Issues That Triggered Texas City, La Marque Outage Identified

Texas-New Mexico Power's assessment of the recent large power outage in Texas City and La Marque has identified what we believe to be the primary causes.

We can confirm information previously shared with the news media: a switch in a substation failed, followed moments later by transmission lines being de-energized. TNMP has identified the reasons these events happened and we're implementing measures to address them.

"TNMP is committed to moving and delivering safe, reliable electricity service in Galveston County and across our service territory," said Keith Nix, vice president of technical services and system reliability.

"We appreciate the frustration felt by residents and businesses during that outage, particularly on a cold evening. We immediately committed resources to look into why that happened and identify how we can prevent similar issues in the future."

Disruption factors

The origin of the Feb. 4 outage was a switch failing at a substation in south Texas City, which caused an electric arc. System-protection devices then de-energized part of the substation to prevent additional damage.

A relay device at another substation moments later detected a fault, based on what happened at the first substation. But that relay didn't operate as intended and de-energized another transmission line (like a household breaker tripping).

Electrical current on an adjacent line, as a result of the prior lines de-energizing, then increased and exceeded operating levels. Protection devices shut down that line to prevent permanent damage.

TNMP's weekly visual and infrared inspection of the switch that eventually failed had revealed no abnormalities just a few days before the outage. All substations in Texas City and La Marque were inspected visually and with infrared cameras during the evening of the outage and again the next day in the daylight.

TNMP, to address issues with the original switch, has ordered new switches and will replace those in Texas City and La Marque that are the same make and model of the device that failed.

TNMP also is implementing additional inspections, training and documentation-handling practices to ensure this issue isn't present elsewhere in the area and to apply those procedures going forward.

Safety and reliability

TNMP, its management and its employees fully appreciate the importance of a safe, reliable electrical system for all customers. We also know well that the nature of industry in Texas City means timely responses to issues can be even more important.

The Feb. 4 outage started about 6:20 p.m. Homes and businesses in the area were restored by about 10 p.m. The remainder of the system was restored by 3:30 a.m. after repairs were made to the switch that failed initially. TNMP then worked with industrial customers as they began to return to normal operations. 

TNMP is a transmission and distribution service provider that delivers power to more than 260,000 homes and businesses on behalf of retail electric providers in Texas. More information is available at tnmp.com/about-us.

Media Contact
Eric Paul