Systems reliability at issue in New Haven’s PSB hearing this week

NEW HAVEN — The Public Service Board on Tuesday will hear from both the town of New Haven and Green Mountain Power, as to whether local power distribution lines are adequate to handle a 350 kW solar array proposed to be built next to the Vermont State Police barracks in New Haven.
The proposed solar array, called SSE New Haven Solar II, would be built next to a 150 kW solar array already in operation in the same location. The developer applied for permission to build the new array in March 2015.
The hearing is significant because it shows that the PSB recognizes the limits of the electric power grid in areas, such as New Haven, that have seen a growing number of solar power generation projects, Department of Public Service Director of Public Advocacy Geoff Commons said.
“There is an increasing penetration of solar generation projects — and that’s consistent with state policy,” Commons said (see story on Page 1). “At the same time, the electrical grid has limits in terms of how much it can sustain. When you get this greater penetration, this increased number of these distributed generation projects, some circuits can get overloaded. And at some point, you can start to strain the electrical system.
“That’s what this criteria is intended to look at and prevent.”
Regardless of whatever decision the PSB ultimately makes on SSE New Haven Solar II, Tuesday’s hearing can be considered something of a landmark win for New Haven.
It appears that New Haven is the first town awarded a PSB hearing on its concerns about the system stability and reliability presented by a proposed solar array. Commons said that such a hearing is certainly “rare” to “unusual.”
Commons also said it was similarly rare to unusual that the Public Service Board had officially joined Green Mountain Power to the proceedings.
Any proposed generation facility must not “adversely affect system stability and reliability,” according to the regulations governing the PSB’s decision-making process. So system stability and reliability are important criteria that the PSB must look at when evaluating any proposed solar project that needs a Certificate of Public Good.
Commons further explained the significance of the arcane language used in the PSB’s formal orders. Joining GMP to the SSE New Haven Solar II proceedings as a party, he said, means “that the board concluded that GMP was really necessary, that the board needed to hear from them in order to fully understand this issue. And to resolve it, they felt that they needed to hear from the entity that actually operates the poles and wires.”
While there are other ways the PSB could have obtained GMP’s testimony, Commons explained further, such as serving a subpoena, “joining them as a party seems to me — and this may be kind of subjective — to be the more straightforward way to ensure their participation.”
Among the specifics to be considered at Tuesday’s hearing are what action needs to be taken given that the SSE New Haven Solar II project failed part of GMP’s Fast Track system analysis.
Typically, what happens next when a power generation project fails Fast Track is more analysis is done — which can include a feasibility study, a system impact study, and a facilities study. But in the case of SSE New Haven Solar II, GMP said that those steps were not necessary. As part of its reasoning for ordering GMP joined as a party to the proceedings, the Public Service Board wrote, “What is not clear is the basis for GMP’s assertion that the Project can interconnect and that no formal studies are required. Furthermore, the filing does not demonstrate that the Project can be interconnected without affecting system stability or reliability.”
The Fast Track criteria that the project failed has to do with what’s known as the “generation-to-load ratio.”
Robert Amelang, an electrical engineering consultant with over 40 years’ experience in the field, provided expert testimony on the part of New Haven and will testify at Tuesday’s hearing. He said that there is a basic rule of thumb for system reliability that one must maintain a 15 percent ratio of total power generated on a circuit to peak demand on that same circuit. For example, if total power generated on a circuit is 150 kW then peak demand on that circuit should be 1,000 kW.
But in its Fast Track analysis of the proposed SSE New Haven project, GMP OK’d a line load of 521 percent — roughly 35 times the standard 15 percent limit — and then dismissed the 15 percent criterion as irrelevant, said Amelang. To return to Amelang’s example of a circuit with peak demand of 1,000 kW, that would be the equivalent of capping generation not at 150 kW but at 5,210 kW.
The town of New Haven has raised the issue of system reliability in every solar project proposal in the town, according to New Haven Town Attorney Cindy Hill, who represents New Haven in a number of cases before the Public Service Board.
“The question of system reliability, the criteria of system reliability that the Public Service Board has to evaluate,” said Hill, “is the question of, Are you going to get power outages? Are you going to get voltage spikes? Are you going to get flicker in your lights? Are you going to have poorer quality power that in our digital age may well affect a number of businesses. Anyone who’s got electrical equipment, computers, they need reliable, good quality, steady energy.”
For their part, Green Mountain Power officials say that they welcome the opportunity to appear before the Public Service Board at Tuesday’s hearing.
“We are looking forward to sharing information with the Public Service Board,” said Kristin Carlson, GMP’s chief spokesperson. “We’re ready to answer any questions. GMP is always focused on customers and grid reliability, and so we’re looking forward to this hearing.”
Reporter Gaen Murphree is at [email protected].

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