Reliability Modeling And Assessment Of Substation Main Equipment Protection Considering Hidden Failure

Power industry is the important basic industry to support the development of national economy. With the rapid development of national economy, the efficiency and size of power system continues increasing, and the complexity and uncertainty of the grid and its operating environment also improves, which brings new challenges and higher requirements to the security and reliability of power system. Relay protection is the first line of defense to guarantee the power system in safe and stable operation status, and its reliability is closely related to the safety of electric equipment and the power supply reliability of power system. Substation is the basic unit of power system, which contains almost all the important equipment in the grid. So it has practical significance to take substation as a research object to establish a comprehensive reliability assessment system.This paper has built substation relay protection assessment system from the three levels of protection devices, protection configuration scheme and protection system. For protection devices, considering all factors and failure modes, and using FMEA method, fault tree analysis method, classical models and Markov state space method synthetically to make reliability assessment. Based on it, take every device as a unit to assess reliability of four kinds of common protection configuration schemes in substation, and analyze the effects of parameter changes on their reliability qualitatively.According to the characteristics that hidden failures of relay protection needs to be triggered by failures of the protected equipment, this paper takes hidden failure status of protection devices and operation status of the protected equipment into consideration to analyze the operation condition and conversion modes of four kinds of relay protection systems, and builds reliability assessment models for them. Dominant failure trip rate, hidden failure trip rate and backup protection hidden failure probability are proposed as new evaluation indexes to distinguish failure status from hidden failure status, which can compensate for the shortage of the normal failure rate index and reflect the actual reliability level of the protection system more accurately and reasonably.