ABB Review Special Report - ABB - ABB Group

and 36th, double tuned 12th and 24th,and C-type 3rd harmonic. Shunt capacitorbanks, with and without dampingreactors, balance the reactive powerrequirement at Jingzhou, Zhengping andHuizhou converter stations.DC filteringRobust passive DC filtering ensures aperformance level of 500 mAp (bipole)/1000mAp (monopole) for bothprojects. Each terminal pole has twofilter arms designed as double tunedfilters, one tuned to the 12th and 24thharmonics and the other to the 12thand 36th harmonics.7Control and protectionThe projects’ control and protectionstrategies are realized with ABB’s stateof-the-artMACH2 system. MACH2features highlevelperformance,lowmaintenance, avery powerfulprogrammingenvironmentand good integrationwithSCADA systems.The SCADAsystems enable information about theoperating status of each converterstation to be accessed remotely by dispatchcenters. These centers have fullremote control capability and can regulatepowertransmissionPower will be transmittedeastward during the peakgeneration period and towardthe central power grid wheneverreservoir water needsto be conserved.Converter transformer arrangement per poleon the link.Terminal-toterminalcommunicationisvia opticalfiber groundwire. Capacitynot neededfor communicationis used for dispatch and for datatransfer on the networks, but could alsobe used for commercial purposes.Control functions such as power ramping,frequency control and dampingmodulation, are also integrated. Thestation engineer can adjust the interfaceand parameters as required bythe system.Converter transformers andsmoothing reactorsThe single-phase converter transformers7 in the Longquan and Jingzhou stationsare rated 297.5 MVA, 525/√3:210.4/√3(210.4 for Y-D) kV, 16% reactance, withan OLTC tap range of +25/-5 (1.25%per step). The Zhengping transformersare rated 283.7 MVA, 500/√3:200.4/√3(200.4 for Y-D) kV, 16% reactance.Here, the OLTC tap range is +26/-2. Inthe Huizhou station the transformersare rated 283.7 MVA, 525/√3:200.6/√3(200.6 for Y-D) kV, 16% reactance, alsowith an OLTC tap range of +28/–4(1.193% per step). Dry-type bushingsare used for the valve hall penetration.The converter transformers at Longquan,Jingzhou and Huizhou are alsoequipped with electronic control,allowing analysis and reporting, plusintelligent fan control to minimizelosses.The smoothing reactors are connectedto the valves via the bushing penetratingthe valve hall wall. An electroniccontrol system for the reactors atLongquan, Jingzhou and Huizhoufeatures the same capability as thatprovided for the transformers.Special ReportABB Review11