Frequency Spectrum Properties and Propagation Features of Typical Partial Discharge in the GIS

Abstract: Partial discharge (PD) is a key index in the on-line monitoring of high voltage switchgears. At present, the ultra-high frequency (UHF) method is widely used to detect PD in the gas-insulated switchgear (GIS). A whole set of GIS system is adopted to build a test platform and investigate FS properties of UHF signals generated by typical defects and leaked from basin-type insulator in the GIS. Several sensors are used to measure UHF signals simultaneously; moreover, propagation attenuation features of UHF signal’s peak-to-peak value and accumulation energy in some typical GIS structures, such as basin-type insulator, L branch, disconnecting switch (DS), and current transformer (CT) are analyzed in details. It is found that PD triggered by floating metals has a wide spectrum of 400MHz-2GHz while PD triggered by metallic protrusion has a narrower spectrum of 600MHz-1GHz as well as 1.4-1.7GHz. Fast Disconnecting Switch (FDS) and CT have the most remarkable influence on PD signals with attenuation of 7dB. When a DS is open, its attenuation effect on accumulation energy is 5dB higher than that with DS being closed. The results can be used to optimize the main frequency band of PD detection, and hence to improve the sensitivity of UHF signals and the layout of sensors, and finally increase the monitoring inefficiency.

Key words: Partial discharge testing, frequency spectrum (FS) properties, UHF detection, GIS, propagation features, frequency band selection

    

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