The Virginia State Corporation Commission approved the continued use of a grid safety device that can make mid-scale solar projects financially exorbitant.
In early February, the state’s SCC permitted utility Dominion Energy to continue requiring direct transfer trip (DTT) on interconnected solar and storage projects, which prevents distributed energy resources from generating power when operating independently from the grid, or “islanding,” when it isn’t necessary.
Producing isolated power in this fashion can pose safety risks, such as keeping downed power lines energized during a grid outage. But critics of DTT believe existing utility and inverter safety protocols and mitigate these risks.
DTTs apply to interconnected solar projects 250 kW or higher. The Interstate Renewable Energy Council (IREC) believes the cost of implementing DTTs can prevent solar and storage projects from happening altogether. IREC reported in a study published in July that DTT communications components, such as radios or fiber optic wiring, can cost tens to hundreds of thousands of dollars, and solar project developers for buying them.
“This is an incredibly disappointing outcome after years of industry-utility collaboration, decades of research and gigawatts of interconnections in other territories all proving that DTT is arbitrary for use in inverter DER applications,” said Brian Lydic, chief regulatory engineer for IREC.
In that report, IREC estimates that an “unintentional island” scenario that could pose safety risks is unlikely — that it would happen “once in about 3,800 to 10,000 years.”
“These claims are supported by empirical data, as only one documented persistent island event has occurred in North America, which happened under highly unusual transmission-level conditions that are not addressed by typical DTT schemes,” the report reads.
While Virginia hinders its community and commercial solar markets by requiring DTTs, other states in the region are installing this scale of solar at a faster rate.
“It is disappointing that — during a time of historic increases in energy prices, in the data center capital of the world — Virginians will have less access to the energy cost savings of community DERs,” said Shay Banton, regulatory program engineer and energy justice lead at IREC.
