Entergy faces risky power grid repair after Gustav

HOUSTON (Reuters) - Entergy Corp faces the risk of triggering a blackout as it begins the effort of restoring power to Louisiana homes and businesses after Hurricane Gustav damaged major power lines serving the New Orleans-Baton Rouge area, the state's largest utility said.

While New Orleans-based Entergy has warned that repairs to its high-voltage system will be "difficult and slow," Louisiana Gov. Bobby Jindal said Wednesday that power restoration is the biggest obstacle hampering the state's recovery.

Jindal said state utility regulators hope transmission service to some large industrial customers can be restored as soon as today.

Jindal offered Louisiana's utilities "whatever resources they need" to hasten restoration of electric service as evacuees begin the return to storm-damaged areas.

"We absolutely need to quicken the pace by which power is being restored," Jindal said.

Entergy said 191 power lines and 210 substations were damaged, citing significant damage at the Willow Glen substation between Baton Rouge and New Orleans, according to Dennis Dawsey, vice president of distribution.

Entergy's biggest problem is damage to 13 of 14 lines that move power into the New Orleans area. Three 500-kilovolt lines and six 230-kv lines at Willow Glen were knocked out of service.

With just one high-voltage line linking Baton Rouge to New Orleans, Entergy was forced to drop New Orleans into a "power island," a situation where the city and a corridor along the Mississippi River - dotted with large refineries - are disconnected from the rest of the Entergy supply network.

Entergy said the power island includes Orleans, Jefferson, St. Bernard, St. James, St. John the Baptist, St. Charles and upper Plaquemines parishes. Limited electric service in the area is coming from three older Entergy power plants, Waterford 1, Nine Mile Point and Little Gypsy.

Early attempts to reconnect the area with the larger grid via a 500-kv line or several 230-kv lines were unsuccessful due to damage which will take several days to repair, Entergy said in a message to transmission customers on Tuesday.

Restoring power to all customers in the area will be delayed until the area can be tied back to the rest of the system, "to maintain the level of electric demand and prevent it from exceeding the available generation in that area."

Reconnecting New Orleans and the river parishes to the larger network will be risky, Entergy said, and will require coordination among generation, transmission and distribution.

Generation in the power island could trip offline before Entergy is able to tie back to the Entergy system, said Gary Taylor, an Entergy group vice president.

"If the islanded generation goes offline, all power in the 'island' zone could be lost," Taylor said.

(Reporting by Eileen O'Grady and Chris Baltimore; Editing by John Picinich)