Hydro-Quebec's defence plan against extreme contingencies

In recent years, Hydro-Quebec has undertaken a major program to upgrade the reliability of its transmission system. Much effort has focused on increasing the system's ability to withstand extreme contingencies, usually caused by multiple incidents or the successive tripping of transmission lines. In order to counteract such events on its system, Hydro-Quebec has adopted a number of special defensive measures, globally called "defence plan against extreme contingencies". The goal of this plan, which will be fully operational by 1998, is to detect and confine incidents that exceed the system's strength. Entirely automatic, it will rely mainly on: a generation rejection and/or remote load shedding system (RPTC) a 735 kV shunt reactor automatic switching system; an undervoltage load shedding system; an underfrequency load shedding system. This paper summarizes Hydro-Quebec's current orientation for safeguarding its system after extreme contingencies and describes the various automatic measures adopted and, in particular, the RPTC system, one of the main components of the defence plan. The RPTC system will detect multiple line losses directly from fifteen 735-kV substations, include four generation rejection sites and a centralized remote load shedding system.