The utility NStar defended its performance in the face of sharp questioning from Boston councilors Friday, rejecting calls for stricter oversight spurred by a massive power outage in March.
Councilors voiced frustration with NStar over the Back Bay outage on March 13, which left thousands without power for two days and cost businesses millions of dollars, and raised doubts about the system’s reliability following another outage this month.
Stephen Murphy, the City Council president, pointing out that the utility has a monopoly in Boston, called for outside inspections of its facilities.
“I think it’s just crazy you’re self-policed,’’ Murphy said at a morning hearing on the outages. “We’re NStar and NStar is us.’’
Craig Hallstrom, vice president of operations for NStar, balked at the idea of outside inspections and said the recent outages were a rare aberration.
“This is a highly reliable system by all utility standards,’’ he said, likening it to grids in New York City and Chicago. “These were the first incidents there in 22 years.’’
The second outage, which lasted less than an hour on May 8, occurred during ongoing repairs to the Scotia Street substation that caught fire in March. Murphy said two outages over a short span showed that not enough is being done to maintain the system, and argued for stricter regulation.
“I think a government entity should inspect substations,’’ Murphy said. “I think that’s where this has to go.’’
Neither city nor state regulators inspect NStar facilities. Other councilors expressed concern about the possibility of fires in substations across the city, particularly those in residential neighborhoods.
NStar, which serves 1.1 million customers in the region, inspects its substations monthly and monitors them constantly, Hallstrom said.
“They are very important assets to us,’’ he said. “We spend a lot of time inspecting, maintaining, and monitoring them.’’
Hallstrom said outside inspections would be difficult given the complexity of the system.
“Someone’s not going to be able to just walk into a substation and inspect it,’’ he said.
A spokeswoman for the state Department of Public Utilities, which oversees NStar, confirmed that the department does not conduct inspections, and is not equipped to do so.
Utilities must provide state regulators quarterly performance reports and more detailed yearly reviews on service.
“We review the reports to determine whether their service is at a high enough quality for the rate-payers, said Catherine Williams, a spokeswoman for the department. “They have to meet benchmarks from the lines to the substations.’’
NStar must submit a report by June 1 that details what caused the outages and what the company has done to strengthen the system. Last week, public utilities commissioner David Cash called the outages unacceptable, and said the company will review the reports closely.
Mayor Thomas M. Menino has called on NStar to provide a full explanation of what caused the fire in March. NStar has hired a consultant to investigate.
Councilor Michael Ross said NStar needs to make sure backup systems are in place to protect against such failures.
“It simply isn’t acceptable for our city to shut down,’’ he said.
Bart Shea, the city’s fire marshal, told councilors the department’s regular communications system faltered during the first blackout, forcing some firefighters to use radios. NStar said the problem was unrelated to the outage.
Work on the substation that caught on fire in March should be completed by mid-June, NStar said.
Hallstrom told councilors the second outage occurred when crews replaced a power supply system that was damaged in the March fire. When it came back on line, it caused a power surge that shut down operations.
“It was an unanticipated event,’’ Hallstrom said. “It’s a mechanical system and sometimes things do break.’’Peter Schworm can be reached at email@example.com. Follow him on Twitter @globepete.