Normal test items for SF6 current transformers are insufficient for diagnosing internal discharge fault in this kind of transformers.This paper analyzes the causes of discharge fault in SF6 current transformers

and introduces two alive detection methods of discharge and their principles.Taking a discharge fault in a SF6 current transformer for example

the features of the ultrasonic partial discharge detection method and the SF6 gas component analysis method are analyzed.The result shows that the former method can be used for preliminary determination of discharge fault through contrasting the discharge waveforms of normal phase and fault phase

and the latter one can be employed to determine the degree of discharge in the transformer according to diagnostic gas contents.