Study On Discharge Detection Of Composite Insulator Based On Ultraviolet Pulse Method

The number and scale of composite insulators are increasing day by day.The insulation performance of composite insulators plays an important role in the safe and reliable operation of transmission lines.Therefore,it is necessary to detect and evaluate the operation status of composite insulators timely and accurately.Ultraviolet pulse method is the method selected in this paper to detect the pollution and operation status of composite insulators.Compared with other methods,it has the advantages of fast response,good linearity,low cost and early warning.And its equipment is portable and easy to carry,so it has broad application prospects.In this paper,based on the ultraviolet pulse method,the influence of pollution parameters on discharge characteristics of composite insulators under laboratory and artificial contamination conditions is studied,and an evaluation method combining time domain and frequency domain is proposed to evaluate the contamination status of composite insulator samples.Firstly,a discharge ultraviolet pulse detection system is built based on the principle of ultraviolet pulse.On this basis,The effects of contamination degree and contamination distribution on discharge ultraviolet pulse and flashover voltage of composite insulator test sample under AC/DC conditions were studied.Then,ultraviolet pulse signals collected under long time constant pressure test are evaluated in time domain and frequency domain.Two parameters,relative fouling discharge ratio and change rate of pollution discharge,are defined in time domain to evaluate the contamination status of composite insulators in a short period of time.The AR model method is used in frequency domain analysis.Select eigenvalues of power spectrum curve as characterization of contamination state reflected by long-term discharge ultraviolet pulse signals of composite insulators with different contamination parameters.Based on this,the pollution status of composite insulators is evaluated by rule and line in time domain and frequency domain.The experimental results show that the higher the contamination degree of composite insulator test sample,the greater the number of ultraviolet pulses under the same voltage,and the lower the flashover voltage under AC/DC conditions.When the polluted layer of composite insulator test sample has dry band,the number of ultraviolet pulses is larger and flashover is more likely to occur.Under AC/DC conditions,the location of the dry band shows completely different influence laws.Under AC conditions,the number of ultraviolet pulses and flashover voltage of high-voltage and low-voltage dry-band samples are approximately the same,and the number of ultraviolet pulses is the largest and the flashover voltage is the lowest in the middle dry-band samples.Under DC condition,the number of ultraviolet pulses in the low-voltage side dry band sample is the largest,the middle dry band sample takes the second place,and the high-voltage side dry band sample is the smallest one.The number of ultraviolet pulses of the middle single dry band sample is larger and the flashover voltage is lower comparing with the middle double dry band sample under the same voltage.Under different contamination degree and contamination distribution,the number of ultraviolet pulses and flashover voltage have high consistency,and it is proved that the ultraviolet pulse method has high accuracy in detecting the contamination state of composite insulators.Aiming at the collected ultraviolet pulse signal,a method for evaluating the contamination status of composite insulators based on time-frequency domain is proposed.According to the specific situation,feature parameters are extracted to evaluate the signal.After testing,the method can accurately reflect the pollution status and operation of composite insulators with different pollution parameters.Under laboratory conditions,this is a more practical and accurate evaluation method,which has a certain practical significance.