• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.552-556
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• 2002

The microstructure and electrical characteristics of A~C's ZnO varistors fabricated according to variable sintering condition, which sintering temperature is $1130^{\circ}C$ and speeds of pusher are A: 2mm/min, B: 4mm/min, C: 6mm/min, respectively, were investigated. In the microstructure, A~C's ZnO varist-ors fabricated variable sintering condition was consisted of ZnO grain(ZnO), spinel phase$(Zn_{2.33}Sb_{0.67}O_4)$ Bi-rich $phase(Bi_{2}O_{3})$, wholly. Varistor voltage of A~C's ZnO varistors sintered at $1130^{\circ}C$ increased in order A < B < C's ZnO varistors. C's ZnO varistor exhibited good characteristics that nonlinear exponent is 31.70. Leakage current of A~C's ZnO varistors exhibited below 2mA at rated voltage. Lightning impulse residual voltage of A's ZnO varistor suited standard characteristics, which is 3.85kV at 2.5kA, 4.4kV at 5kA and 5.16kV at 10kA. After multi lightning impulse residual voltage test of A's ZnO varistor exhibited good discharge characteristics which ZnO varistor reveals no evidence of puncture, flashover, cracking in visual examination. After high current impulse test of A's ZnO varistor exhibited good discharge characteristics, which variation rate of residual voltage is 0.4% before and after test, and revealed no evidence.

• 조명전기설비학회논문지
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• 제28권9호
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• pp.52-59
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• 2014

The aims of this paper are to characterize the transient overvoltages(TOVs) and to evaluate the risk occurring at 22.9kV consumer's substation. The measurements of lightning- and switching-caused TOVs were made during Mar. 2013 and Feb. 2014. As a consequence, 47 events of TOVs were recorded and 4 of them were higher than the input voltage envelope(IVE) of the information technology industry council(ITI) curve. The measured TOVs are characterized by longer front times and longer durations compared to the $1.2/50{\mu}s$ standard impulse voltage waveform, and some of them represent bipolar waves with lower oscillation frequencies. It suggests that the test of non-standard impulse voltage waveforms is needed for effective risk assessments of power apparatus. Lightning- and switching-caused TOVs exceeding IVE of ITI curve are induced at the secondary of 22.9kV potential transformer(PT). We may, therefore, conclude that the surge protection devices should be applied at the secondary of PT and the surge absorbers should be installed at the primary of VCB or PT. The results presented in this paper could be useful to design the reasonable insulation coordination for 22.9kV consumer's substation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.165-166
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• 2007

In these days $SF_6$ mixtures and alternative gas have been studied because of global warming and liquefying at low temperature and high pressure. At present work the breakdown characteristics of $SF_6/CF_4$ mixture in non-uniform field was performed. The experiments were carried out under positive and negative standard lightning impulse (SLT) voltages. The point-plane electrode was used with 3 mm gap distance in the test chamber. The $SF_6/CF_4$ mixture which contain 20% of $SF_6$ was compared with pure $SF_6$ and $CF_4$ gas. Experimental gas pressure ranged from 0.1 to 0.4 MPa. The breakdown voltage under negative SLI is higher than the breakdown voltage under positive voltage. And the breakdown voltage of $SF_6$ 20%, $CF_4$ 80% mixture is similar to that of pure $SF_6$.

• 조명전기설비학회논문지
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• 제16권3호
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• pp.93-100
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• 2002

본 논문에서는 피뢰설비에 대한 국내 규격의 재정립을 위해 관련된 기술을 검증할 목적으로 낙뢰로부터의 건축물 보호에 대한 규정과 기술상의 지침 등을 검토하였고, 국내의 피뢰설비에 관한 규격의 몇 가지 문제점을 해결하기 위란 연구를 수행하였다. 기존의 피뢰침에 대하여 피임펄스시험을 수행한 결과, 비교적 낮은 임펄스 전압에서 피뢰침 수뢰부의 절연체 표면에서 섬락을 일으켰고, 피격전류의 대부분은 피뢰침 지지용 금속판을 통하여 홀렀다. 따라서 피뢰침 지지대 부근에서의 전위경도는 매우 높게 상승하게 되어 피뢰설비로서의 기능을 못하게된다. 피뢰침 절연물의 섬락은 초소형 전자기기의 오동작을 비롯하여 감전이나 전기설비의 파손과 같은 막대한 경제적 손실을 가져오게 된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.227-228
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• 2007

Although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/CF_4$ mixtures. At present study the breakdown characteristics of SFJCF4 mixtures in uniform field was performed. The experiments were carried out under AC and standard lightning impulse (SLI) voltages. The sphere-sphere electrode whose gap distance was 1 mm was used in a test chamber. $SF_6/CF_4$ mixtures contained from 0 to 100% $SF_6$ and the experimental gas pressure ranged from 0.1 to 0.4 MPa. The results show that addition of $SF_6$ to $CF_4$ increase AC and SLI breakdown voltages. Under AC voltages the breakdown voltages of each mixture were linearly increased according to the quantity of $SF_6$. However under SLI voltages the breakdown voltages of each mixture were similar.

