EU30 Winter Generation Availability Factor

The Winter Generation Availability Factor (WGAF) is a percentage of Heritage Asset units in the system greater than 20 MW and available to generate electricity (total hours available for service/total hours) during the critical peak-load period of November 15 to February 15. BC Hydro focuses on WGAF to manage the availability of generation during the critical winter period when customer loads are most likely to reach their annual peaks, and all BC Hydro generating units will remain in-service barring a forced outage or urgent maintenance.

The final fiscal 2011 WGAF is 94.4 per cent, or 96.0 per cent if the planned Cheakamus Unit 2 outage is excluded. This is below the target of 96.4 per cent, and is due to extended planned and forced outages throughout the winter period. BC Hydro planned the extended outage on Cheakamus Unit 2 because it was the best time to complete the work. Significant unplanned outages include: GM Shrum Unit 8, which remained out of service until late December due to an exciter transformer failure; extension of the outage for Lake Buntzen 1 Runner Replacement Project through the winter period; and the Seven Mile Unit 2 forced outage in January due to a unit transformer failure which continued for the balance of the winter period.

BC Hydro also reviews its generation performance against available industry benchmarks such as annual system availability and the frequency of unexpected outages. While these measures provide a means of comparison against other utilities, they do not provide the best measure of reliability performance. For example, annual system availability varies significantly due to outages for planned maintenance and capital upgrades; however, such outages are scheduled so that BC Hydro's ability to generate sufficient electricity to meet customer demand is not adversely affected.