SIMULATE AND ANALYSE LIGHTNING TRANSIENT PROPAGATION IN THE HIGH VOLTAGE TRANSFORMER STATION BY EMTP

VIET NAM NATIONAL UNIVERSITY OF TECHNOLY HO CHI MINH P.F.I.E.V PROGRAM ENERGY SYSTEM o0o - UNIVERSITY THESIS PROJECT SIMULATE AND ANALYSE LIGHTNING TRANSIENT PROPAGATION IN THE HIGH VOLTAGE TRANSFORMER STATION BY EMTP-RV STUDENT : VU DUC QUANG GUIDE : DOCTOR VU PHAN TU Ho Chi Minh City, June 2009 Content INTRODUCTION CONTENT CHAPTER 1: LIGHTNING TRANSIENT PROPAGATION IN THE HIGH VOLTAGE TRANSFORMER STATION 1.1 Lightning 1.1.1 Lightning concept 1.1.2 Characteristics of lightning and its influence on the power system 1.2 Protect the lightning transient propagation in the high voltage transformer station 1.2.1 Reasons 1.2.2 The characteristic of the voltage impulse at the protected equipment 1.2.3 Principle of lightning protection 1.2.4 The equivalent capacity value of the high voltage equipment CHAPTER 2: INTRODUCE EMTP SOFTWAVE 2.1 Brief history of the EMTP 2.2 Applications of EMTP 2.3 States of simulation 2.3.1 Steady-state simulations 2.3.2 Transient simulations 2.4 Architecture of EMTP file 2.5 Device library CHAPTER 3: SIMULATE TRANSFORMER STATION 400kV 3.1 Parameters 3.2 Results of the simulation CHAPTER 4: SIMULATE TRANSFORMER STATION 400kV NHA BE 4.1 Transformer station 500kv Nha Be 4.2 Simulate by EMTP 4.2.1 Parameters 4.2.2 Results of the simulation CHAPTER 5: SURVEY THE EMULATION CASES COMPARE AND EVALUATE THE RESULTS 5.1 Transformer station 400KV 5.1.1 General and danger 5.1.2 Line layout triangle and horizontal 5.1.3 Back – flash and lightning discharge directly on the phase line 5.1.4 Surveying the changes in the lightning maximum stepness 5.1.5 Surveying the changes of the distance between the valve arrester and the transformer 5.2 Transformer station 500KV Nha Be 5.2.1 General and danger 5.2.2 Back – flash and lightning discharge directly on the phase line 5.2.3 Surveying the changes in the lightning maximum stepness 5.2.4 Surveying the changes of the distance between the valve arrester 1 1 2 3 4 7 10 11 13 16 24 37 37 39 42 48 68 68 68 70 71 71 72 73 74 76 77 i and the transformer CONCLUSION REFERENCES 78 80 81 ii A INTRODUCTION The transient is a very important problem in the power system that many phenomena related to it as lightning protection, short circuit faults, cut-out balancing capacitor, etc The transient problems often lead to the resolution of the complex integro-differential equation systems that the analytical method can not be performed The development of numerical methods and calculation software have shown the superiority of it in the resolution of the transient problems EMTP is a software that is widely used to simulate the phenomena of the electromagnetic transient, as well as electromechanic in the power system This thesis, with topic: ”Simulate and analyse lightning transient propagation in the high voltage transformer station by EMTP-RV”, is done on commercial software EMTPRV at the Station Office – Power Engineering Consulting Joint Stock Company (PECC3) - Electricity Vietnam (EVN) with actual data provided by this company to help us look at more specific on this issue The contents of this thesis include: Chapter 1: summary of the theory Chapter 2: introduction EMTP software Chapter 3, Chapter 4: Simulation of the transformer stations 400kV and 500kV Nha Be with EMTP-RV Chapter 5: compare and evaluate the results of the simulation B CONTENTS CHAPTER LIGHTNING TRANSIENT PROPAGATION IN THE HIGH VOLTAGE TRANSFORMER STATION 1.1 LIGHTNING 1.1.1 Lightning concept: Lightning is an atmospheric discharge of electricity usually accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms In the atmospheric electrical discharge, a leader of a bolt of lightning can travel at speeds of 60,000 m/s (220,000 km/h), and can reach temperatures approaching 30,000 °C (54,000 °F), hot enough to fuse silica sand into glass channels known as fulgurites which are normally hollow and can extend some distance into the ground There are some 16 million lightning storms in the world every year Lightning can also occur within the ash clouds from volcanic Page eruptions, or can be caused by violent forest fires which generate sufficient dust to create a static charge The terrestrial atmosphere is very good dielectric located between two conductors - a surface of the ground from below and the top layers of an atmosphere, including an ionosphere, from above These layers are passive components of a global electric circuit Between negatively charged surface of the ground and positively charged top atmosphere the constant potential difference of about 300.000 V is supported Lightning occurs because the bottom of a thundercloud becomes negatively