Study On Failure Characteristics And Reliability Assessment Of Relay Protection Devices

Currently, the major overhaul of protection devices is the implementation of preventive maintenance approach. This approach is lack of development of maintenance strategies and methods. Therefore, studying on the characteristics and reliability of relay protection device failure assessment methods, and evaluating protection device and then adjusting the appropriate maintenance objects and strategies could make the repair project more focused, more scientific. thus, the maintenance work is becomed more effective and economy, and availability of equipments are also improved.This paper focuses on the computation approaches for the constant failure rate of relay protection devices with the field data. And the constant failure rate for the protection devices of a power system with the field data is carried out, and the differences of the estimation approaches are compared. Based on the constant failure rate, the simple and comprehensive reliability assessment model is analyzed. Further, both optimal maintenance cycle and the maintenance strategy are researched for protection system with single set. In addition, the concept "transition state" is introduced in order to distinguish the efficiency of power-off maintenance and power-on in the reliability assessment model of dual-configuration protection. And the optimal co-ordination maintenance cycle of two kinds of maintenance methods is obtained.Further, proposing the estimation approach for the time-varying failure rate of relay protection devices. And time-varying failure rate for the protection devices of a power system with the field data is carried out. Furthermore, according to the geographical features of the power grid, environment, regional factors are considered to calculate failure rate, and the conclusion was draw:mean failure rate was basically consistent; aging failure rate was related to climate. Based on time-varying failure rate, the minimum maintenance model for relay is constructed with the viewpoint of relay reliability and maintenance economy. The "unit life-cycle cost" is applied in protection device reliability assessment to formulate the replacement strategy with the objective of least "unit life-cycle cost". Finally, the optimal replacement cycle for a field operating relay is obtained with the proposed strategy, with the considering for double protection.