Measurement Of The Characteristics Of Partial Discharges In Gas Insulated Substations By UHF Detecting Technique

An experimental model is performed in Lab to find the ultra-high frequency (UHF) features of the partial discharges (PDs) signals in Gas Insulated Substations (GIS).A UHF sensor is designed and fabricated, which mostly consists of antenna, UHF amplifier, high pass filter, and broadband wave detector. Experiments show that the UHF sensor can effectively avoid the effect from corona discharges in air, and can conveniently detect PD signals in GIS.A GIS PD measuring system is established, including a conventional PD measurement system, UHF detecting system and a PD spectrum system. We can obtain PD signal characters by this system, such as UHF transient signal waveforms, UHF demodulating signal waveforms, the PD phase angle in AC, PD spectrum, and discharge quantities.The thesis focuses on some typical patterns of PD in GIS in the ultra-high frequency features. The patterns include the protrusion on the high voltage conductor, high voltage conductor's and grounding conductor's bad contacts, free metal particles, fixed metal particles, single metal particle on the insulation spacers and free metal particles on the tube surface in the GIS. The test results show that different patterns of PD correspond to different demodulating signal waveforms, the PD phase angle in AC, and spectrum characteristics. Therefore the PD patterns can be recognized by the UHF characters of different PD signals in GIS.