Abstract—Ultra-high frequency (UHF) method is one of the main methods of detecting partial discharge (PD) in transformer. Common cases, the built-in sensor of the oil drain valve is used during the maintenance of the transformer, or the sensor is preset by the dielectric window at the side of the tank when the transformer out of the site. However, for the transported transformer, it is difficult to apply those ways. Aiming at the disadvantages of the installation method of the oil drain valve type and dielectric window type sensor, according to the characteristics of the transformer partial discharge UHF electromagnetic (EM) wave that can leak out of the tank gap, a UHF type sensor was designed for the detection of partial discharge at the gap of the transformer tank. First, based on the simplification of the internal structures of the transformer, the finite difference time domain method (FDTD) was used to build the transformer model, and the propagation characteristics of the electromagnetic wave signal excited by the partial discharge source inside the transformer leaking out of the external space through the gap was simulated, and the electrical field structure was further analyzed. Secondly, the deformable planar monopole antenna is designed according to the slot structure and internal electric field structure of the oil tank, and the geometric parameters of the antenna are optimized. Finally, the designed sensor is used to detect PD in the gap of FDTD model. The simulation results show that the UHF electromagnetic wave signal leaked through the gap of the transformer tank has a certain attenuation, and the sensor can effectively detect the partial discharge signal at the gap.

power transformer,partial discharge,fuel tank gap,UHF sensor