Risk Based Voltage Security Assessment

Abstract—The objective of this paper is to provide a risk-based approach to security assessment for a voltage stability constrained power system. It is motivated by a perception that today’s deter-ministic reliability criteria to voltage stability assessment often re-sults in operating restrictions that are not commensurate with the corresponding level of risk. The risk calculation provided in this paper accounts for both the future uncertainties on the system and the consequences associated with voltage collapse and violation of limits. Although the main purpose of this paper is to provide a method of evaluation, we also give an introduction to show how this reliability “leading indicator ” penetrates the traditional rigid reliability boundary and how it may be used to price reliability in order to make a trade off between reliability and economics. Index Terms—Impact, load margin sensitivity, power system se-curity, probability, risk assessment, transmission, voltage collapse. I