An 11-hour outage next week will enable technicians to start construction so that all powerlines run through the Twisp substation, creating a redundant, looped system.
Necessary to do transmission line work over Loup
Electric utilities are launching the final step next week to create a connection that will provide back-up power during an outage to customers of the Okanogan County Electric Co-operative (OCEC).
OCEC customers in Winthrop and Mazama will have an 11-hour overnight outage from 7 p.m. Thursday, April 11, to 6 a.m. Friday, April 12, as part of the changeover. The outage is necessary to temporarily disconnect the Winthrop transmission line from where it links to the Loup Loup transmission line.
Technicians with the Okanogan County Public Utility District (PUD) and Bonneville Power Administration (BPA) will de-energize the Loup line and build a temporary “shoofly” bypass between two power poles. The shoofly link will provide power to Winthrop while the PUD builds a new connection to the Twisp substation.
The new connection, half-a-mile long, will take the Loup Loup line directly into the Twisp substation, where the Winthrop line will have its own protective breaker, according to the PUD. Once that has been completed, the Winthrop transmission line will be fed by the new Pateros-Twisp transmission line and by the Loup Loup line as a back-up. It will be possible to switch between the two in an emergency or during maintenance.
Construction of the new powerline from the Loup to the Twisp substation will start in late April and is expected to be completed by the end of July, according to the PUD. There will be another, shorter power outage, tentatively scheduled for Aug. 2, to transfer the shoofly to the new transmission line.
“Once this is finished, the Winthrop line will have its own breaker at Twisp,” said David Gottula, OCEC’s general manager.
The connection was expected to be swapped last fall, but it was delayed because BPA was working on a required environmental review, said Gottula.
The 27-mile Pateros-Twisp transmission line was energized in October 2017, providing a redundant system for PUD customers so that power can come from either Pateros or over the Loup.
The PUD is reviewing bids for the half-mile-long powerline construction. The project is expected to cost about $550,000 in labor and materials.
OCEC will take advantage of the outage to do other work unrelated to this switchover, said Gottula.
About 10% to 15% of OCEC customers — generally in the Twisp area and on Twisp River Road — are already served by the Pateros-Twisp line and will not be affected by the outage. Anyone with questions about whether a particular residence or business will not have power on the night of April 11 should call OCEC at 996 – 2228.