charged, and repels the negative charge of the ground deeper in so the positive charge is more towards the surface 1.1.2 Characteristics of lightning and its influence on the power system: Most of the causes of the overvoltage is transitional, it only lasts a few micro-second to several period and originate from inside or outside the system The external origination is mainly lightning, a unpredictable phenomenon, create pressure for the power system Lightning is the mainly origination of the harmful overvoltage on the power system, it can be born by lightning discharge directly or back-flash The overvoltage impulse can change from a relatively small value to several times larger than the normal phase-ground voltage These impulse will propagate in the line with the speed of light Therefore, the more understanding the characteristics of the lightning, the more effective in the installation of devices to protect A typical lightning has the very large maximum steepness, meaning that its voltage increases with the rate of millions of volt on a second In the fact, 15% of the top of the lightning occur under 1μs The wave font is connected by the wave tail of a short wave, that means after the voltage reaches the peak value, time that voltage is reduced to half the value of the voltage peaks during 200μs and completely disappear during 1000μs The lightning current is measured by its impact on the equipment The sensitive equipment such as arrester will allow the lightning run through Many modern science devices is used to measure and record the lightning current, has found that the scope of change is very large: 1000A → 200KA The research showed that the current through the arrester is about 1/10 the total value of the lightning current but only about 5% of the lightning on the distribution system exceeds 10kA 1.2 PROTECT THE LIGHTNING TRANSIENT PROPAGATION IN THE HIGH VOLTAGE TRANSFORMER STATION 1.2.1 Reasons: The lightning transient propagate to the high voltage transformer station by the following reasons: a) Back-flash: the lightning discharge on the protecting line or on the structure and then through the insulator to the phase line b) The lightning directly discharge on line phase Page 1.2.2 The characteristic of the voltage impulse at the protected equipment: Value: The largest value of the voltage impulse at the protected equipment is ratio of the distance between the valve arrester and the transformer and the maximum stepness a Wave shape: a damped oscillation 1.2.3 Principle of lightning protection: • The largest value of the voltage impulse at the protected equipment must be smaller than the value of the basic lightning impulse insulation level of the protected equipment • The largest value of the current run through the valve arrester must be smaller than the classifying current of the valve arrester (according to voltage levels and their types) • Distance between the valve arrester and the protected equipment must be in allowed limit The allowed largest distance between the valve arrester and the protected equipment: (U tnx  U pđ )v lcp ≤ 2a + Utnx: basic lightning impulse insulation level of the protected equipment + Upđ: discharge voltage of the valve arrester + Maximum stepness: a = 11kV/às/kVìMCOV ữ2000kV/às/kVìMCOV + v: velocity of the wave propagation; v = 300m/µs 1.2.4 The equivalent capacity value of the high voltage equipment: Equipment Transformer Switch Breaker Bushing Compensator (TU) Capacity (  F) Characteristic Limit value Average value Large power and there is compensator 0.001  0.003 0.0015 Small power and there is compensator 0.0003  0.001 0.0005 When close circuit 0.00004  0.00008 0.00006 When open circuit 0.00003  0.00006 0.00004 When close circuit 0.0003  0.0008 0.0005 When open circuit 0.0002  0.0005 0.0003 Capacitor 0.00015  0.0003 0.0002 Other 0.0001  0.0002 0.00015 0.0002  0.0005 0.0003 Page CHAPTER INTRODUCE EMTP SOFTWAVE 2.1 BRIEF HISTORY OF THE EMTP The EMTP stands for electromagnetic transiets program It is a computer program for the simulation electromagnetic, electromechanical, and control system transients on multiphase electric power systems It was first developed as a digital computer counterpart to the analog Transient Network Analyzer (TNA) Many other capabilities have been added to the EMTP over the years and it has become the standard in the utility industry The EMTP was developed in the late 1960's by Dr Hermann Dommel, who brought the program to Bonneville Power Administration (BPA) When Professor Dommel left BPA for the University of British Columbia in 1973, two versions of the program started to take shape: the relatively small UBC version, used primarily for model development, and the BPA version, which