- Benmore Dam
Benmore Dam is the largest dam within the Waitaki power scheme on the borders of
Otago and Canterbury regions inNew Zealand 'sSouth 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 which is 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. Construction of the dam and hydroelectric station began in 1958, with it commissioned in 1965.
With a generating capacity of 540 MW, Benmore Power Station is the second largest hydro station in New Zealand. It is owned and operated by
Meridian Energy .Benmore is also the southern end of High Voltage Direct Current 500 MW (HVDC) link which joins the North and South Island electricity systems. There are two switchyards, one for AC transmission to the South Island, and the other containing the
static inverter plant for the HVDC link.Otematata is the small town that supports the dam although now with advances in technology the man power needed to maintain the dam is drastically less. Due to this the town is now a small holiday community, with only around 200 permanent residents. The dam is about 8km 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
*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 W verticalFrancis turbine s (Dominion Engineering, Canada), coupled to 6 x 90,000 W 112,50 kVA generators (Canadian General Electric); 6 transformer banks totalling 1,150,000 kVA
* Penstocks: Concrete
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