Below Industry Standards
HMLP currently serves approximately 10,600 customers in Hingham, and the system faces several significant reliability vulnerabilities.
HMLP assesses its system reliability performance against the standards set by the North American Electric Reliability Corporation (NERC), the Independent System Operator – New England (ISO-NE), and the Northeast Power Coordinating Council (NPCC). These standards include evaluating reliability performance under certain events, such as extreme weather or other accidents that could damage support poles or equipment. HMLP does not currently meet these industry reliability standards.
Hingham’s electricity is supplied by two parallel 115 kV transmission lines that share the same double-circuit towers for much of their route. With 22 shared structures between the East Weymouth substation and HMLP’s Hobart 1 substation, a single structural failure could disrupt both lines at once. In that scenario, every customer in Hingham could experience a prolonged outage. For instance, one fallen pole/support unit could result in an outage lasting a week or more.
Even if only one transmission line is out for maintenance or disrupted by an event, a failure on the remaining line could still result in a town-wide outage lasting 8 to 48 hours.
HMLP currently relies on a single substation with no alternate feed. This means there is no secondary substation or other source to provide power during extended outages.
Increasing Reliability Risk
HMLP’s system is at risk of an extended outage today. An increase in storm severity and the possibility of a train derailment or other accident along the active rail line further increase that risk.
The likelihood of outages on the two exposed, concurrent transmission lines increases significantly with an increasing number of extreme weather events. Like other utilities, HMLP is proposing to enhance the reliability of its systems to reduce the risk of outages, given the increasing severity and frequency of extreme weather events.
The 2023 Massachusetts State Hazard Mitigation and Climate Adoption Plan, also known as the 2023 Resilient Mass Plan, identifies damage to electric transmission and utility distribution infrastructure as a priority impact as it assesses the consequences of an increase in frequency and severity of storms and other serious weather events.
When HMLP’s current electric delivery system was constructed in 1986, the adjacent Greenbush train line had been dormant since 1959. With the Greenbush line reactivated, the possibility of an extended power outage caused by a train derailment or other accident along the active rail line was introduced. Accessing an active rail line to make necessary repairs is also extremely difficult and likely would result in a longer power outage.