Research on condition-based maintenance in relay protection

The paper analyzes the critical technology of condition based maintenance in relay protection, and especially pays more attention to the on-line state maintenance of secondary circuits, including AC analog circuit, switch input circuit and breaker operating circuit. Firstly, the paper uses a comparative method to effectively monitor the AC analog circuit. No matter how relay protection devices are configured, any AC analog circuit of the relay protection devices can be paired by other suitable AC analog circuits. Next the paper presents a new way to perform the state detection function with several types of switch input of the secondary circuit and micro-computer protection device, and use additional measuring or state detecting devices to strengthen state detecting of switch input secondary circuit. Finally, the on-line state detection method of breaker operating circuit and tripping contacts is also discussed in the paper.