Research On Reliability Evaluation And Management System Of Power System Protective Relaying

As the first defense line of the power system, the reliable running of relays is an important guarantee for the security and stability of power system. Along with the development of power grid in the direction of high voltage, long distance, large capacity, the power grid structure become increasing complicate, it brings higher requirements to the reliability of protection system. Thus, to evaluate the reliability of protection system efficiently and display corresponding maintenance strategies is of great significance to increasing the reliability of relays, reducing or avoiding the accident as far as possible, ensuring the safety of power grid. In the paper, the reliability evaluation method of protection system which is suitable to engineering application is studied in the perspective of the operation features of relays. Moreover, on the basis of the reliability evaluation, combined with the state information of relays, the condition-based maintenance strategy of protection system is studied as well.Firstlly, based on the analysis of the operation features and primary data of protection system, the reliability indices are defined to reflect the actual operation reliability of protection system in detail and comprehensively. Moreover, by the design and relevant operation of the database, the raw data can be collected and saved, the effective information can be extracted as well, which provide data base for the reliability evaluation and condition-based maintenance of protection system.Secondly, the protection system reliability is evaluated in the perspective of statistic analysis and dynamic evaluation respectively. On the one hand, the reliability of relays is analyzed simply and intuitively through the statistical calculation of the reliability indices defined in the paper. On the other hand, based on the failure features of relays, the life distribution models: exponential distribution model and Weibull distribution model, are applied to the dynamic assessment. The reliability indices such as reliability, failure rate, failure probability density are displayed as a result. Moreover, aimed at the characteristics of high reliability protection system that the volume of failure data sample is small, a protection system reliability evaluation method based on the Bayes-Monte Calo method and protection system reliability evaluation method based on BP neural network method are presented in order to improve the evaluation effect under the small sample situation.Thirdly, a protection system state evaluation method based on multistage fuzzy comprehensive evaluation is introduced, and the corresponding maintenance strategy is given out. After the state data analysis of protection device and the secondary loop, a state index set of protection system is established. Then the multistage fuzzy comprehensive evaluation method is applied to evaluate the state of protection system in a guard interval, and the maintenance strategy is presented, such as maintenance order, maintenance level, optimal maintenance time, maintenance advice and so on.Finally, the protective relaying reliability evaluation and management system software is developed by VC++, and numerical example is proposed to verify the correctness and feasibility of the program. The functions such as calculation of running time, the statistical analysis, dynamic assessment and the condition-based maintenance of protection system are included in the software. It is with friendly interface, easy accessibility, good compatibility and expansibility.