Partial Discharge Detection of Cast Resin Transformers Using High-frequency Equivalent Circuit and Application to Diagnostic Technology

We have proposed a method for determining the dominant frequency of a mold resin transformer (CRTr) by deriving a high-frequency equivalent circuit from impedance frequency characteristics measurements and calculating the partial discharge (PD) detection waveform. In this paper, a new high-frequency equivalent circuit model is proposed based on the frequency characteristics of the impedance in 6.6kV voltage transformer (VT), taking into account the internal winding structure. It was shown that the dominant frequency of the PD current analyzed using the equivalent circuit generally agreed with the actual measurement. In addition, an inductive test was conducted for the 6.6kV-VT by applying voltage to the high voltage terminals. An attempt was made to identify the dominant frequency components of the PD current detected by high frequency CTs installed in the ground wire.