A short circuit trips electrical protective devices because it overloads the system. A ground can trip EPD's through other means such as GFI activation, but the sensing system sounds like a more sophisticated protective device such as frequency or voltage sensing equipment, intended to protect the stadium distribution system from external faults. Sounds like new equipment was installed or the stadium buses were placed into an abnormal lineup and they ran into the front-end of the bathtub curve.
Photograph by Gerald Herbert, AP
Published February 4, 2013
All that is known so far about the Mercedes-Benz Superdome power outage that temporarily halted last night's Super Bowl game is that a crucial piece of sensing equipment operated exactly as designed: It turned the electricity off.
But officials at the Superdome and its energy company, Entergy, said further investigation is needed to get at the root cause of the electricity abnormality that plunged half of the recently renovated stadium into darkness and forced a 34-minute delay of one of the world's most watched sporting events. (See related quiz: "What You Don't Know About Electricity.")
So while sports analysts dissect how the Baltimore Ravens held off the rallying San Francisco 49ers in the second half to secure their 34-31 victory, this year's postgame analysis will include scrutiny by teams of electrical engineers and stadium systems experts.
Despite much online speculation on the subject, it's unlikely that the scale of Beyoncé's dazzling, hologram-assisted halftime show was to blame for the outage, says James L. Kirtley Jr., professor of electrical engineering at the Massachusetts Institute of Technology.
It's possible, he said, that the cause was a simple overload, like what happens in a kitchen when a coffee pot and microwave are run at the same time. "The stadium system is, of course, a lot bigger, but fundamentally [it is] very similar" to a household circuit panel, Kirtley explained.
However, based on public statements from Entergy and the Superdome, Kirtley suspects that "some other piece of equipment failed and put a short circuit across the power circuit, causing a circuit breaker to open and disconnect power to some part of the stadium circuits."
After the stadium went dark, Entergy, which supplies electricity to 2.8 million utility customers throughout the Gulf Coast, quickly announced via its Twitter feed that its service to the stadium had not been interrupted. The problem, Entergy tweeted, was on "the customer's side." A later joint statement from Entergy and Superdome managers said the problems began when a piece of equipment designed to monitor electrical load "sensed an abnormality in the system."
"Once the issue was detected, the sensing equipment operated as designed and opened a breaker, causing power to be partially cut to the Superdome in order to isolate the issue," the statement said. "The fault-sensing equipment activated where the Superdome equipment intersects with Entergy's feed into the facility."
It is standard—in fact, usually required by law—for electrical systems to include circuit breakers that automatically shut off power to prevent wires from overheating and causing a fire. Circuit breakers can trip when there is too much load on a circuit, but a power outage also can be caused by a short circuit or other type of fault.
It's not known how much electricity the Superdome was drawing when the power outage occurred; Entergy said in response to a query that it was confidential "customer" information.
It is known that energy use from the Super Bowl was estimated in advance to be 4,600 megawatts, but that included the power for the NFL hotels and Morial Convention Center during the week of the game. Entergy had agreed in advance to donate carbon credits, or investments in carbon-capture projects, to offset the carbon emissions caused by that energy use—3.8 million pounds of carbon dioxide emissions—as part of a wide-ranging "greening" effort around the game. (See related photos: "Super Bowl Caps Banner Season in NFL Green Drive.") That's as much carbon as 359 U.S. passenger cars typically emit in a year.
Superdome officials had hoped the Super Bowl would showcase to the world the $336 million in renovations that have been made to the stadium since it sustained massive water and wind damage in 2005 due to Hurricane Katrina. Some $156 million of the cost of the renovation was paid by the U.S. Federal Emergency Management Agency. That renovation included work on the stadium's electrical and lighting system, as the Superdome now has a 26,000-LED lighting fixture on 96 concave aluminum panels that ring the building's exterior, a system supported by more than five miles of copper wiring. This system, which draws no more power than a small home, won the 2012 "Excellence in Design" award in the Architainment category from Live Design Magazine, an architecture, design, and event production publication.
