page_title: HVDC Inter-Island
section_title: The Pole 3 Project
hierarchical_section_title: HVDC Inter-Island / The Pole 3 Project
caption_attribution_description: English: View of the lifting operation to place the pre-assembled roof section on the HVDC Pole 3 valve hall building at Benmore
context_page_description: The HVDC Inter-Island link is a 610 km long, 1200 MW bipolar high-voltage direct current transmission system connecting the electricity networks of the North Island and South Island of New Zealand together. It is commonly referred to as the Cook Strait cable in the media and in press releases, although the link is much longer than its Cook Strait section, and the submarine section consists of 3 parallel cables. The link is owned and operated by state-owned transmission company Transpower New Zealand.
  The HVDC link starts at the Benmore Hydroelectric Power Station, on the Waitaki River in Canterbury, on the South Island, and then it travels 534 kilometres on an overhead transmission line through inland Canterbury and Marlborough to Fighting Bay in the Marlborough Sounds. From Fighting Bay, the link travels 40 km via submarine cables underneath Cook Strait to Oteranga Bay, near Wellington, before travelling the final 37 km on overhead lines to Haywards transmission substation in Lower Hutt.
  The HVDC link first became operational in April 1965 to primarily transport electricity from the generation-rich South Island to the more populous North Island.
context_section_description: In May 2008, Transpower submitted an investment proposal to the Electricity Commission for the replacement of the old mercury arc valve Pole 1 converter stations with new thyristor converter stations. In July 2008, the Electricity Commission announced its intention to approve the project.
  This project involved the construction of new converter stations designated as Pole 3, to operate at +350 kV 700 MW, matching the existing Pole 2 (−350 kV, 700 MW). Site works on the $672 million project were formally commenced on 19 April 2010, when Minister of Energy Gerry Brownlee turned the first sod. The new converter stations were to be commissioned by April 2012, but in May 2011, Transpower announced that commissioning was delayed until December 2012 because of difficulties being experienced by the manufacturer.
  Work involved in replacing Pole 1 with the new Pole 3 converter stations included:
  New valve halls adjacent to the Pole 2 valve halls at both Benmore and Haywards, each containing the thyristors converters
  New transformers connecting the valve halls to the 220 kV buses at both Benmore and Haywards
  Connecting the Pole 3 thyristors to the existing Pole 1 lines at both Benmore and Haywards
  Connecting the Pole 3 thyristors to the existing electrode lines at both Benmore and Haywards
  Switching the number 5 Cook Strait cable from Pole 2 back to the Pole 1/3.
  New 220 kV filters on the 220 kV buses at both Benmore and Haywards
  New transformers connecting the four synchronous condensers C7 to C10 to the 110 kV bus at Haywards
  New 5th and 7th harmonic filters connecting to the 110 kV bus at Haywards.
  Removal of the existing converter transformers connecting the Pole 1 mercury arc valves and two of the synchronous condensers to the 110 kV bus at Haywards.
  Removal of all remaining mercury arc valve Pole 1 equipment at both Benmore and Haywards.
  The decommissioning of Pole 1 was scheduled for July 2012, allowing works to switch the existing lines over Pole 3 to occur, and to allow testing of the new pole to occur during the summer months where electricity demand and therefore inter-island electricity transfer is low. The new Pole 3 was able to operate at 700 MW from commissioning, but due to inadequate voltage support at the Haywards end of the link, Pole 2 and 3 combined transfer was limited to 1000 MW. After the commissioning of a new static synchronous compensator (STATCOM) at Haywards in January 2014, Pole 3 was able to operate at its full capacity with Pole 2 in operation (1200 MW total transfer).
caption: Lifting the roof of the Pole 3 valve hall into position at Benmore
exif: {}