Experimental Study On Partial Discharge Location In A 220kV Power Transformer Based On UWB RF Method

This paper focuses on partial discharge (PD) location in a 220kV power transformer by using Ultra Wide Band Radio Frequency (UWB RF) technology. Firstly, a winding structure model is built and the Finite-Difference Time-Domain method is used to simulate the propagation process of electromagnetic wave passing through the winding model. The simulation result shows that the winding will cause electromagnetic wave attenuation and time-delay, which is directly related to the winding structure. Take 220kV transformer winding for example, the attenuation level of the passing through electromagnetic wave is up to 17-26dB. So, a low-noise and wide-band amplifier is needed in on-site detection. Secondly, a discharge model is put forward to meet the demand of electrical feature and mechanical structure of the winding. On-site experiments indicate that the model can discharge steady and has a strong ability to radiate RF signals, the apparent charge of this model is within 400-1000 picocoulombs. At last, experimental study of PD location based on UWB RF method is carried out on a true 220kV power transformer. A set of UWB RF Location detection system is set up and discharge models are placed to typical position inside the windings. Field experiments indicate that the UWB RF location method can be applied to detect and locate the PD inside transformer winding. Related calculation results of space-lattice-search arithmetic show that most of the average location errors are less than 30 centimeters and some of the optimal location errors are about 10 centimeters. Meanwhile, detecting array using muti-sensors can increase detection sensitivity effectively.