Impact of SIPS performance on power systems integrity

An increasing number of utilities are using System Integrity Protection Schemes (SIPS) to minimize the probability of large disturbances and to enhance power system reliability. This trend leads to the use of an increased number of SIPS resulting in additional risks to system security. This paper proposes a procedure based on Markov Modeling for assessing the risk of a SIPS failure or misoperation. The proposed method takes into consideration failures in the three stages of SIPS operation: arming, activation and implementation. This method is illustrated using an example of a Generation Rejection Scheme (GRS) for preventing cascading outages that may lead to load shedding. In addition, system operators tend to have the SIPS always armed to prevent a failure to operate when required. However, this can result in increased probability of SIPS misoperation (operation when not needed). Therefore, the risk introduced to the system by having the SIPS always armed and ready to initiate actions is examined and compared with the risk of automatic or manual arming of SIPS only when required. Sensitivity analysis is also performed to determine how different factors can affect the ability of the SIPS to operate in a dependable and secure manner.