There were fears it could spread to neighbouring properties, but no homes were endangered.
The transformer was destroyed and a shed in a nearby property was charred, but otherwise neighbouring properties escaped damage.
The fire was safely extinguished and crews turned the scene over to Vector, the FENZ spokesman said.
Vector's website said it was notified of the outage at 1.40am, and a crew was sent to investigate at 2.07am.
The fire tripped a feeder, a piece of equipment which supplies the local area with electricity, a spokesman said. This left several streets without power from around 2am until 3am, he said.
A pocket of residents on Puriri Ave were then the only remaining properties without power this morning, he said, and were likely to have their power restored by 8am.