Station’s big revamp
For thousands of motorists who whiz past Haywards substation on State Highway 58, it’s probably just another electricity facility that barely gets a second thought.
But as reporters at a media briefing learned recently, it’s a vital link in the nation’s network – and one undergoing an upgrade to cost about $670 million.
Haywards is usually only home to a skeleton systems maintenance crew of five, although Transfield also uses it as a base for its Wellington field workforce.
But in the last few months, about 80 civil engineering staff have been swarming over the site creating retaining walls and foundations for new buildings.
Worker numbers will peak at about 160 when electrical engineering specialists get busy later this year.
Since 1965, electricity has flowed between the South and North Islands over the high voltage direct current (HVDC) link.
Running 571 kilometres of transmission line, and 40km of submarine cables along the Cook Strait seabed, the HVDC terminates at Benmore substation in the south, and Haywards in the north.
For most of the time, electricity is flowing northwards as hungry heaters and lights in the bigger population centres in the North Island suck up a share of the output of the big southern hydro power stations.
But during periods of low rainfall in the South Island, or when generators want to preserve water storage, electricity flows along the HVDC from the North to South Island.
As Transpower’s project director for the Hayward’s upgrade, Peter Griffiths, explained, the HVDC is a vital cog in the nation’s ability to move around electricity to where – and when – it’s most needed.
While upgrading the HVDC is a huge cost, the extra generation capacity we would have to build without it, using borrowed money, would be much more expensive.
What’s more, the network flexibility afforded by the HVDC improves the economics of the new generation plants – including wind farms – on our horizon.
DC ( direct current) is most efficient for transporting power over long distances. So at Benmore and Haywards, systems are needed to convert generated AC (alternating current) electricity to DC and back again.
Haywards substation doubles as the Wellington region’s major distribution point/ switchyard, and lots of extra equipment is needed to ‘‘chop’’ smooth DC current into lower AC voltages that the local grid can handle.
The big converter systems at Haywards are called Pole 1 and Pole 2.
Solid base: The
number of workers at Haywards substation has jumped to about 80 as foundations for the new Pole 3 building and associated upgrades have taken shape. The construction workforce will peak at 160.