Pumped storage scheme’s HV yard successfully energised

July 8th, 2014, Published in Articles: EE Publishers, Articles: Energize

 

Eskom successfully energised the high voltage (HV) yard and three power lines at the Ingula pumped storage scheme in June 2014. The project is currently under construction near Ladysmith on the border of KwaZulu-Natal and the Free State.

The Ingula pumped-storage scheme, located within the Little Drakensberg mountain range, 23 km north-east of Van Reenen’s, comprises an upper dam (Bedford) and a lower dam (Braamhoek). The upper reservoir site is located in the Free State and the lower reservoir site in KwaZulu-Natal. The escarpment forms the border between the two provinces. The distance between the upper and lower reservoirs is 4,6 km, with an elevation difference of about 470 m.  The reservoirs are connected through underground waterways via tunnels and shafts to an underground powerhouse complex, which will house four 333 MW pump turbines with a total capacity of 1332 MW and four generator transformers.

Fig. 1 Ingula HV yard arieal view - rotated

Fig. 1: Ingula HV yard arieal view

The twin headrace waterways, consisting of concrete and steel-lined headrace tunnels, pressure tunnels and shafts, will link the upper reservoir with the pump-turbines. The draft tubes, concrete-lined surge shafts and a single concrete-lined tailrace tunnel will connect the pump-turbines to the lower reservoir. The upper reservoir is a concrete-faced rock fill embankment dam, 41 m high, with a total capacity of 22,4-million m3 and an active water storage volume of 19,2-million m3. The 39 m high lower dam is a roller-compacted concrete, with a total capacity of 26,3-million m3 and an active storage volume of 21,9-million m3.

Tailrace_Dec2010

Fig. 2: Tailrace

A seven day outage was arranged for the energisation work and the line was fully energised on the eighth day. The integration work was simultaneously carried out by three contractors to keep within the outage time. These are Roshcon, the main contractor, and subcontractors Optipower projects and Babcock Nthuthuka power lines.

The Ingula pump storage scheme will have four generating units of 325 MW each. These units will be capable of supplying 1300 MW to the national electricity grid to address peak electricity demand. The units are expected to come on line starting from 2015. The anticipated operational life of the power station is 50 years.

The final milestones of the Ingula pumped storage scheme will be achieved from 2015 as each generating unit becomes ready for commercial operation. The  output of each unit will be connected to the HV yard using 400 kV cross-linked polyethylene (XLPE) cables. This will be the first installation with 400 kV cables in South Africa. The cable is supplied and installed through a joint venture between a local company, CBI and French company Prysmian. The preparation work for laying the cables in the tunnels joining the HV yard to the power station has already commenced.

The underground power station is said to be equivalent to a 116 storey building. Three million t of rock has been excavated from tunnels, waterways and the powerhouse complex, and about 15 000 t of steel lining in the waterways, and a further 3600 t of steel reinforcement, is being used. The quarry has produced 2,44-million t of aggregate. To accommodate such enormous loads, Ingula has a 265 t crane – arguably the heaviest in Africa. There are 16 km of tunnels and 8,28 km of waterways. The underground cavern’s dimensions are 187 m long, 26 m wide and 54 m high – the largest in mud rock in Africa.

Fig. 2 Main_Access_Tunnel

Fig. 3: Main access tunnel

This energisation completes the first phase of the integration of the power station’s transmission system and was done at a total cost of R1,1-billion.The utility plans to operate the scheme on a weekly cycle and is expected to have an overall cycle efficiency of almost 80%.

Ingula is the largest construction project, in terms of expenditure, in both the KwaZulu-Natal and Free State provinces.Almost 55% (1892 people) of the total Ingula labour force were recruited from local communities and municipalities in the KwaZulu-Natal and Free State provinces. The recruitment of locals from local communities within 100 km from site has always been a priority.

Fig. 5 connecting the cables

Fig. 4: Connecting the cables

Project delays

Eskom has been inundated with delays at all of its new-build power station projects, and Ingula is no exception. An 8 t platform on wheels collapsed 4 km into a hydro-electric tunnel at the site killing six construction workers and injuring many more in November 2013. This caused construction to cease while investigations were underway. Since then, the public has been informed that the Ingula pumped storage scheme will be at least one year late. It is now anticipated to produce first power in the first quarter of 2015.

Conservation at Ingula

At Ingula, Eskom manages about 14 000 hectares of expansive mountainous grassland, including around 1000 hectares of sensitive wetland. To increase awareness of its wetlands, and the Ingula Nature Reserve, an annual wetlands programme is rolled out, giving participants a rare opportunity to experience wetlands first hand.

A partnership was established in 2003 between Eskom, BirdLife South Africa and Middelpunt Wetland Trust. The purpose of the Ingula Partnership, as it is known, is:

  • To ensure integration of environmental factors into the planning and implementation phases of the project
  • To investigate the value of social, economic and environmental values of the area to users, and to measure the impact of the project on users.
  • To effectively monitor and manage environmental impacts relevant to the partnership at the site, before, during and post construction.
  • To initiate and monitor appropriate environmental projects.
Ingula lower dam

Fig. 5: Ingula’s lower dam

The partnership will exist for at least ten years and will be reviewed every five years. Eskom has committed to the funding of projects and studies identified and approved by the partnership steering committee.

Eskom has already entered into the process of proclaiming the property as a nature reserve. There are many reasons for this, the most important being the large expanse of grassland, wetland and escarpment forest.  The wetlands at Ingula’s upper site straddle the continental watershed and serves as a continual supply to the Wilge and Tugela Rivers, with springs flowing throughout the year.  The wetland system hosts a large variety of species, and is in need of protection following years of overgrazing and inappropriate burning. The area fulfils the criteria for proclamation as a Ramsar site and is of international significance.

A team of full-time professional environmentalists monitors all activities on site, ensuring legal requirements are met, and that the project is operated in terms of government’s authorisation. The Ingula conservation area hosts four of South Africa’s critically endangered species (Red Data List) being white-winged Flufftail, Wattled Crane, Rudd’s Lark and Eurasian Bittern. The change in habitat due to the construction of the dams is being monitored by conservation staff, and new species such as spoonbill and flamingo are moving into the area.

Contact Nto Rikhoto, Eskom, Tel. 011 800-3378, mediadesk@eskom.co.za

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