Cable may lack extra capacity

Sat, 03/12/2016 - 7:15am
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“If the Block Island Wind Farm is operating at full capacity, there wouldn’t be much cable capacity available for other generators to send power to the mainland.”

That’s what National Grid Engineer David Campilii told The Block Island Times when asked if there would be any capacity available on the 30-megawatt cable for other generators, or power purchasers, besides what’s being generated by the five turbine, 30-megawatt Block Island Wind Farm. Campilii is the chief engineer involved with installing the 20-mile long, $107 million National Grid cable transmission system, called sea2shore, connecting Block Island to the mainland electrical grid.

The Block Island Power Company (BIPCo) has expressed interest in seeking a waiver to operate as a power producer, as we all as a distributor. If BIPCo is granted the waiver to operate in both capacities, ISO-New England (Independent System Operators for the New England Region) would require five-megawatts of capacity on the cable to receive the power that it produces.

“The (National Grid) cable system is designed to (only) deliver 30-megawatts,” said Campilii. “There is nothing we can do at this point to change that since the cable is already fabricated. If a new generator wants to connect to the system, they would have to either live within the existing system limitations, meaning that they could be limited as to when they could generate based on available cable capacity, or partially, or fully pay for, system reinforcements.” Campilii noted that “ISO-New England has a formal process for doing that.”

The problem is, if the wind farm is operating “at a full 30-megawatt output, and the island electric demand was zero megawatts, then there would be no capacity available on the cable,” said Campilii. “You have to remember that the wind farm generation will go up and down with the wind, and the island load goes up and down during the day and across the seasons. ISO-New England and National Grid control centers would keep track of this very dynamic situation.”

The issues associated with limited cable capacity are something that BIPCo is aware of. “Our consultant is researching this question and we have not had enough information to assess the issue,” BIPCo co-owner Al Casazza told The Times.

Campilii said that “almost any new (power) generator that comes online has to see how they fit into the existing system. Assuming BIPCo went through the ISO process and was allowed to interconnect, it would be up to ISO-New England to determine the need for the BIPCo diesel (generators) to run.”

BIPCo’s sale of energy to the mainland grid would most likely be in times of need, or in emergency situations. 

The issue of BIPCo operating as an emergency backup in case the wind farm was unable to produce power has been debated. Campilii said, “ISO-New England has definitions of emergencies, which generally refer to loss of system components, for example, a transmission line or other component unexpectedly going out of service. There may also be periods of time where there is not enough generation available on the system to supply the electric demand. Those might trigger a call for generators to operate, which is ISO’s call.”

As far as BIPCo storing energy that could be used in emergency situations, Campilii noted that he wasn’t “aware of any significant energy storage facilities on Block Island. If the connection from the island to the mainland power grid went down because of a problem on the mainland, National Grid would typically be able to restore service fairly quickly. If the connection from the island to the mainland power grid went down because the underwater cable failed, a rare event, but it can happen, typical repair time for an underwater cable failure is measured in months. BIPCo would most likely have to run (diesel) generation during such an event. BIPCo will have to determine how much generation to keep on the island going forward.”

Under current law, a utility company cannot operate as both a distributor and a generator. BIPCo is seeking a waiver to operate as both a diesel generator and distributor of energy. EUTG members Barbara MacMullan, Everett Shorey and Bill Penn have been advising the Town Council regarding BIPCo’s rate restructuring case. After the waiver process, BIPCo will file a a rate restructuring case.

In explaining how the system would work from Block Island’s perspective, Penn said that, “BIPCo will pay New England Power for the amount of electricity it uses on the island.” Penn noted that that amount is about four megawatts of electricity during the peak summer season, and roughly between 500 to 1,000 kilowatts in the winter. For reference, one megawatt of electricity is equal to 1,000 kilowatts, or 1,000,000 watts.

As presently contracted, the majority of energy produced by the wind farm will be distributed to mainland ratepayers by the New England Power Company, which is a subsidiary of National Grid. Conversely, four megawatts produced by the wind farm will be sent to BIPCo for distribution to Block Island’s ratepayers. The 30-megawatt wind farm is expected to produce more than 125,000-megawatt hours of electricity annually.