Utility companies reassessing natural gas systems after extreme cold

The extreme cold snap at the end of January, when temperatures across the state hovered around 30 below, tested the state's natural gas utilities.

While most utilities were able to ride out the extreme conditions, about 150 Xcel Energy customers outside Princeton, Minn., lost their heat when the company cut off their natural gas because it was having trouble delivering it.

Representatives from Xcel and other utilities explained their responses to the cold snap in front of the Minnesota Public Utilities Commission Thursday, and outlined for regulators their plans to improve their systems ahead of next winter's demands.

Two-thirds of Minnesota homes are heated with natural gas. And during the cold snap, most utilities didn't have trouble delivering natural gas to their customers, and none reported a shortage of natural gas. But Xcel asked all its natural gas customers to turn down their thermostats to prevent additional outages, after the company had cut off natural gas service to those 100-plus customers in Princeton.

Company officials told PUC regulators Thursday that their process for reliably getting natural gas to all customers wasn't adequate. The Princeton customers whose gas was turned off were at the end of a transmission line. And when customers before them on the line cranked up their heat in the cold weather, it reduced the pressure in the line and made it difficult for the gas to make it all the way to the end. Xcel had to cut off the gas till the pressure evened out again.

Xcel officials said the incident has prompted them to revisit the computer models they use to predict how their system will perform. The company also has plans to reinforce its natural gas transmission system, which will include installing bigger pipes in some places, so that when there's unusually high demand for natural gas — during a cold snap, for instance — the system will be able to handle it.

None of the other natural gas utilities whose leaders testified before the PUC Thursday experienced outage problems like Xcel's, but utilities in several areas around the state are taking a closer look at their systems after the extreme cold.

Officials from CenterPoint Energy said the company had tractor-trailers full of compressed natural gas tanks on standby in a few places, just in case they might need them, though they never ended up tapping into them.

CenterPoint, like Xcel, has plans to enhance its transmission system over the summer, in order to better adapt to whatever next winter brings.

Most utilities already have agreements in place with some businesses to cut back on their natural gas use when the system is under a lot of stress. That agreement was in place during the cold snap at the end of January, and it's another way utilities manage the increased need during extreme weather events.

Overall, state PUC regulators praised the utilities for their efforts at keeping the heat on across most of the state during the extremely cold weather. They took special note of all the gas workers who were out in the 20- and 30-below temperatures, maintaining the companies' delivery systems.

And while these types of prolonged, extreme cold snaps are rare, it's likely Minnesota will continue to experience periods of extreme cold, even as the general trend is moving toward warmer winters as a result of climate change. Climate scientists are studying whether these types of extremes will be more likely in the future.