Method of Operational Risk Assessment on Transmission System Cascading Failure

As cross-region power grid in China is established,power system cascading failures has become a key factor that threatens the stability of bulk power grids.For the purpose of investigating how the failure spreads in transmission system and assessing its operational risk with different protection configurations,this paper presented failure probability model of transmission lines based on real-time operating conditions and hidden failure model based on Markov method.According to hidden failure model and current operating mode of power system,a searching mode of cascading failures was introduced.Based on risk theory,operational risk assessment method and indicators of cascading failure in transmission system were further proposed under market condition,with a good combination of security and economy.Taking IEEE-RTS 79 system as an example,the vulnerable lines in it were identified.The example analysis demonstrates that,reasonable protection configuration can reduce the risks of hidden failures.Improving transmission capacity of lines can effectively reduce the risk of cascading failures.It also illustrates that risk assessment of cascading failures by use of operational reliability theory can reflect the state of the system accurately.