Critical line affecting power system vulnerability under N-k contingency condition

In order to study the critical lines leading to power system vulnerability deterioration under N- k contingency condition,a method of building the critical line model is proposed. Based on the concept of vulnerability and the vulnerability theory of complex network,a model of power system vulnerability is set up,which adopts the minimum load-shedding rate to express the practical transmission efficiency of power grid. Based on the theory of synergistic damage effect and the vulnerability of failure set under N- k contingency condition,a model of critical line affecting the vulnerability of power system under fault condition is built. With the consideration that the adjacent lines may have similar characteristic,an analysis flowchart based on the partition method is proposed. Simulative results of IEEE 39-bus system show the proposed model and method can effectively screen the failure sets. The obtained conclusion is:the highly vulnerable line has low synergistic damage effect while the highly critical line has high synergistic damage effect with low vulnerability.