National Grid (New Zealand)
Encyclopedia
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. The grid is owned and operated by Transpower New Zealand Limited
Transpower New Zealand Limited
Transpower New Zealand Limited is the state-owned enterprise responsible for electric power transmission in New Zealand. Transpower performs two major functions in the New Zealand Electricity Market...
, a State owned enterprise.
Transmission
Existing
New Zealand's national electricity transmission grid is owned, operated, and maintained by state-owned enterprise Transpower New Zealand LimitedTranspower New Zealand Limited
Transpower New Zealand Limited is the state-owned enterprise responsible for electric power transmission in New Zealand. Transpower performs two major functions in the New Zealand Electricity Market...
. In total, the national grid contains 11803 kilometres (7,334.1 mi) of high-voltage lines and 178 substations.
The backbone of New Zealand's national grid is the network of 220 kV transmission lines in each of the North and South Islands, which links the major power stations and the country's major cities. Supplementing this are 110 kV, 66 kV and 50 kV transmission lines, which supply provincial towns and cities with electricity from the 220 kV grid, and also connect smaller power stations to the grid.
The HVDC Inter-Island
HVDC Inter-Island
The HVDC Inter-Island link is a high-capacity, bipolar high-voltage direct current transmission system connecting the electricity transmission networks of New Zealand's two main islands to form the National Grid. The HVDC link is owned and operated by state-owned transmission company Transpower...
is New Zealand's only high voltage direct current (HVDC) system, and links the North and South Island grids together. The line connects to the South Island 220 kV grid at Benmore Dam
Benmore Dam
Benmore Dam is the largest dam within the Waitaki power scheme, located in the Canterbury Region of New Zealand's South Island. There are eight other power stations in the valley....
in Southern Canterbury
Canterbury, New Zealand
The New Zealand region of Canterbury is mainly composed of the Canterbury Plains and the surrounding mountains. Its main city, Christchurch, hosts the main office of the Christchurch City Council, the Canterbury Regional Council - called Environment Canterbury - and the University of Canterbury.-...
, and travels via pylons for 535 kilometres (332.4 mi) to Fighting Bay in Marlborough
Marlborough, New Zealand
Marlborough is one of the regions of New Zealand, located in the northeast of the South Island. Marlborough is a unitary authority, both a region and a district, and its council is located at Blenheim. Marlborough is known for its dry climate, the picturesque Marlborough Sounds, and sauvignon blanc...
. From here, it crosses the Cook Strait
Cook Strait
Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....
via undersea cables for 40 km to Oteranga Bay, west of Wellington
Wellington
Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...
. At Oteranga Bay, the HVDC line converts back to pylons to cover the last 35 km, with the line terminating and connecting to the North Island's 220 kV grid at Haywards in Lower Hutt
Lower Hutt
Lower Hutt is a city in the Wellington region of New Zealand. Its council has adopted the name Hutt City Council, but neither the New Zealand Geographic Board nor the Local Government Act recognise the name Hutt City. This alternative name can lead to confusion, as there are two cities in the...
. The main reason for a HVDC connection between the two islands is due to New Zealand's geography and demographics. The South Island has a large number of rivers suitable for hydroelectricity generation, however 75% of New Zealand's population lives in the North Island. HVDC was chosen to allow reactive power from the South Island's plentiful power supply to travel north to the North Island to meet the North Island's electricity requirements.
Often in the media is the state of Auckland's power grid, which had several famous blackout
Power outage
A power outage is a short- or long-term loss of the electric power to an area.There are many causes of power failures in an electricity network...
s, such as the 5-week long 1998 Auckland power crisis
1998 Auckland power crisis
The 1998 Auckland power crisis was a five-week-long power outage.Almost all of downtown Auckland in New Zealand was supplied electricity by Mercury Energy via four power cables, two of them 40-year-old oil-filled cables that were past their replacement date. One of the cables failed on 20 January,...
or the much shorter 2006 Auckland Blackout
2006 Auckland Blackout
The 2006 Auckland Blackout refers to the massive electrical blackout in Auckland, the largest city in New Zealand, on 12 June 2006. It started at 8:30 am local time, with most areas of Auckland regaining power by 2:45 pm local time...
. Both were caused when crucial elements of the grid failed. Due to the rising power demand and the geographical nature of the grid (almost all of Auckland's power comes from the south, and of these, all but one 110 kV line converges on Otahuhu substation), there was (and still is) only very limited redundancy
Redundancy (engineering)
In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
in the local grid.
On 30 October 2009 at around 8:00am, power was cut to the whole of Northland and most of the northern half of Auckland, affecting 280,000 consumers (14.5% of the country). A forklift carrying a shipping container accidentally hit one of the Otahuhu
Otahuhu
Otahuhu is a suburb of Auckland. It is located to the southeast of the city centre, on a narrow isthmus between an arm of the Manukau Harbour to the west and the Tamaki River estuary to the east...
to Henderson
Henderson, New Zealand
Henderson is a major suburb of Auckland, in the North Island of New Zealand. It is located 13 kilometres to the west of Auckland city centre, and two kilometres to the west of the Whau River, a southwestern arm of the Waitemata Harbour.-Description:...
