中文摘要：

针对现有风险模型考虑系统稳定性过于简单的缺点，在实用动态安全域的基础上提出了一种新的风险指标并将它应用到提高输电线路传输功率极限的计算中，综合考虑超极限运行的经济效益和故障后的紧急控制成本，确定系统最佳运行点。该指标采用事故发生的概率来考虑其不确定性，利用紧急控制成本来衡量失稳事故的严重性。以江苏电网为例的验算结果表明，采用该风险指标确定的系统运行点能有效协调系统运行的安全性与经济性要求，经济、社会效益可观。

英文摘要：

The traditional dynamic security limits, which are set down based on ＂the decision criterion of the most serious accident＂, has greatly reduced the operation risk of power system. However, it is also coupled with the great amount of cost. It is not more and more suitable in case of introducing the electric market. Based on the practical dynamic security region, this paper brought forward a new risk index at first. In this index the accidents are split into two modes, the stability mode, under which the power system could keep stability, and the instability mode, under which the power system couldn＇t keep stability. For the stability mode, only the expenses due to the accident itself are considered. For the instability mode, a simple and effective cost assessment model for emergency control is built to measure the emergency control cost. The probability of accident is also adopted to describe the uncertainty of accident happening in the environment of marketplace. Secondly, the index is applied to the calculation of increasing the transmission power limit of transmission line. During the course of choosing the optimum operation point of sys- tem, both the economic benefit due to the ultra limit operation and the emergency control cost caused by the accident are considered. At last, the Jiangsu power grid is employed as an example. The computational results show that the operation point of power system, which is determined using the risk index proposed in this paper, could effectively assort with the security and economy request in system operation and has brought considerable economic and social benefit.