New Southern California Substation Design including Cable Exits to Existing Overhead and Underground Systems

Substation Design Project Scope:
Total substation design and construction of a new 69kV substation to replace an existing substation scheduled for demolition. Design, supply, install and test an entire system which included structures, 69 kV preferred and alternate bus including all breakers and switches, 12.5kV preferred and alternate bus including all breakers and switches, two 50 MVA LTC power transformers, complete relay/control scheme with building, communication building, separate storage building and landscaping that included a decorative block wall. All construction labor was included and supplied by local craftsman.

Substation Design Factors: The new site was located at an existing shopping plaza. Site conditions such as soil composition, resistivity and underground obstructions were unknown. The relocations of incoming and outgoing underground circuits were challenging due to right of way and access constraints, local businesses, existing and future roadways, and traffic considerations. In addition to the physical problems, a reluctance to change on the part of the end user provided some interesting challenges because in some situations up-to-date standard equipment could not be used.

Substation Design Key Issues :
The existing substation was located in an area slated for a new on-ramp as part of an expansion to a major interstate highway in Southern California. The new substation had to essentially mirror the existing station by matching the three incoming 69 kV circuits and 21 outgoing 12.5 kV distribution feeder circuits. The construction and cutover had to occur without any extended outages since this substation feeds major industry, commercial and residential areas.

Substation Design Engineering & Construction Solutions:
We provided several preliminary routing plans for the new connections to existing loads. These plans allowed ample time to coordinate the routing and cutover procedures with all parties involved. This conceptual engineering allowed the customer sufficient time to coordinate the load shifting and construction procedures with the local merchants and customers that might be affected by the changes. The relay and control schemes were modernized to provide for sufficient protection schemes while not compromising the wishes of the current maintenance personnel. The entire 69 kV/12 kV substation was constructed prior to making any critical circuit cutovers.