AEP lines accounted for most of the 28 lines the Texas grid operator said were out of service recently in the Rio Grande Valley.
Two 345-kilovolt lines belonging to AEP were shut in Cameron County, said spokesman Larry Jones, along with a dozen 138-kv lines and eight 69-kv lines, most serving South Padre Island and Harlingen.
Jones said it was too soon to determine whether the storm damaged transmission tower structures or simply knocked lines out of service.
High wind from the remnants of the storm prevented aerial inspection of the lines early July 24.
Across the storm-damaged area, four 345-kv lines were shut after the storm, according to the Electric Reliability Council of Texas (ERCOT).
ERCOT said the lack of transmission posed no reliability problems.
However, the agency issued an emergency notice for the Brownsville area, saying 50,000 more customers could lose power if the remaining transmission line serving the area shut.
AEP said the number of customers without power fell to 155,500, down from more than 200,000 earlier in the day, according to a company website.