• Title/Summary/Keyword: Overvoltage

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Voltage Swell Compensation using an UPFC in Distribution System (배전계통에서 UPFC를 이용한 순시전압상승 보상)

  • Jang, Won-Hyeok;Rhee, Sang-Bong;Lee, Myoung-Hee;Kim, Chul-Hwan
    • Proceedings of the KIEE Conference
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    • 2008.07a
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    • pp.488-489
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    • 2008
  • Based on the fact that renewable energies such as photovoltaic, wind power, etc. are increasingly used in distribution systems recently which affects overvoltage, this paper implements an unified power flow controller(UPFC) to compensate voltage swell. The implemented scheme employs an ac chopper and a low-pass filter along with a series transformer. The ac chopper converts the amplitude of the voltage down to the nominal value. The low pass filter makes the rough waveform of the output voltage of the ac chopper due to switching smoothly by eliminating harmonics. To verify the effectiveness of the implemented UPFC, the results by Electro-Magnetic Transients Program(EMTP) are presented for various overvoltage cases.

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Analysis of Magnitude and Rate-of-rise of VFTO in 550 kV GIS using EMTP-RV

  • Seo, Hun-Chul;Jang, Won-Hyeok;Kim, Chul-Hwan;Chung, Young-Hwan;Lee, Dong-Su;Rhee, Sang-Bong
    • Journal of Electrical Engineering and Technology
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    • v.8 no.1
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    • pp.11-19
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    • 2013
  • Very Fast Transients (VFT) originate mainly from disconnector switching operations in Gas Insulated Substations (GIS). In order to determine the rate-of-rise of Very Fast Transient Overvoltage (VFTO) in a 550 kV GIS, simulations are carried out using EMTP-RV. Each component of the GIS is modeled by distributed line model and lumped model based on equivalent circuits. The various switching conditions according to closing point-on-wave and trapped charge are simulated, and the results are analyzed. Also, the analysis of travelling wave using a lattice diagram is conducted to verify the simulation results.

Measurement and Analysis of Open Circuit Potential in PEFC (고분자 전해질 연료전지의 개방회로 전위차 측정 및 분석)

  • 김홍건;김유신;김홍열
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.10a
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    • pp.134-138
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    • 2004
  • The discrepancies between theoretical values and measured data of PEFC(Proton Exchange Fuel Cell) is carried out for the machine tool power generation. Rudimental approach of theoretical fuel cell open circuit potential using Gibbs free energy is employed for the examination of PEFC module. The stack temperature, stack voltage and stack current are measured during the operation of PEFC module. It is found that stack voltage and current values show the pronounced discrepancy with the results calculated by Gibbs free energy approach. It is analysed that the discrepancy is due to activation polarization, concentration overvoltage and ohmic overvoltage.

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Feeder Loop Line Control for the Voltage Stabilization of Distribution Network with Distributed Generators

  • Jeong, Bong-Sang;Chun, Yeong-Han
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.1-5
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    • 2014
  • When renewable sources are connected to the distribution network in the form of a distributed generators(DGs), the effect of intermittent output appears as voltage fluctuation. The surplus power at the consumer ends results in the reverse power flow to the distribution network. This reverse power flow causes several problems to the distribution network such as overvoltage. Application of the reactive power control equipment and power flow control by means of BTB inverter have been suggested as the general solutions to overcome the overvoltage, but they are not economically feasible since they require high cost devices. Herein, we suggest the feeder loop line switch control method to solve the problem.

The Lightning Current Parameters that Impact on the Surge Analysis of the EHV Gas Insulated Substation by EMTP

  • Shim Eung-Bo;Han Sang-Ok
    • KIEE International Transactions on Electrophysics and Applications
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    • v.5C no.1
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    • pp.1-7
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    • 2005
  • This paper describes the lightning surge analysis model of extra high voltage GIS using EMTP. Various lightning current parameters were investigated in order to confirm the impact on the lightning surge analysis such as lightning current amplitude, waveform, size of GIS, tower footing resistance and surge arresters. The multi-story tower model and EMTP/TACS model were introduced for the simulation of dynamic arc characteristics. The margin between the maximum overvoltage and BIL of the GIS was about 10 percent and the margin between the maximum overvoltage and BIL of the transformer was 21 percent.

