Research on High-Frequency Current and Electromagnetic Radiation Characteristics During the Switching Process of Tap Changer

During the switching process of vacuum on-load tap changer, high frequency oscillation current is generated in the circuit due to the opening and closing of contacts, and the electromagnetic wave generated can be used to diagnose the status of tap changer. In order to understand the mechanism of high-frequency current and electromagnetic radiation in the process of tap changer switching, the equivalent circuit model of contact opening and closing is firstly established in this paper, and the corresponding relationship between circuit capacitance and inductance parameters and contact size and circuit lead length is analyzed; Then a simulation test platform for tap changer switching is built. The influence of contact opening and closing speed and opening and closing phase on high-frequency current and electromagnetic radiation characteristics cannot be studied experimentally. A method for monitoring arcing time based on electromagnetic radiation is proposed. The research conclusion is of great significance to the state evaluation method of vacuum on-load tap changer.

I. Introduction

According to the CIGRE A2.37 working group's statistics on transformer failure data worldwide, about 30% of transformer failures are caused by tap switch faults [1]. According to the statistics of accidents and defects of transformers with 110kV and above voltage levels, the on-load tap switch causes 27.8% of the accidents.