GRID

Polar vortex temperatures plunged below many power plant operating scenarios, NERC reports

The extreme subfreezing temperatures during last winter's polar vortex siege took down nearly every type of equipment found on electric generating plants, forcing more than 17,700 megawatts of generating capacity to shut down at one point, a regulatory review reported yesterday.

The "Polar Vortex Review," issued by the North American Electric Reliability Corp. (NERC), noted that much of the generation equipment had not been designed to withstand such extreme cold, particularly in the Southeast.

The list of equipment failures due to the bitter weather fills nearly three pages of the NERC report.

Water intruded into gearboxes and valves and froze. Circulating water froze, as did a transmitter, a water injection coil, grease coverings on switches and an output circuit breaker. An air intake inlet was covered with snow and ice. Fuel oil gelled on fuel filters. Frozen lines disabled air pollution controls. Compressor blades iced up. Ice blocked an inlet bird screen.

"Many outages, including a number of those in the southeastern United States, were the result of extreme cold weather that was below the design basis of generating units," the report said.

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The report put a stronger focus on equipment issues than on delivery of natural gas, another issue in the polar vortex event.

NERC, the federally designated grid operations monitor, recommended that power plant operators review cold-weather scenarios in light of last January's blast but did not propose a required review to protect against extreme temperatures that went beyond current planning levels.

It credited grid operators with handling the crisis well, noting that only one deliberate power cutoff to customers was ordered and that affected 300 MW in all, or a fraction of 1 percent of demand in interstate power networks east of the Rockies and in Texas.

NERC recommended generators "consider (where appropriate)" whether plants should be prepared to withstand a repeat of the past winter's extreme vortex temperatures. Generation companies should "continue to follow the Reliability Guideline," a set of NERC recommendations for cold weather operations, it said. Measures to protect generating plants against extreme cold may reduce their summertime output, NERC noted.

Regions that are regularly hit with cold weather were better prepared than warmer areas, the report said. The Midwest Reliability Organization, the NERC region straddling the Mississippi River, is geared for harsh weather and lost 1,379 MW due to weather-related issues. SERC, the NERC reliability group in the Southeast, typically plans for an expected low of 10 degrees Fahrenheit but instead was hit with unusually severe wind chills, losing 11,000 MW of generating capacity on Jan. 7.

James Merlo, NERC's director of reliability and risk management, said in a briefing yesterday that the challenges that generators faced in January were different than those confronting Texas power companies during severe cold-weather outages in 2011.

"Many of those were maybe some lack of preparedness," said Merlo, referring to the Texas outages, "where we didn't see that this time. We saw simply preparedness that didn't go down to the lows that they were being faced with."

"In our opinion, it looks as if those generators were performing as well, or as expected," said Howard Gugel, NERC's director of performance analysis.

The blast of Arctic air that ranged across much of the United States in January was the coldest in 17 years, producing record demands for electricity and also for natural gas -- a steadily growing power plant fuel source. Merchant generating plants that compete daily to serve customers typically do not lock up assured supplies of gas but instead purchase it as it is needed. Utilities providing heating gas sign long-term supply contracts and took priority over many merchant electric power utilities, NERC noted.

Gas prices soared both at the beginning of the month and again in the third week, when severe cold weather returned. Northeast spot gas prices broke all previous records, surpassing $100 per million British thermal units (MMBtu). Prices around $6 per MMBtu were common elsewhere.

The NERC report did not examine reasons for constrained gas supply or price spikes, whether from freezing gas wells, cold-affected pipeline operations or market strategies by gas traders.

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