Faulty connection in substation switchboard caused Wellington power cut

Friday, 3 August 2018

Homes and businesses across Wellington suffer due to major power outage.

The power outage that cut electricity to more than 12,000 Wellington properties was a rare occurrence that, unfortunately, struck one of the city's biggest substations, Transpower says.

On Friday night, the electricity provider was still working to identify exactly what caused a piece of equipment at the Wilton substation to fail, leaving multiple suburbs and businesses – including the city's parliamentary precinct – without power between 12.15pm and 3.17pm.

'There are two diverse parts to the switchboard that supply the load at Wilton,' general manager of grid service delivery Mark Ryall said. 'The piece of equipment that failed connects the two together.'

A map of the Wellington Southern Area Sub transmission Network.

* Auckland's history of power cuts

* Equipment failure causes widespread streetlight outages in Wellington

* Trainee electrician awarded $30k reparation after substation 'flashover'**

Transpower had an asset maintenance and management programme in place to ensure equipment was reliable, but faults still occurred occasionally, Ryall said.

Drivers revert to give way rules in Wellington CBD after a power cut causes traffic lights to be out of order.

WHY WAS THE OUTAGE SO BIG?

The Wilton substation has 12,500 connection points, making it one of the most crucial stations in the Wellington region.

The Central Park and Haywards substations are of a similar size and importance.

An asset management plan produced by lines company Wellington Electricity shows southern Wellington's power is supplied by the Central Park, Wilton and Kaiwharawhara substations, which are all connected to the national grid.

The network of substations supplies power to Wellington's eastern and southern suburbs, as far west as Karori and as far north as Ngaio and Khandallah.

Power was cut to more than 12,000 properties following a major outage in Wellington on Friday.

Ryall said Transpower had isolated the faulty piece of equipment to restore supply, and would repair it on-site

WHAT CAUSES A POWER OUTAGE?

According to electricity retailer Pulse Energy, the complex network of assets that supply power to homes is naturally susceptible to physical damage.

The best efforts of protection systems cannot always protect against Mother Nature, car accidents, or workers occasionally hitting critical cables, its website says.

'Any of these scenarios can put excessive stress on certain network components and increase the risk of an overloaded circuit, which in turn may ultimately lead to a blackout.'

THE IMPACT OF THE WELLINGTON OUTAGE

At the height of the power outage on Friday, about a dozen suburbs and 12,500 properties were affected in some way.

Lectures at Victoria University's Rutherford House were cancelled and Wellington District Court was halted when the power went out.

Fire and Emergency's digital 'Selcal' system - a digital form of communication between on-the-ground crews and central communications - was down for 25 minutes in the central region, with the power outage the most likely culprit.

A couple of people also found themselves temporarily stuck in elevators.

NZ'S WORST BLACKOUT

This country's worst power outage in recent history was the 1998 Auckland Power Crisis. The city's CBD relied almost entirely on four gas-insulated cables that powered two substations at Quay St and Liverpool St.