expanded to address the needs of utility engineers The BPA version of the EMTP grew as a result of the co-operative development effort of Dr Scott Meyer and Dr Tsu-huei Liu from BPA, as well as a number of other contributors from North American power companies and universities In order to rationalize the development of the program and to attract funding from other utilities, the EMTP Development Coordination Group (DCG) was founded in 1982 Original members of the DCG included BPA, the US Bureau of reclamation, Western Area Power Administration (WAPA), the Canadian Electrical Association (CEA), Ontario Hydro, and Hydro Quebec Since the inception of DCG, a number of changes have taken place in the EMTP community In 1986, Dr Scott Meyer left DCG (due to what at the time was described as philosophical and political differences) to develop, and to aggressively advocate an independent version of the EMTP which he called the ATP (Alternative Transients Program) In 1989, UBC further developed and marketed the original version of the EMTP and concentrated on PC platforms under the trade name MicroTran In the mid 80's Manitoba HVDC Research Centre developed a version of the EMTP (EMTDC) targeted primarily for the simulation of HVDC systems As these developments took place, DCG continued to fund EMTP research and program development efforts At the same time, the membership of DCG increased At present, North American members of DCG include WAPA, the US Bureau of Reclamation, American Electric Power Service Corporation, Electrical Power Research Institute (EPRI), ASEA Brown Boveri ltd., Canadian Electricity Association (CEA), Ontario Hydro, Hydro Quebec (BPA officially left DCG in 1990) DCG members outside North America include Trang CRIEPI (Central Research Institute of Electric Power Industry) from Japan, Eletricité de France, and NEG (Nordic EMTP Group) representing Imatran Voima Oy of Finland, Sydkdraft AB and Vattenfal AB of Sweden These efforts resulted in the release of version of the DCG version of the EMTP in 1996 (EMTP96) EMTP96 represents the last version of the EMTP based on the original BPA code This program will be superseded by the results of a complete re-structuring of the EMTP code presently under development by DCG, and scheduled to be released in 2001 This third-generation version of the EMTP will include all the functionality of EMTP96, but will also include advanced features such as variable time step, plug-in solution modules, dynamic memory allocation, and more EMTP-RV is the end result of the "EMTP Restructuring project" undertaken by the DCG in 1998 for modernizing the EMTP96 software EMTP-RV is the enhanced computational engine and EMTPWorks its new graphical user interface (GUI) The package is a sophisticated computer program for the simulation of electromagnetic, electromechanical and control systems transients in multiphase electric power systems It features a wide variety of modeling capabilities encompassing electromagnetic and electromechanical oscillations ranging in duration from microseconds to seconds Examples of its use include switching and lightning surge analysis, insulation coordination, shaft torsional oscillations, ferroresonance and power electronics applications in power systems In addition to the versions of the EMTP mentioned above, there are other transients analysis programs for electrical circuits worth mentioning in this context: NETOMAC (Siemens, commercial product) Morgat and Arene ( Eletricite de France, commercial products) PSIM (commercial product, aimed at power electronics studies) SABER (commercial product, aimed a power electronics studies) SPICE, PSPICE (commercial product, for electronic circuits, occasionally used in power electronics studies) 2.2 APPLICATIONS OF EMTP The EMTP is a very versatile simulation tool, and it can be used for most steadystate calculations, as well as most transient simulatons generally not exceeding one or two seconds The EMTP is generally used for one of two purposes: To aid in the design and specification of the power system and its components In other words, the EMTP is used in insulation coordination studies, specification of equipment ratings, protective device specification, control system design, power quality assessment, harmonic studies, etc To find solutions to existing system problems such as unexplained outages or equipment failures A partial list of typical EMTP studies follows: Switching Surges Deterministic line energization Probabilistic line energization Single-pole switching High-speed reclosing Capacitor switching Trang Transient recovery voltages Cable switching transients and sheath protection Lightning Surges Backflashover Direct strokes