• Title, Summary, Keyword: Overvoltage

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A Study on SVL Transient Characteristics by Switching Overvoltage at Single Point Bonding Section in Underground Transmission Cables (개폐과전압 발생시 지중송전선로 편단접지 구간에서 SVL에 미치는 과도특성에 관한 연구)

  • Jung, Chae-Kyun;Kang, Ji-Won
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.6
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    • pp.764-769
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    • 2014
  • This paper describes sheath voltage limiter(SVL) transient characteristics by switching overvoltage considering single point bonding in underground transmission cables. The crossbonding system is generally used for grounding methods of underground transmission system. However, the single point bonding system is used in selective area which is difficult to consist of crossbonding major section. The sheath voltage limiters are connected between joints in the single point bonding. Specially, the high overvoltage might be generated in that section as well as the aging of sheath voltage limiter might be progressed by various electrical stress including lightning overvoltage, switching overvoltage and power frequency overvoltage. Therefore, in this paper, the switching overvoltage characteristics in underground cables are firstly analysed using EMTP simulation. Then, the switching overvoltage of sheath voltage limiter is also studied in single point bonding. Finally, the reduction method of sheath voltage limiter switching overvoltage is proposed by various simulation studies including circuit breaker operating order.

Introduction of Insulation Coordination for UHV AC Systems

  • Shim, Eungbo;Zaima, Eiichi
    • Journal of Electrical Engineering and Technology
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    • v.10 no.3
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    • pp.1293-1297
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    • 2015
  • This paper introduces the insulation coordination study results for UHV AC systems which was performed by CIGRE working group. The study results will be discussed within IEC technical committee in order to amend the IEC Insulation Coordination 60071-1 Ed. 8 2010 and 60071-2 Ed. 3, 1996. This paper includes the insulation coordination of transformer, gas insulated switchgear, metal oxide arresters and clearances of transmission towers. This article also illustrates the overvoltage specific to UHV systems such as TOV(temporary overvoltage), switching overvoltage, lightning overvoltage and VFTO(very fast transient overvoltage).

Analysis of Switching Overvoltage in 345kV Underground and Combined Transmission Systems (345kV 지중 및 혼합 송전계통에서의 개폐 과전압 해석)

  • 정채균;이종범;강지원
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.12
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    • pp.713-721
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    • 2003
  • This paper analyzes the switching overvoltage occurred on 345kV underground power cable system as well as combined transmission system using EMTP. Cable length and closing time, preinsertion resistance have effect on switching overvoltage. Therefore, this paper analyzes the switching overvoltage occurred on conductor and sheath with change of those parameters. Specially, the cross bonding position becomes discontinuity point because of the difference between surge impedance of metal sheath and that of lead cable. Thus, the transmission and the reflection of traveling wave complexly occur at this connection point. According to these influences, voltage between sheath and earth as well as voltage between joint boxes rise. Time to crest point of switching overvoltage is longer than lightning overvoltage. Even though the voltage induced by switching surge is smaller than lightning surge, that voltage may have serious effect on the metal sheath. Therefore, this paper also analyses the reduction effect of switching overvoltage when the preinsertion resistance of circuit breaker is considered.

Overvoltage Protection Controller Design of Distributed Generation Connected to Power Grid Considering Islanding Condition

  • Cha, Jae-Hun;Park, Kyung-Won;Ahn, Hong-Seon;Kwon, Kyoung-Min;Oh, Jin-Hong;MAHIRANE, Philemon;Kim, Jae-Eon
    • Journal of Electrical Engineering and Technology
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    • v.13 no.2
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    • pp.599-607
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    • 2018
  • Distributed generation (DG) is being highlighted as an alternative for future power supplies, and the number of DG systems connected to conventional power systems is steadily increasing. DG generators are designed using power electronics and can give rise to various power quality problems, such as overvoltage or overcurrent. Particularly, unintentional islanding operation can occur in a conventional power system when the power grid is separated from the DG systems. Overvoltage may occur in this situation, depending on the power generation and power consumption. However, overvoltage phenomena might not happen even when islanding occurs. Therefore, it is necessary to analyze the fault characteristics during islanding. In this study, a fault analysis of islanding operation was carried out using PSCAD/EMTDC, and a countermeasure for the overvoltage problem is proposed.

Analysis on Overvoltage induced on Power Distribution line by Lightning surge (배전선로의 유도뢰 해석)

  • Kim, H.J.;Choi, S.Y.;Jung, H.S.;Shin, M.C.;Park, N.O.
    • Proceedings of the KIEE Conference
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    • pp.279-281
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    • 1998
  • This paper present overvoltage induced on distribution power line by lightning surge. It is important problem that overvoltage threatens credit and security of the power system. In this paper induced overvoltage was calculated. From the line being modeled in really actual practice. Also, the proper suppressing effects of a surge arrester against lightning induced voltages were suggested.

