Study On Electromagnetic Radiation Of Typical Partial Discharge

Nowadays,UHF electromagnetic radiation monitoring and diagnosis technology is widely used in the bureau monitoring of high voltage devices such as GIS.However,it has a few shortcomings in distinguishing the degree and type of discharging.Therefore,this paper focuses on investigating three typical discharges including corona discharge,surface charge and suspended discharge.Measurement,analysis and calculation of their formation and features are established to improve the ability of recognizing discharging degree.Firstly,a mini UHF sensor for discharge electromagnetic radiation detection is manufactured.Under the condition of realizing fundamental functions,the size of the mini UHF is optimized from 182*182mm2 to 32*32mm2,which is also suitable for actual detection system.Since the discharging electromagnetic radiation comes from fast changing discharging current,features of discharging currents and electromagnetic radiation of three typical discharges is studied.For the corona discharge,there exists segmentation phenomenon in positive polarity current rising edge during long brush discharge stage.For the surface discharge,it happens in voltage rising edge and the phase zero crossing point.For the suspended discharge,it will appears partial discharge in low voltage,which will cause subsequent corona.According to current waveforms,the current discharging electromagnetic radiation during long brush stage also exist segmentation phenomenon and its spectrum is quite low;the spectrum of surface discharge gathers around 125MHz;the spectrum of suspended discharge is wider,whose amplitude is quite near around 25 MHz,75MHz and 125 MHz.Based on XFDTD,the electromagnetic radiation of three discharge model is simulated.Partial previous mentioned experimental phenomenon is verified.Meanwhile,electromagnetic radiation waveforms produced by current pulse is estimated by analytical equations.In the research of AC corona discharge,it is observed that there are two completely different basic types in the process of positive continuous corona discharge: first corona and subsequent corona.The first-corona waveform is almost unchanged under different voltage,different gap distances and different tip types,because there is no background charge of the previous discharge.The subsequent-corona waveform differs greatly from the first-corona waveform due to the influence of the background residual charge of the first corona,and it has a great change in the non-pre-breakdown stage and pre-breakdown stage,leading to the double peak fusion phenomenon which has an important impact on the characteristics of electromagnetic radiation signals.This paper proposed died-streamer model to explain the double peak fusion phenomenon.The above research has a good guidance to the relevant identification system which monitors partial discharge and similar insulation failure by electromagnetic radiation.