Test Research On Close Erosion Characteristics Of 252KV SF₆ Circuit Breakers

Closing inrush current of capacitor-bank switch in UHV system in our country is about 9.3kA-10kA and the frequency is 200Hz-400Hz.It will produce serious closing erosion which makes arcing contacts inadequate to erosion obviously. In the UHV system, it needs long-life capacitor bank breaker which is at least more than 3,000 times in order to meet the requirement of reactive power compensation. Electrical life of existing specialized circuit breakers is only one thousand times which is a serious problem.Aimed at the problem of insufficient electrical life of circuit breaker, the related theoretical analysis and experimental research have been carried on in this thesis in order to provide a reliable basis for improving structure design of arcing contacts.Firstly, closing erosion mechanism and characteristics have been studied in this thesis it is proposed that unlike breaking erosion, closing erosion includes two physical processes which are pre-breakdown and mechanical wear, arc erosion of contact materials mainly for materials evaporation and splash, and arc contact mechanical wear is mainly for the contact between the adhesive wear. Based on the close erosion mechanism and characteristics, mathematical model is introduced and studied.Secondly, based on switch close erosion model, test circuits and measurement circuits, five arcing contacts have been tested each is 100 times. Waveforms of current, voltage and acceleration sensor have been recorded every time. After every 25 times test, waveforms of dynamic contact resistance and no-load closing are measured by 3 times. Recoveries of SF6 gas, replacement of arc contacts, vacuum and recharge SF6 gas and so on have been done after every 100 trials.Measure the quality of contacts by the electronic balance while checking the arc time according to the high pressure probe and acceleration sensor. The thesis also analyzes erosion resistance and contact travels through the dynamic resistance instrument then get the variation of each arcing contacts.Finally, different test current, speed as well as manufacturers have been studied in this thesis to analyze the characteristic of erosion. It provides a lot of scientific data for improving structure design of arcing contacts.