Application And Study On A Novel Combined Current And Voltage Transformer Which Can Be Used In GIS

Electronic transformers have many advantages compared with conventional iron-core type transformers, such as lightweight, good linearity and convenient interface with digital measuring and protection equipments etc. A novel combined current and voltage transformer, which can be used in 220kV GIS has been developed. The transformer consists of a current sensor, a voltage sensor and a digital converter. The current measurement is based on the principle of a Rogowski coil, and the voltage measurement is based on a capacitive voltage divider. The digital converter converts the signals come from the current sensor and the voltage sensor to digital values, which are transmitted to local control cubicles through an optical fiber. In order to improve temperature stability of the transformer, a digital integrator is used to reproduce the original current and voltage signals in the converter. A test equipment for electronic transformer has been developed to assess and prove the measuring accuracy of the transformer. The principle, structure and test results of the transformer are presented in this paper. Test results show that the current measuring accuracy of the transformer can reach class 0.2.