Complex Power System Cascading Failures In Risk Assessment Studies

Cascading failures in power system are rare processes but often bring severe consequences. Severe cascading failures may cause large scale blackouts or even system collapse. With the development of power system and the emerging of power market, the operation of power network is nearer to its limit than it is before. The security and reliability assessment for cascading failures of the power system is important and necessary.In this paper we firstly analyze large blackouts in resent years and present the existing models for cascading failures in power system on the basis of researching the mechanism of cascading failures. Secondly principle and calculation methods for reliability evaluation are discussed, meanwhile risk theory is introduced and compared with other traditional methods. At last the paper presents an approach to evaluate the risk of cascading failures for complex power system, which simulates the general expansion process of cascading failures and associates the occurrence probability of cascading failures with their consequences, then a quantitative risk index is proposed by which the hidden trouble of power system can be discovered and the potential safety hazard can be revealed. On this basis, the software for risk assessment of cascading failures in power system is developed according to risk theory. Taking NPCC 48-machine system for example, the simulation result shows that the proposed method is advanced and effective.