Abstract
The fiber optic current transformer (FOCT) is affected by complex environment in actual operation which will lead performance deteriorate or even malfunction. This paper introduces the application status and common fault modes of FOCT, and a fault diagnosis algorithm of FOCT based on Wavelet-Allan variance is presented. Wavelet transform is used to identify the jump signal for the mutation fault diagnosis, and Allan variance analysis is used to analyze the noise distribution for the gradual fault diagnosis. By combining the two methods above, the condition monitoring and fault diagnosis of FOCT can be realized without changing the structure of the original transformer or adding additional detection equipment. This method is proved to be effective and accurate by diagnosing faults from FOCTs in substation.