Loss of synchronism detection, a strategic function for power systems

As a major North American power utility, Hydro-Quebec is operating a modern, extended and complex power system that requires efficient and innovative automatic protection schemes. Its transmission system is actually defended by a series of coordinated Special Protection Schemes that were developed during the last twenty years. However, these SPS require continuous adaptation and innovation due to the increasing capacity and complexity of the transmission system. In this context, Hydro-Quebec and AREVA research and development teams are jointly developing two novel relays, RPS and DLI, for loss of synchronism detection in transmission substations and power plants. These protection devices have been designed to improve actual SPS performances and to provide new system protection alternatives. They are able to anticipate loss of synchronism using local variables only and are based on a fuzzy logic multi-criteria algorithm. The main characteristics and performances of these two new relays as well as their application on Hydro-Quebec transmission system are presented.