配电网用气体间隙开关触发腔性能劣化进程及剩余寿命预测方法OA北大核心CSTPCD

The mechanical and electrical performance of gas gap switch'trigger cavity inevitably decreases caused by repeated trigger discharge,causing a serious problem of trigger failure.In order to achieve stable trigger conduction of the gas gap switch,the study of the degradation process of the gas switch trigger performance under repeated trigger discharge was carried out based on the trigger lifetime research platform,the trigger conduction parameters strongly correlated with the deterioration process of the gas switch trigger cavity performance were obtained.Ultimately,a trigger lifetime prediction model of gas gap switch based on long short term memory(LSTM)network was established to predict the remaining trigger lifetime. From the experimental results,it can be concluded: (1)At the early stage of trigger lifetime,the plasma jet height is up to 10.1 mm,leading to the excellent trigger conduction performance of gas gap switch,with breakdown delay and contact delay as low as 68 μs and 77μs.Under the effect of intense ablation along the surface arc current,the inner diameter at pin electrode and the nozzle diameter of trigger cavity increases gradually,the pressure difference between the inside and outside of the trigger cavity nozzle decreases,leading to a decrease in the plasma jet characteristics parameters,weakening the distortion effect of the background electric field in the main gap,resulting in the increase of the breakdown delay△t1 and trigger delay △t2.Within 500～800 trigger discharge times,pre-breakdown effect occurs obviously during the trigger conduction process of gas gap switch,leading to the breakdown delay and trigger delay disperse notably with the fluctuation value up to 30 μs.At the end of trigger lifetime,the jet height is as low as 5.5 mm,which cannot meet the needs for stable trigger conduction of gas gap switch,causing the trigger failure of gas gap switch with a trigger lifetime of up to 1 200 times. (2)Under repeated trigger discharge,the ablation holes appear on the inner wall of trigger cavity at pin electrode and develop from point and line to plane,the carbonization products on the inner wall of trigger cavity at nozzle accumulate to form the pits and bulges,suppressing the generation and accumulation process of plasma in the trigger cavity.Furthermore,after the accumulation effect of high temperature arc ablation,PTFE has undergone intense electrochemical reaction,and the decomposition products are mainly CF4,C2F4,C2F6,C3F6 and other strong electronegative gases.In SF6 trigger environment with a sealed cavity,taking into account the electronegative effect of decomposition products produced by discharge ablation,the development process of plasma jet is obviously inhibited and the trigger lifetime is restricted. (3)Based on GRA and PCC,considering the correlation law between plasma jet characteristic parameters(jet height,jet diameter and jet area),trigger discharge delay(△t0,△t1,△t2)and the trigger performance degradation of gas gap switch,the plasma jet height is used as the predictor.Firstly,the gas switch trigger lifetime prediction model based on LSTM was established.Dropout technology is introduced to the model to avoid the over-fitting caused by model complexity.Secondly,the original trigger conduction characteristic parameters are divided into multiple subsequences by sliding time window,and the dependence between sequences is introduced,so as to better capture the characteristics and laws in the data sequence.Finally,the Dropout ratio,the number of hidden layer units,and the time step were optimized to decrease RMSE and MAPE between the model predicted value and the experimental value,ensuring the prediction accuracy of model.The remaining trigger lifetime prediction error is within 10％,which can well meet the requirements of gas switch trigger lifetime prediction.