Partial Discharge Detection of insultors in GIS: Effectiveness and Limitation

Partial discharge (PD) is not only an important sign of insulation deterioration, but also an important means to detect insulation defects. However, recent operation experience shows that there may be some limitations for the conventional PD detection method, which will result in detection failure. In this paper, a high-sensitivity detection system was established, and the screening tests for the 1100 kV insulators were carried out. Under the PD test condition, the discharge level of good insulators was obtained. Additionally, the experiments of simulated defects and actual defects on the insulator surface were carried out. The results show that under the PD test condition, for the 1100 kV good insulators, the intrinsic PD level is smaller than 0.1 pC. For some micro defects, such as the polish and dirt contaminant on the insulator surface, they will not induce PDs, or even if they provoke PDs, the PDs are only approximately 0.1 pC and even much lower than 0.1 pC. The discharge level of defects such as micro metal particles and cracks on the insulator surface is generally smaller than 1 pC (lower than the conventional detection sensitivity), indicating that there is indeed detection limitation of the conventional detection method. This paper is of great interest for further understanding the intrinsic PD level of good insulators as well as the detection effectiveness of conventional PD detection methods.