Application Study On Reliability Evaluation Of Power Automation Control System

The secondary equipments and system are used to assure safe and stable operation of power system, and reliability is a basic requirement for them. In recent years, chain-reacting outage accidents of wide ranges happened in many countries and areas, which caused huge losses and affects. The investigation results indicate the failures of safe equipments and power automation control system are important reasons caused calamity accidents. With the development of power system, reliable requests on secondary system are more and more strict. So it has great theory value and practical significance to systemic and quantitative research on the reliability of secondary system.Power automation control system is made up of control center, SAS and communication network. The paper quantitatively analyzes and evaluates the reliabilities of secondary equipments, SAS and power automation control system.According to the characteristics of secondary system, the paper establishes the reliability model of hardware, software and their integrations on the secondary equipments, and quantitatively evaluates their reliability indices. The reliability of digital protection is estimated, based on structure reliability model of protection, and reliability indices are gained, which are including: mis-operation failure rate, mal-operation failure rate and total failure rate. According to reliability theory, the modules' redundancy effects on protection actions in the schemes of single protection system and double protection system are studied to get protection system reliability indices: mal-operation probability and mis-operation probability.Aimed at the trait of different influences of SAS secondary equipments to system reliability, the paper introduces importance coefficient to express the important degrees of equipments and calculates their equivalent reliability indices. Fault tree analysis method is used to estimate the reliability of SAS. Through qualitative analysis, quantitative calculation and sensitivity analysis, the reliability indices of SAS are calculated and weak links are found out. The paper presents the measures to improve system reliability. The results prove this method can remarkably boost up the reliability of SAS.The reliability of power automation control system is not only related with reliability of equipments, but also related with their interrelationships. After evaluating the reliabilities of equipments and subsystems, the effects of time factors on system reliability are considered and the reliability models of communication network considering time factors are established to get equivalent reliability indices of them. FTA is used to quantitatively estimate the reliability indices of power automation control system in the conditions of considering time factors and neglecting time factors. The compared results reveal the transmission delays have important influences on system reliability, and the communication channel of bad delays is the weakest link. The improvement measures are presented. The computed results of examples prove the methods of reliability evaluation in this paper are reasonable and feasible, and can be applied in practices.