Rocky Reach looks to replace decades-old spare transformer

WENATCHEE — Chelan County PUD is moving toward replacing a decades-old spare transformer at Rocky Reach Dam, where the backup equipment available in the event of a transformer failure dates to the early 1970s.

Commissioners voted Sept. 8 to reject bids for a new universal spare generator step-up transformer after prices came in more than 25% above the engineer's estimate, allowing PUD staff to negotiate with the two responsive bidders.

The new transformer would provide a modern backup capable of serving generators of different sizes at Rocky Reach, reducing the amount of time a generating unit could remain out of service following a transformer failure.

Generator step-up transformers perform a critical job between a hydroelectric generator and the regional transmission grid. Electricity leaves a generator at a comparatively lower voltage, and the transformer raises, or “steps up,” that voltage before the power enters high-voltage transmission lines. Sending electricity at higher voltage allows the same amount of power to travel with less current, substantially reducing energy lost as heat over long distances.

Rocky Reach's operating generator step-up transformers were replaced in the 1990s, but commissioners heard that the spare dates to approximately 1972.

The spare sits on a dedicated transformer deck at the dam, ready to be moved into service if an operating transformer suffers a failure.

PUD project manager Jacob Ellis said the replacement is being designed as a universal spare.

“It can work for any of the units, regardless of the size of the unit,” Ellis said.

A failure also does not necessarily mean the damaged transformer must be replaced permanently.

“Depending on the fault, transformers can be repaired,” Ellis said.

Having a compatible spare available while repairs are made can significantly reduce the time a generating unit remains unavailable.

Purchasing that replacement, however, has proven more expensive than anticipated.

Pralar USA of Houston submitted a base bid of approximately $6.81 million, while Olsson Industrial Electric of Springfield, Oregon, bid approximately $7.43 million. A third bidder, Virginia Transformer, submitted a bid that was determined to be noncompliant.

Because the responsive bids exceeded the engineer's estimate by more than 25%, the PUD could reject them and enter negotiations rather than simply awarding the contract at the bid price.

The price discrepancy prompted discussion about the difficulty of estimating costs for large transformers in the current market. Staff said historical pricing data has become less useful since the COVID-19 pandemic as transformer prices have been affected by supply-chain constraints and changing global market conditions.

The bids did contain one relative bright spot: delivery.

The PUD had anticipated a three- to five-year lead time for a transformer of this size. Ellis said the bids instead indicated delivery in approximately two and a half years.

The long manufacturing timeline is part of the reason utilities maintain spare transformers. Unlike equipment that can be readily purchased following a failure, a large power transformer is specialized equipment that can take years to replace.

Commissioners unanimously authorized staff to reject the bids and negotiate with the two responsive bidders.

The eventual purchase would replace a spare that has stood ready at Rocky Reach for more than half a century, giving the PUD a backup designed to serve multiple generating units if one of the dam's operating transformers fails.

Andrew Simpson: 509-433-7626 or andrew@ward.media