.
This paper describes a study made in an actual 500 kV AC transmission system considering two alternatives in order to limit switching surge overvoltages during line energization: the use of metal oxide surge arresters at both line ends and along the line and the use of synchronized closing of circuit breakers.
Digital simulations have been made with PSCAD/EMTDC. The degree of shunt compensation is considered as independent parameter.
|Murray, N., Arrillaga, J., Watson, N. R. & Liu, Y. H.||Improved Simulation of an HVDC Test Case through Power-flow Initialization (abstract)||EMTDC, PSCAD, Power Flow, Multi-level conversion, HVDC Transmission||Session 18 - Solution methods and modeling techniques|
|Abstract: The steady state solutions derived from EMTP and power flow simulations differ due to the idealised and purely fundamental frequency system representation of the latter. This paper shows, however, that a preliminary power flow assessment of the operating condition can help to reduce substantially the initialization time of the EMTP solution. The test is carried out with reference to a new concept designed to exercise independent reactive power control in a multi-level CSC-HVDC scheme used for bulk power transmission from a remote power generating station.|
|Mäki, K., Kulmala, A., Repo, S. & Järventausta, P.||Studies on Grid Impacts of Distributed Generation in a Combined Real-Time Simulation Environment (abstract)||distributed generation, protection, RTDS, dSPACE, real-time simulation||Session 26 - Real Time Simulation|
|Abstract: The increasing amount of distributed generation in public networks sets new requirements for the traditional network protection schemes. Actual problems have been experienced relating for instance to fault levels, reclosings and earth faults. As the complex protection is often considered a barrier against more wide-scale use of distributed energy resources, new development is needed. New generation units are often equipped with power electronic converters, whose behavior during faults and disturbances requires accurate modeling.
This paper focuses on protection impacts of distributed generation and on the possibility of applying a novel simulation environment for these studies. The environment is described and some motivation for building such system is discussed. An example case is studied using the simulation environment. Some observations are made based on the results.
|Nishiwaki, S., Nakamura, T. & Miyazaki, Y.||A Special Ferro-resonance Phenomena on 3-phase 66kV VT-generation of 20Hz Zero Sequence Continuous Voltage (abstract)||Ferro-resonance, Voltage transformer, 20Hz zero sequence continuous voltage, One line grounding fault, 3-phase circuit||Session 8 - Ferroresonance|
|Abstract: When an one line grounding fault in a transmission line was removed, the insulation of the earthed voltage transformer(VT) broke down at the substation of a petroleum refinery which was provided with electric power from both an on-premises power generation plant and an outside power company. At this time, the abnormal 20 Hz zero sequence continuous voltage was recorded. Initially, the cause was not known, however it was found from an analysis using EMTP that this was a ferro-resonance phenomenon of the VT. This abnormal 20 Hz zero sequence continuous voltage could be reproduced by computation. It is thought that the main causes of the ferro-resonance were the existence of a single phase VT connected in addition to a 3-phase VT, and also the fact that the system became completely ungrounded neutral system after the one line grounding fault was removed.|
|Noda, T.||Object Oriented Design of a Transient Analysis Program (abstract)||Circuit simulation, Electromagnetic transient analysis, Object oriented programming, Power systems, and Software maintenance||Session 2 - New Tools and New Techniques|
|Abstract: This paper presents a design methodology of an electromagnetic transient analysis program based on an objectoriented approach. Two important features of the object oriented programming are (i) abstraction of data and their procedures using classes and (ii) derivation of a new class from an existing class using the concept of inheritance. In the proposed design methodology, first the base class, from which all kinds of circuit components are derived using inheritance, is defined. When a specific circuit component is derived from the base class, the parameters, the internal variables, and the behavior of the component are defined and described in the code defining the derived class. This means that each circuit component manages its data and knows how to initialize and update itself, that is, the circuit solver does not have to manage and know them. In this way, we can separately write the code of the circuit solver and that of circuit components, and thus, coding is simplified and code maintainability isenhanced. Especially, adding a new component does not require modifications in the circuit solver code. Using the proposed approach, a new transient analysis program named “XTAP” (eXpandable Transient Analysis Program) has been created. Some practical implementation issues are also presented in the paper.|
|Ortiz, V., Zuñiga, P., Naredo, L. & Gutierrez, A.||Patterns from Transient Signals in Dynamics Series Compensated Lines for Neural Protection (abstract)||neural network protection, power electronics, fault and switching events||Session 4 - System Protection Analysis and Models|
|Abstract: This paper presents a procedure to obtain patterns from propagating signals in a SSSC FACTS device. The acquired patterns are suitable for neural network relay protection schemes for Fault Detection (FD), Phase Classification (PC) and Fault Zone Estimation (FZE). By considering two fault scenarios, the patterns are obtained through digital simulations which include effects of transducers and noise filters.|
|Osborne, M. M., Xemard, A., Prikler, L. & Martinez, J. A.||Points to Consider Regarding the Insulation Coordination of GIS Substations with Cable Connections to Overhead Lines (abstract)||GIS, Insulated Cables, Surge Arresters, Insulation Coordination, Lightning Overvoltages, Modelling, simulation, EMTP||Session 7 - Lightning Surges|
|Abstract: Gas Insulated Switchgear (GIS) when coupled with short cables complicates insulation co-ordination practice particularly regarding fast front transients. The impact of an over-voltage in GIS can be worse than air insulated switchgear (AIS), since a flashover in solid insulation or GIS can result in permanent faults which require long term outages before repairs can be made.
Although, a number of insulation coordination studies have discussed controlling over-voltages due to lightning and switching in Gas Insulated Switchgear (GIS) and transformers, not many deal with the additional complexity raised when cables are used to connect overhead lines to the new equipment.