Incoming surges at stations Arrester specification Insulation coordination Overhead lines Underground cables Outdoor Stations Gas-insulated substations Arrester duty Shaft torsional stress - subsynchronous resonance High Voltage DC (HVDC) Controls Electrical transients Harmonics Static VAR Compensation Controls Overvoltages Harmonics Temporary overvoltages Power electronics and FACTS (HVDC, SVC, VSC, TCSC) General purpose electrical and electronic circuit simulations Power quality issues Carrier frequency propagation Harmonics Ferroresonnance Distribution networks and distributed generation Power systems dynamics and load modeling Subsynchronous resonance and shaft torsonial stresses Power systems protection issues Series and shunt resonance Motor starting Out-of-phase synchronization Islanding or other disturbing events General control systems Grounding Asymmetrical fault current evaluation Phase conductor transposition Ground wire losses Steady-state analysis of unbalanced systems Capacitor bank switching Series capacitor protection Trang This is only a partial list One of the EMTP's major advantages is its flexibility inmodelling; an experienced user can apply the program to a wide variety of studies, many of which were not even considered when the EMTP was first designed Unfortunately, with flexibility often comes complexity: the EMTP is not easy to use The difficulty lies not so much in the absence or presence of graphical user interfaces, but rather in the fact that the phenomena the EMTP is normally used to simulate are usually conceptually complex and difficult to model The user is expected to have a fair understanding of the phenomena being simulated 2.3 STATES OF SIMULATION Typical EMTP studies deal with steady-state and switching or lightning transients We will now establish working definitions for these 2.3.1 Steady-state Simulations As the name indicates it, steady-state is the normal operating state of an electrical power system In power system analysis, steady-state calculations are typically made in the “frequency domain” using phasor analysis In other words, instead of using the time domain representation of a voltage as V  Vocos(t  ), in the frequency domain it become Vrms, the angular frequency  is implicitly 50 or 60 Hz Phasor analysis simplifies calculations significantly in traditional power system analysis, it is the basis of most load flow and short-circuit analysis programs The EMTP uses steady-state calculations in the frequency domain to initialize the network in preparation for a transient simulation (rather than starting the transient simulation from zero initial conditions) Trang The current of the valve arrester of the line 576 Phu My on phase A, B, C The current of the valve arrester of the line 576 Phu My on phase A, B, C Page 67 CHAPTER SURVEY THE EMULATION CASES COMPARE AND EVALUATE THE RESULTS 5.1 TRANSFORMER 400KV Calculate the allowed largest distance between the valve arrester and the transformer 400kV: lcp ≤ (U tnx  U pđ )v 2a following IEEE standard: + Utnx: basic lightning impulse insulation level of the transformer 400kV; Utnx = 1425kV + Upđ: discharge voltage of the valve arrester; Upđ = 1100kV + Maximum stepness: a = 11kV/às/kVìMCOV ữ2000kV/às/kVìMCOV = 11 ì 209 = 2299kV/µs + v: velocity of the wave propagation; v = 300m/µs  lcp ≤ (U tnx  U pđ )v 2a  (1425  1100)  300 = 21.205 (m)  2299 Therefore the position of the valve arrester SiC to protect the transformer 400kV in this simulation is located within the allowed limit (17m) Next we will survey the largest value of the voltage impulse at the transformer 400kV compared with the value of the basic lightning impulse insulation level of the transformer 400kV is 1425kV and survey the largest value of the current run through the valve arrester compared with the classifying current of the valve arrester 400kV is 1015kA(ANSI/IEEE) The case survey: 5.1.1 General and danger: The general case was examined in chapter The dangerous case is the case of lightning discharge on the line 1, the lines is connected to the bus, while the lines 3, and are not connected to the bus The one-line circuit diagram of stations in this case are shown in the below picture: Page 68 Table results of the simulation: The largest value of the voltage impulse at the transformer: General Danger Diffirence Phase A 1146557.478 V 1151631.220 V 0.44252% Phase B 1107871.253 V 1264856.489 V 14.16999% Phase C 1158344.650 V 1312668.874 V 13.32282%  The largest value of the voltage impulse at the transformer in case the danger is greater than the general case but in both cases these values are smaller than the value of the basic lightning impulse insulation level of the transformer 400kV is 1425kV