Study on Fractal Butterfly Antenna Sensors Detecting Partial Discharge UHF Signal Propagating from GIS Placing Hole

Detecting the Ultra-High Frequency (UHF) electromagnetic wave has been acknowledged as an effective method in the measurement of varied kinds of partial discharges in Gas Insulated Switchgear (GIS). However, electromagnetic wave has been shielded completely owing to the steel flange around the insulator in recent years. Detecting the electromagnetic wave propagating from the placing hole in the steel flange becomes the only practicable method. The traditional sensors enter a bottleneck stage when they are used to detecting the electromagnetic wave propagating from the placing hole. The sensitivity declines a lot and output signal becomes weaker. At present, there are no relevant sensors, which are professionally applied in detecting UHF electromagnetic wave propagating from placing hole. By adopting the fractal technology, back cavity and loaded resistor, the UHF sensor of fractal butterfly antenna was developed based on the software of High Frequency Structure Simulator(HFSS). Equivalent height was tested in the platform of Giga hertz Transverse Electromagnetic(GTEM) chamber. Detection sensibility and validity was tested via an experimental platform of 220kV GIS. It is concluded that the fractal butterfly antenna sensor belongs to the linear polarized antenna. The available frequency range is concentrated in 0.8-2GHz. The average equivalent height of fractal butterfly antenna is twice more than the traditional sensors. Detecting sensitivity of partial discharge is lower than 20pC.