The State Evaluation Method Of Relay Protection And Its Use In Maintenance Decision

With the developed revolution of Chinese electric system, electric power enterprisesare facing more and more pressures arisen from increasing competitive power whilereducing the cost. One of the most effective ways is increasing the repairing benefitsand efficiencies of power equipments. Condition-based maintenance is a maintenancemodel which judges the running state and predicts the fault trend of equipments basedon condition monitoring and diagnosis technology. As the important equipment inpower system, relay protection equipment’s maintenance technology which had littleresearch is also very important. Therefore, this thesis focuses on the state evaluatingmethods of relay protection and its applications in maintenance decisions, andinvestigates the realization of the condition-based maintenance of relay protection.The state monitoring technology, failure mode, and impact results of the existingrelay protection was reviewed. According to the reliability block diagram analysis, theconclusion that the whole failure of protection system is relied on the typical bathtubcurve model was verified. Then the weibull distribution based fitting method of relayprotection failure model was deduced. The fitting example of parameters of weibulldistribution was proposed.According to multiple factors effect of state evaluation, the state calculating methodand the corresponding quantized method based on the fuzzy theory was proposed. Thismethod established the condition evaluation factors aggregate of relay protection. Theweight allocation of condition evaluating factors was realized using fuzzy analytichierarchy process, thereby effectively overcoming the problem of difficult decisionthrough regular analytic hierarchy process. Meanwhile, the membership function ofeach evaluating factor was established from fuzzy distribution models and professionalsuggestions, resulting in the fuzzy comprehensive evaluation based condition evaluatingmethods of relay protection. The effectiveness of the proposed method was proved bycalculation examples.To ensure the maximum maintenance deadline of protection equipment, thealgorithmic method of real-time failure rate based on the running condition wasestablished according to the exponential distribution between the equipment runningcondition and real-time failure rate. The practical operating years and equivalentoperating years were defined. Employing the concept of equivalent operating years, a method to calculate the current running state based maximum maintenance deadline ofequipment was deduced.The preventive maintenance strategies of single and double protection were proposed.The state evaluating results were introduced into the state space models as real-timefailure rates and the necessity of the preventative maintenance was proved by Markovequation. In addition, by fixing the available rate of protection system as theoptimization object, the optimized time of preventative maintenance in different statecombinations between single protection and primary equipment was simulated, givingthe suggestions on the preventative maintenance time in different state combinations.