The paper reports on aspects of work being done within the CIGRE Working Group on Insulation Coordination. (C4.301). An introduction is provided to the sensitivities which affect the magnitude of fast front transients occurring in a typical arrangement including overhead-lines connected to GIS and transformers using short cable sections. This considers factors including lightning, cable length, tower footing impedance and substation running arrangements. Generic sensitivities will be examined for a 400kV circuit, using studies carried out in EMTP to establish the nature of these over-voltages within the substation and the effectiveness of control methods to mitigate their impact.
|Pack, S., Kornhuber, S. & Reisinger, F.||Transient Voltage Stress of 400 kV Urban System Evaluated by Numerical Calculations (abstract)||Session 20 - Transmission Lines and Cables|
|Abstract: Overhead lines, high voltage cable systems and substations are important elements of the high voltage network. More and more close combinations of these elements are used in urban networks. This leads to new transient situations and a more complex transient behaviour in case of lightning or switching events. Additionally the requirements of a constant power supply ask for new efforts to predict impacts caused by interruptions.
Based on this fact this paper deals with investigations to evaluate the transient behaviour of a close combined 400 kV urban system. Numerical tools are basically a modern method to estimate transient stresses, help to optimize the insulation coordination and can simulate various circuit states. Thus, temporary faults can be reduced or avoided at all.
One of the major aspect of this work is the close connection of an overhead line, a cable section and a substation related to the 400 kV system. Additionally attention was paid to the transformers and the secondary side of the system, a 110 kV urban distribution network.
A number of calculations were carried out to get an overview of the transient stress caused by lightning or switching in numerous network nodes of the substation. Of additional interest have been different circuit states at the 400 kV GIS and the transient behaviour at the arrestors. Amplitudes and the energy consumption at the arrestors were taken into account.
These actual investigations were carried out to get useful information's about the transient stress in this important Viennese 400 kV substation, which was officially put into operation in May 2006. As an output of these investigations the results influence the strategy in running the network.
|Park, H. S., Woo, J. W., Kang, J. W., Han, K. S. & Han, S. O.||Analyzing TRV of CB When Installing Current Limit Reactors in UHV Power Systems (abstract)||CLR (Current Limit Reactor), EMTP (Electro Magnetic Transient Program), TRV (Transient Recovery Voltage), SLF (Short Line Fault), BTF (Bus Terminal Fault)||Session 14 - Switching Transients, Circuit Breakers|
|Abstract: Due to the high-capacity and complexity in power systems, an increase of high transmission capacity lowers the system impedance of the power system. Generally, according to the lower equivalent impedance of the system, system stability will be improved, but fault current also increases.
Regarding high-fault currents, KEPCO (Korea Electric Power Corperation) plans to use CLR (Current Limit Reactors) on UHV transmission lines or the bus in substations to limit the magnitude of fault currents. CLRs make a significant contribution to reduce the severity of the TRV (Transient Recovery Voltage) experienced by the feeder and bus circuit breakers when clearing feeder faults. Based on the conclusions of investigating actual circuit breaker failures while performing this duty, the mitigation of the TRV associated with the reactors is described.
This study describes the underlying principles of current breaking, insulation recovery, the occurrence of TRV and its analysis methods (2-parameter and 4-parameter methods) with regard to the rise in fault currents and TRV using EMTP . Through the analysis of real fault cases, measurements which can be readily implemented in the field are closely studied and suggested. Also this paper describes two models ; one is Short Line Fault (SLF), the other is Bus Terminal Fault (BTF) . The TRV of bus circuit breakers are in three positions in the 345kV substation when a three-phase short circuit fault occurs. The other case shows the TRV of two bus circuit breakers in four positions when a three-phase short circuit fault occurs and in two positions when a one-phase line-ground fault occurs.
|Park, K. W., Rhee, S. B., Seo, H. C. & Kim, C. H.||A Calculation Method of Neutral Current of Two Step Type Pole in Distribution Line (abstract)||One Step Type Pole, Two Step Type Pole, Distribution Line, Equivalent Circuit Analysis, Vector Analysis, EMTP||Session 15 - Solution methods and modeling techniques|
|Abstract: In most wye connected distribution system, a neutral current exist and flow on the neutral line because of unbalanced three-phase current. The neutral current which on the overhead distribution line, produces a harmful induce voltage to a communication line. So, the Korea Electric Power Corporation (KEPCO) restricts within 20% of neutral current compare with normal phase current in overhead distribution line. For reliable operation, a One Step Type Pole (OSTP) is changed into a Two Step Type Pole (TSTP). But, there are many different views whether unbalanced current increase or decrease in neutral wire. This paper conducts the calculation and analysis of neutral current in OSTP and TSTP using the equivalent circuit analysis, vector analysis and EMTP simulation. To compare and analyze neutral current according to the type of distribution pole, this paper carried out the simulation using EMTP by changing the simulation conditions.|
|Pattanapakdee, K. & Banmongkol, C.||Failure of Riser Pole Arrester due to Station Service Transformer Ferroresonance (abstract)||Station Service Transformer, Riser Pole Arrester, Underground Cable, Ferroresonance, ATP/EMTP||Session 8 - Ferroresonance|
|Abstract: This paper presents the explosive problem of riser pole arresters during the operations of disconnector switches in the feeder having a station service transformer. In order to determine the cause and the practical solutions, field tests and computer simulations with ATP/EMTP program were conducted. The field tests revealed that in the case of switching without arrester installation, chaotic transient and 3rd sub-harmonic overvoltages appeared in the opened phase during switching. In the case of switching with arrester installation, the restricted spike overvoltages were found. The arrester on the last closed phase exploded because it suffered ferroresonant overvoltages for a long time. The simulation results agree with the results of field test. They show that the switching angle has significant effects on ferroresonant initiation, and associated overvoltages. To avoid and mitigate ferroresonant overvoltages, alternation of switching procedures and application of a resistive load were considered. The results of counter-measures were verified by using both simulations and field tests.|
|Perera, N., Rajapakse, A. D. & Jayasinghe, R. P.||On-line Discrete Wavelet Transform in EMTP Environment and Applications in Protection Relaying (abstract)||Electromagnetic transient simulation, Wavelet transforms, Applications of wavelet transform in power system, Power system protection, Power quality||Session 4 - System Protection Analysis and Models|
|Abstract: This paper describes the development of an on-line discrete wavelet transform tool for an electromagnetic transient simulation program. Multi-resolution properties of wavelet transform make it ideally suitable for analyzing power system transient signals which consist of non-periodic high frequency oscillations superimposed on power frequency signal. New power system devices such as power quality monitors and protective relays based on algorithms involving wavelet transformation are emerging. Thus, it is highly useful for power system electromagnetic transient simulation programs to have integrated capability for wavelet transformation. This paper also briefly presents several applications of wavelet transformation in power system protection and power quality monitoring.|
|Piasecki, W., Bywalec, G., Florkowski, M., Fulczyk, M. & Furgał, J.||New Approach Towards Very Fast Transients Suppression (abstract)||Session 25 - Transformers|
|Abstract: Very high frequency components in the power networks pose a risk to the electrical equipment as they can destroy motors, transformers and other electrical equipment due to internal resonant phenomena resultine in local amplification of voltage. Overstressing the insulation system reduces significantly the equipment lifetime and often leads to internal short-circuit.
