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침상 접지봉의 임펄스접지임피던스에 미치는 지중방전의 영향
유양우(Yang-Woo Yoo),조성철(Sung-Chul Cho),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2014 조명·전기설비학회논문지 Vol.28 No.5
Soil discharges near the ground rod play an important role to reduce the ground potential rise and the ground impedance and to help the fault current to spread into the earth. This paper presents the effects of soil discharges on the transient and conventional ground impedances when the lightning impulse voltage was applied to a ground rod with radial needles. The current-voltage (I-V)curves and transient ground impedance curves were calculated based on the measured current and potential traces. Soil discharge behaviors related to I-V curves and transient ground impedance curves were analyzed as a function of the magnitude of lightning impulse voltages. As a result, the soil discharges occurred near the ground electrode contribute to the reduction of conventional ground impedance and limits the ground potential rise effectively under lightning impulse voltages.
토양의 이온화영역에서 소규모 접지전극의 과도접지임피던스 특성 분석
유양우(Yang-Woo Yoo),엄주홍(Ju-Hong Eom),조성철(Sung-Chul Cho),이태형(Tae-Hyung Lee),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2009 조명·전기설비학회논문지 Vol.23 No.6
본 논문은 토양의 방전 영역에서 소규모 접지전극의 과도접지임피던스의 측정결과를 제시한다. 접지전극 주변에서 이온화 특성을 사실적으로 분석하기 위해서 세 가지 형상의 접지전극을 실외에 설치하고, 고전압 임펄스 발생기를 사용하여 시험전류를 인가하였다. 접지전극에서 대지로 흐르는 전류와 응답 전압을 분석한 결과, 접지전극 주변의 이온화는 높은 대지저항률의 토양에서 접지임피던스 감소에 기여하며 대지전위상승을 효과적으로 제한하는 것이 확인된다. 하지만 낮은 대지저항률의 토양에서는 이온화 임계전계강도가 작아서 전극 형상이 과도접지임피던스에 거의 영향을 주지 못한다. 그리고 전극형상에 따른 실험결과, 판전극보다 침부봉전극이 이온화 영역 전압범위내에서 과도접지임피던스 저감에 보다 효과적이다. This paper presents measurement results of transient impedance for small-sized ground electrodes in a discharge region of soil. For a realistic analysis of ionization characteristics near the ground electrode, three types of ground rod installed outdoors and high voltage impulse generator were used for injecting test current. From the analysis of response voltage and current flowing ground electrode to earth, it is verified that the ionization near the ground electrode contributes to reduction of ground impedance and limits the ground potential rise effectively in high resistivity soil. As a threshold electric field density for ionization is small in low resistivity soil, the shape of ground electrode rarely contributes to the transient impedance. And, from the experiment result with shape of ground electrode, the rod with needles is more effective to reduce the transient impedance than the plate electrode in the voltage range including with ionization regions of soil.
유양우(Yang-Woo Yoo) 한국조명·전기설비학회 2011 한국조명·전기설비학회 학술대회논문집 Vol.2011 No.11
In this paper, real-time electrical equipment monitoring system using smart-phone for preventing electrical equipment accident and improving maintenance efficiency is described. Electrical equipment monitoring system using smart-phone largely consisted with accessing security parts and electrical equipment condition monitoring and diagnostics parts. Adoption of this monitoring system will help for reducing electrical equipment accident such like distribution panel and increasing maintenance efficiency.
토중방전을 수반하는 접지봉의 임펄스응답에 대한 기초적 연구
유양우(Yang-Woo Yoo),조성철(Sung-Chul Cho),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2014 조명·전기설비학회논문지 Vol.28 No.4
This paper deals with the fundamental characteristics of transient and conventional ground impedances associated with soil discharges when the lightning impulse voltage was applied to a small-sized ground rod. The potential rise responses of the test ground rod to impulse currents were observed. The current-voltage (I-V)curves, transient and conventional ground impedance curves were examined.. To analyze the transient behaviors of ground rod attendant upon soil discharges, the impulse responses of ground rod were compared with those of non-inductive resistor. As a consequence, the potential rise and impedance of ground rod were reduced and the currents dispersed into the earth were increased due to soil discharges near the ground rod. Soil discharges are classified into two regimes; ionization and breakdown phenomena. The potential rise and impulse impedance of ground rod are significantly decreased by breakdown processes in soil.