Design and Realization of the on - Line Monitoring Device for the Partial Discharge of the High Voltage Switchgear

Insulation breakdown is one of the common faults in the operation of high voltage switchgear. The most effective way to prevent insulation breakdown is to detect the partial discharge(PD) phenomenon of high voltage switchgear in operation timely and accurately. The ultrasonic method and the UHF method are so expensive that are only suitable for regular inspection. To this end, this paper presents and designs an on-line monitoring device for PD of the switchgear cabinet based on the transient earth voltage and the spectrum analysis. This device uses the high-frequency current transformer and capacitance sensor where the three-phase electrostatic display is to obtain the pulse current when discharge occurs from the switchgear to the ground. After high-pass filtering, this device catches frequency signals with the help of FPGA and AD9236 which is a high-speed acquisition chip. Using the microprocessor, this design obtains the spectrogram of discharge pulse. With the help of the measurement of high-frequency signal in the spectrogram, this device determines whether PD occurs in the switchboard and the PD levels. Having tested, the device can qualitatively monitor the partial discharge condition of switchgear, and meet the requirements of PD's online monitoring. Because the on-line monitoring device for PD does not require expensive sensors, it's easy to promote the application.