Development of Optical Voltage and Current Transformers for 72kV Three-Phase in one Enclosure Type Gas Insulated Switchgear

Abstract

We developed optical voltage and current transformers (PT and CT) for 72kV three-phase in one enclosure type Gas Insulated Switchgears (GIS). We used Bi₁₂GeO₂₀and flint glass as device material used in the optical PT and CT, respectively. We also designed an optical PT unit with a pin hole type grounded electrode and intermediate electrode in the pin hole and an optical CT located at the ground level with optical transmission by an optical fiber instead of free space light propagation. We assembled the optical PT and CT into GIS and conducted withstand voltage test, ratio error characteristic test, and other-phase influence test, obtaining good assessment results. Finally, we suggested that the developed optical PT and CT have a possibility of practical use.