Napier power cut: It was the cat’s volt

Redclyffe Substation, from where the power supply has been cut twice this year, by a cyclone and by a cat. Photo / Warren Buckland

Investigators hot on the tale of the cat burglar that paid the ultimate price when it short-circuited Napier’s power supply and plunged the city into darkness on Wednesday night are trying to find out how the cat got into the works at Redclyffe Substation.

The paws button turned the lights out on over 6000 Unison Networks consumers immediately and up to 25,000 across Napier and further north as staff worked to restore supply, with most regaining it within 40 minutes.

Some parts, in Mārewa and Maraenui, were not affected as that area’s supply comes from a substation at Whakatu, a Unison spokesperson said.

The stations are run by national grid operator Transpower, and general manager Mark Ryall said birds and rodents get “caught up” in the equipment from time to time, but cats do not get in “very often”.

“There are a range of measures that we take to prevent animals getting into equipment, and we will be looking at how the cat got in and how we can prevent it happening again,” he said.

“At this stage, we aren’t sure how the cat got in there,” he said. “We also don’t know if it was someone’s pet but, given the location of the substation [near Napier City Council’s Redclyffe Refuse Transfer Station], it is more likely to be a wild cat.”

A dead cat was found in the area, and Taradale Vet Hospital reported a deceased feline had been delivered, purportedly from the Redclyffe area, and it was not microchipped to link to any owner. As of late Thursday afternoon, the cat had not been claimed.

The cat perished when it came into contact with the “live” environment of a transformer at the site, which has been undergoing major reinstatement after its failure when it was flooded during Cyclone Gabrielle on the morning of February 14, after which most of Napier was without electricity for up to a fortnight.

Ryall said a lot of work had been done to restore security to the electricity grid in Hawke’s Bay and the East Coast since the cyclone, and the cat may have snuck in by a fatal whisker.

“We have this week restored the region to pre-cyclone levels of security everywhere, apart from for customers supplied by Unison Networks from Redclyffe Substation, and it is unfortunate that the cat found this one remaining weak spot,” he said.

Redclyffe has two transformers supplying the area. Transpower can’t run them in parallel until new protection systems are in place, which is expected to be done by September, Ryall said.

“This means one is in operation and one is on standby, and if a fault happens, we need to get someone to the site to manually switch the transformers,” he said.

“In normal operating conditions they would switch automatically, but running them in parallel without adequate protection would risk damaging both at once, leading to a lengthy power cut,” he said.

While there is an increased risk of power cuts “as a result of this configuration”, outages are likely to be of short duration, as it was on Wednesday night, when power was restored to most properties within 40 minutes.

Transpower is still considering Redclyffe Substation’s future in light of Cyclone Gabrielle’s devastation, with options including elevating it on the site to improve resilience or moving all or part of it to a new site.

Experts are producing updated flood modelling for the site and will be raising critical equipment to improve flood resilience in the interim, but there’s no word on whether the behaviour of felonious felines is also being considered.