LED lights, in addition to being efficient, would be capable of coming on instantly after such an outage. But they are not bright enough to illuminate a field, so they provide only accent lighting. Most stadiums rely on high-intensity gas discharge fixtures for the main lighting of the venue. Such lights take some time to power up to full brightness—a half hour is common.
After emergency generators restored power to the playing field, fans still had to cope with reduced power, with escalators and credit-card machines shut down, and walkways lighted by small banks of light. Broadcasters and NFL officials also had to scramble.
Pretty reasonable to assume the PR writer meant 4600MWh, as 3.8mlb of CO2 production would correspond to a somewhat lower-than-average, yet reasonable, CO2 production rate of 826lb/MWh. http://cfpub.epa.gov/egridweb/ghg.cfm .
Chuck, I agree. Something is wrong.
First of all 4,600 megawatts is not a unit of energy as stated in the text. It's power. Perhaps it is missing the unit of time and should read "4,600 megawatt*HOURS. 4,600 MWh seems reasonable and at $.12/kWh it would cost about $552,000 for the week. Assuming 7 days, your number (4600kW)*168hours*$.12/kWh, it would cost $92,736 for the week.
"Indianapolis Super Bowl XLVI Host Committee are partnering with Green Mountain Energy to purchase 15,000 megawatt hours of renewable energy certificates (RECs) generated at wind farms in North Dakota to offset the power associated with the event.” And these renewable energy credits don’t just cover the game—they cover a month’s worth of activity!
Read more at http://cleantechnica.com/2012/02/05/super-bowl-2012-greenest-super-bowl-ever-infographic/#mzb2PG9J46WZdK2x.99 "
divide 15,000 MWh by four weeks (3750 MWh/week) and now 4600MWh/week for 2013 seems reasonable.
Hi Chuck, I'm energy editor here at National Geographic online news, and I, too, was troubled by the 4,600 megawatt figure that we got from the New Orleans Host Committee's press materials on its greening efforts: http://www.prnewswire.com/news-releases/new-orleans-hosts-greenest-game-in-super-bowl-history-189707741.html The largest nuclear plant in the United States, Palo Verde in Arizona, only has a capacity just under 4,000 MW. Most importantly, megawatts (or kilowatts) is a figure that reflects capacity, not power use.
So this morning I calculated what the power use would actually be if the Super Bowl generated 3,800,000 pounds of carbon dioxide, which is the amount Entergy said it would offset. Using the U.S. Environmental Protection Agency's excellent carbon equivalency calculator http://www.epa.gov/cleanenergy/energy-resources/calculator.html you can see that represents the amount of energy used by 258 U.S. homes over the course of a year. With the average U.S. home using 11,319 kilowatt-hours annually, that factors out to be 2.9 million kilowatt-hours energy use for the Super Bowl. Remember, that's not just the game itself but the NFL hotels & convention center activities in the run-up to the big event!
At this point, with the Superdome and Entergy not saying anything beyond their original statement, we really don't have clarification on the 4,600 MW figure they used in their pre-game press materials, nor do we know how much power was used during the game or whether it exceeded the system's capacity. Hopefully we'll know more as the investigation continues. We hope to continue to follow this story, which has captured the interest of sports fans and anyone who cares about electricity systems and reliability!
@Marianne Lavelle Wow, thanks for responding! It's a relief to see there are still publications which care about the accuracy of their material in a time when yellow journalism seems to be running rampant.
" 4,600 megawatts" doesn't sound right. A 3-reactor nuclear plant has trouble hitting 4,000MW. "4,600 kilowatts" would be a more realistic figure.
Anthony, I have heard that theory too. I asked Kirtley about it and he said the draw from a cell phone charger couldn't have tripped the system.
There was a story going around about a guy plugging in a cell phone charger and blowing a fuse or something. I saw it on YouTube.
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