Development of Combined Instrument Transformer for Gas-Insulated Switchgears

Abstract

Accurate measurement of current and voltage information is essential to the safe reliable operation of railway substations. This paper dealt with a combined instrument transformer (CIT) built in a spacer for the purpose of miniaturization and eco-friendliness of a GIS, rated 72.5 kV and 2,000 A. A D-dot sensor and a Rogowski current sensor were applied to voltage and current measurement, respectively, to secure the insulation of the CIT in high-voltage and high-current conditions. As a result of an evaluation based on IEC 60044-7 and IEC 60044-8, the performance of the prototype CIT was found to sufficiently satisfy Class 0.5. When the CIT proposed in this paper was applied to a GIS of rated 72.5 kV, it was possible to reduce the size by 33% in length, 11% in height and 90% in weight per bay of the GIS compared to conventional iron-core transformers. In addition, since the amount of SF6 will be reduced by 15% in terms of volume, it is expected that this method can be used for the digitization, miniaturization and eco-friendliness of railway substations.