The Influence of Gap Length and Tip Radius on Breakdown of Electrical Insulating Oil

전기절연유의 절연파괴에 미치는 전극간격 및 곡률반경의 영향

  • Kang, Seong-Hwa (Department of Industrial Safety Engineering, Chungcheong College) ;
  • Chae, Hong-In (Department of Radiology, Juseong College) ;
  • Lee, Jong-Pil (Department of Electrical Engineering, Kwangwoon University) ;
  • Lim, Kee-Joe (Department of Electrical Engineering, Chungbuk National University)
  • Published : 2004.03.01


In this paper, we investigated the influence of gap length and tip radius on breakdown of mineral based insulation oil. Applied voltages were DC and AC voltage. Electrode system was needle-plane structure. The tip radius of needle electrode was 5, 10, 20 and 25${\mu}m$, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. Electric breakdown strength at tip was calculated using Mason's equation contained geometric figure. As gap length increased, breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by the phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage, breakdown strength was higher when polarity of needle was negative than positive. It is because of the space charge effect in accordance with the influence of liquid motion.


electrical insulating oil;breakdown strength;gap length


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