Utilizing Ratio Frequency Signal in Online Monitoring on High Voltage Vacuum Cubicle Switchboard

The vacuum degree of vacuum interrupter, the isolation contact and the surface insulation condition, when in bad status, are all possible causes of serious insulation or current carry failures to high voltage vacuum cubicle switchboard. A large series of experiments have been executed in this paper to verify the feasibility of using Ratio Frequency (RF) signal emitted by the partial discharge under those situations to online monitor the condition of high voltage vacuum cabinet. Firstly, A floating electrode gap was adopted and its discharge characteristic under different vacuum degree (6.7times10^-3~1times10⁵Pa) has been studied. The experiment results indicated that when vacuum degree descend to some extent, partial discharge will occur in the gap. Furthermore, the start voltage and the characteristics of the discharge have direct relations to vacuum degree. The discharging or not of such a gap fixed in the vacuum interrupter can indicate whether the vacuum degree is in normal range. Secondly, a series of experiments on bad contact and surface insulation have been carried out, and it has been proved by the experiments that the intensity of the RF signal (above 10 mV) can show the development and situation of the isolation contact and surface insulation failure. While high gain like 60 dB was needed to the antenna. Since the intensity of the signal acquired was strongly affected by the position of the sensor and the case of shielding, locating the failure and identifying the disturbance from outside of the cubicle switchboard can be realized.