A 735 kV shunt reactors automatic switching system for Hydro-Quebec network

In recent years, Hydro-Quebec has undertaken a major program to upgrade the reliability of its transmission system. Much efforts have been directed toward increasing the system's capacity to withstand extreme contingencies, usually caused by multiple incidents or the successive tripping of transmission lines. In order to counter such events, Hydro-Quebec has adopted a defensive scheme. Based entirely on automatic action, this scheme will mainly rely on: a 735 kV shunt reactor switching system (called MAIS); a generation rejection and/or remote load-shedding system (called RPTC); an underfrequency load-shedding system. The MAIS system, which is the subject of this paper, will be implemented in 22 substations and is required to control voltage on the system after a severe event. Each MAIS system, acting locally is' entirely independent and will close or trip shunt reactors in response to local conditions.