Design and Validation of Automatic Switching Board for Open Circuit Voltage of Secondary Multi-Tap Current Transformer

Aiming at the high-voltage operation risk and inefficiency of manual switching in the open circuit voltage test of the secondary multi-tap winding of current transformer (CT), this paper proposes an intelligent switching system design scheme based on high-voltage reed relay. Based on the design of a highvoltage reed relay and microcontroller STC8H1K08 as the control core of the automated switching board, integrated RS485 optocoupler isolation communication, multi-stage power filtering and protection and ‘first disconnect and then close’ interlocking mechanism, to achieve 4.5 kV high-voltage environment, the tap automatic switching. Comparison of engineering applications shows that, for a variety of commonly used secondary multi-tap current transformers, in the 4.5 kV open circuit voltage test, the maximum leakage current is less than $0.8 \mu \mathrm{~A}$, the switching response time is less than 10 ms, the consistency error is less than $0.3 \%$, which significantly reduces the risk of manual operation, reduces the testing and inspection time, and improves the testing safety and data reliability. It provides an effective solution for automated testing of electrical equipment in high-voltage environment.