• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.94-99
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• 2003

A strong need to improve the quality of electric power is increased because of increasing use of the sensitive and small-sized electronic devices. The transient overvoltages on low-voltage AC power distribution systems are induced by direct or indirect lightning return strokes, and they can cause damage and/or malfunction of the utility systems for home automation, office automation and factory automation as well as medical equipment. The behaviors of lightning overvoltages transferred through the transformer to the low voltage AC power distribution systems were experimentally investigated using a Marx generator. The surge voltages in low-voltage ac power systems are rarely limited by the application of the surge arrester to the primary side of distribution transformer and a custom service ground.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.118-125
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• 2007

The lightning surge and switching surge could be injected to the underground distribution line through the riser pole in the mixed distribution line of overhead and underground. These surges travel along the cable and are reflected at the end of cable. It can be doubled and affecting underground distribution facilities. It was made a underground distribution model representing KEPCO's distribution system. It was measured propagation characteristics by applying lightning surges to this underground distribution model. Meanwhile, this system was simulated with ATP-EMTP and compared these real test results md tuned up the EMTP parameters. EMTP simulation results showed that accord with real test result by adjusting the cable insulation permitivity, arrester characteristics, surge wave shape.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.398-403
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• 2006

This paper describes the evaluation of the long duration current impulse withstand characteristics of ZnO blocks for high voltage surge arresters. Four ZnO varistors were manufactured with the general ceramic production method and the long duration current impulse withstand test, electrical uniformity evaluation test and microstructure observation were performed. All varistors exhibited high density, which was in the range of $5.42{\sim}5.46g/cm^3$. In the electrical properties, the reference voltage of samples was in the range of $5.11{\sim}5.25\;kV$ and the residual voltage was in the range of $8.314{\sim}8.523\;kV$. In the long duration current impulse withstand test, sample No.2 and No.3 failed at the 2nd and 4th shot of series impulse currents, respectively, but the rest survived 18 shots during the test. Before and after this test, the variation ratio of the residual voltage of samples survived was below 0.5 %, which was in the acceptance range of 5 %. According to the results of the test, it is thought that if the soldering method is improved, ZnO varistors would be possible to apply to the high voltage arresters like the station class and transmission line arresters in the near future.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1761-1769
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• 2010

This paper describes switching surge analysis on reclosing decision in 154kV combined transmission line with power cables. Reclosing should be operated in combined transmission line based on the technical evaluation because of insulation problem of power cable section. If the surge strikes on power cable, the breakdown can occur at week point of cable insulation. Therefore the detailed analysis is required by considering several conditions such as length ratio of power cable, arrester, fault resistance, charging rate and grounding resistance, etc.. In addition, sheath voltage on IJ(Insulated Joint) is analyzed to confirm the protective level. Simulation is performed by EMTP/ATP. Analysis results show that reclosing can be operated without any special problem by the single line-to-ground fault with fault resistance of $1\Omega$ to $50\Omega$ occurred at the overhead transmission section in 154kV combined transmission lines and trap charge of 100% and 110%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.1-7
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• 2013

This paper analyzes the flashover rate by lightning in Korea distribution system. Because of random characteristics of lightning, the Monte Carlo method is applied to estimate the lightning performance. The magnitude of lightning stroke is based on the curve measured in field. The classification of direct and indirect lightning depends on the striking distance. The striking distance and flashover rate are calculated by using the method based on Central Research Institute of Electric Power Industry(CRIEPI). The distribution system and lightning is modeled by using EMTP and MATLAB, and the accuracy of modeling is discussed. The simulations for the various spacing between two adjacent surge arresters and the various grounding resistance of GW according to the existence of GW are performed and the simulation results are analyzed.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1519-1520
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• 2006

This paper describes a selection and application recommendations of ZnO arresters on DC electric traction vehicles. We measured and analyzed the system voltages applied to arresters and the surge currents flowing arresters on DC electric traction vehicles under operation to decide the Continuous Operating Voltage($U_C$), the Rated Voltage($U_R$), and the Nominal Discharge Current($I_n$). System voltages measured up to 1,800 V during anti-breaking in 1,500 V-system, and surge currents were recorded up to 3 times per running-service-route and their magnitudes were ranges of $150A{\sim}2kA$. From these results and the standard EN50163, we proposed the Continuous Operating Voltage($U_C$) the Rated Voltage($U_R$) for the $1,500V_{dc}$ electric traction vehicles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.486-487
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• 2007

This paper describes the evaluation of long duration current impulse withstand characteristics of ZnO blocks for high voltage surge arresters. Four ZnO varistors were manufactured with the general ceramic production method and three abroad varistors were also prepared to be compared. All varistors exhibited high density, which was in the range of $5.42{\sim}5.49g/cm^3$. In the electrical properties, the reference voltage of all samples was in the range of 5.11~5.72kV and the residual voltage was in the range of 8.314~9.305kV. In the long duration current impulse withstand test, sample 2 and 3 failed at the 2nd and 4th shot of series impulse currents, respectively, but the rest survived 18 shots during the test. Before and after this test, the variation ratio of the residual voltage of samples survived were below 1.7%, which were in the acceptance range of 5%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.474-481
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• 2013

It is anticipated that AC distribution system can be replaced by DC distribution system in the near future because of the operation of various distributed source or microgrid system. However DC distribution system replacing 22.9kV AC distribution line is not sufficiently studied still. This paper describes lightning overvoltage analysis among many research fields should be studied to realize DC overhead distribution systems. DC distribution system is modeled using EMTP and overvoltage is analyzed according to interval of arrestor location, earth interval of overhead grounding wire and grounding resistance. It is evaluated that analysis results can be effectively used to design of future DC distribution system.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.104-106
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• 2003

본 논문은 이상전압으로부터 배전선로 및 전력기기를 보호하기 위해 사용되는 폴리머피뢰기에 대해 침수 시험을 실시하여 침수 전후 폴리머피뢰기의 특성변화를 평가하였다. 침수 시험은 수온 95[$^{\circ}C$]에서 20일 동안 실시하였다. 침수 시험 전후 폴리머피뢰기의 특성분석은 푸리에변환 적외선분광기(FTR : fourier transform infrared spectrophotometer), 유전열분석(DETA : dielectric thermal analyzer), 발수성 측정, 절연저항 측정, 누설전류 측정, 동작개시전압 측정 둥으로 연구 하였다. 이를 통해 침수시험의 열화 효과에 대해 검토하였다.

• 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).