Published Friday, 20 July 2012
It is believed the fire at the substation was started deliberately. (© Presseye)
The fire, close to Galliagh's Ferndale Road, was reported at 6.45pm on Friday.
It initially left 3,000 customers in the dark, NIE said on Friday night, but power has since been restored for 2,700.
A spokesmen for the electricity company said extra engineers had been brought in to address the problem, but as the substation must be rebuilt, for some people, their electricity would be out "several hours".
It is understood that rubbish was set on fire close by the substation, which then caught alight.