Partial Discharge Measurement And Its High Frequency Characteristics In Cast Resin Transformer

Cast resin transformer (CRTr) adopting the solid insulation method is superior in flame resistance as compared with the transformer adopting other insulation method. In addition, since it can be made compact and lightweight, it is used in various industries. However, internal defects such as voids and delamination are likely to occur in the manufacturing process. Partial discharge (PD) generated by such defects causes dielectric breakdown and ultimately leads to equipment failure. So, early detection of defects by PD detection is desired. Therefore, in this research, to establish an optimal detection method of PD for CRTr is aimed. PD signal has components in various frequency bands, that depend on test system and equipment. To understand the frequency component of PD signal in advance makes it possible to distinguish it from noise and lead to highly sensitive PD detection. From the above, in this paper, the influence of test system and sample on frequency characteristics of PD current and electromagnetic wave (EMW) is studied for CRTr and artificial void sample. It was found that PD EMW dominantly has a frequency component depending on test system and sample as well as PD current in addition to the high frequency radiated from the defect. Furthermore, since it was found that PD signal dominantly has a component of the tens of MHz band dependent on CRTr itself, elucidation of the cause was addressed.