Scobie Pond 345 kV Substation Upgrade

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Client:  Public Service of New Hampshire
Location: New Hampshire

POWER Engineers was responsible for the addition of a 450 MVA 345/115 kV autotransformer into an existing substation. POWER’s services included physical, civil and protection design, relay settings, oil containment design, and commissioning. Settings for the multi-function numerical relays associated with the new transformer and the substation expansion were provided. These relays included transformer differential relays from two manufacturers, a transformer differential relay used for bus protection, overcurrent relays used in breaker failure schemes, and backup distance relays. POWER also provided settings for the new transformer LTC controllers to be used with the transformers in stand-alone or parallel operation, and prepared a study to determine load sharing between the two transformers under varying loading and tap position.