In the present article a new approach towards suppressing VPTs with the use of a compact series impedance element is presented. The approach developed enables one to construct a compact protective device introducing a series impedance upstream in the protected equipment. The device is particularly suitable for protecting transformers connected to low loss cable lines with the use or a Vacuum Circuit Breaker (VCB).
Experiments have shown that the use or the series impedance element enables one to efficiently suppress overvoltages and HP oscillations associated with the switching operations.
|Popov, M., van der Sluis, L. & Smeets, R. P. P.||Complete Analysis of Very Fast Transients in Layer-Type Transformer Windings (abstract)||Transformer, very fast transients, high-frequency model, ATP-EMTP||Session 11 - Transformers|
|Abstract: This paper deals with the measurement, modelling and simulation of very fast transient overvoltages in layer-type distribution transformer windings. Measurements were performed by applying a step impulse with 50 ns rise time on a single-phase test transformer equipped with measuring points along the winding. Voltages along the transformer windings were computed by applying multi-conductor transmission line theory for transformer layers. The secondary voltage of the transformer was simulated with another model implemented in ATP-EMTP which takes into account the surge capacitance between the primary and secondary transformer winding. It was found that, when an impulse with a short rise time is applied, internal resonance occurs, which results in a very high secondary voltage. The computations were verified by measurements.|
|Porkar, B., Vakilian, M., Shahrtash, S. M. & Iravani, M. R.||Passivity Enforcement via Residues Perturbation for Admittance Representation of Power System Components (abstract)||Quadratic Programming, Routh array test, bisection method, Hamiltonian matrix, passivity enforcement||Session 15 - Solution methods and modeling techniques|
|Abstract: Employing an admittance representation in form of a black box model approximated by rational functions for linear power system components or network equivalents to be included in electromagnetic transient studies is a well-known method which improves the calculation efficiency. All of the methods that have been proposed to solve the rational approximation problem, have made efforts to overcome the problem of preserving passivity of the final model. Passivity is a vital property, since a nonpassive model may lead to an unstable transient simulation in time domain. The passivity violation regions are detected via a purely algebraic approach based on the existence of purely imaginary eigenvalues in the Hamiltonian matrix obtained from the state-space representation of the reduced-order model. Also a fast test method is presented to check passivity without direct calculation of eigenvalues of Hamiltonian matrix. Then a postprocessing technique based on Quadratic Programming (QP) for passivity enforcement is presented. To increase calculation efficiency and faster convergence only one inequality constraint, in where eigenvalue of Hamiltonian matrix is in minimum, is considered in solving process of QP problem. The mentioned minimum point is detected by the bisection method instead frequency sweep method and therefore the efficiency of computation increases significantly.|
|Rauhala, T. & Järventausta, P.||Testing the Quality of PMU Output Data Based Subsynchronous Damping Analysis in Real-Time Simulation Environment (abstract)||Subsynchronous oscillations, SSO, Phasor Measurement Unit, PMU, subsynchronous damping, damping analysis, real-time simulation||Session 26 - Real Time Simulation|
|Abstract: This paper describes an approach on subsynchronous damping analysis based on measurement data obtained using Phasor Measurement Unit located in vicinity of a turbine-generator unit. The subsynchronous damping analysis are performed using subsynchronous components extracted from PMU output data using filtering and spectral analysis techniques. The quality and validity of subsynchronous damping analysis based on different output quantities is analyzed and most suitable approach on damping analysis is proposed. The performance of the methods to detect oscillations was evaluated under laboratory conditions using Real Time Digital Simulator. The validity of subsynchronous damping calculation based on PMU output data was verified using well-established benchmark models created for subsynchronous oscillations related studies.|
|Ribeiro, H. & Anunciada, V.||Impact and Characterization of Voltage Transients as a Problem to Sensitive Loads (abstract)||Switch Mode Power Supplies, Susceptibility, Voltage Events, Electronic Equipment, Sensitive Loads||Session 21 - Power Quality and Harmonics|
|Abstract: In the last three decades, the loads connected to the mains network had been changing. Due to constant progress in electronic equipments, the number of electronic and sensitive loads increases considerably in domestic and industrial environment. Short duration voltage transients can have a several economic impact in these equipments. The authors identify the sensitive loads connected to the mains network and realize a study of their susceptibility to transient voltage perturbations in the mains network.|
|Rioual, M. & Martinez, M.||Energization of Two Transformers in Series Through Long Lines: Correlation Between Fluxes in Both Transformers, and Determination of the Efficiency of Palliative Solutions (abstract)||Power restoration, transformer energization, modeling, harmonics, residual fluxes, temporary overvoltages, ferroresonance||Session 25 - Transformers|
|Abstract: The energization of power transformers following a complete or partial collapse of the system is an important issue. This paper describes a method for the modeling of the electric network between the source and a target transformer, when two transformers are involved, with a correlation between fluxes in both equipment. This method has been applied for the energization of an auxiliary transformer via a step-transformer.
