A problem of supply

BIRD'S EYE VIEW: A helicopter at work near Kaikohe, checking for line damage after last week's power cut. PICTURE/DEBBIE BEADLE

Top Energy electrical engineers believe they have found the fault that caused Friday's district-wide power outage. The chief suspect is a broken insulator in the Kaikohe sub-station, with repairs scheduled to start yesterday afternoon.

The company would attempt to fix the equipment without disrupting power supplies, but warned that should the insulator fail again there would be another outage affecting the entire Mid and Far North.

Engineers conducted extensive testing over the weekend and all day yesterday. Together with Transpower engineers they analysed the sequence of protection mechanisms that operated on Friday. A corona camera was used in the early hours of Saturday and Sunday mornings to measure the level of electrical discharge from the insulators within the sub-station and lines, early morning being the time when arcing is most likely to occur. Nothing out of the ordinary was detected.

Yesterday they dug deeper into the protection operation and settings, and commissioned acoustic testing on the sub-station, which Top Energy acquired from Transpower in 2012.

"We acquired these assets from Transpower at the end of their lifespan and in very poor condition, precisely because we felt they were a priority for the security of the electricity supply in our region," Top Energy CEO Russell Shaw said.

"Since acquiring the Kaitaia and Kaikohe sub-stations we have been flat-out conducting asset replacement and renovation works. Over the past 12 months alone we have spent $5 million on upgrading this particular asset. It's frustrating that we hadn't yet replaced the piece of kit which likely caused Friday's outage."

He recalled that two years ago one of the transformers at the Kaitaia sub-station failed, although Top Energy was able to manage that incident without cutting power to the town. That was another Transpower asset the company had bought in 2012. The transformer was replaced with a new unit in March.

"We've been refurbishing and replacing these assets as quickly as we possibly can," Mr Shaw added.

"We apologise sincerely for Friday's disruption, and I can assure our business and domestic customers that we will keep up the pressure to bring these assets back up to the standard that we require and that they, quite rightly, demand of us."

-Black Friday, see page 7 of the Northland Age for more.