• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2135-2142
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• 2010

This paper studies the validity about a joint operation of neutral wire and overhead grounding wire in combined distribution systems. The overhead grounding wire and neutral wire are currently installed separately and grounded by common. However there is no any ineffectiveness or electrical problem in case of the proposed system, such system can be operated at real distribution system. Therefore this paper describes the suitability of a joint operation through lightning surge analysis on combined distribution systems. Lightning surge analysis is carried out by EMTP/ATPDraw to obtain the overvoltage of overhead line and underground cable in various conditions such as locations and current types of lightning stroke. Overvoltage gained by the analysis show that the insulation strength of the joint operation case is not stable compare with the current operation case.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.337-338
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• 2008

KEPCO has built, for the first time in the world, 765㎸ double circuit transmission lines which use vertically arranged phase conductor, while 765㎸ transmission lines in other countries are single circuit lines and use horizontally arranged phase conductor. System operating voltage, switching overvoltage, and lightning overvoltage were considered in determining the air gap. Recently, however, lightning outage rate of some 765㎸ transmission lines in KOREA shows that it is more than what is expected. Lightning fault of 765㎸ transmission lines is mostly single phase grounding fault which can be reclosed. But it still needs to be carefully managed, for the bulk system like 765㎸ transmission lines have huge effects on whole power system. This paper introduces analysis and countermeasure of KEPCO's 765㎸ transmission line lightning outage.

• 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.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.176-179
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• 1992

This paper presents results of typical sutdy on lightning overvoltages of underground distribution systems and discusses effective insulation coordination schemes. Typical lightning current and system parameters are used to analyze lightning overvoltage distribution on underground distribution systems by EMTP (Electro-Magnetic Transients Program).

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.8
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• pp.454-460
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• 2004

The effects of surge arresters for protection of transmission systems against direct lightning strokes have already been reviewed using Electromagnetic Transients Program(EMTP). Distribution lines are spanned in much larger area than transmission lines, and therefore, are more susceptible to lightning strokes. We have modelled the 22.9kV underground distribution cable systems that have arresters and grounding wires. And this paper analyzes the overvoltages on underground distribution cable systems when direct lightning strokes strike on the overhead grounding wire using EMTP. Then we investigated that (1) the effects of lightning stroke according to underground distribution cable length (2) voltages at the riser pole and at the cable terminal according to installation of arrester. This study will provide insulation coordination methods for reasonable systems design in 22.9kV underground distribution cable systems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.140-143
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• 2000

The primary function of ZnO lightning arrester is to protect transmission and distribution equipment from overvoltages and to absorb electrical energy resulting from lightning or switching surges and form temporary overvoltage. However, ZnO lightning arrester are known to exhibit an increases in resistive current with time, the rate of increase being exacerbated with increasing applied voltage and ambient temperature. So, it is important to the leakage current measurement of ZnO lightning arrester. In addition, since the resistive leakage current caused by deterioration of ZnO lightning arrester mainly caused an increase of the third harmonic component, thereby it is possible the arrester degradation diagnosis by measuring the third harmonic component in the total leakage current. The leakage current and third harmonic component are measured and used to investigate the degradation diagnosis of ZnO element of arrester. Also the SEM photography is used to investigate the change of crystal structure of ZnO element with degradation.

• KIEE International Transactions on Power Engineering
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• v.5A no.4
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• pp.366-370
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• 2005

To meet increasing power demand, 500 kV power systems are under consideration in the regions of some Middle Asian countries. As the power system voltage becomes higher, the cost for the power system insulation increases significantly. 500 kV transmission systems will become the basis of a region's power system and they require much higher system reliability. Consequently, by the methods of limiting overvoltages effectively, a reasonable insulation design and coordination must be accomplished. In particular, the Substations must be constructed to be of outdoor type. In order to determine the various factors for the insulation design, the EMTP (Electro-magnetic transient program) is used for the magnification of transient phenomena of the 500 kV systems in the planned network. In this paper, we will explain the calculation results of lightning overvoltages by the EMTP for lightning protection design for the 500 kV substations. To obtain reliable results, the multi-story tower model and EMTP/TACS model are introduced for the simulation of dynamic arc characteristics.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.157-158
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• 2006

This paper describes the overvoltage of branch line in underground distribution systems when the direct lightning surge strikes on conductor of overhead line. Distribution systems are very complex because that includes so many branch lines, transformers, switches and so on. Therefor model systems consist of overhead distribution lines, underground cable include branch lines, lightning source and switches. Those are established by EMTP/ATPDraw. Simulation analyzes surge behavior on branch lines considering various conditions in underground distribution systems. Simulation results shoe overvoltage with location in various cases.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.148-150
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• 2006

This paper describes the overvoltage at the branch line in underground distribution systems when the direct lightning surge strikes on conductor of overhead line. Distribution systems are very complex because it includes many branch lines, transformers, switches and so on. Therefore model system consists of overhead distribution lines, underground cable include branch lines, lightning source and switches. Analysis are performed using EMTP to understand and evaluate the surge behavior on branch lines considering various conditions in underground distribution systems. Simulation results show overvoltage with location in various cases. It is evaluated that result will be used to establish protection methods in actual underground distribution systems.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.1949-1955
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• 2010

This paper describes the characteristic and effectiveness of combined GIL transmission line through lightning surge analysis. In addition the XLPE cable is analyzed in the same condition to compare with GIL. Lighting surge analysis is carried out by EMTP/ATP-Draw to obtain overvoltage of GIL and XLPE cable at service-point and load-out area of underground line. Propagation velocity is calculated in combined transmission lines with GIL and XLPE cable. The overvoltage is also analyzed on GIL and XLPE cable with or without arrester operation. The Analysis results show that overvoltage of GIL is occurred higher than XLPE cable at the same condition. Therefore it is evaluated that the application of GIL at the field should be considered cautiously when more detailed transient analysis, another electrical testes and economic evaluations are implemented.