ABB Review Special Report - ABB - ABB Group

3HVDC Light extrudedsubmarine cable, with doublearmoring (80 kV rating)(one for each drive), physically separatedfrom each other on the sea floor.The two cables in each pair are operatedin bipolar mode, one having a positiveand the other a negative polarity.To make sure that the cables will notbe damaged by anchors or trawling,they are laid in trenches on the sea bedformed by water jetting, or coveredwith rocks where this is not practicable.Motorformer drives the compressorsFollowing the introduction in 1998 ofnew, innovative cable winding technology,ABB’s engineers soon began toconsider the possibility of using HVcable windings in place of conventionalwindings in electrical motors in orderto radically increase the motors’ voltageratings. Such a motor can then be connecteddirectly to the HV grid, doingaway with the need for a costly stepdowntransformer.The first product to be based on thisprinciple was an HV cable-wound generator.Shortly afterwards, the same conceptwas applied to motors, resulting inthe development of a synchronous machine,dubbed Motorformer (see panelon page 55). The first unit was installedin 2001 at an air separation plant inSweden, where it drives a compressor.This motor is directly connected to a42-kV bus. In the meantime, ABB offersHV motors of this kind for voltages upto 70 kV. Work is currently under wayto develop units rated at 150 kV.Apart from eliminating the step-downtransformer and related switchgear,Motorformer reduces the total systemlosses by as much as 25% 4 . Beingepoxy-free, it also has important environmentalbenefits, including easy recyclability.And fewer components meanhigher system reliability and availability,plus reduced costs for service, maintenanceand spares.A challenging environment forhigh-voltage equipmentOffshore equipment design is constrainedby the need to keep both footprintand weight to a minimum. HVDCLight and Motorformer offer importantadvantages in precisely these areas:Smaller filters and the absence of synchronouscondensers make HVDCLight more compact and lighter thantraditional HVDC systems.No large, heavy transformer is requiredto connect the Motorformerto the HVDC Light converter.4InputpowerUse of Motorformer TM eliminatestransformer losses (A). Only motorlosses (B) remain.ConventionalsystemABMotorformersystemBShaftpowerallowed to come into contact withhigh-voltage equipment.Environment: The high-voltage equipmentmust be protected from thedamp, salt-laden sea air.Availability: Given the daily productionof gas worth US$ 10–15 million, highequipment availability is essential.HVDC Light and Motorformer are innovativetechnologies with all the qualitiesneeded to power offshore platformsfrom shore for maximum economicaland environmental benefit. Troll A isthe first such platform anywhere to bepowered in this way, the electric drivesystem being part of a program tomaintain and expand production capacity.The elimination of CO 2 emissionsand a smaller equipment footprint arejust two of the benefits enjoyed byStatoil as a result.Dr. Tom F. NestliMagnus J. JohanssonABB Automation Technologiestom.f.nestli@no.abb.comOther design considerations in connectionwith this project were:Safety: Troll A produces large quantitiesof hydrocarbon gas, which is notLars StendiusArne AbrahamssonDr. Philip C. KjaerABB Power Technologies[1] G. Asplund, K. Eriksson, K. Svensson: HVDC Light – DC transmission based on voltage sourced converters. ABB Review 1/1998, 4–9.[2] G. L. Eriksson: Motorformer – A new motor for direct HV connection. ABB Review 1/2001, 22–25.56Special ReportABB Review