Study Of The Condition Assessment For SF₆ High Voltage Circuit Breaker And Its Maintenance Decision

With the continuous expansion of the scale of power grids, the reliability of SF₆ high voltage circuit breakers（HVCB） which take on control and protect in power system is more important. Currently, the maintenance of SF₆ HVCB is still in the state of preventive maintenance, not only costs a lot of repair work, manpower and resources, but also has the problem of excessive or inadequate maintenance. To solve these problems, the power supply enterprises begin to use Condition Based Maintenance（CBM） to optimize the maintenance of SF₆ HVCB. The foundation of CBM is reasonable and effective equipment condition assessment. However, existing research has focused on the single factor evaluation which results in insufficient and inaccurate evaluation result, and still needs a lot of academic research.Based on the full analysis of related test items and operation parameters of SF₆ HVCB, the paper setups the condition assessment model of SF₆ HVCB based on fuzzy comprehensive evaluation. Firstly, the condition assessment index system is established, by analyzing electrical properties, mechanical properties, insulating properties, and other factors of SF₆ HVCB operation condition. Secondly, according to the steps of fuzzy comprehensive evaluation, the paper uses normal cloud model to determine the index membership degree, and this method takes into account the fuzziness and randomness of index value. Thirdly, the constant weight of assessment index is determined by improved analytic hierarchy process with proposed optimal transfer matrix, saving the complicated process of consistency checking. And, the balance function is applied to calculate the variable weight, which makes the weight become more reasonable and flexible. Finally, the fuzzy comprehensive evaluation results are obtained by using the weighted average fuzzy arithmetic operators, which has considered the the influence of main factors and secondary factors. The assessment results are determined according to the principle of maximum membership degree.In addition, the paper uses the assessment results to calculate real-time failure rate of SF₆ HVCB based on health index. And then, this rate is combined with Weibull failure distribution curve to obtain the actual operating age. In the process of building the failure rate model of SF₆ HVCB, the paper introduces the age reduction factor and failure rate increase factor to modify the failure rate after maintenance, which makes it more consistent to real work condition.Through the actual analytical examination and software assessment results, the condition assessment model for SF₆ HVCB building by the paper is effective, and it pvovides a better guidance for maitenance.