New 115kV Substation to Replace Existing on the Same Site; Poor Soil Conditions in California Location

Project Scope: Design Build Substation
Design, supply and install a total system including structure, one 115kV/12.47kV, 20 MVA transformer; one 115kV circuit breaker; three 15kV regulators; one 15kV walk-in switchgear; all above-grade appurtenances; all underground and civil work; new outgoing pole line taps; engineering coordination and start-up.

Design Build Substation Key Issues:
The manufacturer's existing utility-supplied substation had become inadequate for their power needs. The substation also was built on "diatomaceous" soil which required special foundation design considerations. The special soil factors were not properly accounted for in the original design and, as a result, substation equipment was beginning to sink and suffer from differential settlement. The customer specified a time constraint of 28 weeks for completion of the project, and required minimal disruption of the existing service.

Engineering & Construction Solutions:
To overcome the soil problems, foundation designs were based on supplying two "floating" pads, which provided multiple equipment foundations and oil containment curbs. The physical design incorporated a 90-degree bus turn to accommodate the only available space.