Secondly, as those transformer energizations may lead those severe stresses, different palliative solutions have been addressed, including solutions using the Network capabilities, and also solutions related to circuit-breakers and surge arresters.
|Rocha, P. E. D., Lima, A. C. S. & Carneiro Jr., S.||Propagation Characteristics and Overvoltage Analysis on Unconventional Submarine Cables (abstract)||Frequency-Dependent Pipe-Type Models, Electromagnetic Transients||Session 19 - Transmission Lines and Cables|
|Abstract: There are some submarine cables also known as umbilical cables which are finding a growing use in the oil industry. One of the advantages of such cables is that they can combine both structural and electrical cables thus providing a more compact installation. From the electrical point of view these cables can be seen as a pipe-type inside another pipe-type. The electrical parameters, namely the impedance and admittance per unit of length of such cables cannot be calculated using conventional cable parameters subroutine available in Electromagnetic Transient (EMT) Programs such as EMTP-RV, ATP. However the procedures used in those subroutines can be expanded for the analysis of the umbilical cases.
This paper presents a review of the basic procedures commonly used for evaluation of the cables impedance and admittance per unit of length as well as outlines the changes needed in order to represent the umbilical. The cable parameters are used in a Frequency Domain program to assess an overvoltage analysis as well as an analysis of the propagation characteristics of the submarine cable system.
|Roux, M. O., Coutu, A. & Beaulieu, G.||Practical Modeling of Large Rectifier Loads for the Estimation of Low-order Non-characteristic Harmonics (abstract)||Harmonics, Voltage Unbalance, Rectifier Loads, Converter Impedance, Damping, Resonances, EMTP-RV||Session 21 - Power Quality and Harmonics|
|Abstract: The paper reports modeling efforts undertaken to ensure adequate estimation of low-order harmonics injected into the AC network by an important rectifier load. For this purpose, measurement results obtained from a large aluminium smelter were compared to the simulation results of a detailed time-domain model developed in EMTP-RV. Using the EMTP-RV time-domain model, it can be shown that rectifiers do not act like constant current sources at low-order non-characteristic harmonics. This type of model is useful to evaluate harmonics for a given configuration of the installation and of the network. However, it may become too laborious to use such a time-domain model for doing sensitivity analysis in order to determine the worst conditions. A model that takes into account the damping and frequency displacement effects on resonances of converters is presented in the paper.|
|Sadovic, S. & Sadovic, T.||Overhead Line Switching Surge Simulator (abstract)||Electromagnetic transients computation, Transmission line modeling, System decomposition, Thevenin equivalents, Switching surge overvoltages, Risk of failure||Session 2 - New Tools and New Techniques|
|Abstract: This paper describes methodology for the electromagnetic transients computation, which is based on the system decomposition. A phase domain transmission line model is used. This approach is implemented in the software used for the overhead line switching surge studies. Overhead line is divided into short segments, enabling determination of the overvoltage distribution along the line.|
|Saha, M. M., Izykowski, J., Rosolowski, E. & Molag, R.||ATP-EMTP Investigation of a New Algorithm for Locating Faults on Power Transmission Lines with Use of Two-End Unsynchronized Measurements (abstract)||ATP-EMTP, power transmission line, fault simulation, digital measurement, unsynchronized measurements, fault location algorithm||Session 3 - System Protection and Fault Location|
|Abstract: This paper presents an algorithm for locating faults on two-terminal power transmission lines. Unsynchronized two-end voltages and currents are processed in the algorithm for determining the distance to fault and the synchronization angle. The calculations are performed initially for the lumped model of the transmission line. Then, these results are used as the initial data for the Newton-Raphson method based iterative calculations, in which the distributed parameter line model is utilized. The delivered fault location algorithm has been tested and evaluated with the fault data obtained from versatile ATP-EMTP simulations of faults in the power network containing the 400 kV, 300 km transmission line. The sample results of the evaluation are reported and discussed.|
|Salem, S. & Sood, V. K.||Simulation and Controller Design of an Interline Power Flow Controller in EMTP-RV (abstract)||FACTS, SSSC, IPFC, Series Compensation||Session 9 - Power Electronics Applications|
|Abstract: An Interline Power Flow Controller (IPFC) is a converter-based FACTS controller for series compensation with capability of controlling power flow among multi-lines within the same corridor of the transmission line. It consists of two or more Voltage Source Converters (VSCs) with a common dc-link. Real power can be transferred via the common dc-link between the VSCs and each VSC is capable of exchanging reactive power with its own transmission system. In this paper, a control scheme of an IPFC system with two VSCs to compensate the impedances of two similarly dimensioned parallel transmission lines is presented. The model is simulated with the EMTP-RV program to demonstrate the system behavior of the IPFC.|
