The power system wide area protection and control system uses wide area information to effectively deal with the threat of power grid failures caused by natural disasters or other factors. But this function of the system relies heavily on the reliability of the communication system. With the grid wide area monitoring analysis protection control (WARMAP) system as an example

a method is proposed to study the impact of communication system interruption on the wide area protection and control system. First

the impact of communication interruption on the analysis and control functions of the wide area protection and control system is qualitatively analyzed. Then

the risk index based method is proposed to identify the important communication links for the wide area protection and control system. Also based on the risk index

a method for generating the power-communication combined contingency is presented. The effectiveness of the proposed method is verified by a case study using an actual example of a provincial level WARMAP system. A number of recommendations on how to improve the reliability of communication network of the wide area protection and control system are finally provided. This work is supported by State Grid Corporation of China.