Innovation in Global Power - Parsons Brinckerhoff

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Transporting Power Across the Grid http://www.pbworld.com/news_events/publications/network/ Rehabilitation and Reconstruction of Abu Dhabi Transmission Network By M.R. Jayasimha, Abu Dhabi, 971 50 4554907, jayasimhaM@pbworld.com The author tells how PB is assisting Abu Dhabi Water and Electricity Authority to further enhance the reliability of the emirate’s transmission and distribution network. He focuses on a modification to the switchgear and replacement of power transformers and a substation. Abu Dhabi’s electricity transmission network was established in the early 1970s at mainly 220 kV and 132 kV levels. Since then, the country’s rapid rates of growth and development and characteristic high increases in load demand have led to an expansion of the network and upgrading to 400 kV. In addition, the Abu Dhabi Water and Electricity Authority (ADWEA) initiated a repair and rehabilitation project in 1999 to further enhance the reliability of the existing power transmission and distribution network. 1 PB was selected as consultant for this important and technically complicated project. Once we completed the first phase of the project by 2002, we were awarded an extension for the second phase, which included new substations and a new scope of services for the rehabilitation and replacement of existing switchgear in transmission substations. Starting in January 2003, seven construction contracts worth US $70 million were awarded. These contracts included: • Single to double bus bar modification of 13 2kV gas insulated switchgear (GIS) in five substations • Replacement of ten 132/11 kV 40 MVA power transformers • Replacement of the existing 132 kV substation in the Taweelah Power Station Complex. 2 Single to Double Bus Bar Modification The single to double bus bar modification of 132 kV GIS in five energised substations was a very specific and demanding task. The GIS in these substations was already in service for up to twenty years. The modification works required partial and in some cases complete shutdowns of the substation. The works were planned during the winter season because during the summer in Abu Dhabi maximum system demand occurs due to the high air conditioning loads. In one of the substations, the bus bar protection was replaced with numerical low impedance busbar protection during the modification works. In the other four substations, existing low impedance busbar protection was adapted for double bus bar type switchgear. Of the three types of switchgear to be modified, manufacturers had discontinued production of two of them. The busbar and isolator modules required for this modification were manufactured specifically for this purpose by the original equipment manufacturers. Figure 1 shows the switchgear before and after the modification. Replacement of Power Transformers Figure 1: W59 substation before single to double bar modification of 132kV GIS (top) and after (bottom). For the replacement of ten ageing 132 kV/11 kV 40 MVA power transformers, the design of the new power transformers was adopted to suit the existing transformer compound dimensions and the length of the existing high voltage cables. The opportunity was taken to also replace the transformer protection relays with latest numerical protection relays. In one of the GIS substations, a bus reactor bay was modified to provide a fourth 40MVA transformer. Ten new 11 kV feeders were also provided in this substation to receive power from the newly installed transformer. Existing 132 kV cables were reused providing new terminations at the transformer end, (page 67) 1 For more information about Abu Dhabi Water and Electricity Authority’s (ADWEA’s) introduction of control systems in its transmission substations and PB’s involvement in this work, please read “Experiences and Trends in Automating Transmission Substations in Abu Dhabi” by Oleg Matic in PB Network’s 20th Anniversary issue (Issue 66), pp. 88-89. or on the the Web at http://www.pbworld.com/news_events/publications/network/issue_66/pdf/66_37_Matic_ExperiencesAndTrends.pdf Another of ADEWA’s projects to augment Abu Dhabi’s electricity supply is covered in “400 kV Interconnection of Abu Dhabi Island” by Walter Bullock, PB Network Issue 65, pp.79-80 or on the Web at http://www.pbworld.com/news_events/publications/network/Issue_65/pdf/079.pdf 2 For information about the use of a PB invention that cut fuel consumption at the Taweelah complex, see “How Innovation Can Open Market Opportunities” by Paul M. Willson, PB Network Issue 63, pp 71-72 and on the Web at http://www.pbworld.com/news_events/publications/network/issue_63/63_26_willson_howinnovationcanopen.asp PB Network #68 / August 2008 62
Transporting Power Across the Grid http://www.pbworld.com/news_events/publications/network/ HVDC Transmission Strengthening in Southern Africa By Paul Tuson, Johannesburg, South Africa, 27-11-787-4141, tusonP@pbpower.co.za The author discusses some findings from a study PB did to help determine the best technical/financial solutions to improving the electricity transmission system in southern Africa. He tells of potential HVDC projects in the region and proposes a possible HVDC transmission link to the Cape that is fed from generation sources mostly in the north of the country. Africa’s electricity system is characterized by dispersed loads and generation sources spanning hundreds and in some cases thousands of kilometres. Connecting these generating sources and load centres is a challenge. Hired by Eskom, the South Africa electricity public utility, to derive the least-cost and best technical solution for strengthening power transmission for the Cape in South Africa, we looked into a possible high voltage dc (HVDC) solution to the challenge. Eskom plans to spend more than ZAR 345 billion (US $49.5 billion) on generation, transmission and distribution capital projects in the next five years. Among its projects underway are: • 4800 MW coal-fired Medupi Power Station, for which PB is serving as technical advisor and project manager • 4800 MW Bravo power station • 1400 MW Ingula pumped storage project, for which PB provided engineering services 1 Similarly, many of the South African Development Community (SADC) countries have major generation and transmission projects in progress or at various stages of planning. The power utilities in the SADC countries will be seeking to maximize their reserve margins and trade any surpluses of power using transmission systems that connect the large new power sources with the large load systems in compliance with the South African Power Pool (SAPP). Acronyms/Abbreviations ac: alternating current dc: direct current DRC: Democratic Republic of the Congo HVDC: High-voltage direct current SADC: South African Development Community SAPP: South African Power Pool The Connection Challenge Loads in the South African region are growing at an annual rate of between 3 percent and 6 percent. Eskom’s 2007 maximum demand exceeded the record achieved in 2006 by more than 1500 MW. As loads continue to grow in the SADC countries, the challenge will be to connect them to new and dispersed generation sources. Figure 1 depicts some possible HVDC solutions in the SAPP. The thick, dotted lines depict possible future HVDC transmission interconnectors. In the figure, dc lines are shown connecting the Capanda hydro generation in northwest Angola to the Ruacana hydropower station in northwest Namibia. Another possible dc interconnector connects Namibia with Zambia (via a dc link from Gerus substation in Namibia to Figure 1: Possible dc interconnectors in the South Africa Power Pool. 1 For more about pumped storage technology and the Ingula project, please read “Pumped storage technology: recent developments, future applications” a following article by Ian McClymont and Paul Reilly. 63 PB Network #68 / August 2008 Katima Malilo in the Caprivi strip) and Botswana (via a dc link from Auas substation in Namibia to Isang substation in Botswana). Other possibilities we identified include the following: • A dc transmission link interconnecting the Kariba hydro generation in Zambia with South Africa and indirectly connecting the DRC hydro generation with South Africa in advance of the proposed WestCor Project, which would connect an initial 4000 MW and eventually 40 GW from the Inga power station in the DRC, 3000 km (nearly 2,000 miles) from South Africa, to various African countries. • A dc system connecting existing and planned hydro generation and planned coal-fired thermal generation in the centre of Mozambique with Maputo in the South of Mozambique or with Richards Bay in South Africa. • A dc transmission line connecting Zambia to Tanzania via Kabwe or Pensulo substations in Zambia and Iringa or Singida substations in Tanzania. • Connecting the major generating centre in the north of South Africa with large load centres in the Cape and Kwazulu Natal areas.
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