Research On The Simulation Analysis Of Characteristics Of Partial Discharge And The Evaluation Of Insulation In Switchgears

As manifested by statistics and practice, the events of partial discharge mainly contribute to insulation aging even fault in switchgears, therefore the detection about the events of partial discharge has become the main mean in the detection of partial discharge and evaluation of insulation in switchgears. Based on the understanding of the experimental characteristics and the physical process of partial discharge, the simulation model of partial discharge is established to make a thorough study about the mechanism, characteristics and development of partial discharge, which will conduce to the detection and diagnosis of partial discharge, and evaluation of insulation.Referring to existed research about partial discharge, the process of partial discharge in voids, which from the generation of initial electrons to the formation of avalanches and ultimately streamer discharge through impact ionization, was disserted in detail; according to the attenuation of charge produced during partial discharge in the void, the discharge delay time was calculated under different situations; electrical signals caused by partial discharges in external circuit were expressed by equations; and the relation between the temperature in voids and the characteristics of partial discharge was deduced; thereby the theory of partial discharge was established in this thesis.In view of the problems of the existed simulation model of partial discharge, the explanation of the rationality that simulating insulation material with capacitance was illustrated, and the simulation model of insulation material with single void was put forward, which lead up the additional capacitance that caused by induced charge during partial discharge, and the calculation of the characteristics of partial discharge related to the temperature and pressure in voids. Compared w simulation results that obtained from orginal model, ones produced by MATLAB can conform well to the theory of partial discharge, and simulate partial discharge effectively.The parameters and analysis tools used to represent the characteristics of partial discharge were defined, and the characteristics of partial discharge that under the condition of different amplitude and frequency of supply voltage, and different shape and dimension of voids in insulation material were mainly studied. The characteristics of partial discharge in insulation material in different degradation degree, including the phase of multiple insulation defects existing, the phase of entire deteriorating, the phase of electrical trees appearing, and the phase of insulation breakdown, were simulated, analysed and summarized to be used to the evaluation of insulation.The simulation model of partial discharge, put forward in this thesis, can be applied to the research of the detection of partial discharge and evaluation of insulation in power facilities such as switchgears and power cables. And the related research results obtained in this thesis will provide some reference for following research.