New 230 kV substation to replace existing utility-supplied 12.47 kV services in Northern California

High Voltage Substation Design Project Description:
Total system responsibility for a new 230 kV substation to replace existing utility-supplied 12.47 kV services.

High Voltage Substation Design Problems: An existing utility substation was supplying the customer with a service voltage of 12.47 kV. With a major expansion currently underway and future needs to consider, the customer required more capacity than the existing utility substation could provide. To meet their power requirements, the customer would have to buy power at the 230 kV level. Under its current practice, the utility could not supply a new substation but was willing to provide space in their yard for the construction of a customer-owned substation. Space was at a premium, and existing incoming utility lines and outgoing distribution lines posed additional constraints. To further complicate matters, the project had to be completed without delay during the wettest winter in the history of northern California.

Completed three-feed switchyard after expansion

Original two-feed switchyard

High Voltage Substation Design Factors: The utility offered space that allowed the customer to construct his own 230/12.47 kV substation by accepting three 230 kV feeds from the existing substation bus in the immediate area. All construction had to be accomplished without interrupting the existing substation. Plus, the new substation design had to accommodate the already cramped facility and meet with the approval of the utility as well as the customer.

Engineering and Construction Solutions:
We modified the utility's incoming 230 kV buses to maximize the allowable area for substation construction. The substation design consisted of three individual bays. The foundations required special design considerations to provide the required oil containment systems, electrical equipment, and construction vehicles that had to share the cramped space. The 12.47 kV cables were then routed underground through the existing utility substation yard to the outgoing overhead transmission lines. All work was accomplished without disruption of service to either the customer or the utility.

High Voltage Substation Design Scope:
Design, supply and install a total system which included structures; 230 kV utility metering units; three 230 kV SF6 gas circuit breakers; 230 kV disconnect switches; three 230 kV/12.47 kV, 30 MVA transformers; three 15 kV vacuum circuit breakers; line relaying and substation relaying packages and one all inclusive relay and control building. We provided all engineering, coordination, project management, labor, testing and start-up as one turnkey operation to the customer.