Partial discharge detection on cast resin power transformer

Partial discharge test is an efficient technique for the detection of early failure of high voltage apparatus. Depend on application, acoustic, optical and electrical methods may be utilized. For electrical detection, UHF method is widely used to PD measurements. With regard to the noise issue, it is the more sensitive than other methods. However, the UHF antenna often install at the specific location near the device under test (DUT). It is difficult to detect the partial discharge everywhere with same sensitivity. Also, the lower frequency PD signal such as high frequency (HF: 0.3-30 MHz) is not easy to measure using UHF antenna. In this study, we design wide bandwidth coils to detect radiating frequency (RF) from partial discharge. Three identical RF coils with equal turns are installed near the surfaces of the cast resin power transformer. It is found the partial discharge occur at the peaks and valleys of 60 Hz sine wave. From the occurrence of the partial discharge induced on the coils and the sequence of R-S-T phase voltage, the location of the partial discharge can be identified.