SolarCity & Oregon State University

This 1435kW (DC) photovoltaic project is installed on Oregon State University lands west of the main campus and interconnected with the PacifiCorp 20.8kV distribution system in Corvallis, OR. TriAxis was responsible for the medium-voltage interconnection design and protective relay support. This project uses three 500kW inverters delivering power through step-up transformers to an interconnection recloser and medium-voltage meter. The protection system is designed to prevent harmful islanding of the inverters under load and includes a fiber-optic transfer trip scheme. 

Completion Date: 2014

Design work for which TriAxis was responsible:  medium-voltage design including transformer specification, protective recloser design, programming of recloser control, coordination with PacifiCorp.

Contact: SolarCity, San Mateo, CA

Rabbit Research Lab

TriAxis Engineering provided interconnection support, low-voltage and medium-voltage design, and was the electrical engineer of record for this 1.5MW electric photovoltaic project developed by SolarCity of California and built on the Oregon State University campus in Corvallis, Oregon. The work included underground 600VAC and 20.8-kV design, transformer specification, protection design, and interface with the local utility (PacifiCorp) through the System Impact Study and Facilities Study interconnection process.

The plant includes over 5700 250Wdc photovoltaic modules on fixed supports, DC-system combiners and recombiners, 500-kW Xantrex inverters, 208V-20.8Y/12.0-kV 500-kVA padmount transformers, 25-kV underground cabling, a 25-kV Siemens padmount recloser to provide interconnection isolation from the utility system, and a 25-kV class padmount primary meter per utility standards. The interconnection protection scheme includes fiber-optic based transfer trip to the utility substation.

Completion Date:  2013

Design work for which TriAxis was responsible:  100%


Joseph Community Solar

The project included design of a medium-voltage collection system and a utility interconnection of a 500kW photovoltaic installation, with a PacifiCorp distribution system located near Joseph, OR.

Scope included development of interconnection protection, creating specifications for power transformer, grounding transformer, pole/padmounted recloser, and overhead line elements. Interconnection support included close interface with PacifiCorp protection and distribution engineers and designers to develop a suitable and effective system. 

Completion Date:  2012

Design work for which TriAxis was responsible:  100%