Experimental Analysis on Partial Discharge Location in Power Transformers Using UWB RF Method

Ultra-wideband(UWB) radio frequency(RF) partial discharge(PD) location technique is a new method for PD source location on power transformers,which is based on multi-antenna PD detection and Huygens-Fresnel principle.In this paper,a novel sensor with 2~8 GHz bandwidth for UWB RF detection was designed.By optimizing the constitution and parameters of the antenna,the average measured rise time of the coupling output waveform can be up to 150 pico-seconds(ps),while its single oscillation time duration reaches 200 ps or so,therefore the time difference of arrival(TDOA) resolution can be improved within the scope of 200 ps.A new location algorithm named the Space-Grid-Search algorithm was proposed which could greatly eliminate the divergent effect of analytical method.Two typical artificial PD models were applied to a real 220 kV transformer.Then experiments were carried out for PD location on the transformer using UWB RF technique.For preference PD sources,the location results indicate that the average least error is 30 cm when the RF electromagnetic wave speed is set as 19.8 centimeters per nanosecond or 19.9 centimeters per nanosecond,sensitivity of the detection system is not less than 100 pC.