• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권2호
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• pp.62-67
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• 2002

This paper provides the results of accelerated aging test of 18kV ZnO lightning arresters to investigate the leakage current characteristics. It was impossible to establish the replacement criterion for field operating lightning arrester because conventional aging test was only focused on the aging of ZnO elements. In general, it is possible to replace the aged arresters before the failure in the field using the leakage current measurement because it must be increased by the aging. But we can not use the method because we don't know the characteristics of the installed lightning arresters. Therefore in this paper we applied operating voltage and accelerating cycle which consists of temperature and humidity to the arresters. Then we measured the variation of total and resistive leakage current and found out the characteristics of the acted lightning arresters.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권3호
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• pp.131-137
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• 2005

This paper describes a new approach to the algorithm and fundamental characteristics of the device for monitoring the leakage currents flowing through zinc oxide (ZnO) surge arresters. In order to obtain a technique for a new on-line monitoring device that can be used in the deterioration diagnosis of ZnO surge arresters, the new algorithm and on-line leakage current detection device for extracting the resistive and capacitive currents using the phase shift addition method were proposed. The computer-based on-line monitoring device can sense accurately the power frequency leakage currents flowing through ZnO surge arresters. The on-line leakage current monitoring device of ZnO surge arresters proposed in this work has the high sensitivity compared to the third harmonic leakage current detection devices. As a consequence, it was found that the proposed leakage current monitoring device would be useful for forecasting the defects and degradation of ZnO surge arresters.

• 조명전기설비학회논문지
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• 제23권4호
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• pp.79-85
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• 2009

이 논문은 피임펄스전류의 입사에 따른 ZnO 피뢰기의 열화 특성에 대하여 기술하였다. 뇌서지에 의한 ZnO 피뢰기의 열화특성을 분석하기 위해 시료 ZnO 피뢰기에 8/20[${\mu}s$], 2.5[kA]의 표준뇌임펄스전류를 인가하였다. 뇌임펄스전류를 인가한 것과 인가하지 않은 ZnO 피뢰기에 흐르는 상용주파수 AC 및 DC 누설전류를 측정하였다. 그 결과 임펄스전류의 인가횟수가 증가함에 따라 누설전류는 증가하였고 AC전압에서 누설전류의 비 대칭성은 뚜렷하게 나타났다. 뇌임펄스전류를 인가하지 않은 ZnO 피뢰기의 ZnO 입자는 균일한데 반해 뇌임펄스전류를 인가한 ZnO 피뢰기의 ZnO 입자는 불균일하게 변형되었다. 또한 뇌임펄스전류 인가에 따른 $Bi_2O_3$의 감소가 입계층의 결핍을 발생시키며 입계층의 결핍에 의한 전류의 집중이 ZnO 피뢰기 소자의 비선형 특성의 열화에 대한 중요한 요인으로 작용한 것으로 밝혀졌다.

• 조명전기설비학회논문지
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• 제22권9호
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• pp.62-68
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• 2008

이 논문은 ZnO 피뢰기의 외부환경 변화에 따른 전기적 특성을 기술하였다. 뇌임펄스전류에 의한 ZnO 피뢰기의 열화특성을 분석하기 위해 8/20[${\mu}s$], 2.5[kA]의 임펄스전류를 시료에 인가하였다. ZnO 피뢰기의 누설전류를 다양한 외부 온도와 주수 상태에서 상용 주파수 교류 전압을 인가하여 측정하였다. 그 결과 임펄스전류의 인가횟수와 외부 온도가 증가함에 따라 누설전류가 증가하였고, 누설전류의 비대칭성도 뚜렷하였다. 또한 주수 시험에서 ZnO 피뢰기의 외피를 통하여 흐르는 전류는 피뢰기 소자의 누설전류보다 크게 나타났다. 본 연구의 결과는 피뢰기의 감시시스템 성능과 신뢰성 향상의 요소로 적용할 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1158-1161
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• 2004

This paper presents structural characteristics of station class lightning arresters and electrical characteristics of manufactured ZnO varistor blocks which are usable in those arresters. Three types of station class lightning arresters were investigated and those are a ceramic arrester, a FRP tube type polymer arrester, and a FRP rod type polymer arrester. Each arrester has merits and demerits with structural characteristics. In general, polymer arresters were made of silicon rubber for housing materials, FRP tube or rod for mechanical strength, ZnO blocks for electrical characteristics, and metal parts for electrical contact and the silicon rubber, the housing materials, was directly injected to the arrester module which was assembly composed of electrodes, ZnO blocks and FRP tube or rod, and to prevent the nonlinear electric fields distribution on upper parts of arresters, the grade ring was adopted to the upper electrodes. The reference voltage, nonlinear coefficient, residual voltage, and voltage ratio of manufactured ZnO varistors are 4.90kV, 50, 9.54kV, 1.94, respectively. Compared to designed electrical characteristics, the reference voltage was low for 600v and the voltage ratio was slightly high. However, the characteristics of discharge withstand was so excellent that the mechanical destruction does not occur at the impulse current of $8/20{\mu}s$ 10kA for 100 times.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.190-193
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• 2001

ZnO varistors have been widely used to protect power system and electronic system against overvoltages based on their excellent nonlinearity. In order to increase their protection capability, the fracture and protection technologies of arresters have to study according to their applications, namely ImA DC voltage, leakage currents, impulse residual voltages, withstanding capability to impulse surge, and energy absorption capability. ZnO varistors which have nonlinear current-voltage characteristic name a number of failure mechanism when ZnO elements absorb surge energies. Failure mode by thermal stress and Pin hole are among the most common failure mechanism at the high current surge current. In this study, the fracture mechaism of power arresters are introduced and protection technologies are researched. In particular the effect of thermal stress by surge currents to ZnO elements and methods against arc surge energy through withstand structure design of arrester are discussed.

• 한국전기전자재료학회논문지
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• 제19권4호
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1869-1871
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• 2004

The primary role of ZnO arresters is to protect transmission and distribution equipments against lightning surges. The extremely nonlinear V-I characteristics of the ZnO arrester obviates the need for isolation gaps and consequently it is continuously connected to line voltage. For this reason, ZnO arresters are degraded with increasing with time in actual power systems. In this work, the characteristics of the luminous events between the ZnO block and electrodes were investigated. As a result, the luminous events were effected by the impulse and the near polarity of the luminous event was intense near the grounded electrode. Also the luminous event may cause the degradation of ZnO arrester block.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.26-28
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• 2004

The primary role of ZnO arresters is to protect transmission and distribution equipments against lightning surges. The extremely nonlinear V-I characteristics of the ZnO arrester obviates the need for isolation gaps and consequently it is continuously connected to line voltage. For this reason, ZnO arresters are degraded with time in actual power systems. In this work, the characteristics of the luminous events caused between the ZnO block and electrodes according to the electrode area were investigated. As a result, the luminous events were effected by electrode area and the longer electrode areas were increased, the more luminous events were decreased. Also the reduction of luminous events was fumed up to the degraded ZnO arrester block.

• Journal of Electrical Engineering and information Science
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• 제2권6호
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• pp.111-115
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• 1997

ZnO varistors are widely used as surge arresters in power system based on their excellent nonlinearity. The property of power loss of ZnO varistors is related to the thermal stability and their life-spans of ZnO surge arresters. The power losses of ZnO varistors under different temperatures and applied voltages were measured, and the properties of power losses were analyzed. The Artificial Neural Network (ANN) was used to simulate the power losses properties of ZnO varistors which is an adaptive nonlinear dynamic system, and the results calculated by ANN simulating model were in good agreement with the tested ones.