Applicability of oscillating wave test system for on-site PD diagnosis of high voltage power capacitors

Most of the aged high-voltage (HV) power capacitors are the oil-immersed paper capacitors in Japan. Hence, it is necessary to establish an on-site partial-discharge (PD) diagnosis of the oil-immersed paper capacitors. The capacitance of the capacitors is very large, so it is difficult to apply HVAC to the capacitors. Therefore, it is difficult to perform the PD measurements of the capacitors. These difficulties may be overcome by an oscillating-wave test system (OWTS) that has the compatibility between high output and compactness. In this paper, to investigate the applicability of OWTS to PD diagnosis of the capacitors, PD measurements of the aged capacitor were attempted by OWTS. Furthermore, the various countermeasures against high charging current of capacitors in PD tests by high-frequency current transformer (HFCT) were investigated.