Sta­tion’s big re­vamp

Kapi-Mana News - - FEATURE - By SI­MON ED­WARDS

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.

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