Secondary System Failure Risk Assessment Based on Copula Function

The improvement of substation intelligence brings more uncertainties to the secondary system reliability analysis. The traditional secondary system reliability analysis method usually starts from the independent equipment in the system, lacking the analysis of equipment correlation and system integrity, and cannot accurately match the requirements of the secondary system failure risk assessment of intelligent substations. In this regard, a secondary system failure risk assessment method based on Copula function is proposed. The reliability model of the equipment is established through the exponential distribution to characterize the life distribution of individual equipment in the secondary system. The Copula function is used to analyze the correlation of different devices in the same power supply circuit of the secondary system and to establish a system reliability analysis model considering the mutual influence of different devices in the same power supply area. For the power supply module, main board and communication port module in the secondary system, a fault chain is established and combined with the reliability model of a single power supply area to derive the reliability model of the whole secondary system. The effectiveness of the secondary system failure risk assessment method proposed in this study is verified by simulation, and it is proved that increasing the number of power supply loops can effectively reduce the secondary system failure risk under the condition of increasing the length of fault chains due to the improvement of substation intelligence.