• 한국철도학회논문집
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• 제9권4호
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• pp.357-361
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• 2006

This paper dealt with the performance evaluation and the diagnostic techniques of lightning arresters for DC electric traction vehicle. Field Measurements on the protective operation of lightning arresters against surge currents were carried out on running vehicles to acquire the data necessary for the diagnosis. The frequency and the magnitude of surge events were analyzed. Surge currents of $1\sim3$ times were recorded in one running service route and their magnitudes were ranges of $150A\sim2kA$. Also, an acceleration experiment on a lightning arrester by the standard lightning impulse current of 8/20 us and 5 kA was performed to know the aging characteristics. After the surge current application of 3,000 times, the reference voltage decreased by 4.5 %, and the leakage current was below 10 uA at the continuous operating voltage and about 50 uA at the rated voltage. From the experimental results, we propose a decision level of leakage current for the arrester used in this paper and designed an arrester tester which analyzes arrester condition by the magnitude of leakage current.

• 조명전기설비학회논문지
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• 제22권2호
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• pp.128-133
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• 2008

이 논문은 반구형 수조에 설치되어 있는 침전극과 구형전극에 표준뇌임펄스전압을 인가하였을 때 나타나는 수중 방전현상과 절연파괴특성을 나타낸다. 이 논문의 목적은 뇌서지에 대한 과도접지임피던스와 관련된 기본적인 특성을 파악하는데 있다. 인가전압의 극성과 물의 저항률에 따른 방전광을 촬영하였고 절연파괴전압의 의존성을 측정하였다. 침전극과 구형전극의 끝단에서 스트리머코로나가 발생하였고 접지된 수조를 향하여 단계적으로 진전하였다. 저항률에 따른 절연파괴전압은 V자 형태를 나타내며, 구형전극의 절연파괴전압-시간곡선이침전극보다 높게 나타났다.

• 한국전기전자재료학회논문지
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• 제15권2호
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• pp.190-197
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• 2002

In this thesis, ZnO varistors with various formulation, such as A∼E, were fabricated according to ceramic fabrication method. The microstructure, electrical properties, and surge characteristics of ZnO varistors were investigated according to ZnO varistors with various formulation. In the microstructure, A∼E\`s ZnO varistor ceramics sintered at 1130$\^{C}$ was consisted of ZnO grain(ZnO), spinel phase (Zn$\_$2.33/Sb$\_$0.67/O$\_$4/), Bi-rich phase(Bi$_2$O$_3$) and intergranuler phase, wholly. Lightning impulse residual voltage of A, B, C and E\`s ZnO varistors suited standard characteristics, below 12kV at current of 5kA. On the contrary, D\`s ZnO varistor exhibited high residual voltage as high reference voltage. In the accelerated aging test, leakage current and watt loss of B, C and D\`s ZnO varistors increases abruptly with stress time under the first a.c. stress(115$\^{C}$/3.213kV/300h). Consequently, C varistor exhibited a thermal run away. On the contrary, leakage current and watt loss of A and C\`s ZnO varistors which show low initial leakage current exhibited constant characteristics. After high current impulse test, A\`s ZnO varistor has broken the side of varistor but impulse current flowed. On the contrary, E\`s ZnO Varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After long duration impulse current test, E\`s ZnO varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After high current impulse test and long duration impulse current test, E\`s ZnO varistor exhibited very good characteristics which variation rate of residual voltage is 1.4% before and after test.

• 한국전기전자재료학회논문지
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• 제17권6호
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• pp.683-689
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• 2004

The microstructure and electrical characteristics of A ∼ C's ZnO varistors fabricated according to variable sintering condition, which sintering temperature was 1130 $^{\circ}C$ and speeds of pusher were A: 2 mm/min, B: 4 mm/min, C: 6 mm/min, respectively, were investigated. The experimental results obtained from this study were summarized as follows: The sintering density of A ∼C's ZnO varistors sintered at 1130 $^{\circ}C$ were decreased by sintering keep time to shorten, such as A: 9hour, B: 4.5hour and C: 3hour. A's ZnO varistor exhibited good densification nearly 98 % of theory density. In the microstructure, A∼C's ZnO varistors fabricated variable sintering condition was consisted of ZnO grain(ZnO), spinel phase(Z $n_{2.33}$S $b_{0.67}$ $O_4$), Bi-rich phasc(B $i_2$ $O_3$), wholly. Varistor voltage of A∼C's ZnO varistors sintered at 1130 $^{\circ}C$ increased in order A