02. Aratiatia
Overview [ Technical Information ]
Levels
Structure
Due to its small storage capacity, water is stored at Aratiatia for only a short time after release from Lake Taupo.
At the power station, water passes through a tunnel and then into a surge tank. From there, three steel penstocks take water to the turbines. The 18 million-litre surge tank, built of high-strength concrete, allows a steady flow of water to the turbines by diverting excess flow into the surge chamber and releasing it slowly, when required.
Francis turbines drive the three generators. For 1 MW of electricity to be generated at the Aratiatia powerhouse, 3.7 tonnes of water is required every second. Each of the three generators produces electricity at 11,000 volts. Transformers step the voltage up to 220,000 volts for transmission over the national grid.
Like all the power stations on the Waikato River, Aratiatia is remotely operated from our control room in Hamilton which monitors, controls and co-ordinates the output of each station on the river.
Role
As the smallest of the hydro reservoirs, Aratiatia's lake level fluctuates through its storage range regularly throughout the day. Aratiatia is largely a 'run of river' station, passing water released from the Taupo Gates down to Lake Ohakuri.
02Aratiatia Statistics
Average annual energy generated
Total kilowatt output
Net head
3 Vertical Francis turbines
3 generators
Transformer capacity
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331 GWh
84,000 kW*
33.5
31,300 kW each 136 rpm
30,000 kW at 0.9 pf,11 kV each
33,333 kVA, 11/220 kV each
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Lake area
Powerhouse
Tunnel
Weir
Spillway - Gates
Spillway - Intake
3 steel penstocks
Surge Tank
Commissioning Dates
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0.55 km2
Length 71.32 m
Length 370 m
Length 110 m
Height 9 m
Length 39 m
Length 30 m
Height 17 m
Capacity 18 million litres
Generator No.1
Generator No.2
Generator No.3
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Width 18.59 m
Diameter 9 m
Height 5 m
Width 6 m
Width 25 m at mouth,
9 m at rear
Diameter 5.5 m
Diameter 37 m
March 1964
April 1964
May 1964
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*Turbines never achieved design output