220 kV circuits while the other circuit was out for maintenance, leaving the region supplied by four low capacity 110 kV circuits. Power was restored to the entire region around 11:00am.
Proposed
One of the largest and most contentious projects (as of 2009) is the North Island Grid Upgrade (NIGU) between the southern Waikato and Central Auckland. The plan involves a 220kV switching stationElectrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...
at Drury, upgrading the existing 220kV Otahuhu to Whakamaru C line, new capacitors at Otahuhu, Penrose, and Hepburn Road substations, and the construction of a new 220/400kV transmission line between Whakamaru and Pakuranga
Pakuranga
Pakuranga is an eastern suburb of Auckland, in northern New Zealand. Pakuranga covers a series of low ridges and previously swampy flats, now drained, that lie between the Pakuranga Creek and Tamaki River, two estuarial arms of the Hauraki Gulf...
.
The proposal is being fought by numerous local farmers and lifestyle block
Hobby farm
A hobby farm is a smallholding or small farm that is maintained without expectation of being a primary source of income. Some are merely to provide some recreational land, and perhaps a few horses for the family's children...
owners who consider that the new pylon
Electricity pylon
A transmission tower is a tall structure, usually a steel lattice tower, used to support an overhead power line. They are used in high-voltage AC and DC systems, and come in a wide variety of shapes and sizes...
lines and upgrades to existing lines would cause significant amenity loss. They also allege that the process that led to the decision to construct the network upgrade was legally flawed. An appeal currently being prepared to go to the High Court of New Zealand
High Court of New Zealand
The High Court of New Zealand is a superior court of New Zealand. It was established in 1841 and known as the Supreme Court of New Zealand until 1980....
is expected to cost up to NZ 1 million. Anger about the proposal, claimed to intend the construction of pylons three times as high as previous New Zealand projects, has already led to threats of sabotage against a future line.
Other major projects currently proposed include:
- A NZ$600 million HVDC Inter-Island upgrade, which involves replacing the aging mercury arc rectifier Pole 1 with a new thyristor valve pole, and upgrades at the endpoints of Benmore and Haywards to allow the link to carry up to 1000MW with future provisions for 1400MW
- A NZ$521 million upgrade between central Auckland and North Shore. This involves building a new 220 kV cross-harbour underground link between Pakuranga, PenrosePenrose, New ZealandPenrose is an industrial suburb in Auckland City, New Zealand. It is located to the southeast of the city centre, at a distance of about nine kilometres, between the suburbs of Oranga and Mount Wellington, and close to the Mangere Inlet, an arm of the Manukau Harbour...
, Hobson Street (Auckland CBDAuckland CBDThe Auckland CBD is the geographical and economic heart of the Auckland metropolitan area. Bounded by several major motorways and by the harbour coastline in the north, it is surrounded further out by mostly suburban areas...
), Wairau Road (North Shore City), and AlbanyAlbany, New ZealandAlbany is a northern suburb of Auckland, one of the several cities in northern New Zealand. The name derives from Alba and its Latinisation. It is located to the north of the Waitemata Harbour, 15 kilometres northwest of the Auckland city centre. The suburb is in the Albany ward, one of the...
, crossing the Waitemata HarbourWaitemata HarbourThe quite famous Waitemata Harbour is the main access by sea to Auckland, New Zealand. For this reason it is often referred to as Auckland Harbour, despite the fact that it is only one of two harbours surrounding the city, and is crossed by the Auckland Harbour Bridge. The Waitemata forms the north...
underneath the Auckland Harbour BridgeAuckland Harbour BridgeThe Auckland Harbour Bridge is an eight-lane box truss motorway bridge over the Waitemata Harbour, joining St Marys Bay in Auckland with Northcote in North Shore City, New Zealand. The bridge is part of State Highway 1 and the Auckland Northern Motorway...
. This is to increase supply security to central Auckland, the North Shore, and further afield to Northland.
See also
- List of power stations in New Zealand
- Electricity sector in New ZealandElectricity sector in New ZealandThe electricity sector in New Zealand uses mainly renewable energy sources such as hydropower, geothermal power and increasingly wind energy. The 70% share of renewable energy sources makes New Zealand one of the lowest carbon dioxide emitting countries in terms of electricity generation....
- New Zealand electricity marketNew Zealand Electricity MarketNew Zealand's electricity market is regulated by the Electricity Industry Participation Code administered by the Electricity Authority . The Authority was established in November 2010 to replace the Electricity Commission and its publication explains how the market works.- Overview :Until 1987,...
External links
- Grid New Zealand - information about Transpower's existing and future investment in the National Grid
- Transpower New Zealand