ABB Review Special Report - ABB - ABB Group

Power take-offElectric power generation in China tends to be located in the northeast (coal-fired), and in thewest and southwest (hydropower), while the main consumer areas are in the eastern coastalarea and southern industrial region of Guangdong.China’s total generating capacity of more than 350,000 MW (end of 2002) needs to grow to atleast 500,000 MW by the end of the decade to cope with increased demand. Due to its fastgrowingeconomy, many areas, including Shanghai, Guangdong and Zhejiang provinces, arealready today suffering from a significant power supply shortfall. Guangdong province, for example,has a deficit of over 30,000 MW, some of which is met through imports from neighboringHong Kong.China now plans to start adding 25,000 to 30,000 MW each year through 2005, for an annualgrowth of 7% to 8%. Both AC and DC transmission are foreseen for the extensions. Over the nextten years, the HVDC market – long-distance transmissions and back-to-back stations to interconnectthe regional networks – is estimated at 40,000 MW.DC-side breakers and switchesSF 6 breakers are used for all the highspeedDC switches: metallic returntransfer breakers, neutral bus groundingswitches, neutral bus switches andground return transfer switches. Theground return transfer switch is theonly one of these to be of conventionalpassive design. All the others have anactive auxiliary transfer circuit consist-ing of a capacitor and a charger. Thecharger gives the DC switches extracurrent commutation capability, enablingthem to handle even the highestoverload currents.Operating configurationsThe links can be operated in many differentconfigurations and modes. Emergencyoperation is provided for, as is“A remarkable achievement in the history of ABB’s HVDC technology”The inauguration of the Three Gorges – Changzhou HVDC link in August 2003 in the presenceof representatives of the Chinese government, State Council Three Gorges Office, State PowerGrid Corporation and ABB, marked the successful completion of trials and the start-up of commercialoperation. The 500-kV, 890-kilometer long HVDC link can operate at world record levelsof up to 3,480 megawatts, and when the Three Gorges generators begin operating later thisyear it will transmit electricity to millions of consumers in eastern China. The largest and longestbipole DC power transmission link in China was completed on schedule in four years.“Considering the project’s technical complexity, this is a remarkable achievement in the historyof ABB’s HVDC technology,” says Peter Smits, head of ABB’s Power Technologies division.“By delivering this challenging project on time almost to the day, we have demonstrated ourcommitment to speed and precision, and to improving the quality of life for millions of Chinesecitizens.”operation without telecommunication.Through accurate measurement andcontrol it is ensured that in the case ofbipolar balanced operation with localstation ground the unbalance current toground will be zero.The operating modes are:BipolarMonopolar earth return and metallicreturnReduced DC voltage (from 500 kV to350 kV)Reverse power operationBipole and pole power controlPole synchronous and emergency(separate) power controlPole backup synchronous control(for modulation of DC current withoutinter-station telecommunication)Pole current controlMeeting China’s energy demandChina plans to substantially expand itsgenerating capacity by 2010 in order tocope with the predicted growth indemand (see panel). At the same time,two new regional networks will becreated as the basis for a new nationaltransmission grid. HVDC, with all itsadvantages for long-distance transmission,is expected to play a major rolein the extensions.Leif EnglundMats LagerkvistRebati DassABB Power TechnologiesSE-771 80 LudvikaSwedenleif.englund@se.abb.commats.lagerkvist@se.abb.comrebati.dass@se.abb.comReferences[1] Introduction to China’s Yangtze River Three Gorges Project. The PRC State Council Three Gorges Construction Committee, Ministry of Land andResources, State Environmental Pollution Administration, State Bureau of Cultural Relics, September, 2002.[2] Z. Xiaoqian, D. Gongyang, G. Ricai: The Three Gorges power grid and its development. Cigré 1998, 37–203, Paris.[3] Z. Xiaoqian, et al: Design Features of the Three Gorges – Changzhou ±500 kV HVDC Project. Cigré 2000, 14–206, Paris.12Special ReportABB Review