About 28,000 Pennsylvania Power & Light Co. customers in southern Lancaster County lost electric service Tuesday morning (11/5) after an error occurred during maintenance work on a company transmission line.

The power outages began at about 7:45 a.m. All electric service was restored by about 9 a.m.

"One transmission line was out of service for maintenance. The error resulted in the temporary loss of a second large transmission line, creating a power supply problem," said Larry Downing, PP&L's community development director for the Lancaster region. "Fortunately, we were able to correct the situation quickly and restore power."

Downing said PP&L will conduct a full investigation into the cause of the problem.

The temporary loss of the transmission lines caused a portion of southern Lancaster County to be disconnected from the rest of PP&L's transmission network. The area temporarily functioned as an "island" separate from the system.

Power from the Holtwood and Safe Harbor hydroelectric power plants on the Susquehanna River served the disconnected area. The small power plants, however, don't produce enough electricity to meet the customer demand that was coming from the "island" area.

"The customers that lost power had to be taken out of service by PP&L to match customer demand to the generation that was available," Downing said. "This is a safety measure that allows us to preserve the entire system and keep most customers in service. The system worked as it's designed and we were able to restore everyone in a short period of time."