Protection System Hidden Failures Research Articles

Probabilistic Study of Undervoltage Load Shedding Scheme to Mitigate the Impact of Protection System Hidden Failures

The investigations on recent blackouts have disclosed that one of the main reasons for cascaded tripping of protection systems is hidden failures (HFs). This involves an in-depth study of the different modes of HF in protection systems to assess their impact on cascading events in a power grid. This paper portrays a detailed study on the modeling of different HF modes and proposes a supervised undervoltage load-shedding scheme to further reduce the likelihood of cascading events caused by HFs. The proposed methodology uses two different probabilistic models of HFs to assess HFs’ impact on cascading events. The proposed methodology is validated through numerous case studies on the IEEE 57-bus network. It is also observed that inclusion of self-monitoring and control features in digital relays significantly reduces the risk of wide-area blackouts. The methodology can be effectively adopted for planning, inspection, and repair of the protection system and the maintenance of it where investment guarantees its reliability.

Risk assessment of catastrophic failures in electric power systems

The declining reliability of the US electric power system is raising major concerns among both politicians and power engineers in the USA. One of the reasons put forward by the North Electric Reliability Council (NERC) is the detrimental role played by the protection systems during large disturbances, which tend to help the perturbations to propagate through over-tripping of fault free system components due to hidden failures. It turns out that the present practice in power transmission planning and online security analysis is to neglect the impact of the protection systems. In addition, the aim is to mitigate the vulnerability of the system to the loss of a single piece of equipment only by carrying out an N-1 security analysis. Consequently, the risk of cascading failures leading to blackouts and brownouts is neither assessed nor managed. This paper describes methodologies together with algorithms that assess the conditional risk of catastrophic failures in electric power networks due to hidden failures in protection systems. A catastrophic failure, defined as one that results in the outage of a sizable amount of load, may be caused by dynamic instabilities in the system or exhaustion of the reserves in transmission due to a sequence of line tripping leading to voltage collapse. Only the latter case is being considered. The aim of these algorithms is to identify the weak links in the systems, which are defined as those branches of the network whose tripping due to a fault lead to the highest probabilities of a catastrophic failure. The proposed methods are demonstrated on a 7-bus and a 61-bus system.

Solution for the crisis in electric power supply

New techniques for grid monitoring, protection, and control have been perfected, and their judicious application can help reduce the frequency and severity of catastrophic failures. This article describes the development of an innovative multiagent approach to prevent and control catastrophic failures in large power systems. The research has created understanding of the origin and nature of catastrophic failures. This is achieved by an analysis of hidden failures in protection systems. Vulnerabilities associated with the power system, the information network, and the communication network are also evaluated. The approach is characterized by the extensive use of real-time information from diverse sources, coupled with the development of an evolving dynamic decision event tree. A novel multiagent based platform is used to evaluate system vulnerability to catastrophic events taking in account the market environment and competing entities. Several new concepts associated with wide-area measurements and controls, networked sensors, and adaptive self healing are used to reconfigure the network to minimize the system vulnerability. Approaches developed in this research will provide important solutions for power systems and other interconnected networks of the future.