Study On The Maintenance Of Relay Protection Based On Its Condition And Reliability

The conventional relay protection maintenances bring more maintenance work and greater maintenance cost due to the sharp grown in the use of relay protections. The lack of maintenance and excessive maintenance of relay protection happen often. Unnecessary power cut caused by repeated maintenance reduces the economic benefits of power grid. The conventional relay protection maintenances do not fit the current situation due to the reliability increase of the extensively use of microcomputer relay protections. The condition-based relay protection maintenances considering the real condition of relay protection should be proposed. The carry out of relay protection maintenance with comprehensive consideration of relay protection real condition and power grid running condition is key to the condition-based relay protection maintenance. This paper researches:Reliability of relay protection evaluation is the base for condition-based relay protection maintenance. The conventional reliability evaluation method takes the statistical data as the research base which only cares the protection device itself without the other devices in secondary circuit. The new reliability of relay protection evaluation fitting the condition-based relay protection maintenance is proposed. The health index and fault probability are gained according to the real condition of each device of relay protection. Then the reliability index which is the protection successful probability is calculated according to the reliability model of relay protections which established by GO method. This reliability index shows the current situation of whole relay protections and provides the base for condition-based relay protection maintenance.The condition-based relay protection maintenance includes the fault risk assessment is focusing on that the current relay protection maintenance only cares the protection device itself without considering the running condition of power grid. The calculation of fault risk assessment of relay protection is the base for condition-based relay protection maintenance strategy considering the system fault risk. This condition-based relay protection maintenance has obvious advantages using the result of reliability assessment of relay protection to determine the maintenance and the maintenance sequence.The condition-based relay protection maintenance is applied in the IEEE 14 node system for example which determines the maintenances of each protection in the system. The maintenances are determined considering the real condition of relay protection and the impacts of protection fault to the system. The result proves the method correct and determination reasonable.