Tumut 1 Underground Power Station

Located downstream of Tumut Pond Dam and 366 metres (1,201 ft) below ground level,^[2] Tumut 1 Power Station is situated approximately 2.25 kilometres (1.40 mi) south-west from Cabramurra, under Happy Valley Rd. A Lift & Ventilation Shaft^[3] is on Happy Valley Rd.
The conventional hydroelectric power station has four turbine generators, with a combined generating capacity of 330 megawatts (440,000 hp) of electricity; and a net generation of 847 gigawatt-hours (3,050 TJ) per annum.^[4] The power station was completed in 1959, and has 292.6 metres (960 ft) rated head.^[2]

The first 330 kV transmission lines were commissioned in New South Wales at the Tumut 1 Power Station during the 1950s. These cables were manufactured in England and linked to the underground transformers at Tumut 1, and connected with the transmission line. The lines carried power to Sydney where new sub-stations were established, to handle the upgrade from 132 kV transmission lines. This innovative plan, which faced significant scepticism initially, was considered to be at the forefront of technology which challenged designers and overseas manufacturers. Extra high voltage was in its infancy in the early 1950s. The lines were subject to a 1000 kV test on the cables prior to them going into service. These cables and the transmission system have been in service for over 50 years.^[5]

The original transformer at Tumut 1 weighed 81.2 tonnes (89.5 short tons); and each assembled generator rotor is in excess of 203 tonnes (224 short tons) necessitating delivery in component pieces and assembly on site.^[6]

The station is connected to the National Electricity Market via the 330kV Upper Tumut Switching Station, 2.75 kilometres (1.71 mi) North of Cabramurra.

The Upper Tumut Works is sometimes used as a colloquial term to refer to both Tumut 1 and Tumut 2 Underground Power Stations as well as their respective dams, tunnels and the Upper Tumut Switching Station.

Tumut 2 Underground Power Station

Tumut 2 Power Station is situated approximately 5.91 kilometres (3.67 mi) north of north-west from Cabramurra, under Goat Ridge Rd, some 244 metres (801 ft) below ground level.^[7]
The conventional hydroelectric power station has four Francis turbine generators, with a combined generating capacity of 286.4 megawatts (384,100 hp) and a net generation of 787 gigawatt-hours (2,830 TJ) per annum. The power station was completed in 1962, and has 262.1 metres (860 ft) rated head. Water flows through the turbines at the rate of 118.9 cubic metres per second (4,200 cu ft/s).^[7]

The conventional gravity-fed hydroelectric power station is fed by water held in Tumut Two Pondage and from water discharged from Tumut 1 Power Station.

The station is connected to the National Electricity Market via the 330kV Upper Tumut Switching Station, 2.75 kilometres (1.71 mi) North of Cabramurra.

Tumut 3 Power Station

Tumut 3 Power Station is the first major pumped storage hydroelectric power station in Australia.^[8] Pump-storage schemes use off-peak energy to pump water to a reservoir on a higher level. This water then passes through turbines to generate electricity when prices are higher.^[9] The sole powerhouse is located above ground, below Talbingo Dam.^[10]

The power station is fitted with six Toshiba turbines, each equipped with Melco-manufactured generators,^[10] has a combined generating capacity of 1,800 megawatts (2,400,000 hp) of electricity. Three of the six units can operate as pumps. The design for the power station was managed by Peter Hughes AM.^[11] It was completed in 1973, upgraded in 2012 and has 150.9 metres (495 ft) rated head. Water is carried in six pipelines, each 488 metres (1,601 ft) long and 5.6 metres (18 ft) in diameter,^[12] delivering water both from and to Talbingo Reservoir. The pumps draw water from Jounama Pondage at the rate of 297 cubic metres per second (10,500 cu ft/s), returning water to Talbingo Reservoir for later generation use in periods of peak-demand.^[10]

During 2003, Snowy Hydro commissioned six 150 kilowatts (200 hp) micro-hydro generators on the existing cooling water systems on each of the six generating units at Tumut 3 Power Station. These GreenPower accredited units enable Snowy Hydro to save approximately 3,137 tonnes (3,458 short tons) of carbon dioxide per annum. In addition, this installation not only captures previous wasted renewable energy, but also will be substantially reducing the noise that was associated with the previous pressure reducing valves on the six generating unit's cooling systems.^[13][14] Between 2009 and December 2011, there was a major upgrade of Tumut 3, adding additional capacity in the range of 25 megawatts (34,000 hp) to 50 megawatts (67,000 hp) per unit.

The station is connected to the National Electricity Market via the 330kV Lower Tumut Switching Station, 500m North West of Tumut 3 or 3.0 km south of south-west from Talbingo.