|Salim, R. H., Caino de Oliveira, K. R. & Bretas, A. S.||Fault detection in Primary Distribution Systems Using Wavelets (abstract)||Power distribution systems, Power system protection, Fault detection, Wavelet transform||Session 10 - System Protection and Fault Location|
|Abstract: This paper presents a new methodology for phaseto-ground fault detection in primary distribution systems. The wavelet transform is the tool used, through the multiresolution analysis of the current signals measured at the relay point. Traditional tools such as the Fourier Transform and the Short-Time Fourier Transform have a frequency resolution inversely dependent of time resolution, providing a lower level of robustness to the fault detection procedure. In this paper, the proposed technique is designed and validated through several computational simulations in the IEEE 37 bus test feeder. The proposed technique is also compared to a Neural Network approach, using the same simulations and protection philosophy. Test results show that the proposed scheme is an efficient methodology for single phase fault detection in unbalanced distribution systems, including faults with high impedance.|
|Sekioka, S., Aiba, K. & Okabe, S.||Lightning Overvoltages on Low Voltage Circuit Caused by Ground Potential Rise (abstract)||Lightning hit to ground, Ground potential rise, Lightning-induced voltage, Low voltage circuit, EMTP||Session 23 - Lightning Surges|
|Abstract: The lightning overvoltages incoming from an overhead line such as a power distribution line and a telecommunication line, and an antenna to a residence are studied actively. However, a relation between a lightning hit to ground near the residence and the overvoltages on low voltage circuit in the residence is still unclear. The authors proposed a simulation method to estimate the lightning overvoltages in the residence due to ground potential rise by the lightning hit to the ground based on the Thevenin theorem. The method can be realized in the EMTP. This paper describes simulation results of the lightning overvoltages due to the ground potential rise and the radiation field generated by return stroke current.|
|Sekioka, S. & Funabashi, T.||Effective Length of Long Grounding Conductor in Windfarm (abstract)||Grounding electrode, Windfarm, Lightning, Effective length, Surge characteristic||Session 17 - Wind Turbine Transients and Harmonics|
|Abstract: Windfarms need low steady-state grounding resistance. A horizontal long grounding electrode is often used to obtain the low grounding resistance. The long grounding conductor has an effective length for lightning currents. The authors propose analytical formulas of sending-end voltage of the conductor in time domain using the lattice diagram method. This paper discusses the effective length of the grounding systems of the windfarms using the proposed formulas.|
|Shah, N. M., Sood, V. K. & Ramachandran, V.||Modeling, Control and Simulation of a Chain Link STATCOM in EMTP-RV (abstract)||Chain link converter, VSC, SVC, STATCOM, FACTS, EMTP-RV||Session 9 - Power Electronics Applications|
|Abstract: This paper describes an alternative STATic synchronous COMpensator (STATCOM), by connecting a number of Gate Turn Off (GTO) thyristor converters in series on the ac side of the system. Each GTO converter forms one ‘link’ of a 1-phase, full-bridge Voltage-Source-Converter (VSC) and is referred to as a ‘Chain Link Converter’ (CLC). Each GTO of a CLS, is switched ‘ON/OFF’ only once per cycle of the fundamental frequency by using a Sinusoidal Pulse Width Modulation (SPWM) technique. Approximate models of a 3-phase Chain Link STATCOM (CLS) using dq-transformation are used to design two controllers for controlling reactive current and ac voltage to stabilize the system voltage at the Point of Common Coupling (PCC). A novel technique, called the Rotated Gate Signal Pattern (RGSP), is used for balancing the voltages of the link dc capacitors. The performance investigation of the CLS system when used in a radial line is carried out under steady- and transient-state operating conditions by means of the simulation package; EMTP-RV and the results are presented.|
|Shibuya, Y., Wada, K. & Muto, H.||Analysis of High Frequency Oscillations in Voltage Transformer (abstract)||Voltage transformer, High frequency, Oscillation, Winding, FFT||Session 27 - Transformers|
|Abstract: The voltage transformers (VTs) used in medium voltage circuit have a large number of turns more than 10000. They are reported to be sometimes vulnerable to fast rising abnormal voltages due to lightnings or switchings. It has been regarded difficult to analyse such a high frequency phenomenon in the VT because of the large number of turns.
A high frequency model of VT is obtained in a form of lumped constant circuit, and is analysed using the Fast Fourier Transform (FFT). The circuit constants of model are calculated from the winding specification data based on turn-to-turn basis, but the circuit is analysed in terms of multiple-turn groups reducing the order of equations to a manageable level. The dissipation related constants are introduced in the equivalent circuit considering the skin and proximity effects in the conductors as well as the dielectric loss in the insulation.
Firstly, the state equation of VT model circuit is solved for a range of FFT frequencies. Then, the time domain analysis is performed using the inverse FFT technique. Both the frequency and time domain characteristics are verified by the experiment on an actual 6.6 kV VT, in which internal voltage oscillations are observed through taps. The general tendencies of high frequency oscillations are investigated using a simpler model. It is found the interlayer insulation near the input terminal is disproportionally highly stressed for impulses with fast rise time.