Page 69 The largest value of the current run through the valve arrester: General Danger Diffirence Phase A 4035.324 A 4276.018 A 5.965% Phase B 3316.841 A 4749.790 A 43.202% Phase C 2952.451 A 4927.357 A 66.890%  The largest value of the current run through the valve arrester in case of danger is greater than the general case but in both cases these values are smaller than the classifying current of the valve arrester 400kV is 10-15kA Conclusion: The protection of the valve arrester are safe to transformer 5.1.2 Line layout triangle and horizontal: Table results of the simulation: The largest value of the voltage impulse at the transformer: triangle layout horizontal layout Diffirence Phase A 1146557.478 V 1089024.372 V -5.018% Phase B 1107871.253 V 1181175.089 V 6.617% Phase C 1158344.650 V 1217665.721 V 5.121%  The largest value of the voltage impulse at the transformer in the case of horizontal line layout is dangerous than the triangle line layout but in both cases these values are smaller than the value of the basic lightning impulse insulation level of the transformer 400kV is 1425kV The largest value of the current run through the valve arrester: triangle layout horizontal layout Diffirence Phase A 4035.324 A 4828.836 A 19.664% Phase B 3316.841 A 3929.024 A 18.457% Phase C 2952.451 A 4067.514 A 37.767%  The largest value of the current run through the valve arrester in case of horizontal line layout is greater than the triangle line layout case but in both cases these values are smaller than the classifying current of the valve arrester 400kV is 10-15kA Conclusion: The protection of the valve arrester are safe to transformer Page 70 5.1.3 Back – flash and lightning discharge directly on the phase line: Table results of the simulation: The largest value of the voltage impulse at the transformer: Back – flash Phase A 1146557.478 V lightning discharge directly on the line phase A 1101701.245 V lightning discharge lightning discharge directly on the line directly on the line phase B phase C 1133321.476 V 1148601.498 V Phase B 1107871.253 V 1147773.517 V 1131589.498 V 1204869.798 V Phase C 1158344.650 V 1164368.578 V 1212557.782 V 1195860.833 V  The largest value of the voltage impulse at the transformer in the back – flash case and the lightning discharge directly on the phase line cases are smaller than the value of the basic lightning impulse insulation level of the transformer 400kV is 1425kV The largest value of the current run through the valve arrester: Back – flash Phase A 4035.324 A lightning discharge directly on the line phase A 3677.433 A lightning discharge lightning discharge directly on the line directly on the line phase B phase C 4912.187 A 5095.553 A Phase B 3316.841 A 3637.960 A 3288.109 A 3838.982 A Phase C 2952.451 A 3244.419 A 4310.527 A 3721.677 A  The largest value of the current run through the valve arrester in the back – flash case and the lightning discharge directly on the phase line cases are smaller than the classifying current of the valve arrester 400kV is 10-15kA Conclusion: The protection of the valve arrester are safe to transformer 5.1.4 Surveying the changes in the lightning maximum stepness: Table results of the simulation: The largest value of the voltage impulse at the transformer: 100kV/μS 150kV/μS 200kV/μS Phase A 1146557.478 V 1149106.015 V 1155870.995 V Phase B 1107871.253 V 1135356.324 V 1150836.469 V Phase C 1158344.650 V 1211379.439 V 1206459.609 V  The change of the lightning maximum stepness bring to the change of the largest value of the voltage impulse at the transformer Page 71  The largest value of the voltage impulse at the transformer in the cases of changing the lightning maximum stepness are smaller than the value of the basic lightning impulse insulation level of the transformer 400kV is 1425kV The largest value of the current run through the valve arrester: 100kV/μS 150kV/μS 200kV/μS Phase A 4035.324 A 4655.580 A 4610.884 A Phase B 3316.841 A 3108.126 A 3382.315 A Phase C 2952.451 A 3732.774 A 3851.902 A  The largest value of the current run through the valve arrester in the cases of changing the lightning maximum stepness are smaller than the classifying current of the valve arrester 400kV is 10-15kA Conclusion: - The largest value of the voltage impulse at the transformer is ratio of the lightning maximum stepness - The protection of the valve arrester are safe to transformer 5.1.5 Surveying the changes of the distance between the valve arrester and the transformer: (lcp ≤ 21.205m) Table results of the simulation: The largest value of the voltage impulse at the transformer: l = 7m l = 14m l = 20m Phase A 1132458.547 V 1138910.660 V 1115264.919 V Phase B 1061803.635 V 1093483.739 V 