HVDC Cahora Bassa

from Wikipedia, the free encyclopedia
HVDC Cahora Bassa with a line pole in the Kruger National Park
Course of the HVDC
HVDC converter systems in Apollo near Pretoria

The HVDC Cahora Bassa ( English : Cahora Bassa HVDC ) is a cross-border high-voltage direct current transmission line (HVDC), which is used to transmit electrical energy between the Cahora-Bassa dam in northern Mozambique and the industrial conurbation around Johannesburg and Pretoria in South Africa .

history

The transmission line was built between 1977 and 1979 by the ZAMCO consortium ( AEG , BBC and Siemens ) and went into full operation on March 15, 1979. In 1981 it was damaged by the events of the Mozambican Civil War and remained unused for a long time.

When the plant went into operation in 1976, almost the entire generation capacity of 2000 MW was intended for South Africa. The electricity supplies to Eskom were a very important source of income for the Frelimo government in convertible currency for Mozambique. The deal turned out to be extremely fragile under the conditions of the civil war of the 1980s. The dam and its technical systems could be adequately protected. With the approximately 900 kilometer long route of the double transmission line to the border with South Africa, however, things looked different. The anti -government RENAMO gangs used explosives to blow up overhead line pylons. Finally, they dismantled such masts step by step in order to steal the steel profile parts. The Cahora Bassa power plant ceased operations in 1980. This civil war and its consequences prevented the transmission of energy over this double line for 17 years.

After the civil war, the line was renovated by Siemens from 1995 to 1998 and put back into operation

In 2006, Eskom commissioned ABB to upgrade the switchgear in Apollo. This work was carried out until 2008, whereby the transmission capacity could be increased from 1920 MW to 2500 MW. At the same time, it was retrofitted in order to be able to transmit 3960 MW in the future.

A technical improvement and refurbishment of the systems in Songo were commissioned to ABB in 2012 by Hidroeléctrica De Cahora Bassa (HCB). The relevant work was then carried out from 2013 to 2014.

Heavy rains caused massive land flooding in the Mozambican province of Gaza in January 2013 . The Limpopo stepped over its banks. This also affected a 5.3 km long section of the HVDC, whereby first one mast had overturned and then four more masts had been dragged along. The energy transmission via Zimbabwe had to be temporarily diverted. The repair contract was awarded to Quanta Services Africa in February 2013 . The two biggest challenges for the repair work were the logistics in the rough terrain and the possibility of encountering landmines from the former civil war during the work. The security against landmines was carried out by the South African arms company Denel Mechem . Communications, including faxes, had to be handled via satellite phone connections. Two helicopters were used for the duration of the work.
Due to the structural deformations in the damaged section, the cables were under very high tensile stress and had to be removed before the actual repair work. The largest span between two masts achieved during this work is 812 meters, because the flood damage and the short repair period made it impossible to erect a new mast in place of a damaged one. The resulting higher mechanical load in the system was compensated for with a different cable than previously used ( Aluminum Composite Core Conductor - ACCC), because it is lighter because of the use of aluminum.

The transmission line was again severely damaged by the weather events of cyclone Idai in March 2019. Pylons overturned. The power transmission then had to be stopped. For South Africa and some industrial customers in Mozambique, this may mean short-term difficulties because, as a result of the shutdown, a previously permanent 1150 MW feed into the South African grid ended abruptly. The Foreign Affairs Committee in the South African parliament dealt with the humanitarian catastrophe of the cyclone and the consequences for the energy supply.

Route

The line begins at the village of Songo ( power converter station Songo ) in Mozambique and ends after 1,420 kilometers in the South African converter station Apollo near Pretoria (station Apollo ), which borders the Rietvlei Nature Reserve to the southwest . As a result, it is already on the territory of the Ekurhuleni Metropolitan Municipality . World iconWorld icon

Over a length of 900 kilometers with 4,200 masts it runs in Mozambique near the border with Zimbabwe. The transmission line has a length of 518 kilometers on South African territory. It reaches the territory of South Africa south of the Pafuri border crossing (border crossing of the HVDC ). World icon

technical features

For the electronics built by AEG , Wacker Chemie has developed large silicon wafers for the first time in order to be able to switch the 2 kA current  with a thyristor . For the remote control of the converter elements on porcelain insulators via glass fibers in the insulators, Telefunken has created the basis for fast optical communication. Before that, the cutoff frequency of optical transmission systems was in the order of 10  kHz .

The transmission capacity is 1920  MW with a bipolar DC voltage of ± 533  kV , with the two poles each running over separate routes with their own masts. As at the border crossing between South Africa and Mozambique, the routes for the two poles run at a distance of approx. 1.5 km. Due to the spatial separation of the routes with a possible return line via the earth, the function with half the transmission power is possible even if a pole is interrupted.

In contrast to other HVDC systems, the two converter stations at both ends of the line are not set up in a hall, but outdoors. The thyristors of the converters are housed in oil-filled containers which are under high voltage during operation and which are mounted on electrical insulators . The HVDC in its current form was renovated by Asea Brown Boveri (ABB) and is operated by the electricity supply company Eskom .

