Benmore Dam
Encyclopedia
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.
The dam is the largest earth-filled water-retaining structure in New Zealand. Its core is impermeable clay-like gravel, supported by two massive shoulders of river gravel. Lake Benmore
has a volume of 12.5 million cubic metres, about 1.5 times as much water as Wellington Harbour
. The dam's spillway can cope with 3,400 cubic metres of water per second, about 10 times the mean river flow. With a generating capacity of 540 MW, Benmore Power Station is the second largest hydro station in New Zealand.
The $62 million construction of the dam and hydroelectric station began in 1958. It was commissioned in 1965, and officially opened by Prime Minister Sir Keith Holyoake
on 15 May that year. It was built for the New Zealand Electricity Department; since 1999 it has been owned and operated by Meridian Energy
.
From 2008 to 2010 the six turbines are being refurbished at a cost of $67 million. This will enable a 5% reduction in water use for the same generation capacity, increasing annual generation by 70 GWh. New switchboards and an upgrade to the switchyard are also planned.
Benmore is the South Island terminus of the HVDC Inter-Island
link between the North and South Islands of New Zealand. The static inverter plant is on the west side of the tailrace, and converts 220 kV AC power to +270/-350 kV DC for the 610 km (379 mi)journey to the North Island static inverter plant at the Haywards sub-station in Lower Hutt.
Otematata is the small town that supports the dam, although with advances in technology the staffing needed to maintain the dam is drastically smaller. Due to this the town is now a small holiday community, with only around 200 permanent residents. The dam is about 8 kilometres (5 mi) up the valley from the township.
sub-station). The importance is largely due to the HVDC Inter-Island static inverter plant located at it.
The main AC switching station is on the east bank of the tailrace, and electricity generated by Benmore is injected into the national grid here. Three major 220 kV lines containing five circuits run from the Benmore substation. Clockwise from south, they are:
The HVDC Inter-Island static inverter plant is located on the west side of the tailrace, connected to the AC switching station by lines over the tailrace. The +270 kV mercury-arc Pole 1 has its valve hall on the north side of the site, near the powerhouse. The -350 kV thyristor Pole 2 has it valve hall on the south side of the site. A new +350 kV thyristor Pole 3 is currently under construction to replace the ageing Pole 1, and its valve hall will be located adjacent to the existing Pole 2 valve hall.
Waitaki River
The Waitaki River is a large river in the South Island of New Zealand, some 110 km long. It is the major river of the Mackenzie Basin.It is a braided river which flows through Lake Benmore, Lake Aviemore and Lake Waitaki. These are ultimately fed by three large glacial lakes, Pukaki, Tekapo,...
power scheme
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
, located in the Canterbury Region of 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...
's South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
. There are eight other power stations in the valley.
The dam is the largest earth-filled water-retaining structure in New Zealand. Its core is impermeable clay-like gravel, supported by two massive shoulders of river gravel. Lake Benmore
Lake Benmore
Lake Benmore is a lake located in the South Island of New Zealand. It was artificially created in the 1960s by construction of Benmore Dam. The lake covers an area of approximately 75 km²...
has a volume of 12.5 million cubic metres, about 1.5 times as much water as Wellington Harbour
Wellington Harbour
Wellington Harbour is the large natural harbour at the southern tip of New Zealand's North Island. New Zealand's capital, Wellington, is on the western side of Wellington Harbour. The harbour was officially named Port Nicholson until it assumed its current name in the 1980s.In Māori the harbour is...
. The dam's spillway can cope with 3,400 cubic metres of water per second, about 10 times the mean river flow. With a generating capacity of 540 MW, Benmore Power Station is the second largest hydro station in New Zealand.
The $62 million construction of the dam and hydroelectric station began in 1958. It was commissioned in 1965, and officially opened by Prime Minister Sir Keith Holyoake
Keith Holyoake
Sir Keith Jacka Holyoake, KG, GCMG, CH, QSO, KStJ was a New Zealand politician. The only person to have been both Prime Minister and Governor-General of New Zealand, Holyoake was National Party Prime Minister from 20 September 1957 to 12 December 1957, then again from 12 December 1960 to 7...
on 15 May that year. It was built for the New Zealand Electricity Department; since 1999 it has been owned and operated by Meridian Energy
Meridian Energy
Meridian Energy Limited is a New Zealand state-owned electricity generator and retailer. The company generates the largest proportion of New Zealand's electricity, generating 32 percent of the country's electricity in the year ending 31 December 2009, and is the fourth-equal largest retailer, with...
