An Ultrawideband Conical Monopole With Radome for Detection of Partial Discharges

Localized electric field strength in high-voltage (HV) equipment results in electrical discharges which radiate electromagnetic waves in ultrahigh frequency (UHF) range of 0.3-3 GHz. Due to the large antenna dimensions in UHF regime and lack of radome, existing UHF sensors have limited use in HV equipment for online partial discharge (PD) detection. In this work, we present the design and experimental verification of a UHF antenna with relatively small aperture and radome for PD detection. The proposed UHF sensor is a compact conical monopole with ground plane and protective radome. The monopole shape was optimized for broadband operation and directional radiation pattern using electromagnetic simulations. A cylindrical radome transparent to electromagnetic waves was designed without perturbing the radiation characteristics of the optimized UHF antenna. The 130 mm diameter fabricated sensor has directional radiation pattern, UHF bandwidth of 0.5 - 3 GHz and compact radome of 150 mm diameter. PD signals gathered for three defects in gas insulated test cells indicate better detection capability and sensitivity for the proposed UHF sensor than the reference sensor.The improved performance of the proposed sensor suggest that it could be used for PD detection in HV equipment such as gas insulated switch gear and transmission line.