It happens every time BC Hydro takes its northwestern customers off of its provincial grid so it can do maintenance or make repairs.

The provincial crown corporation then shifts to power produced by Rio Tinto含羞草研究社檚 Kemano generators which provide the juice to run the company含羞草研究社檚 Kitimat aluminum smelter.

But because Rio Tinto含羞草研究社檚 power has a faster hertz, or cycle rate, than does BC Hydro含羞草研究社檚 power, clocks using electricity also run faster.

BC Hydro calculations place its own power at 60 hertz and Rio Tinto含羞草研究社檚 at 60.3 hertz, fast enough to add 12 seconds an hour to a clock being run on electricity, a factor called 含羞草研究社渢ime error含羞草研究社�, said David Mosure from BC Hydro.

含羞草研究社淚n other words if the system is running fast for 10 hours, clock time will be 120 seconds faster than real time,含羞草研究社� he said.

In this most recent power switch of two weeks ago, electric clock users found them running approximately 15 minutes faster.

The switch affected BC Hydro含羞草研究社檚 northwestern customers as far east as Burns Lake with the crown corporation using Rio Tinto power as well as power from other independent power producers.

When BC Hydro isolates a region for maintenance or repairs, it含羞草研究社檚 then called an electrical island.

Power was back to normal over the weekend of Aug. 20-Aug. 21.

Clock applications in computers, smartphones or other devices tied into the internet are not affected as they take their times from the internet through satellite-based calculations.