Surface flashover patterns of GIS basin insulator under impulse voltage

Basin insulator is an important component of SF6 gas insulated switchgear (GIS), and its fault is also one of the major causes of GIS equipment failure. Due to the large capacity of high voltage power system, the faulty basin insulators are generally burned severely by the high energy arc, so the fault diagnosis is very difficult. In this paper, the surface flashover pictures of several full scaled GIS basin insulators under impulse voltage are collected, and the morphology features of flashover traces initiating from different positions are summarized. As a result, the surface flashover patterns are divided into three types: 1) surface of shielding electrode initiated flashover, 2) triple junction initiated flashover and 3) surface of insulator initiated flashover. The inception and development process of flashover are also summarized. Besides, the diagnosis method of discharge inception position is proposed. Firstly, check the ablation points at high voltage terminal. If there is a ablation point on the surface of shielding electrode, the flashover initiates from there. If there is only ablation point at the triple junction, the inception position depends on the flashover trace morphology: when the flashover trace disperses in a single direction towards grounding electrode or high voltage electrode, the flashover initiates from the opposite triple junction; when the flashover trace disperses towards both electrodes, the flashover initiates from the insulator surface. The dispersion direction could be directly distinguished from the black carbonized dendritic traces, or from the white dendritic traces with the auxiliary methods. The conclusions could help the substation maintenance staff do the root cause analysis of the surface flashover, and assist the researchers in the structural optimization design of basin insulator.

Automated summary

Basin insulator is a crucial component in SF6 gas insulated switchgear, and its fault can lead to equipment failure. This study analyzes surface flashover patterns under impulse voltage, categorizing them into three types based on initiation points. The findings provide insights for diagnosing and preventing surface flashovers in GIS equipment.