Studies on Location Technique of Corona and Measurement of Space Charge in Transformer Oil

Abstract

An investigation has been made in order to develop the location technique of corona discharge in insulating oil, on behalf of the development of the UHV transformer. This paper describes the principle of analysing the corona location by making use of electrostatic probes. The corona produces a space charge in the oil, and induces charges on the probes electrostatically. Thus, the location as well as the space charge quantity of the corona can be analyzed, based on the induced charges of the probes. For this investigation, a needle-plane electrode and four probes were arranged in the oil, and a lightning impulse voltage was applied to the gap. Then, the corona produced in the gap was investigated by measuring the corona current and the induced charges on the probes, and then taking photographs of the corona. From these experiments, it was proved that this technique was quite useful for analyzing the location of the corona.