Editing Cook Strait (section)

== Cables ==
{{see also|HVDC Inter-Island}}
In 1866, the first [[telegraph]] cable was laid in Cook Strait from [[Lyall Bay]] on Wellington’s south coast to Whites Bay, north of [[Blenheim, New Zealand|Blenheim]], connecting the South Island telegraph system to Wellington.<ref name="cable">[https://nzhistory.govt.nz/page/submarine-telegraph-line-laid-across-cook-strait Telegraph line laid across Cook Strait – 26 August 1866]. ''[[New Zealand History Online]]'', Ministry for Culture and Heritage. Updated: 9 July 2020.</ref><ref name="EvolvingAuckland8.4">{{Cite book |last1=Mander |first1=Neil |title=Evolving Auckland: The City's Engineering Heritage |publisher=Wily Publications |year=2011 |isbn=9781927167038 |editor-last=La Roche |editor-first=John |editor-link=John La Roche |pages=195–202 |chapter=COMPAC Submarine Telephone Cable System}}</ref> In 1879 the vessel ''Kangaroo'' laid a further {{convert|120|nmi|km|adj=mid|-long}} telegraph cable across Cook Strait from [[Whanganui]] to [[Wakapuaka]], near Nelson.<ref>{{Cite web |title=History of the Atlantic Cable & Undersea Communications from the first submarine cable of 1850 to the worldwide fiber optic network: 1879/1880 Cook Strait Cable (Wanganui - Wakapuaka, New Zealand) |url=https://atlantic-cable.com/Cables/1879NZ/index.htm |access-date=28 January 2025 |website=atlantic-cable.com}}</ref>

In 1964, three submarine power cables were installed across Cook Strait between Oteranga Bay in the North Island and Fighting Bay in the South Island as part of the [[HVDC Inter-Island]] link, to enable transmission of electricity between [[Benmore Dam|Benmore]] in the South island and [[Haywards]] in the North Island.<ref>{{cite web |title=The original Cook Strait cable is hauled ashore at Ōteranga Bay on Wellington's south-west coast in 1964 |url=http://www.teara.govt.nz/en/energy-supply-and-use/6/2/3 |accessdate=20 September 2011 |publisher=[[Te Ara: The Encyclopedia of New Zealand]]}}</ref><ref name="Taylor">{{cite book |author=Taylor, Peter |title=White Diamonds North: 25 Years' Operation of the Cook Strait Cable 1965–1990 |publisher=Transpower |year=1990 |isbn=0-908893-00-0 |location=Wellington |page=47}}</ref><ref>{{cite Q|Q113031154|p=178}}</ref>

In 1991 three new power and two communication cables were laid to replace the original cables. Each of the replacement HVDC power cable operates at 350&nbsp;kV, and can carry up to 500&nbsp;MW, with Pole 2 of the link using one cable and Pole 3 using two cables. The link's total capacity was increased to 1200&nbsp;MW (500&nbsp;MW for Pole 2 and 700&nbsp;MW for Pole 3).  The cables are laid on the seabed within a legally defined zone called the cable protection zone (CPZ). The CPZ is about {{convert|7|km|mi|0}} wide for most of its length, narrowing where it nears the terminals on each shore. Fishing activities and anchoring boats are prohibited within the CPZ.<ref name="Transpower">{{cite web |year=2006 |title=Cook Strait submarine cable protection zone |url=http://www.transpower.co.nz/f1223,149142/149142_cook_strait-2006.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120307220129/http://www.transpower.co.nz/f1223,149142/149142_cook_strait-2006.pdf |archive-date=7 March 2012 |access-date=23 September 2008 |publisher=Transpower}}</ref> From 1994, the HVDC link across Cook Strait has been operated by [[Transpower New Zealand Limited|Transpower]].

Fibre optic cables carry telecommunications across Cook Strait, used by New Zealand's main telecommunication companies for domestic and commercial traffic and by Transpower for control of the HVDC link. In 2002 two further communications cables were laid.{{Citation needed|date=January 2025}} 

In May 2025, Transpower announced that it was planning for replacement of all three existing Cook Strait HVDC cables laid in 1991. The forecast cost of replacement was $NZD 1.4 billion and the project was scheduled for completion by 2031. The replacement plan included adding a fourth cable to increase inter-island transmission capacity and resilience, together with enhancements to the cable terminal stations on either side of Cook Strait.<ref>{{Cite news |last=Franks |first=Raphael |date=7 May 2025 |title=Transpower proposes $1.4 billion replacement for ageing Cook Strait electricity cables linking North, South Islands |url=https://www.nzherald.co.nz/nz/transpower-proposes-14-billion-replacement-for-ageing-cook-strait-electricity-cables-linking-north-south-islands/JXXXBSJGKVGMPNVOAUI7TALW6I/ |access-date=7 May 2025 |work=[[The New Zealand Herald]]}}</ref>