Protection performance monitoring of a transmission network

Given the increasing pressure from customers who require an improved service, electric utilities have to ensure their quality of supply is at least maintained and if possible enhanced. Correct protection operation in the event of a power system fault has been highlighted as being of particular importance. In the event of a false protection operation, or isolation of a larger part of the network than required when clearing a power system fault, many customers can be disconnected unnecessarily, increasing the customer minutes lost (CML). Similarly, quality of supply can suffer if a power system fault is cleared slowly causing voltage dips throughout parts of the power network. Hence, it is important that protection scheme operations are validated following a disturbance allowing any possible problems to be identified and rectified quickly. In response to the need to fully understand how the power system behaved during a fault, many data gathering systems have been or are currently being implemented. Under normal operating conditions these systems provide a valuable insight into the power system behaviour. Unfortunately, during extreme conditions, when such data is invaluable, the sheer volume of data can lead to important events being overlooked. This paper reports on a decision support system (DSS) for protection engineers which collates and interprets the large volumes of available data in order to monitor and, when required, diagnose the transmission network´s protection schemes