For the second time in a less than a year, a major Twin Cities utility has had to cut off gas service to customers in cold weather after a failure in its system.
An outage in Shakopee that started Monday evening and went into Tuesday left about 600 of CenterPoint Energy's residential and business customers without gas for several hours. Most of them were in Shakopee's downtown business district, with some in areas to its north and south.
Service was restored gradually, and by 8:30 p.m. Tuesday all but 17 customers were back online, said Ross Corson, a CenterPoint spokesman. The temperature at the Minneapolis-St. Paul airport bottomed out early Tuesday at 5 degrees.
In late January, when temperatures plunged to 30 degrees below zero, about 180 Xcel Energy customers — mostly in the Princeton area — lost service. With the cold, gas demand spiked and Xcel's pipeline pressure dropped. Xcel, fearing low pressure would spread, asked all 460,000 of its gas customers to turn down their thermostats to 63 degrees.
Minneapolis-based Xcel is the state's second-largest gas utility; Houston-based CenterPoint is the largest with 870,000 customers.
On Monday evening, CenterPoint had begun getting calls from Shakopee customers who seemed to be losing gas pressure, Corson said. Some were losing heat, while others weren't getting a full flow of gas to their appliances.
An estimated 600 customers ended up losing heat for "several hours" due to the low pressure, Corson said.
CenterPoint crews worked through the night and fixed the problem by 5 a.m., he said. But after the repair, CenterPoint's employees had to go into every house or business, a safety procedure to ensure that service was restored and no gas had leaked. "Technicians are going door to door," Corson said Tuesday afternoon.
Natural gas demand surged statewide Monday as temperatures dropped to unseasonable lows. Monday marked the coldest high on Nov. 11 in three decades in the Twin Cities.
Gas service to Shakopee failed due to a problem at a pressure regulator station that was built last summer, Corson said. The regulator station steps down pressure from a high-pressure main gas pipeline to lower-pressure distribution lines.
CenterPoint said it does not yet know what caused the pressure regulator to fail.
In January, pressure dropped on the edges of Xcel's metro gas distribution system as demand escalated. The company essentially lacked adequate capacity in the Princeton and Hugo areas, causing service outages of up to a day.
Xcel has since installed larger pipes aimed at reinforcing delivery pressures in Princeton and Hugo, as well as in Blaine, Becker, Big Lake and Chisago Lakes.
Altogether, Xcel spent $7.7 million on the improvements and laid 13.6 miles of new pipe. Xcel also improved its cold temperature modeling, which state regulators found to be flawed in a postmortem of how Minnesota utilities handled the brutal cold snap between Jan. 28 and Feb. 1.
Before that deep freeze, CenterPoint identified two points of potential concern on its own network and deployed temporary compressed natural gas stations to those areas when the severe cold struck, according to filings with the Minnesota Public Utilities Commission. One was near Cambridge, the other in Richfield.
CenterPoint did not need to use the backup compressed natural gas in Cambridge, though it did in Richfield for one hour each on Jan. 30 and 31 in order to keep pipeline pressure up. CenterPoint has since reinforced its pipe system in those two areas, the company said in a PUC filing earlier this month.