7631 FFWD Sum04.qxd - ABB

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HVDCHigh voltage direct current (HVDC) transmission has come of age.The technology pioneered by ABB was first used half a century agoto bring power from the Swedish mainland to a remote Baltic island.The golden era of HVDCIn 50 years HVDC has evolved froma pioneering technology to a wellproven, effective and economic methodof transmitting power over longdistances. The first ever HVDCconnection has recently celebrated itsfiftieth anniversary. The story is one ofunending development.Fifty years ago the world’s first high voltagedirect current (HVDC) link was inauguratedbetween the Swedish mainland and the Balticisland of Gotland. The new power connectionnot only brought down costs for consumers,it opened up a new era for the island’seconomy.Gotland lies 80km off the east coast ofSweden. It has an area of 3,140 sq km and apopulation of more than 57,000 people. Themain industries are agriculture, fishing andtourism.The advent of power from the mainland wassponsored by the Swedish government in a bidto reverse worrying trends in unemploymentand a declining population. The technologychosen was HVDC delivered via a 90km,100kV, 2MW submarine cable.HVDC has proved itself in this andsubsequent installations as an ideal vehicle forbulk power transmission and interconnectingindependent power grids. HVDC lines cannotbe overloaded, and so protect grid reliability anderadicate the ‘loop flows’ found in AC systems.ABB pioneered HVDC with the Gotlandlink and has gone on to supply more than halfof all the HVDC converter stations installedover the years. ABB has an installedtransmission capacity of about 40,000MWout of a world total of 70,000MW.Apart from the first installation, ABB hascreated the highest voltage HVDC link, thelongest HVDC lines, above and below ground,the highest converter power rate and the longestsubmarine cable.ABB’s unique HVDC Light, the latestpatented innovation, is designed for underwaterand underground transmission. The technologyrelies on voltage source converters and cablesand its first installation was made in 1997.STEPPING UP THE POWERFor Gotland, the first submarine cable waslaid in 1953 between Västervik on the mainlandand Ygne a town 10km south of the island’scapital, Visby. The power connectioncommenced with a rated voltage of 100kV anda transmission capacity of 20MW.In 1970 the stations were supplemented withthyristor valves, connected in series with themercury-arc valves. This made it possible toraise the voltage to 150kV and the transmissioncapacity to 30MW.In 1983 a new cable was laid providing arated voltage of 150kV with a 130MWtransmission capacity. The converters were builtup of thyristor valves. The two connectionsoperated independently. This additional powermeant that all the islands’ needs could besupplied by the link and the local power stationclosed.The third connection, planned in 1985,anticipated demand for 147MW. This is usuallyused in conjunction with the second link toform a bipolar link but can also also operateindependently.1321 Pulling the Gotland DC cables ashore in the 1950s.2 An ABB engineer on site in Gotland.3 In a large HVDC station, it must be possible to isolate the powercircuit. This is done in the AC switchyard with help of instrumenttransformers and 500kV circuit breakers.10 FFWD >> Summer 2004
RVT – the ultimate power factor controllerABB’s RVT power factorcontroller is the‘ultimate’ controller for theflexible monitoring andswitching of capacitor banksin power factor control (PFC)applications. It features easycommissioning and automaticset-up, a user-friendly menubasedoperator interface witha full graphic display, and ahighly efficient switchingstrategy that combinesintegral, direct and circularswitching.product roundupThe RVT providescomprehensive measurement,monitoring and event-logging ofnetwork and capacitor bankinformation including: active andapparent power; reactive power;voltage and current; temperature;total harmonic distortion onvoltage (THDV) and totalharmonic distortion on current(THD I); and frequency.Programmable parameter settingenables the operator to set theswitching strategy, with theflexibility to determine differentcontrol targets for day and nightoperation, and to enter alarmthresholds to protect the capacitorbank against such events as overandunder-voltage, overtemperatureand excessiveharmonic distortion.The standard RVT has thefacility to trigger external alarms,while the RVT-Modbus versionis fitted with an RS485 Modbusadapter which makes all itsoperational parameters accessibleand downloadable for fullintegration within a BMS.New-generation PQF activefiltersABB has launched a new generation ofits PQF (Power Quality Filter) range ofmicroprocessor controlled active filters designedto solve the growing problem of harmonics inlow voltage electrical networks. Two newmodels are now available, the PQFM for smallto medium three-phase industrial loads and thePQFK, a three-phase, four-wire unit for industrialand commercial networks with high triplen (thirdand its odd multiple) harmonics.The increasing use of non-linear loads in alltypes of industrial and commercial applicationshas resulted in the introduction of potentiallyharmful harmonics into the power network thatcan lead to overheating of cables, motors andtransformers, damage to sensitive equipment,tripping of circuit breakers and blowing of fusesas well as premature ageing of the installation.ABB PQF active filters provide a reliableand cost-effective solution to this problem bycontinuously monitoring the current in real timeto determine which harmonics are present andthen injecting harmonic currents in the networkwith exactly the opposite phase to thecomponents that are to be filtered. The twoharmonics effectively cancel each other out sothat the feeding transformer sees a clean sinewave.ABB PQF active filters are factoryassembled and tested, ready to install and useat site. They have a modular construction,which allows easy extension to cater for futureload growth. There is also no need to apply ade-rating factor when PQF units are coupled inparallel, which makes it feasible to achieve ahigh rating within a small footprint. Since thePQF does not operate according to theconventional low harmonic impedance principleemployed by passive filters, it remainsunaffected by changes in network parametersand can not be overloaded.The PQF offers features such as: eventlogging with real-time stamp, programmableload balancing, isolation between control andpower units by optical fibre link, digital I/O andModbus communication.The fully programmable filters can either bepre-programmed by ABB or programmed onsite using PQF-Manager, a simple, user-friendlyfront panel module that offers direct control,programming and monitoring capability. ThePQF can also be controlled by a standard PCvia its RS232 port and the optional PQF-Linksoftware. PQF units can also adopt thesecondary roles of reactive powercompensation and load balancing.Summer 2004 >> FFWD 11
Page 5 and 6: Rail visibilitynewsINTERNATIONAL NE
Page 7 and 8: R&Dinsulation, current interruption
Page 9: enewablesPeter Jones, Sector Manage

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