Reliability in Storms

The winter of 2006-2007 was one of the most severe storm seasons faced by British Columbians. In total, 14.7 million of the 19.6 million customer-hours lost this year were storm-related. To put this in perspective, prior to this, the highest total number of customer-hours lost was 7.4 million in fiscal 2004 for the entire year.

Four of the five major storms affected communities from Hope to the Lower Mainland and Vancouver Island. At the height of the storm on December 15, the number of customers without power at any one moment peaked at 240,000. Over 170,000 customers in the Lower Mainland and Vancouver Island were affected by three of the storms, and some customers were without power for up to six days.

The 2007 Storm Season The winter of 2006-2007 was one of the most severe storm seasons faced by British Columbians in recent memory. Arctic fronts swept through the northern Interior and left 75 to 120 centimetres of snow. Pacific storms brought pounding rain and destructive winds across the Lower Mainland and Vancouver Island. In all, over 800,000 BC Hydro customers, or an estimated 1.6 million residents, experienced at least one power outage between late October and the middle of January. Three quarters of all customer-hours lost to power outages in 2006-2007 was the result of these storms. For all the storms, however, the vast majority of affected customers (80%) were restored to service within 48 hours. This was mainly due to the hard work and dedication of BC Hydro and contractor crews that worked many long days to restore power, often under adverse conditions. In many ways, our customers were well served by those who removed fallen trees and limbs, made downed wires safe, snow shoed through the backwoods to access damaged lines, worked countless hours in the rain and cold, and ultimately restored power to customers. As a result of our experiences this past winter, we have identified areas for improvement, such as updating our internal procedures and emergency preparedness plans, improving outage communication with our customers, and undertaking system improvements to increase overall reliability, to better prepare ourselves and the public in advance of next year’s storm season.

ASAI

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CAID

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Reliability is def ned as a combination of Average System Availability Index (ASAI) and Customer Average Interruption Duration Index (CAIDI). These indices are electric utility industry standards. Customers Experiencing Multiple Interrupts (CEMI) and Customers Experiencing Longest Interruption Duration (CELID) are new customer reliability measure to further support the reliability issue. Reliability metrics are defined as:

• ASAI refers to the percentage of time power is available.
• CAIDI refers to the average interruption hours per interrupted customer.
• CEMI-4 (customers experiencing multiple interruptions) refers to the percentage of customers experiencing four or more outage interruptions per year, excluding major events.
• CELID-6 - (customers experiencing longest interruption duration) refers to the percentage of customers experiencing the longest interruption duration of six or more hours, excluding major events.

ASAI and CAIDI actual results are below target due to a series of major windstorms sweeping across the Lower Mainland, the North and Vancouver Island during the months of October to January. The storms caused widespread disruptions to the distribution system, resulting in 2.5 million customer interruptions and 14.7 million customer-hours lost, more than what the system experienced during an entire year prior to fiscal 2007. The most severe windstorm during December 11 to December 15 interrupted power supply to more than 240,000 customers for 5.7 million lost hours. Excluding the storms, normalized (excluding major events) ASAI and CAIDI are close to meeting their respective annual targets based on normal operating conditions.

BC Hydro was in the third quartile of Canadian and U.S. utilities for ASAI and CAIDI actual in fiscal 2006. Data for benchmark comparison in fiscal 2007 is not yet available. However, it is expected that BC Hydro will be in the fourth quartile in terms of ASAI and CAIDI actual because of the severe impact of the winter wind and snow storms on reliability performance.

CEMI-4

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CELID-6

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CEMI-4 and CELID-6 are customer-focused reliability measures implemented in fiscal 2007 to provide an intuitive understanding of the reasonableness of BC Hydro's reliability performance. At year-end, CEMI-4 is 7.30 per cent which translates into 127,000 customers having experienced four or more outages in fiscal 2007. CELID-6 is 13.54 per cent, which means that 235,000 customers have had an outage lasting six or more hours in fiscal 2007. Including the major weather events during October to January and March, 20 per cent or 347,000 customers have experienced four or more outages and 40 per cent or 701,000 customers have had outages of six hours or longer durations.

As fiscal 2007 is the first year of reporting CEMI-4 and CELID-6, it is expected that targeting setting will continue to be refined for several years, taking into consideration actual performance, initiatives to strengthen the distribution system and focused investment aligned with customer needs and expectations.

Asset Health Risk Index

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Asset Health Risk Index is defined as the percentage of Distribution wire assets rated in fair or poor health through an annual assessment of its asset health. Assets in good health are expected to perform their intended function for the next 10 years. Assets in fair health are those that will have an adverse impact on BC Hydro’s operations within the next 10 years unless an appropriate management program is in place. Assets in poor health are those that require immediate attention and for which an active program is in place to mitigate the risk.

The Asset Health Risk Index improved in fiscal 2007 and was close to meeting target due to improved health in the overhead and underground distribution system offsetting declining health in vegetation brought about by the mountain pine beetle problem and trees weakened by wind and snow storms in the fall 2006 and winter 2007. Improved health in the overhead and underground distribution system is the result of applying a more rigorous assessment methodology as well as prioritized funding to address declining health in specific asset types in order to ensure system sustainability over the long term.