Research Of Condition-based Maintenance And Condition Assessment System Of Relay Protection

The purpose of condition based maintenance of relay protection is to improve the reliability of the system.In this paper,the indicator of the reliability, life distribution and calculating models for system reliability are summarized based on the mathematical theory of reliability. Risk factors and the consequences of risk of relay protection system are analyzed based on failure mode and effects analysis method.Considering the fault detection methods have an effect on risk,the occurrence, severity and detectability are chosen as the assessment indexes.The risk of protective relaying devices is analyzed and assessed. According to the feature that digital protection is consisted by a large number of electronic components, the failure analysis and testing methods of electronic components are discussed. Then the maintenance of the secondary system is compared with those of the primary system.The condition assessment of protection system is introduced in this paper, and a Markov probability model is established to evaluate the reliability of protection system under condition-based maintenance. The state space method is used to calculated the states probabilities and reliability.Compared with routine maintenance, the influence of condition-based maintenance on relay unavailability and the optimum routine test interval is analyzed.The condition assessment system is proposed based on the contents of repair work and the structures of both protective relaying devices and the secondary circuits. Different reliability indicators were applied in the condition assessment of the protective relaying for making corresponding maintenance decision. Test based condition assessment can reveal the degradation in effective environment or performance of the equipments. The system reliability assessment is mainly applied in the reliability assessment of the equipments which stay in stable operational conditions, which is convenient for maintenance arrangement. The relative quality condition assessment is used when the reliability of the equipment in question is a variable, and it considers both the assessment of aging stages and the gradual enhancement in the reliability of new equipments. By assessing relative quality, the components which need precautionary update can be found.