The proposed analysis is considered to be useful since it can be performed when the geometrical specifications of VT are available.
|Shoup, D., Paserba, J. & Mannarino, A.||Ferroresonance Conditions Associated With a 13 kV Voltage Regulator During Back-feed Conditions (abstract)||ferroresonance, distribution, back-feed, voltage regulator, network transformers, resonance, grounding transformer, protective relaying||Session 8 - Ferroresonance|
|Abstract: This paper describes ferroresonance conditions for a 13 kV feeder circuit with a voltage regulator connected under back-feed conditions, where high overvoltages developed causing the failure of distribution class surge arresters. Key parameters of equipment and circuit conditions are described that lead to zero sequence, i.e., 3rd harmonic, resonance conditions where the only path for the magnetizing current of a voltage regulator to flow is through the capacitance of connected cable circuits, isolated from the rest of the system by delta-wye connected network transformers. The results of the study provide guidance for the identification of potential ferroresonance circuits in distribution systems and potential means of mitigation through the application of grounding transformers, modification to protective relaying strategies, and consideration to circuit connectivity.|
|Silva, K. M., Neves, W. L. A. & Souza, B. A.||EMTP Applied to Evaluate Three-Terminal Line Distance Protection Schemes (abstract)||Power system protection, three-terminal transmission lines, distance schemes, EMTP||Session 4 - System Protection Analysis and Models|
|Abstract: Digital protection schemes have been around for decades. Although there are many relay schemes reported in the literature, the protection engineer may gain more insight on how schemes work properly if well known cases are previously simulated with the EMTP to evaluate relay algorithms. Here, a very simple case study is presented in which the EMTP is used to evaluate the off-line performance of distance protection schemes applied to the three-terminal line of a 230 kV three-bus power network. The digital relays were modeled considering the logic of different distance schemes and relay-to-relay communication. The EMTP is a powerful tool to pinpoint limitations on the applicability of these distance protection schemes and may help engineers to develop new protection schemes.|
|Smith, K. S.||JET Fusion Experiment 36 kV Enhancement Studies (abstract)||Fault Current Limiter, Joint European Torus, JET, PSCAD-EMTDC, pulsed power, short circuit, tokamak||Session 13 - Switching Transients|
|Abstract: The electrical pulsed power loads at the Joint European Torus (JET) fusion research facility have increased since operations began in 1983. As a consequence the transient voltage swings on the three 36 kV switchboards during JET pulsing are unacceptably large on occasion. This paper describes the use of the PSCAD-EMTDC program to determine the improvement in the system performance that would be possible by reconfiguring the system. A transient load flow model demonstrates that operating the incoming transformers in parallel improves the voltage regulation. Parallel operation increases the prospective fault currents to levels that exceed the ratings of the existing 36 kV equipment. Pyrotechnic fault current limiters (FCLs) are proposed to overcome this. Models are developed for the FCL tripping logic that is based on instantaneous current and rate of change of current measurements. Studies confirm that trip settings can be selected for the FCLs so that they will not operate incorrectly when switching the largest converter transformers or the reactive power compensation capacitors. An aggregated load model in which the transient load demand on each 36 kV switchboard is represented by two thyristor converters is described and used to assess the stability of the FCL solution to the transients produced by the JET pulsed power load. On the basis of these simulation studies the better overall engineering solution compatible with the unique characteristics of the JET loads can be identified.|
|Solís, N., Gutiérrez, J. A., Naredo, J. L. & Ortiz, V. H.||Analysis of Complex Faults in Distribution Systems (abstract)||Arcing faults, high impedance faults, evolving faults, covered conductors, distance protection, over-current protection.||Session 4 - System Protection Analysis and Models|
|Abstract: Distribution systems are exposed to natural events like storms, fall of tree branches, lightning strokes, etc. These events often cause evolutionary faults involving arc phenomena. This paper focuses in the analysis of these complex faults and it explores the possibility of identifying and locating high impedance faults by conventional distance relays. A considerable number of records have been collected from actual faults on a distribution system belonging to the Mexican Federal Power Commission. These records have also been complemented with measurements from faults staged in the actual system, as well as from lab measurements.|
|Soultanis, N. L., Tsouchnikas, A. I., Hatziargyriou, N. D. & Mahseredjian, J.||Dynamic Analysis of Inverter Dominated Unbalanced LV Micro-Grids (abstract)||distributed generation (DG), micro-grids, inverter control, low voltage networks||Session 5 - System Dynamics, SSR Studies|
|Abstract: This paper presents simulation of the dynamic behavior of low voltage micro-grids both under grid connected and autonomous operation. In LV micro-grids it is most likely that the sources participating in the system are connected to the network with inverters. This results in the formation of an inertia - less system. Modeling has to allow for the representation of all characteristic unbalances encountered in the LV network. The simulation is conducted using the electromagnetic transient analysis program EMTP-RV.|
|Tiberg, M., Bormann, D., Gustavsen, B., Heitz, C., Hoenecke, O., Muset, G., Mahseredjian, J. & Werle, P.||Generic and Automated Simulation Modeling Based on Measurements (abstract)||Transformer, wide band model, electromagnetic transients, EMTP-RV, measurement||Session 2 - New Tools and New Techniques|
|Abstract: SoFT is a new method and tool which measures and models linear electrical network components in a wide frequency band with unprecedented accuracy. This is achieved by a special modal based measurement technique in combination with suitable rational fitting and passivity enforcement methods. The models are easily imported into most commonly used simulation software.
This paper demonstrates the SoFT tool computations in a comparison between A) time-domain measurements of a lightning impulse test of a power transformer, B) simulation of the test results using a SoFT model, and C) simulation of the test results using a lumped-element circuit simulation model based on geometrical transformer design information.
|Uglešić, I., Ivanković, I. & Milardić, V.||Switching Surges in Transformer Provoked by Sequential Tripping of Circuit Breakers (abstract)||Transformer, Switchyard, Switching, Overvoltage, Computation, Fault, Protection||Session 25 - Transformers|
|Abstract: A study of switching surges in a 400/110 kV substation was carried out in order to detect the causes of severe damage to the power transformer, which happened after a busbar fault. The busbar protection generated tripping signals for several circuit breakers and after their sequential tripping, the surge arresters installed on the 10.5 kV stabilizing windings inside the transformer were destroyed. The computer simulations were carried out on an appropriate model, which was developed for the study. The comparison between the recorded and computed fault currents showed good correspondence. Overvoltages of small magnitudes occurred on all three voltage levels: 400 kV, 110 kV and 10.5 kV. The energy generated by overvoltages was below the nominal value of the absorption capacity of the surge arrester installed on the stabilizing windings and the inspection of the arresters showed their defective characteristics.|
|Vollet, C. & de Metz-Noblat, B.||Vacuum Circuit Breaker Model : Application Case to Motors Switching (abstract)||Switching overvoltage, vacuum circuit breaker, MOA surge arrester, C-R surge suppressor, motor, EMTP/ATP||Session 14 - Switching Transients, Circuit Breakers|
|Abstract: In an industrial plant equipped with HV motors, several severe stator failures occurred in spite of the installation of surge arresters. All of these motors were switched with vacuum circuit breakers.
