The US Federal Energy Regulatory Commission (FERC) and the North American Electric Reliability Corporation (NERC) are to hold a joint inquiry into the operations of the bulk-power system during the extreme winter weather conditions currently being experienced in parts of the USA. The severe cold weather has contributed to power outages affecting millions of electricity customers.

The two-unit South Texas Project nuclear power plant (Image: NRC/STP)

An arctic air mass has brought snow, ice, and extreme cold temperatures from the Canadian border as far south as Texas, causing record winter power demand and impacting power generation, the US Department of Energy (DOE) said. Austin, in Texas, has experienced its heaviest snowfall in 72 years.

"As temperatures dropped in Texas over the weekend, demand for electricity spiked," Patricia Hoffman, acting assistant secretary for the DOE's Office of Electricity and Office of Cybersecurity, Energy Security and Emergency Response, said. "At the same time, extreme weather conditions reduced the state's ability to generate power. Nearly 40% of Texas's electricity generation capacity has gone off line, largely driven by cold weather impacts on natural gas, coal and even nuclear facilities." There had also been "limited impacts" from iced-over wind facilities, she added. As well as outages that left over 4.5 million homes and businesses in Texas without power, states including Louisiana and Oklahoma have also experienced power outages.

Three out of Texas's four nuclear reactors have continued to operate at 100% power through the extreme weather. One reactor - unit 1 at the two-unit South Texas Project plant, near Bay City, 90 miles south-west of Houston - automatically tripped due to low steam generator levels. According to operator STP Nuclear Operating Company, the loss of feedwater was attributed to a cold weather-related failure of pressure sensing lines to the feedwater pumps, which occurred in the secondary (non-nuclear) side of the plant. The 1280 MWe (net) unit has since restarted and had reached 14% power by the afternoon of 17 February, the NRC said via social media.

According to the US Nuclear Energy Institute, Texas generates 53.4% of its electricity from natural gas, 19.1% from coal, 17.5% wind and 8.6% nuclear (South Texas Project units 1 and 2 and Comanche Peak units 1 and 2), with 1.5% from other sources.

Independent systems operators the Electric Reliability Council of Texas (ERCOT) which manages the flow of about 90% of Texas's electrical load, the Southwest Power Pool and the Midcontinent Independent System Operator, directed utilities to implement controlled power outages to manage load.

FERC is closely monitoring the extreme weather conditions and their impact on electric reliability and its staff have been directed FERC staff to coordinate closely with the RTOs/ISOs, utilities, NERC, and regional reliability entities to help safeguard the reliability of the bulk power system, the regulator's chairman Richard Glick said.

"Our hearts go out this morning to the millions of people in Texas and across the country who remain without power, as well as those served by utilities in MISO and SPP who experienced rolling blackouts this week in the midst of extreme winter weather," he said today. "We all know power outages are always challenging. But losing power for days during an historic and prolonged cold snap constitutes a humanitarian crisis. People are, literally, dying."

"This is simply unacceptable," Glick said. "The short-term focus must be on restoring power to the grid. But we also have a responsibility to ensure this does not happen again.

FERC and NERC's joint enquiry will see the two organisations work with federal agencies, states, regional entities and utilities to identify problems with the performance of the bulk-power system and, where appropriate, solutions for addressing those issues.

Researched and written by World Nuclear News