.
From 2008 to 2010 the six turbines are being refurbished at a cost of $67 million. This will enable a 5% reduction in water use for the same generation capacity, increasing annual generation by 70 GWh. New switchboards and an upgrade to the switchyard are also planned.
Benmore is the South Island terminus of 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...
link between the North and South Islands of New Zealand. The static inverter plant is on the west side of the tailrace, and converts 220 kV AC power to +270/-350 kV DC for the 610 km (379 mi)journey to the North Island static inverter plant at the Haywards sub-station in Lower Hutt.
Otematata is the small town that supports the dam, although with advances in technology the staffing needed to maintain the dam is drastically smaller. Due to this the town is now a small holiday community, with only around 200 permanent residents. The dam is about 8 kilometres (5 mi) up the valley from the township.
Key statistics
- Lake Benmore area: ~ 75 kilometres square
- Lake Benmore shoreline: 116 km
- Dam crest length: 823 metres
- Dam crest height: 110 metres
- Dam width at base: 490 metres
- Dam width at crest: 10.6 metres
- Dam fill: 28 million tonnes
- Head (hydraulic): 92 metres
- Average river water flow: 340 m³/s
- Nominal annual generation: 2,200 GWh
- Installed capacity: 540 MW
- Machinery: 6 x 93,000 kW vertical Francis turbineFrancis turbineThe Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....
s (Dominion Engineering, Canada), coupled to 6 x 90,000 kW 112,500 kVA generatorsElectrical generatorIn electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
(Canadian General Electric); 6 transformer banks totalling 1,150 MVA - Penstocks: Concrete
Transmission
Benmore is a major switching point in the New Zealand national grid and one of two major switching stations in the Waitaki Valley (the other being TwizelTwizel
TwizelUrban AreaPopulation:1,000Extent:Territorial AuthorityName:Mackenzie District CouncilPopulation:Mayor:Website:Extent:Regional councilName:Environment Canterbury...
sub-station). The importance is largely due to the HVDC Inter-Island static inverter plant located at it.
The main AC switching station is on the east bank of the tailrace, and electricity generated by Benmore is injected into the national grid here. Three major 220 kV lines containing five circuits run from the Benmore substation. Clockwise from south, they are:
- A double-circuit line to the Twizel sub-station, with one circuit going via Ohau COhau COhau C is a power station operated by Meridian Energy in the South Island of New Zealand.It is a twin station with Ohau B and is part of the Waitaki hydro scheme which consists of eight power stations operated from a control centre near Twizel...
power station and one circuit going via Ohau BOhau BOhau B is a power station operated by Meridian Energy in the South Island of New Zealand.It is a twin station with Ohau C and is part of the Waitaki hydro scheme which consists of eight power stations operated from a control centre near Twizel...
power station. - A single-circuit line to Islington sub-station in ChristchurchChristchurchChristchurch is the largest city in the South Island of New Zealand, and the country's second-largest urban area after Auckland. It lies one third of the way down the South Island's east coast, just north of Banks Peninsula which itself, since 2006, lies within the formal limits of...
, via Twizel sub-station and Tekapo B power station. - A double-circuit line to Aviemore DamAviemore DamThe Aviemore Dam is a dam of the Waitaki River in New Zealand. Built from earth and concrete in the 1960s to dam Lake Aviemore, it is one of the major dams of Meridian Energy, and is used to power a hydroelectric power plant...
The HVDC Inter-Island static inverter plant is located on the west side of the tailrace, connected to the AC switching station by lines over the tailrace. The +270 kV mercury-arc Pole 1 has its valve hall on the north side of the site, near the powerhouse. The -350 kV thyristor Pole 2 has it valve hall on the south side of the site. A new +350 kV thyristor Pole 3 is currently under construction to replace the ageing Pole 1, and its valve hall will be located adjacent to the existing Pole 2 valve hall.