Abstract: Deterministic N-1 principle is widely used in power grid planning to evaluate the security level of the system at present. However, the probabilistic or stochastic nature of system behavior and component failures is not included in this approach. The evaluation for power grid planning, based on probabilistic risk analysis method with considering the random characteristic of power grid, was not only a useful supplement to the N-1 principle, but also could provide quantitative risk information for planning and design personnel. This paper applied probabilistic risk analysis method in the planning work of transmission network, carried on the static and transient risk evaluation combined with engineering cases, and compared the risk level of planning scheme. Based on the proposed risk indicators of root cause failure and weak link, the weakness of power grid was found to improve the rationality of the planning scheme.

Key words: power grid planning, risk evaluation, practical