NERC: Extreme weather, gas and hydro constraints pose winter reliability risks

The U.S. and Canada have sufficient power reserve margins to meet or exceed forecast peak demand this winter, the North American Electric Reliability Corp. reported Nov. 18.

But extreme or prolonged cold weather, disruptions to natural gas infrastructure, and low hydropower conditions could threaten reliability in some regions, NERC said in its reliability assessment for winter 2021-2022.

The organization, which crafts reliability standards for the bulk power system, expects winter reserve margins to meet or surpass mandated levels in all areas NERC assessed. However, the report outlined several potential vulnerabilities.

Extreme weather, including extended bouts of colder-than-normal temperatures, would "create unique challenges in maintaining grid reliability," NERC said.

In February 2021, a winter storm brought a cold blast across the southeastern and central U.S. that resulted in widespread power outages. In Texas, more than 4.5 million customers lost power and at least 210 people died from hypothermia, carbon monoxide poisoning from indoor heating and other related afflictions.

For the upcoming winter, NERC said that with an anticipated reserve margin of 42%, the Electric Reliability Council of Texas Inc. should have enough capacity reserves to meet forecast peak demand and handle the types of severe weather events regularly experienced in the area.

However, if the region should once again experience unusually extreme weather conditions along with above-normal winter peak demand and generation outages, the report warned that ERCOT's reserve margin could plunge to negative 37.1%. This, in turn, "could result in the need to employ operating mitigations ... including load shed," the report stated.

The report added that peak demand and generator outages that exceed forecasts due to extreme weather would also be expected to cause power supply emergencies in the Midcontinent ISO and Southwest Power Pool Inc.

In a new report on the grid outages, staff with NERC and the Federal Energy Regulatory Commission stressed the need to safeguard natural gas-fired power plants and related pipeline infrastructure against extreme cold weather. FERC in August also approved new cold weather reliability standards that require generators to implement cold weather preparedness plans.

At the state level, Texas utility regulators recently approved a new weatherization standard for power plants in response to the deadly Arctic blast. The state has also worked to identify load-critical gas facilities and stepped up inspections of generator units.

Despite the state and federal action, NERC warned in its Nov. 18 assessment that "some plant vulnerabilities can be anticipated for the upcoming winter."

"We're seeing more exposure in the grid to the effects of extreme weather," NERC's manager of reliability assessments, Mark Olson, said during a webinar on the report.

NERC, therefore, urged generators to be proactive by preparing for winter conditions and communicating with grid operators. In addition, it said grid operators should be prepared to implement cold weather operating plans and poll generators on their fuel and availability status and asked load-serving entities to review critical loads to prevent inadvertent disruptions and prepare customers.

Other risk areas

Natural gas supply disruptions in infrastructure-limited areas pose another risk this winter. Once again citing Texas' woes earlier this year, NERC said disruptions to gas pipelines and gas production sites could affect bulk power system reliability.

The report also said that New England faces gas infrastructure constraints during periods of high demand, which along with limited liquid fuel inventories, "may exacerbate the risks for fuel-based generator outages and reductions."

In addition, southern California and the U.S. Southwest have limited gas storage and "lack redundancy in supply infrastructure," the report said, creating the risk of fuel supply curtailment or disruption during extreme weather.

NERC does not foresee reliability impacts from the supply chain challenges some generators are facing to obtain fuel as economies rebound from the coronavirus pandemic. But it advised fossil fuel-fired generators to "monitor their coal and fuel oil stores and natural gas contracts as late-stage acquisitions are less assured this winter," particularly as surging LNG exports are anticipated in the coming months.

"These potential constraints could challenge many owners of fossil-fired plants over the winter and underscore the need for operators at the Balancing Authorities and Reliability Coordinators to include generator fuel surveying in their operating plans," NERC said.

Turning to other potential power reliability risks, the report noted that the western U.S. is challenged by reduced hydroelectric output amid an extended, climate change-driven drought.

Although resources are expected to satisfy peak demand, "higher demand from more extreme temperatures in the Northwest could cause a shortfall," NERC said. "Low hydro conditions can reduce transfers needed to mitigate a wide area cold weather event."