A Multi-Evidence Fusion Based Integrated Method for Health Assessment of Medium Voltage Switchgears in Power Grid

Switchgear is a key equipment in the power grid and its health status has a critical impact on the overall reliability of the grid. While several health and condition assessment methods have been developed for transformers or cables, they cannot be directly applied to switchgear because switchgear is a more complex apparatus comprising various movable and fixed parts, which consists of multiple subsystems of electrical, mechanical, and insulation. In this paper, an integrated health assessment method for medium voltage switchgear is proposed based on Dempster-Shafer (D-S) multi-evidence fusion. The principle is to combine the condition and performance indicators of each switchgear subsystem into an integrated Health Index (HI). Firstly, a weighted-sum method is used to establish the independent mapping relation from subsystem diagnostic parameters to their respective subsystem HIs. Subsequently, the HIs of separate subsystems are incorporated into the same sample space under the D-S method framework and then combined into an integrated HI which can comprehensively evaluate the health status of switchgear. Case studies on a 12kV and a 35kV switchgear show a 0.964 health estimation confidence level of the integrated HI, which is a 20% performance improvement compared to separate HIs.