Competing project

Mozambique is planning to build another HVDC transmission system (800 kV, direct current transmission, according to earlier information 500 kV), for which the name CESUL project (Centro-Sul, German: Center-South) is used. The transmission line is to run from the region around Tete to the crossing of the Zambezi, virtually parallel to the previous HVDC overhead line leading to South Africa and from there directly into the Maputo area. The generation site is to be a new dam project, about 61 kilometers downstream from Cahora Bassa, and is called the Mphanda Nkuwa hydropower project . Cataxa or Matambo are planned as the location of the planned transformer station at the starting point of the line. In addition, a 400 kV line with alternating current is planned from these stations via a completely different route to the south of the country.

At the beginning of 2019 it was announced that the Gabinete de Implementação do Projecto Hidroelétrico de Mphanda Nkuwa - GMNK ( Mphanda Nkuwa Hydroelectric Project Implementation Office ) has now been established by the Mozambican Ministry for Raw Materials and Energy to further continue and coordinate the project . With this, President Filipe Nyusi put an end to the previous project status , according to which a consortium of three companies, the Mozambican group Insitec and the Brazilian construction company Camargo Corrêa , each with 35%, and the state energy provider Electricidade de Moçambique (EdM) with 30% shares for the Development was responsible. Instead, the project is now to be promoted jointly by Hidroelectrica de Cahora Bassa and the Electricidade de Moçambique under the control of GMNK.

Individual evidence

  1. ↑ a b Siemens 1996 - 2020: [ https://new.siemens.com/global/en/company/about/history/news/siemens-supplies-south-africa-with-electricity.html Cahora Bassa. Siemens supplies South Africa with electricity . www.new.siemens.com (English)
  2. ↑ a b Joni V. Klüss: HVDC Historical Advances. Development Review of High Voltage DC Transmission - Early Stages to Modern Day Application ]. Aalto ELEC , 2011, pp. 28–29 PDF document, pp. 29–30 (English)
  3. ↑ ECA: South African Power Pool (SAPP), Transmission & Trading Case Study . London 2010. PDF document p. 27 at www.esmap.org (English)
  4. ↑ Anonymous: Cahora Bassa comes back to life . Posted May 11, 1998 by International Water Power & Dam Construction, online at www.waterpowermagazine.com
  5. ↑ FIG: The Cahora Bassa HVDC transmission system . at www.abb.com (English)
  6. ^ Siemens: HVDC - High Voltage Direct Current Transmission. Cahora Bassa, South Africa / Mozambique . PDF document p. 45, at www.energy.siemens.com (English)
  7. ↑ a b FIG: Cahora Bassa. The Cahora Bassa HVDC transmission system is an important source of imported power for the South African grid . at www.new.abb.com (English)
  8. ^ Mike Rycroft: Cahora Bassa HVDC line emergency restoration . on www.ee.co.za (English), In: EE Publishers (Ed.): energize, July 2013, pp. 36–37
  9. ^ Club of Mozambique: Limpopo river flood damages electricity transmissions export lines ( Memento of April 2, 2015 in the Internet Archive ). News from January 24, 2013, archive version on www.archive.is (English)
  10. ^ ACCC Conductor News: Substantial Flooding in Mozambique Impacts Power Delivery to South Africa . at www.archive.constantcontact.com (English)
  11. ^ Terence Creamer: HCB, Eskom work on Cahora Bassa line refurb plan after disruptions . News from January 25, 2013 on www.engineeringnews.co.za (English)
  12. ↑ Sabelo hermitage, Thanduxolo Jika: A suspect contract blew the fuse . Message from Mail & Guardian of March 22, 2019 on www.mg.co.za (English)
  13. ^ Parliament of the Republic of South Africa: Committee on IR Calls for Assistance to Tropical Cyclone Idai Victims . Statement from March 19, 2019 on www.parliament.gov.za (English)
  14. ↑ Chanel Retief, Yanga Sibembe: Picking up the pieces after Cyclone Idai . Announcement at Daily Maverick from March 19, 2019 on www.dailymaverick.co.za (English)
  15. ↑ Dhevandhra Govender: A Study of the Electrical Environment Below HVDC transmission lines . University of KwaZulu-Natal (Bachelor thesis) p. 26. PDF document p. 43 on www.146.230.128.141 ( Memento from April 2, 2015 in the Internet Archive ) (English)
  16. ↑ Satellite image of the border region with the course of the two cable routes from right or left below
  17. ^ Adriana Lafleur; Stephen Lindley: SRESA of a Regional Transmission Development in Mozambique . IAIA13 Conference Proceedings, 33rd Annual Meeting of the International Association for Impact Assessment, Calgary May 13-16, 2013, online at www.conferences.iaia.org
  18. ^ Electricidade de Moçambique: Mozambique Regional Transmission Backbone Project . Maputo, April 2011 (PDF document, pp. 11–12, English), online at www.edm.co.mz
  19. ^ Mustafa Zakir Hussain et al .: Mozambique Energy Sector Policy Note. Energy Sector Policy Work . Document of the World Bank: Report No: ACS17091 dated November 30, 2015 (PDF document p. 79), online at www.documents.worldbank.org
  20. ↑ Joseph Hanlon: Confusion over Mphanda Nkuwa . News from August 27, 2018 on www.clubofmozambique.com (English)
  21. ↑ Macauhub: Mozambican government Creates entity to develop Mphanda Nkuwa dam . on www.macauhub.com.mo (English)

literature

Web links