220kV combined optical voltage and current transformer

摘要

This paper presents a new optical transformer which can measure high voltage (up to 220kV) and large current (up to 3000A) simultaneously. The measurement of voltage is based on the Pockels effect. A novel structure is proposed to realize an optical voltage sensor which has better stability. The measured high voltage is directly applied on the optical voltage sensor without using any capacitive voltage divider. The measurement of current is based on the Faraday effect. A bulk glass closed-loop structure for optical current sensor is used. The optical voltage sensor is in the middle of the HV polymeric insulator which is full of SF_6 gas, and the optical current sensor is on the top of the same insulator. This transformer offers many advantages such as immunity of electromagnetic interference, no saturation, no oil inside, wide band range, excellent transient characteristics and light weight etc. The principles, structures and testing results of the combined optical voltage and current transformer are described in this article.