Experimental Study of Critical Cascading Flashover on Insulator Assembly Using Model Arrangements (Part II) : The Influence of a Floating Electrode, Placed on a Porcelain Board, on the Formaiton of a Flashover Path

Abstract

This paper describes the phenomena of cascading flashovers in model arrangements for experimental analysis of critical cascading flashovers occuring in an insulator assembly used on high voltage transmission lines. The testing model used consisted of a pair of rod-rod electrodes, a potentially floating copper wire and a porcelain board. The applied lightning impulse voltage of positive or negative polarity was much higher than the breakdown voltage, when the flashover occurred for only a short time lag. The experimental results included flashover paths and pre-breakdown corona distributions, and cascading flashover rates. The flashover phenomena on the testing model clarified that the cascading flashover rate was related to the position of the porcelain board with the floating wire and that the corona from the floating wire was generated just before the corona from the rod electrode reached the floating wire. In the summary, the influence of the floating electrode on the formation of flashover paths discussed in comparison with previous reports. As a result of this series of experiments, it was clarified that a cascading flashover occurred only through coexistence with the porcelain surface and floating metal.