Update: Snettisham back on line

By November 24, 2011Energy & Mining

Uphill pole of Tower 3-4 leaning onto guy wires of middle pole - Photo courtesy of AEL&P

November 26, 2011 11:18 pm update
Alaska Electric Light and Power’s Snettisham hydroelectric facility is back in service. 

The workhorse of AELP’s system was turned back on Saturday afternoon at 2:30, two and a half-days after anchor bolts for tower guy wires failed and a tower leaned on a conductor, causing a power outage Thanksgiving morning. 

Generation engineer Scott Willis says he began shutting down diesel generators as soon as the hydro project was on line. 

Willis says it’s not clear what caused the anchor bolts to fail, but it was not an avalanche.

Estimated time of repairs had been three to seven days.

November 24, 2011 5:20 pm
Repairs are expected to take about three to seven days for a set of guy wire anchors for a tower on the Snettisham transmission line.

Two of the anchors failed Thanksgiving morning, causing one pole of a three pole tower structure to lean into another pole. The conductor for the leaning pole touched a guy wire for the middle pole, creating a path to ground and a short that led to the area power outage early yesterday.

Scott Willis of Alaska Electric Light and Power says the outage last from about 6:30 to about 7:45, an hour and fifteen minutes.

Repairs could start as soon as Friday.

Willis says 60-percent of Juneau electricity is being supplied by diesel generation. The other 40-percent from hydroelectric projects like Lake Dorothy, Salmon Creek and Annex Creek facilities.

November 24, 2011 12:15 pm
Alaska Electric Light and Power officials say this morning’s power outage may have been caused by a pair of transmission tower guy wires that broke, eventually causing a phase, or one of the transmission lines to touch another and cause a fault.

The tower was located about three miles from the Snettisham hydroelectric facility. Scott Willis of AEL&P says Tower 3-4 is a three-pole structure that replaced the original single-tower structure at that location. Willis says the original Tower 3-4 was outside of the 2008 avalanche path, but it got pulled down when an adjacent tower got hit by the snowslide.

The uphill pole of the three pole structure for the current Tower 3-4 is supported by four guy wires. Willis says it appears the two uphill guy wires came loose from their concrete anchors. That caused the entire pole to lean over to the middle one and both transmission lines, or conductor cable, touched.

Willis says the tower was not destroyed and none of the conductor was broken.

It is unclear what caused the guy wires to separate from their anchors, whether it was wind, a tree, or a small avalanche that was not immediately visible. It is also unclear how much damage there was to the tower poles.

A line crew surveyed the transmission line during a helicopter flight over the area this morning. More details will be available later after they return to town.

Willis says the one question that everyone asks is whether this means that rates will be going up. Probably not. Willis says repairs will likely last a few days to a week at most. That probably would not be long enough to trigger an Emergency Cost Of Power Adjustment. Any use of diesel generators this week will likely be a small surcharge added to next quarter’s rates.

Willis says hydroelectric projects like Lake Dorothy, Salmon Creek, and Annex Creek are currently providing about 40-percent of the current demand for electricity.

November 24, 2011 7:53 am
Alaska Electric Light and Power reports an areawide power outage this morning that lasted about an hour and fifteen minutes. Electricity went out about 6:30 a.m. with all areas restored about 7:45 a.m.

AEL&P generation engineer Scott Willis says it appears the outage was caused by a fault on the transmission line between the Snettisham and Lake Dorothy hydroelectric projects. He says a helicopter is already being prepared for a first-light survey of the transmission line to determine the nature of the fault.

Juneau’s electricity is now being supplied by diesel generators with additional power by other in-town hydroelectric facilities like Salmon Creek and Annex Creek. Willis says the Lake Dorothy generator was tripped off, but the line from that project to Juneau appears to be still intact. Lake Dorothy will be used to supplement power to Juneau once the generator comes back on-line.

Check back here later for further updates.

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