A New Method of On-line Medium Frequency Partial Discharge Monitoring for Power Transformer Based on Double Sensors Directionally Coupling Signal

This paper introduces an on-line monitoring method for power transformers, using double magnetic core current sensors directionally coupling signal to limit interference using a polarity discrimination method. The transient models of transformer windings are set up, and considering the characteristic of the current sensors and transformer windings, the testing frequency band is chosen from 1MHz to3MHz. The reliability of polarity discrimination method to limit interference is verified over this frequency range.