Performance Analysis for the Modified Excitation System of Synchronous Machine Connected to HVDC System

  • Kim, Chan-Ki
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.2B no.3
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    • pp.109-114
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    • 2002
  • This paper analysis the transient performance of the modified excitation system using 4-quadrant chopper for a synchronous machine connected to HVDC system. Conventionally, capacitors are used to supply reactive power requirement at a strong converter bus. And the installation of a synchronous machine is essential in an isolated weak network to re-start after a shutdown of HVDC and to increase the system strength. However, a conventional static excitation system has some problems which are harmonic instability and the system stress due to overvoltage. To reduce these problems, the new excitation system, which has 4-quadrant chopper, is proposed. As the proposed system provides the capability to allow reverse current and isolate between AC network and excitation power, problems of overvoltage and harmonic instability can be solved. The investigation is performed and confirmed by the time domain digital simulation using PSCAD/EMTDC program.

Lightning Overvoltage Characteristics in Distribution System with Arrester Application (피뢰기 적용에 따른 다양한 배전계통의 뇌과전압 변화특성)

  • Kim, Sang-Kuk;Jung, Chae-Kyun;Lee, Jong-Beom;Ha, Dong-Hyuk
    • Proceedings of the KIEE Conference
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    • 2002.11b
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    • pp.355-357
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    • 2002
  • Distribution lines are spanned on a much large area as compared to transmission lines, and therefore, are more often susceptible to lightning strokes. The selection of the proper value of basic insulation level(BIL), for particular insolation components of distribution structures in specific, is very important. Lightning strikes has current risetimes ranging from 0.1 to several $\mu s$ and can produce transient overvoltages substantially greater than the BIL of many distribution systems in spite of lightning arresters. This paper describes lightning overvoltage of a 22.9kV distribution system due to lightning strike. This study will provide the information on insulation coordination studies to adopt BIL.

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Dynamic Property of Ground Overvoltage Relay in Large Turbine Generator (대용량 터빈발전기에서 접지과전압 계전기의 동작 특성)

  • Kim, Hee-Dong;Lee, Young-Jun;Kim, Byong-Han;An, Joon-Young;Chae, Gyu-Jin
    • Proceedings of the KIEE Conference
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    • 1999.11d
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    • pp.1044-1047
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    • 1999
  • This paper deals with the dynamic property of ground overvoltage relay in large turbine generator. Relay operation is based on detecting the fundamental voltages originating from the generator. Calculations of fault voltage and current are reviewed for the neutral ground resistance. The frequency, ampitude and waveform of individual harmonics were measured using power quality analyzer and memory hi-corder at the secondary side of ground potential transformer. The ac and dc high-potential tests were applied to evaluate the condition of generator, main and auxiliary transformer, isolated phase bus, potential transformer, surge capacitor and arrester.

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Insulation coordination of 765 KV double circuit transmission line (765 KV 2 회선(回線) 송전선(送電線) 절연협조(絶緣協助))

  • Kim, Jeong-Boo;Min, Suk-Won;Lee, Dong-Il
    • Proceedings of the KIEE Conference
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    • 1988.07a
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    • pp.774-777
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    • 1988
  • This paper covers the insulation coordination of 765 KV transmission line in Korea Electric Power Corporation. The design for the lightning, switching surge, and contamination was conducted to increase the reliability of 765 KV line. The authors have used the result of a limited Westinghouse ANACOM swiching surge study of the Korea Electric Corporation's 765 KV Expansion plan. The study investigated the switching surge overvoltage distribution and maximum switching overvoltage when relosing 765 KV lines. They used the technical data of the suspension insulator for the contamination design, which was available from a foreign insulator manufacture. From this paper, the authors find out that the contamination design dominates to determine the number of insulator and the SOV design dominates the air clearance in the tower. Afterwards the authors will confirm this design by Demonstration Test with Korea Electro-technology Research Institute.

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Analysis of Lightning Overvoltage on the Combined Power Transmission Line and Actuation of Arrester (혼합송전계통에서 뇌과전압해석 및 피뢰기 동작특성 검토)

  • Kim, Nam-Yoel;Kim, Kyoung-Ho;Lee, Jong-Beom;Cho, Han-Goo
    • Proceedings of the KIEE Conference
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    • 2001.07a
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    • pp.491-493
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    • 2001
  • This paper describes the effect of lightning current on combination transmission line. In the paper, an lightning current which can generate 2/80[${\mu}s$]. 20[kA] - 40[kA] waveform is modeled in ATPDraw. The lightning current invaded to the overhead power transmission line propagates to the underground power cable. The simulation was performed to analyze the effect of arrester location and overvoltage occurred in power cable.

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