1129165.733V Phase C 1156146.057 V 1157803.353 V 1158524.344 V  The change of the distance between the valve arrester and the transformer bring to the change of the largest value of the voltage impulse at the transformer  The largest value of the voltage impulse at the transformer in the cases of changing the distance between the valve arrester and the transformer are smaller than the value of the basic lightning impulse insulation level of the transformer 400kV is 1425kV The largest value of the current run through the valve arrester: l = 7m l = 14m l = 20m Phase A 5164.564 A 4249.567 A 3604.680 A Phase B 2833.316 A 3212.782 A 4073.530 A Phase C 4125.978 A 3100.116 A 2788.554 A Page 72  The change of the distance between the valve arrester and the transformer bring to the change of the largest value of the current run through the valve arrester, this distance is smaller so that the largest value of the current run through the valve arrester is bigger, that means the ability to put the lightning current down to ground is better  The largest value of the current run through the valve arrester in the cases of changing the distance between the valve arrester and the transformer are smaller than the classifying current of the valve arrester 400kV is 10-15kA Conclusion: - The largest value of the voltage impulse at the transformer is ratio of the distance between the valve arrester and the transformer - The protection of the valve arrester are safe to transformer, the position of the valve arrester is closer to the transformer so the protection is safer 5.2 TRANSFORMER 500kV NHA BE Calculate the allowed largest distance between the valve arrester and the transformer 500kV Nha Be: (U tnx  U pđ )v lcp ≤ 2a following IEEE standard: + Utnx: basic lightning impulse insulation level of the transformer 500kV; Utnx = 1550kV + Upđ: discharge voltage of the valve arrester; Upđ = 1100kV + Maximum stepness: a = 11kV/às/kVìMCOV ữ2000kV/às/kVìMCOV = 11 ì 318 = 3498kV/µs + v: velocity of the wave propagation; v = 300m/µs  lcp ≤ (U tnx  U pđ )v 2a  (1550  1100)  300 = 19.297 (m)  3498 Therefore the position of the valve arrester SiC to protect the transformer 500kV Nha Be in this simulation is located within the allowed limit (9.325m) Next we will survey the largest value of the voltage impulse at the transformer 500kV Nha Be compared with the value of the basic lightning impulse insulation level of the transformer 500kV is 1550kV and survey the largest value of the current run through the valve arrester compared with the classifying current of the valve arrester 500kV is 10-15kA (ANSI/IEEE) The case survey: Page 73 5.2.1 General and danger: The general case was examined in chapter The dangerous case is the case of lightning discharge on the line 575 Phu My, the lines Phu Lam is connected to the bus, while the line 576 Phu My are not connected to the bus The one-line circuit diagram of stations in this case are shown in the below picture: 576 PHÚ MỸ 575 PHÚ MỸ PHÚ LÂM 75 35 35 35 47 47 47 35 35 35 79 39.5 39.5 32 9.325 75 35 79 16 85.5 39.5 39.5 75 16 32 32 16 32 39.5 16 9.325 Page 74 Table results of the simulation: The largest value of the voltage impulse at the transformer 575 Phu My: General Danger Diffirence Phase A 1029672.777 V 1065895.631 V 3.518% Phase B 1211561.057 V 1197423.785 V -1.167% Phase C 1184800.256 V 1174437.466 V -0.875% The largest value of the voltage impulse at the transformer 576 Phu My: General Danger Phase A 1091545.585 V Phase B 1102835.399 V null null Phase C 1121835.578 V null  The largest value of the voltage impulse at the transformer in two cases are smaller than the value of the basic lightning impulse insulation level of the transformer 500kV is 1550kV The largest value of the current run through the valve arrester 575 Phu My: General Danger Diffirence Phase A 4806.123 A 5151.552 A 7.187% Phase B 5055.165 A 5535.585 A 9.504% Phase C 4876.977 A 5613.798 A 15.108% The largest value of the current run through the valve arrester 576 Phu My: General Danger Phase A 5052.896 A null Phase B 4900.394 A null Phase C 4786.009 A null  The largest value of the current run through the valve arrester in case of danger is greater than the general case but in both cases these values are smaller than the classifying current of the valve arrester 500kV is 10-15kA Conclusion: The protection of the valve arrester are safe to transformer Page 75 5.2.2 Back – flash and lightning discharge directly on the phase line: Table results of the simulation: The largest value of the voltage impulse at the transformer 575 Phu My: Back – flash Phase A 1029672.777 V lightning discharge directly on the line phase A 1166391.758 V lightning discharge lightning discharge