NERC’s Polar Vortex Review Bares Natural Gas Dependency, Equipment Vulnerabilities

Despite record low temperatures and widespread generation outages during the polar vortex, bulk power system reliability was maintained, says the North American Electric Reliability Corp. (NERC) in a newly released analysis of the extreme cold weather event that engulfed most of the nation this January. 

The Jan. 6–7, 2014, weather condition that resulted in temperatures of 20F to 30F below average in the Midwest, South Central, and East Coast regions of North America caused a record loss of generation capacity nationwide (infographic)—substantially more than the February 2011 Southwest cold weather event.

However, while system operators were faced with “many difficulties,” they “were able to successfully maintain reliability through extensive previous training and preparation,” says the entity tasked with ensuring the reliability of the bulk power system in the U.S., Canada, and a part of northern Mexico in a 49-page review of the event released on Tuesday.

Balancing authorities and load-serving entities in both the Electric Reliability Council of Texas (ERCOT) and the Eastern Interconnection were mostly able to maintain their operating reserve margins and serve firm load, NERC says. Only one balancing authority—South Carolina Electric and Gas—was required to shed firm load, but the amount shed was less than 300 MW, representing less than 0.1% of the total load for the Eastern and ERCOT Interconnections.

Load reduction techniques employed by system operators to maintain reliability during the polar vortex included voltage reduction, interruptible loads, and demand-side management. “Many System Operators also made effective use of emergency procedures to manage loads and generation,” the report says.

Significantly, the event exposed industry’s vulnerability to various challenges with fuel supply and delivery as related to its increased reliance on natural gas, the report suggests. It also says that potential risks associated with increased dependence on natural gas are most acute in areas where power generators rely on interruptible natural gas pipeline transportation.

Natural gas will contribute well over 50% of on-peak power by 2023, with the addition of 40 GW of planned gas-fired capacity over the next decade. NERC warned that to avoid future reliability lapses during extreme cold events, industry must work with gas suppliers, markets, and regulators to identify issues with gas supply and transportation.

Many outages during the event—including a number in the southeastern U.S.—were otherwise “the result of extreme cold weather that was below the design basis of generating units,” the report notes. This was despite improvements made in winter preparation activities by generation facilities since February 2011.

Of the estimated 19,500 MW of capacity lost due to cold weather conditions, more than 17,700 MW was due to frozen equipment, the report says. The numbers are much lower than the 82 GWof forced outages and derates reported by Federal Energy Regulatory Commission staff in an April 2014 presentation.

NERC recommends that generators review and update power plant weatherization programs as a result of lessons learned from the polar vortex event. That includes a review of plant procedures, training programs for severe weather and winter weather events, and availability of material and equipment for response to these events. It also calls on entities to continue to follow reliability guidelines in the “Generating Unit Winter Weather Readiness – Current Industry Practices.”

NERC will host a webinar on cold weather lessons learned on Oct. 2.

For more, see POWER‘s October 2014 issue for a collection of stories designed to help power generators prepare their coal, gas, nuclear, and renewable plants for cold weather operations.

Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)

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