NEW ORLEANS -- The company that supplied electricity to the Super Bowl took the blame Friday for the power outage that brought the big game to a halt, explaining that a device designed specifically to prevent a blackout failed and plunged the game into darkness for more than half an hour.
The device called a relay had been installed to protect the Superdome from problems in the cable that links the company's incoming power line with the lines that run into the stadium.
Officials from Entergy New Orleans said the relay functioned with no problems during January's Sugar Bowl and other earlier events. It has been removed and will be replaced.
All systems at the Superdome are now working, and the dome was to host a major Mardi Gras event Saturday night, said Doug Thornton, an executive with SMG, the company that manages the stadium for the state.
The device was installed in a building near the stadium known as "the vault," which receives a line directly from a nearby Entergy substation. Once the line reaches the vault, it splits into two cables that go into the Superdome.
Sunday's power failure cut lights to about half of the stadium for 34 minutes, halting play between the Baltimore Ravens and San Francisco 49ers.
Not long after Friday's announcement, the manufacturer of the relay, Chicago-based S&C Electric Co., released a statement saying that the blackout occurred because system operators had put the device's so-called trip setting too low to allow the device to handle the incoming electric load.
The statement did not name the operators, but the equipment was owned and installed by Entergy New Orleans, a subsidiary of New Orleans-based Entergy Corp.
"If higher settings had been applied, the equipment would not have disconnected the power," said Michael J.S. Edmonds, vice-president of strategic solutions for S&C.
In a follow-up statement, Entergy said that tests conducted by S&C and Entergy on the two relays at the Superdome showed that one worked as expected, the other did not.
Entergy spokesman Mike Burns said both relays had the same trip setting.
Entergy's announcement came shortly before company officials were to answer questions about the outage from a committee of the City Council, which is the regulatory body for the company.
During the committee hearing, City Council member Susan Guidry asked Entergy executives whether they were "fairly certain" that the relay was faulty.
"That is correct," said Dennis Dawsey, an Entergy vice-president.
However, when asked if the outage was caused by the design or a defect in a part of the equipment, Entergy New Orleans CEO Charles Rice said that had not been determined.
"The equipment did not function properly," Rice said. "At this particular time, based upon our analysis, we cannot say definitively that there was a defect in design. What we do know is that the equipment for some unknown reason, at this particular time, did not react the way that it should have."
Asked if Entergy and SMG still plan to hire a third-party investigator to get to the bottom of the cause, Rice said that possibility remains open.
"We'll work closely with SMG, and if there is a need for a third-party investigation, we will do that," Rice said, adding that Entergy was also working with the manufacturer.
Shabab Mehraeen, an assistant professor of electrical engineering at Louisiana State University, said the relay device is a common electrical fixture in businesses and massive facilities such as the Superdome.
"They are designed to keep a problem they sense from becoming something bigger, like a fire or catastrophic event," said Mehraeen, who holds a doctorate from the Missouri University of Science and Technology in Rolla, Mo.
The devices vary in size. Mehraeen, who was not familiar with the relay at the Superdome, said he "wouldn't be surprised if it was bigger than a truck."
Mehraeen said the reasons the devices fail are the subject of much academic research into the interaction of relays with the complex electrical systems they regulate.
"It's not unusual for them to have problems," he said. "They can be unpredictable, despite national testing standards recommended by manufacturers."
Entergy and SMG had both upgraded lines and equipment in the months leading up to the Super Bowl. Rice said the new switching gear, with the faulty relay, was installed as part of a $4.2 million upgrade by Entergy, including the installation of a new power line dedicated solely to the stadium.
In a separate project, SMG replaced lines coming into the stadium after managers expressed concerns the Superdome might be vulnerable to a power failure like the one that struck Candlestick Park during an NFL game in 2011. That outage was blamed at least partly on a transformer explosion.
Thornton stressed Friday that the dome was drawing only about two-thirds of its power capacity Super Bowl night, and said typical NFL games in late August or September can draw a little more.
City officials had worried that the Super Bowl outage might harm New Orleans' chances of getting another NFL championship game.
But NFL Commissioner Roger Goodell downplayed that possibility, saying the NFL planned to keep New Orleans in its Super Bowl plans. Mayor Mitch Landrieu said the city intends to bid for the game again in 2018.