Capacitive sensor for the measurement of transients in gas-insulated switchgears

A capacitive sensor has been developed for the measurements of very fast transient over-voltages (VFTO) in GIS. Step response measurement was performed on the sensor. It is shown from the test that the settling time is less than 20 ns and the response time is less than 2 ns, suitable to the IEC1321-1. The sensor has been calibrated by power frequency voltage, impulse voltage, the division ratio of the power frequency voltage is almost as the same as that of the impulse voltage, the maximum error was less than 1.3%. The sensor was mounted in a 126 KV GIS test setup to measure the transients produced by the air gap discharges. The measurement results demonstrated that the sensor is able to measure the transients with 10 ns rise-time successfully.