The purpose of this paper is to demonstrate the necessity of complementary protection against overvoltages by adding C-R (capacitor - resistor) surge suppressors.
This paper will first give an overview of the types of switching surges that can occur in this network configuration. Secondly, network simulations using EMTP/ATP software are presented, including a complete simulation of a vacuum circuit breaker. The object of these simulations is to calculate the overvoltages created during motor switching, to study the evolution of these overvoltages as a function of cable length and motor power, and to check if additional protection needs to be installed on these motors. The comparison is made between the simulated voltages and the motors withstand voltage capability defined in the IEC 60034-15. This comparison is done not only with magnitude criteria but also with time rise.
It can be concluded that even with two MOA (Metal-Oxide Arrester) surge arresters the protection of the motor is not guaranteed and that full motor protection is provided by installing C-R surge suppressors thus eliminating multiple reignitions.
|Vuorenpää, P., Rauhala, T., Järventausta, P. & Känsälä, T.||On Effect of TCSC Structure and Synchronization Response on Subsynchronous Damping (abstract)||Thyristor controlled series capacitor, TCSC, subsynchronous oscillations, SSO, time-domain analysis||Session 5 - System Dynamics, SSR Studies|
|Abstract: This paper illustrates the effect of thyristor controlled series capacitor (TCSC) structure and synchronization response on subsynchronous damping. In spite of various studies concerning subsynchronous behaviour of TCSC, effect of these factors on subsynchronous damping are rarely discussed. Studies have been executed using PSCAD transient simulation program with general power system and TCSC simulation models. Studied system consisted of first IEEE benchmark model for subsynchronous resonance studies and TCSC model controlled with open-loop control mode. Open-loop control mode was used in order to isolate the effect of TCSC structure and synchronization from the effect of closed loop controls of TCSC on subsynchronous damping. It’s evident that this approach has only minor significance regarding the effect of real TCSC installations on subsynchronous damping. Nevertheless, together with the results of similar analysis performed using different closed-loop control and firing pulse generation approaches, the results presented here will provide more insight on the effect of TCSC on subsynchronous damping and its subsynchronous response.|
|Wang, P., Muthumuni, D., Zhou, Z., Alonso, J. C., Wilson, P., Wachal, R. & Waddell, J.||Transient Analysis of Capacitor Bank Installation at Distribution Stations with PSCAD/EMTDC (abstract)||capacitor switching, distribution system, transient analysis, PSCAD/EMTDC, E-TRAN||Session 13 - Switching Transients|
|Abstract: Capacitive compensation has been widely used in power system at different voltage levels. Manitoba Hydro (MH) is planning to return to service 41 units of 2.4MVAr 12.47kV distribution level Pad Mount Capacitor (PMC) banks located at 17 substations to provide the needed power factor correction and VAR support. To ensure safe and successful operations of the PMC banks, unfavorable transient issues associated with capacitor switching and potential nearby faults must be thoroughly evaluated. The heavily interconnected MH distribution system presents a challenge to analyze the impact due to addition of those capacitor banks.
This paper presents details of various PSCAD/EMTDC models of the MH distribution system to determine required inductance for limiting both inrush and out-rush transient currents, frequency scans for network compliance, arrester energy duty during transient over-voltage (i.e. re-strikes and fault clearing), and breaker TRV ratings. Based on the transient analysis, several recommendations were suggested to modify the installation.
|Woo, J. W., Han, K. S., Yoon, J. Y., Kweon, D. J. & Won, Y. J.||Analysis on Transients Recovery Voltage of Circuit Breaker according to Different Loads Condition at 345 kV MTR Tertiary Side (abstract)||TRV(Transient Recovery Voltage), Circuit Breaker, Substation, Overvoltages, EMTP(Electro-magnetic Transient Program)||Session 14 - Switching Transients, Circuit Breakers|
|Abstract: By several purposes in KEPCO, there are the different loads at 345 kV MTR tertiary side, which are connected by circuit breaker. There are reactors, condensers and transformers. During normal operation of a power system, circuit breakers will be operated several times in a day. During opening, interruption of inductive/capacitive currents will cause overvoltages. In contrast to fault interruption duties, where the breaker may never be exposed to its full rated fault duty in its lifetime, the breaker is exposed to the same severe stress each and every time it switches inductive/capacitive currents.
