ISO-NE presented the Planning Advisory Committee on Thursday with potential study conditions to identify transmission needs under increased penetration of distributed energy resources, renewables and energy storage resources (ESRs) and increasing imports via HVDC interconnections.
In addition to responding to different system conditions in this “future grid,” planners also will need to consider new approaches to data collection to ensure accurate modeling, said Dan Schwarting, transmission planning supervisor for ISO-NE.
The RTO said the discussion Thursday was the first of many it plans with stakeholders this year; studies with new assumptions may begin in 2021.
While the RTO’s current study methods and assumptions work well, Schwarting said, they may be inadequate in a decade, when these new resources become increasingly ubiquitous.
With a higher penetration of DERs, primarily solar PV, and continued offshore wind generation development, Schwarting said, “what we’re finding is that as time goes on, and these trends continue to accelerate — we continue to see more wind interconnections and more distributed energy resources — we really need to rethink some of these approaches.”
For example, ISO-NE lacks visibility on, and control of, storage assets on the distribution system. New England currently has less than 5 MW of solar PV connected to its distribution systems, but by December 2029, that will increase to 7,796 MW, according to the 2020 Capacity, Energy, Loads, and Transmission (CELT) report.
In addition to the 30 MW of offshore wind generation currently in service, an additional 1,504 MW have secured state contracts, with 156 MW committed through the Forward Capacity Market and another 1,600 MW of state contracts under negotiation.
To date, New England’s planned offshore wind interconnections are located in southeastern Massachusetts and Rhode Island.
“There’s not a real lot of geographic diversity yet,” Schwarting said. “That may change further down the road.”
Low wind production at peak load could lead to high imports for the Southeast Massachusetts/Rhode Island region, while high wind and solar production at low load levels could lead to high exports. High wind production could also lead to voltage control challenges because of a smaller number of synchronous generators online.
As DER penetration increases, Schwarting said, net load will not accurately define system conditions. He cited two examples of an 8,000 MW net load level: at 3 a.m. on a mild spring night with 8,000 MW consumed and no solar, versus 1 p.m. on a mild, sunny spring day when 14,000 MW is consumed but is partially offset by 6,000 MW of solar.
The revised assumptions will be used in future needs assessments and solutions studies in addition to studies of market efficiency and public policy transmission upgrades.
Studies already underway will continue under existing planning assumptions and not restarted, Schwarting said. Solutions already planned or under construction based on previous studies will not be re-examined either.
“There’s still a lot of different areas that we have to explore. We don’t think that we’ll be ready to start a new study with these assumptions for at least quite a few months at this point, so we don’t want to put all of our existing studies on hold, especially those that are discovering time-sensitive needs,” Schwarting said. “We also don’t expect that a lot of the upgrades that we’re identifying will be significantly different under the new proposal.”
ISO-NE is taking feedback from stakeholders on the proposals until Oct. 9, with further discussion slated for future PAC meetings. In the meantime, RTO staff will continue their development of study assumptions concerning ESRs; areas with noncoincident peak loads; conventional generator outages; interface transfers; and light and shoulder load conditions in proposed plan application studies. Staff will also talk to distribution providers to obtain data on DERs.
Lower Maine 2030 Needs Assessment Draws Questions
Transmission planning engineer Meena Saravanan gave the committee a presentation on the scope of work for the Lower Maine 2030 Needs Assessment, which ISO-NE announced on Sept. 10.
The assessment is intended to evaluate the reliability and identify needs in Lower Maine under future load conditions reflecting the 2020 CELT report; resource changes based on Forward Capacity Auction 14 results; and reliability over a range of generation patterns and transfer levels. It also will seek coordination with needs assessments in Upper Maine and New Hampshire.
ISO-NE began a statewide needs assessment in June 2017 but split it into Upper and Lower Maine studies because of the need to consider the proposed New England Clean Energy Connect (NECEC) HVDC transmission line. RTO staff are conducting a solutions study based on the results of the Upper Maine assessment, which was completed in March.
The Lower Maine assessment could not proceed until NECEC’s system impact study was completed and its required system upgrades were known, Saravanan said.
The primary triggers for the Lower Maine assessment were compliance with reliability standards; transfer capability; short-circuit performance; and system performance considering delist bids and cleared demand bids.
One area that drew a sharp line of questioning from a stakeholder was the 2030 peak load assumptions for Phase II HVDC, from Quebec to New England, which was given a dispatch range of 950 MW.
Bruce McKinnon, who represents the Norwood Municipal Light Department in Maine, said Phase II normally carries at least 1,200 MW.
“I find that to be a little bit of a problem,” McKinnon said. “I can understand maybe doing some studies with it one way or the other. But the fact that you’re not pushing it to what it is normally contributing to the system, I think, is a failure of an assumption — and I’d like the minutes to say so too.”
Schwarting acknowledged that the line has operated at higher levels. “The 950 MW is essentially everything that we can contractually count on,” he said.
Comments on the work scope will be collected until Oct. 9. The assessment is expected to be completed and presented to the PAC in the first or second quarter next year.
SWCT 2027 Solutions Study Concludes
ISO-NE told the PAC that the Southwest Connecticut 2027 Solutions Study is complete because the time-sensitive needs identified in the corresponding needs assessment have been addressed by Eversource Energy’s Glenbrook static synchronous compensator (STATCOM) asset condition project.
The assessment’s minimum load analysis found four buses with N-1-1 high-voltage violations for contingency events that included the loss of both STATCOMs at Glenbrook and the loss of a 345-kV reactor in the region.
Eversource presented its proposed solution at the July PAC meeting, saying maintenance or refurbishment of the existing STATCOMs — which were installed in 2004 and have an availability rate of only 81% — was not feasible.
The project replaced the two Glenbrook STATCOMs by repurposing the existing STATCOM building and outdoor equipment. The replacement STATCOMs, which would have the same reactive capability as the existing STATCOMs under normal operating conditions, eliminate the common mode failure.
The project is estimated at $21.6 million and has a targeted in-service date of April 2021.