Scope
This project involves the design and construction of a 125 MW PV array, a 31.25 MW/125 MWh Battery Energy Storage System (BESS), and a 230/34.5 kV substation. ASEC’s scope covers the Gen-Tie transmission line design (800 feet, 230 kV), civil and structural design for the PV system and substation, as well as protection/control systems for the interconnection with PG&E. ASEC is responsible for the collection system’s medium voltage (MV) cable design, foundation layouts, grounding systems, and system studies.
Technical Challenges:
- Design Modifications: The client introduced several modifications to the design during the early phases, including additional equipment to improve the PV system’s efficiency, which necessitated frequent updates to the electrical and structural components.
- Multiple Off-Takers: The PV array was required to serve two separate utility off-takers, adding complexity to the metering and protection systems. This also required adjustments to the substation configuration to ensure operational reliability.
- Crossings and Clearances: The Gen-Tie and PV system design required multiple road crossings, both county and state roads, which needed to comply with underground utility installation regulations. Additionally, the project site is located within a high-seismic zone, requiring comprehensive foundation designs and seismic assessments.
Value-Added Engineering:
ASEC’s engineering team implemented several optimization strategies, such as minimizing tree removal in the project’s cable routing to reduce costs. Additionally, ASEC utilized advanced PLS-CADD and CYMCAP modeling to optimize the transmission line sag and tension characteristics, ensuring compliance with clearance requirements. The team also addressed seismic risks through the design of foundations and structures capable of withstanding high seismic loads, verified by shake-table testing.