directly on the line directly on the line phase B phase C 1170852.542V 1090872.479 V Phase B 1211561.057 V 1168861.556 V 1150814.058 V 1125614.441 V Phase C 1184800.256 V 1184992.415 V 1243218.095 V 1116543.682 V The largest value of the voltage impulse at the transformer 576 Phu My: Back – flash Phase A 1091545.585 V lightning discharge directly on the line phase A 1096599.604 V lightning discharge lightning discharge directly on the line directly on the line phase B phase C 1137425.343 V 1132671.368V Phase B 1102835.399 V 1159895.491 V 1098724.779 V 1126658.012 V Phase C 1121835.578 V 1129353.492 V 1166871.888 V 1149697.066 V  The largest value of the voltage impulse at the transformer in the back – flash case and the lightning discharge directly on the phase line cases are smaller than the value of the basic lightning impulse insulation level of the transformer 500kV is 1550kV The largest value of the current run through the valve arrester 575 Phu My: Back – flash Phase A 4806.123 A lightning discharge directly on the line phase A 4906.843 A lightning discharge lightning discharge directly on the line directly on the line phase B phase C 5030.029 A 5453.835 A Phase B 5055.165 A 5004.741 A 4977.790 A 5131.471 A Phase C 4876.977 A 5174.022 A 5006.646 A 4848.956 A The largest value of the current run through the valve arrester 576 Phu My: Back – flash Phase A 5052.896 A lightning discharge directly on the line phase A 5117.332 A lightning discharge lightning discharge directly on the line directly on the line phase B phase C 5104.315 A 5839.268 A Phase B 4900.394 A 5017.927 A 5044.604 A 4930.150 A Phase C 4786.009 A 4846.487 A 5450.253 A 4956.785 A Page 76  The largest value of the current run through the valve arrester in the back – flash case and the lightning discharge directly on the phase line cases are smaller than the classifying current of the valve arrester 500kV is 10-15kA Conclusion: The protection of the valve arrester are safe to transformer 5.2.3 Surveying the changes in the lightning maximum stepness: Table results of the simulation: The largest value of the voltage impulse at the transformer 575 Phu My: 100kV/μS 150kV/μS 200kV/μS Phase A 1029672.777 V 1105692.882 V 1119608.470 V Phase B 1211561.057 V 1145195.912 V 1139598.142 V Phase C 1184800.256 V 1142215.375 V 1154830.182 V The largest value of the voltage impulse at the transformer 576 Phu My: 100kV/μS 150kV/μS 200kV/μS Phase A 1091545.585 V 1070527.609 V 1077302.692 V Phase B 1102835.399 V 1101170.288 V 1109145.506 V Phase C 1121835.578 V 1121300.606 V 1129570.083 V  The change of the lightning maximum stepness bring to the change of the largest value of the voltage impulse at the transformer  The largest value of the voltage impulse at the transformer in the cases of changing the lightning maximum stepness are smaller than the value of the basic lightning impulse insulation level of the transformer 500kV is 1550kV The largest value of the current run through the valve arrester 575 Phu My: 100kV/μS 150kV/μS 200kV/μS Phase A 4806.123 A 4789.860 A 4793.555 A Phase B 5055.165 A 5381.741 A 5229.060 A Phase C 4876.977 A 4935.858 A 4710.597 A The largest value of the current run through the valve arrester 576 Phu My: Phase A 100kV/μS 150kV/μS 200kV/μS 5052.896 A 5313.215 A 5096.347 A Page 77 Phase B 4900.394 A 5112.269 A 5062.976 A Phase C 4786.009 A 4825.870 A 4955.652 A  The largest value of the current run through the valve arrester in the cases of changing the lightning maximum stepness are smaller than the classifying current of the valve arrester 500kV is 10-15kA Conclusion: - The largest value of the voltage impulse at the transformer is ratio of the lightning maximum stepness - The protection of the valve arrester are safe to transformer 5.2.4 Surveying the changes of the distance between the valve arrester and the transformer: (lcp ≤ 19.297m) Table results of the simulation: The largest value of the voltage impulse at the transformer 575 Phu My: l = 7m l = 13m l = 19m Phase A 1112159.375 V 1117881.063 V 1058061.462 V Phase B 1177011.420 V 1204102.884 V 1227207.821 V Phase C 1175848.069 V 1172131.073 V 1191156.628 V The largest value of the voltage impulse at the transformer 576 Phu My: l = 7m l = 13m l = 19m Phase A 1082339.686 V 1106866.561 V 1085349.256 V Phase B 1095061.296 V 1115017.428 V 1125321.540 V Phase C 1121467.726 V 1120977.419 V 1123602.897 V  The change of the distance between the valve arrester and the transformer bring to the change of the largest value of the voltage impulse at the transformer  The largest value of the voltage impulse at the transformer in the cases of changing the distance between the valve arrester and the transformer are smaller than