Corona Discharge Characteristics and Free Gas Generation Law in Insulating Oil

The gas in the transformer Buchholz relay was caused by the faults operating inside the transformer such as electrical and thermal faults. In order to further use the gas accumulated in the Buchholz relay to determine the fault type in the transformer, this paper conducts lots of experiments based on the corona discharge model in oil, studies the pulse signal change characteristic of the corona discharge in the oil, and analyzes the change characteristic of free gas generated during the development process of the discharge. The experimental results show that the corona discharge type fault in the oil takes 4 hour and 40 minutes to develop to breakdown under a constant voltage of 20kV. There is no free gas generated during most of the experiment process, and it will only appear when the discharge is defined as disruptive discharge. Then a large amount of gas is produced and part of it becomes free gas, which combustible gas component is mainly H2, C2H2, CH4 and CO. At that time, the pulse repetition frequency reaches the magnitude of 0.4C/s, which is a serious fault. This data can be used as an improvement basis for the existing gas protection.