Programmable load shedding-systems-Hydro-Quebec´s experience

Programmable load shedding systems (PLSS) are key elements of Hydro-Quebec´s special protection system (SPS). These systems perform control and monitoring tasks. They are programmable to offer a customized solution to power system protection. They monitor power system frequency and voltage and can shed load on predefined conditions. Furthermore, these systems can receive load shedding orders from other systems. Operating conditions of the PLSS can be programmed on-site or remotely. A new generation of PLSS will be installed shortly in HydroQuebec´s substations. The replacement of the existing equipment was necessary to improve filtering characteristics and frequency measurement algorithm. Furthermore, the maintenance of this equipment has become complicated due to unavailability of spare parts.