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Snohomish County PUD

Snohomish County PUD is a municipal corporation of the state of Washington, formed by a majority vote of the people for the purpose of providing electric and/or water utility service. The largest of 27 other PUDs in Washington State and the 12th largest in the nation in terms of customers served.

Snohomish County PUD Woods Creek Hydro Switch Gear Replacement

Selection of a new 480-volt, 1600-amp, horizontal bus switchgear with three draw-out power circuit breakers and one molded-case circuit breaker for station service.
Incorporated arc-flash mitigating safety features such as maintenance mode, relays with optical arc flash detection, and remote racking of breakers.
Replaced two sets of electromechanical generator protection relays with SEL 700Gs.
Replaced switchgear main breaker electromechanical relays with SEL 751.
Upgraded two existing voltage regulators with new Basler DECS-150 voltage regulators.

Project Description

Woods Creek Hydro is a 650 kW hydroelectric power installation featuring two generators operating at 480V and a step-up transformer to grid voltage of 12.47 kV. The station contributes base load power to the grid, particularly during the wet season.

Casne Engineering provided crucial design and construction assistance services to Snohomish County PUD for a Switchgear Replacement at Woods Creek Hydroelectric Station. Their responsibilities encompassed the selection of switchgear and low voltage distribution equipment, with considerations for arc flash protection and other safety features like maintenance mode, relays with arc flash detection capability, and remote racking of breakers. The design involved the replacement of existing switchgear with modern alternatives, upgrading electromechanical relays to Schweitzer Engineering Laboratories (SEL) relays, and exchanging voltage regulators with Basler AVR's.

Casne also prepared engineering specifications for the manufacture, installation, and testing of the new switchgear and equipment. They developed relay settings that integrated with the existing control cabinet and PLC, as well as AVR settings. To ensure successful equipment commissioning and testing, Casne created and executed test plans.