the value of the basic lightning impulse insulation level of the transformer 500kV is 1550kV The largest value of the current run through the valve arrester 575 Phu My: l = 7m l = 13m l = 19m Phase A 4794.353 A 4807.487 A 4926.889 A Phase B 5456.747 A 5159.898 A 4855.187 A Page 78 Phase C 4778.591 A 4853.700 A 4997.171 A The largest value of the current run through the valve arrester 576 Phu My: l = 7m l = 13m l = 19m Phase A 5051.389 A 5082.395 A 4948.505 A Phase B 4947.847 A 4919.234 A 4868.342 A Phase C 4994.870 A 4875.049 A 4975.983 A  The change of the distance between the valve arrester and the transformer bring to the change of the largest value of the current run through the valve arrester, this distance is smaller so that the largest value of the current run through the valve arrester is bigger, that means the ability to put the lightning current down to ground is better  The largest value of the current run through the valve arrester in the cases of changing the distance between the valve arrester and the transformer are smaller than the classifying current of the valve arrester 500kV is 10-15kA Conclusion: - The largest value of the voltage impulse at the transformer is ratio of the distance between the valve arrester and the transformer - The protection of the valve arrester are safe to transformer, the position of the valve arrester is closer to the transformer so the protection is safer Page 79 CONCLUSION The achieved results: This thesis introduced EMTP software, a commercial software is optimal in resolution of the transient problem in the power system Simulate successfull the lightning transient propagation in the high voltage transformer station by EMTP-RV with the parameters of reality Simulate successful many different cases of the lightning transient propagation in the high voltage transformer station and evaluate, compare the results of the transient waves Survey is the transient waves at the different points on the station line Evaluate the results of the transient waves at the transformer and the valve arrester, compare with the theory standard and practice standard hence conclude the lightning protection ability of the stations Survey the influence of the maximum stepness of the lightning on the largest value of the voltage impulse at the transformer Survey the rationality of the distance between the valve arrester and the transformer, compare with the theory calculated value and its influence on the largest value of the voltage impulse at the transformer  The rationality of the results between theory and practice standards through the simulation as well as the fast calculate ability of the software helps the simulation to become reliable in the surveying, installation of the valve arrester equipment to protect the actual transformer stations Development of this thesis: The development of this thesis is using the EMTP software to simulate of the other transient problems of the power system such as short circuit, dismiss load, cut balancing capacitor, etc and building the great power system circuits such as the power system 500kV, 220kV, 110kV of Vietnam Page 80 REFERENCES [1] – EMTP Theory Book Branch of System Engineering Bonneville Power Administration Portland, Oregon 97208-3621 United States oh America [2] – EMTP Rule Book [3] – Hoang Viet (2005) High Voltage Technique (part 2), Overvoltage In Power System Publisher University of National City - Ho Chi Minh City [4] – Tran Van Top (2007) High Voltage Technique, Overvoltage And Overvoltage Protection Publisher science and technology [5] – Tran Bach (2005) Grid And Power System (part 3) Publisher science and technology [6] – Tibor Horváth Understanding lightning and lightning protection John Wiley & Sons, Ltd [7] – E Kuffel – W.S Zaengl – J Kuffel High Voltage Engineering: Fundamentals Newnes [8] – G Vijayaraghavan – Mark Brown – Malcolm Barnes Grounding, Bonding, Shielding and Surge Protection Newnes [9] – Book, Lectures of the subject “model and problems” of the Vietnam – France program [10] – The catalog, Datasheet, pdf files of internet articles and IEEE articles Page 81 ... TRANSIENT PROPAGATION IN THE HIGH VOLTAGE TRANSFORMER STATION 1.2.1 Reasons: The lightning transient propagate to the high voltage transformer station by the following reasons: a) Back-flash: the lightning. .. it is simulated by using the Thevenin equivalent phase source is connected with line 576 Phu My and line Phu Lam The lines and bus in the transformer station are simulated by using the single... this voltage level In the case of this study, it is simulated by using the Thevenin equivalent phase source is connected with line and line The lines and bus in the transformer station are simulated