In these conditions, we had experienced the several circuit breaker’s failures. So, we had investigated the transient phenomena by switching different loads. When these different loads were opening between the circuit breaker contact gaps could lead to very steep overvoltages. This study has been carried out by the simulation calculation using the software ATP/EMTP. For analysis, we had considered the normal operation and fault clearing operation per different loads condition. From calculation results by APT/EMTP, we had compared with TRV standards of KEPCO, IEC and IEEE.
|Yadee, P. & Premrudeepreechacharn, S.||Analysis of Tower Footing Resistance Effected Back Flashover Across Insulator in a Transmission System (abstract)||Tower footing resistance, back flashover, insulator||Session 12 - Lightning Surges|
|Abstract: This study describes analysis of tower footing resistance effected the backflash voltage across insulator in a transmission system. This paper studies the 115 kV transmission lines from Lampang substation to Lamphun substation which is double circuit in the same steel tower with overhead ground wire, 73 kilometers length each. The factor of this study includes magnitude of lightning stroke, front time of lightning stroke, and structure of tower. The frequency dependent model is used as model of transmission between substations. Steel tower uses Bergeron line model. The assumption of studies based on the return stroke current ranged 1-200 kA, front time of lightning stroke between 1.2 μs to 50 μs and insulation strength using 550 kV BIL class insulators. The simulations study the effect of varying tower footing resistance that affect the lightning current. Simulation results are analyzed lightning overvoltage that causes back flashover at insulators. The simulation results are compared with TFlash program. This study helps to know causes of problems of backflash the transmission line system, and also be as a guideline solving the problem for 230 kV and 500 kV transmission line systems.|
|Yamamoto, K., Noda, T., Yokoyama, S. & Ametani, A.||Experimental and Analytical Studies of Lightning Overvoltages in Wind Turbine Generation Systems (abstract)||wind turbine generation systems, lightning, surge, FDTD method, overvoltages||Session 17 - Wind Turbine Transients and Harmonics|
|Abstract: This paper presents the results of the experimental and analytical studies undertaken for the lightning protection of wind turbine generation systems by using a reduced-size wind turbine model. In the analytical studies, the FDTD (Finite Difference Time Domain) method is used. This study focuses on the overvoltages observed at the wavefronts of lightning surges. The lightning strokes on one of the blades and on the nacelle were considered, and the experiments and analyses were carried out by considering the cases of summer and winter lightning. The voltages and currents at various positions on the wind turbine model were considered.|
|Yang, X. & Dennetière, S.||Modeling of the Behavior of Power Electronic Equipment to Grid Ripple Control Signal (abstract)||Ripple control, harmonic impedance, time domain modeling, frequency domain modeling, transient voltage, voltage source converter, interharmonic, steady state analysis||Session 21 - Power Quality and Harmonics|
|Abstract: The paper presents time domain simulation for power electronic device equivalent impedance computation at ripple control signal frequency.
The ripple control used by the grid is a low frequency voltage signal superimposed at MV substation. In France, the frequency used by grid ripple control systems is 175 Hz. It is well-known that some customer loads can disturb ripple control signal transmission such as capacitor bank, distributed generator, etc. These equipments can influence or disturb ripple control signal by two main ways: presence of a small impedance or an important interharmonic current injection at ripple control frequency. In transient state, even a symmetrical static converter can produce interharmonic currents.
In site studies, some customer power electronic device (Variable Speed Drive for example) is often modeled by an infinite impedance at ripple control frequency. However site measurements and simulations show that this simplification can cause in some case important error in ripple control signal level assessment.
The main purpose of this study is to define ripple control frequency equivalent impedances of typical converters used in industry. The study shows that a voltage source converter (rectifier with DC capacitor structure) gives a relative small impedance at ripple control frequency. It is recommended to integrate this impedance in performing ripple control signal propagation study by means of frequency domain software.
|Yasuda, Y. & Funabashi, T.||Analysis on Back-Flow Surge in Wind Farms (abstract)||wind power generation, wind turbine, lightning, surge arrester, grounding (earthing), transient analysis||Session 17 - Wind Turbine Transients and Harmonics|
|Abstract: When a wind turbine in a wind farm is struck by lightning, the phenomenon of surge invasion to the distribution line is categorized as “back-flow surge”. It has been reported that this back-flow surge sometimes burns out surge arresters or breaks low-voltage circuits even far from the point of the lightning-struck. In practice, many such incidents that have occurred not only involved the wind turbine that was actually struck but also other affected wind turbines that had not been struck.
The present report analyzes incidents of burnout to surge arresters resulting from winter lightning at wind farms using PSCAD/EMTDC. Calculations were performed to clarify the mechanism of how the back-flow surge propagates to other turbines from the directly struck wind turbine.
The calculations clarified that burnout incidents could easily occur even in a turbine next to the lightning-struck one. It also became evident that burnout incidents can be reduced when interconnecting grounding wire are installed between wind turbines.
|Zanetta Jr., L. C. & Pereira, M.||Limitation of Line Fault Currents with the UPFC (abstract)||FACTS, short-circuit, UPFC||Session 9 - Power Electronics Applications|
|Abstract: This paper analyses the instantaneous characteristic of series connected VSI-based compensators in fault currents limitations of compensated lines. The magnitude of the series voltage plays a very important role, and the possible use of values higher than those of steady state operation, during short periods, can reduce the undesirable effects of short-circuit currents. The effectiveness of the UPFC was investigated by exploring the series voltage behavior in three and single-phase faults.|
|Zgainski, F., Caillault, B. & Renouard, V.||Validation of Power Plant Transformers Re-energization Schemes in case of Black-Out by Comparison Between Studies and Field Tests Measurements (abstract)||black-out, transformer re-energization, field tests||Session 25 - Transformers|
|Abstract: The EHV network and power plant restoration plan is a key process of a fast re-energization of customers.
The first step after a black-out consists in re-energizing lines and transformers, both on the network and in power plants, as soon as possible, without taking too much risks. To validate the strategy based on identified schemes, the following methodology is detailed: first the critical point to deal with is the evaluation, by using computation tools, of the temporary harmonic overvoltages generated by the transformer re-energization. If the conclusion is positive, field tests are performed. Finally, measurements are compared with simulations results in order to validate the initial feasibility study.
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