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A Study on the Reclosing Overvoltage in 345 [kV] Transmission Line (345kV 계통 재투입과 전압 해석)

  • Yoon, Jae-Young;Park, Dong-Wook;Whang, Chi-Woo
    • Proceedings of the KIEE Conference
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    • pp.166-169
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    • 1990
  • The purpose of the circuit breaker on power system is to disconnect the faulty part from the system and to maintain the integrity of the system. With switching overvoltages are generated. When the system voltages become higher, switching overvoltage is important factor in insulation co-ordination. Since the no-load reclosing overvoltage with inductive source is severe, this paper deals with the reclosing overvoltage and the effect of closing resistor. This reclosing overvoltage of 27-bus model system with and without closing resistor is analyzed by using EMTP (Electro-Magnetic Transients Program) for both deterministic and Stochastic model.

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Analysis of the Harmonic Resonance of Primary Restorative Transmission System Using PSCAD/EMTDC PART II (PSCADI/EMTDC를 이용한 시송전계통의 고조파 공진현상 분석 II)

  • Lee H. J.;Yoo W. K.;Lee K. S.;Park S. M.
    • Proceedings of the KIEE Conference
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    • pp.48-50
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    • 2004
  • The energization of high voltage transmission lines and transformers, that is an inevitable process in most countries as the first restorative action for wide-area blackout, may induce overvoltages such as sustained overvoltage, transient overvoltage and harmonic resonant overvoltage. And these may cause damages to power system equipments or failure of surge arresters. The harmonic resonant overvoltage originates in switching operations and nonlinear characteristics of equipments. Actually it is difficult to predict the occurrence of harmonic overvoltage, since they result from nonlinear characteristics of transformers and other equipments. This paper describes the analysis of domestic primary restorative transmission system using PSCAD/EMTDC. The harmonic resonance is verified and the solution to prevent harmonic resonance is proposed in this paper. As a result, the PSCAD/EMTBC simulation showed slightly conflictive results that had been presented by IEEE Power System Restoration Working Group report.

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Analysis on the Effect of LCR Filter to Mitigate Transient Overvoltage on the High Voltage Induction Motor Fed by Multi Level Inverter (멀티레벨 인버터 구동 고압유도전동기에시 발생하는 과도과전압 저감을 위한 LCR필터의 효과분석)

  • Kim, Jae-Chul;Kwon, Young-Mok
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.3
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    • pp.45-52
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    • 2006
  • In this paper, we analyze on the effect of LCR filter to mitigate transient overvoltage on the high voltage induction motor fed by H-bridge cascaded 7-level inverter. The switching surge voltage that it was occurred in inverter appears transient overvoltage at the motor input terminal. the transient overvoltage becomes the major cause to occur the insulation failure by serious voltage stress in the stator winding of high voltage induction motor. The effect of transient overvoltage appears more serious in high voltage induction motor than low voltage induction motor. We selected LCR filter for reduction of the transient overvoltage. Consequently, we demonstrated that the LCR filter connected to the invertor output terminals greatly reduces the transient voltage stress and ringing. The results of simulation show the suppression of transient overvoltage at the motor end of a long cable. using EMTP

Improved Gate Drive Circuit for High Power IGBTs with a Novel Overvoltage Protection Scheme (과전압 제한 기능을 갖는 새로운 IGBT 게이트 구동회로)

  • Lee, Hwang-Geol;Lee, Yo-Han;Suh, Bum-Seok;Hyun, Dong-Seok;Lee, Jin-Woo
    • Proceedings of the KIEE Conference
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    • pp.346-349
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    • 1996
  • In application of high power IGBT PWM inverters, the treatable power range is considerably limited due to the overvoltage caused by the stray inductance components within the power circuit. This paper proposes a new gate drive circuit for IGBTs which can actively suppress the overvoltage across the driven IGBT at turn-off and the overvoltage across the opposite IGBT at turn-on while preserving the most simple and reliable power circuit. The turn-off driving scheme has adaptive feature to the amplitude of collector current, so that the overvoltage is limited much effectively at the larger collector current. The turn-on scheme is to decrease the rising rate of the collector current by increasing input capacitance during turn-on transient when the gate-emitter voltage is greater than threshold voltage. The experimental results under various normal and fault conditions prove the effectiveness of the proposed circuit.

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A Study on the Protective Coordination of Generator Overexcitation and Overvoltage Relay (발전기 과여자 및 과전압 계전기 보호협조에 관한 연구)

  • Park, Ji-Kyung;Kim, Kwnag-Hyun;Kim, Chul-Hwan;Lyu, Young-Sik;Yang, Jeong-Jae
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.8
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    • pp.1187-1194
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    • 2017
  • After North American wide area black out on August 14, 2003, various studies have been conducted to find out the reason of the disaster. One of main reasons was misoperation of generator protection system. Since then, protective coordination between generator protection system and excitation system controls has been hot issue among electrical engineers. Among various generator protection relays, in this paper, we focused on generator overvoltage and overexcitation relay, which protect the over-flux condition of the generator. Thus, at first, we modeled the generator overvoltage, overexcitation relay and detailed power system including excitation system, governor and etc., based on actual field data. And then, we reviewed the protective coordination of generator overvoltage and overexcitation relay using electromagnetic transient program. In addition, we discussed the protective coordination method for redundant protection relays in both automatic voltage regulator and generator side.