Senior electrical engineering staff from Top Energy worked over the weekend to identify the cause of Friday’s power outage but do not have any answers yet.
Together with engineers from Transpower they have analysed the sequence of protection mechanisms which operated on Friday. This has narrowed down the location of the cause to within 1,000 metres either side of where the national grid feeds into the Top Energy network at Kaikohe.
“We know that the fault has gone to ground from the transmission system and we know that it happened somewhere along a two kilometre stretch of line,” said Top Energy’s network general manager David Worsfold.
“In most cases with a fault of this level there are physical signs of damage to equipment that direct us to what went wrong. In this instance, though, there are absolutely no visible signs.”
Engineering teams from both companies had helicopters in the air to inspect the lines within an hour of the outage occurring. The lines have also been looked at closely from the ground.
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 substation and lines. Early morning is when arcing is most likely to occur due to the presence of dew. Nothing out of the ordinary was detected.
“Today we will dig deeper into the protection operation and settings, continuing to work together with Transpower,” Mr Worsfold said. “We have commissioned acoustic testing on the Kaikohe substation and the first 1,000m of the 110 kV line to Kaitaia and hope to have this completed by Tuesday.”
Top Energy CEO Russell Shaw and Transpower chief executive Alison Andrew acknowledged the “tremendous disruption” caused by Friday’s region-wide outage and said both organisations were prioritising the search for the cause. The companies are working together closely and will keep the communities and businesses of the Mid and Far North updated on progress.