An External Fast Transient Overvoltage Sensor of GIL Based on Capacitive Divider

Discharge faults in the gas-insulated transmission lines (GIL) induce fast transient overvoltages. The voltage traveling waves generated by the discharge faults are characterized by their high amplitudes, short rise times, and high frequencies. Traditionally, sensors installed inside the GIL enclosure are used to measure the transient overvoltage signals. However, it is difficult to be applied to the substations under operation. In order to measure transient overvoltage safely and conveniently, this paper proposed a sensing method based on capacitive divider which is outside the GIL enclosure. The high-voltage arm capacitor is composed of stray capacitance between the GIL lead-out line and the electrode plate. And the low-voltage arm of the sensor is chip capacitors. Calibration and field tests proved that the sensor has a broad bandwidth response and can accurately measure the overvoltages caused by GIL discharge failures. The external overvoltage sensor provided a new solution for GIL discharge fault monitoring in the GIL.