The least squares method for VCB electrical endurance parameters predicting research based on breaking current weighted cumulative method

Calculating method of the current index alpha and the theoretical total wear Q is emphatically analyzed based on the electrical endurance curve, which adopt advanced breaking current weighted cumulative method (BCWC) used for predicting the remaining electrical endurance of vacuum circuit breaker (VCBs) contact system. The purpose of this work is to provide a clear and concise engineering description for VCBs contact system on-line monitoring practically. The mathematical and theoretical model of electrical endurance for VCBs contact system is established. The current index alpha and the theoretical wear Q are analyzed in detail based on the method of least squares. Then the parameters predicting method used for prognosticating remaining electrical endurance is proposed. Comparative study was carried out, through which the validity and feasibility of researched method can be verified. The results of this work show that the achievement and the researched procedure are correct and reasonable, which indicate the total wear of a VCB contact system is certain once contact material and structure type is determined. Moreover, based on the method provided, the relation between breaking current and already operation time is also can be gained. So the current index alpha and the theoretical wear Q applying to the advanced breaking current weighted cumulative method are obtained. Finally, the hardware and software for VCB contact system electrical wear on-line monitoring device is fulfilled based on the research results mentioned above. This work can provide some reference for engineering application for electrical endurance on-line monitoring of VCBs contact system.