Nanosecond streak photography of discharge initiation on ice surfaces

Abstract

This paper presents an exploratory experimental study of discharge initiation on surface of ice. The phenomena underlying these processes are, as yet, poorly understood. To elucidate the initiation process in particular, ultra high-speed streak photography was used to observe and analyze the first visible discharges and a number of parameters were investigated. It could be shown that ambient temperature, conductivity of ice surface and the presence of imperfections on the ice surface influence not only the critical voltage for discharge initiation, but also the velocity of discharge development. Some parameters could be identified, which should be investigated further. The present paper is the first stage of a long-term research effort in this new field. This study should enable further experimental investigations and mathematical simulations to gain better understanding of ice surface discharges, specifically in the context of electrical insulation integrity of support insulators in power systems operating under severe atmospheric conditions. Index Terms -Ice surface, streak camera, visible discharge initiation, surface charge, breakdown voltage, outdoor insulators. LIST OF SYMBOLSU 50% breakdown voltage, V. 50 % s Standard deviation of the 50 % breakdown voltage. t Apparent time of insulator bridging, s. bridging Conductivity of the freezing water, Srcm. T Ambient air temperature, ЊC. a Location of the ice-free slot, measured from the high voltage electrode, m. d Distance between the electrodes, m. 1070-9878r r r r r04r r r r r$20.00 ᮊ 2004 IEEE 450

Insulator Leakage Distance Dimensioning in Areas of Winter Contamination using Cold-fog Test Results

“…Snow behaves more like cold fog with an exponent of n=-0.26. There are matching differences in the impulse flashover characteristics on humid and dry ice surfaces: Humid surfaces were found to have an exponent of n=-0.20 and dry surfaces have n=-0.31 [19].…”

Mechanisms of arc propagation over an ice surface /

“…Some work has been done on characterizing discharge over ice surfaces [19,25], but there is still no complete physical understanding of the mechanisms and nature of these discharges. Although some theories have been proposed to describe the mechanisms involved in the development of electric discharge along an ice-covered insulator surface [19,26,27], understanding of the related physical processes is still deficient.…”

“…Most of these studies were performed on small physical ice surface models under conditions, which were sometimes different from those observed on ice-covered insulators in the field [25,26]. Furthermore, these studies focused on the formation and propagation of the streamer only, in which there is no significant thermal ionization.…”

“…Previous researches [19,25,26] were conducted on small setups (a few centimeters) that are not representative of foil-scale insulators and in which thermal ionization does not play a significant part. Those investigations concentrated on the initiation and propagation of streamers.…”

Approche physique du développement de streamers positifs sur une surface de glace =

“…Dans de précédentes investigations effectuées à la CIGELE, quelques paramètres de décharges en présence de surface de glace ont été étudiés et comparés avec ceux obtenus dans l'air en présence de surfaces synthétiques tels le téflon (PTFE) [9,11,12,16].…”