Design and Fabrication of 3-D Cube UHF Antenna for Partial Discharge Detection

Partial discharge (PD) is one of electrical phenomena which might occur in high voltage (HV) equipment and can be used for diagnosing the condition of equipment. PD emits electromagnetic wave that can be detected by antenna device. Many types of ultra-high frequency (UHF) antenna have been developed to achieve a better sensitivity and accuracy in certain bandwidth (300 MHz-3.0 GHz) for detecting the UHF component generated by PD. This paper presents a new concept design of a small, easy to fabricate, 3-D cube antenna made of copper sheet as main material. Three antenna prototypes are proposed which operate at three different dominant frequencies, 1.46GHz, 2.26GHz and 2.82GHz. Each antenna prototype was designed with a three-dimension finite difference time domain (FDTD) simulation software (CTC Co.; MAGNA TDM version 8.3). Measurements of frequency dependence of return loss of thus designed antenna prototype were made with a vector network analyzer (VNA). PD measurement in electrode system including artificial PD source was also conducted to evaluate the performance of the developed antennas. In consideration of high frequency PD component, the experiment was using artificial PD object; needle-plane electrode 2mm gap and rod-plane electrode 0.2mm gap with 1m distance from the antenna prototype. Electromagnetic wave (EM) intensity and frequency captured by the antenna prototype then compared. It was found that the antenna prototype detected average PD magnitude value ranged in the order of 1500pC for the object PD source. Measurement of antenna prototype directivity is also examined and obtained a good agreement with the simulation result.