SIEMENS the h Class to Korea Brochure

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Bugok 3: Bringing the H Class Gas Turbine to Korea

Reprint from:Modern Power Systems, September 2011

Authors:Alfred Kessler, Thomas HagedornSiemens AG, Erlangen, Germany

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(S EPS, Koreas first independentpower producer, founded in 1996 asan offshoot of LG, and now owned70% by GS Holdings and 30% byOman Oil, is continuing its track record ofinnovation. Unit 3 at the companys Bugoksite will be one of the first power plants in theworld to employ the new Siemens H class gasturbine, which makes possible a combinedcycle efficiency of over 60% (LHV basis) but

also provides considerable operationalflexibility, enabling cycling and frequent andrapid starts/stops.

Siemens, in consortium with GS E&C, issupplying the complete H class single-shaftcombined cycle plant for unit 3, rated at >415MWe gross, to GS EPS on a turnkey basis,with a scheduled commercial operation dateof 31 August 2013. The turnkey contract wassigned on 11 January 2011 and the

groundbreaking ceremony for the newproject, which represents an investment ofabout 460 billion won ($420 million), was heldon 19 April 2011.

Units 1 and 2 at the site (both 550 MWemulti-shaft (2-on-1) combined cycle plants,which entered commercial operation in July2001 and March 2008, respectively) alsoemploy Siemens gas turbines, of the earlier Fclass type.

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The first deployment of Siemens new path-breaking H class gas turbine and combined cycle technology in

Asia will be at the LNG-fuelled Bugok site of GS EPS (Electric Power and Services) Ltd.

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The fuel for all three units at Bugok is LNG,and they all employ seawater cooling.

Unit 3 will have an efficiency of >55% HHVbasis, equal to >60% LHV basis.

The scope of the unit 3 project, whichemploys a single shaft combined cycleconfiguration, includes the following: 60 Hz version of the Siemens H class gas

turbine, SGT6-8000H (a directaerodynamic scaling from the 50 Hzversion, the SGT5-8000H, now incommercial operation at Irsching 4 inGermany, but with 12 can-combustorsrather than 16). Irsching 4 has recently set anew world record for combined cycleefficiency, for the first time breaking the60% efficiency barrier, see pp 00-00. Hotcommissioning of the lead SGT6-8000Hmachine, installed on the Siemens test bedin Berlin, started on 21 July 2011. As well asthe Bugok 3 order, a further six SGT6-8000H machines have been ordered by USutility FPL.

SST6-5000 steam turbine with laterallyinstalled condenser, coupled to thegenerator by SSS clutch.

Common hydrogen cooled generator,SGen6-2000H type, for the steam and gasturbines.

Triple pressure reheat heat recovery steamgenerator with HP once through (Bensontype) boiler and natural circulation LP/IPboiler design, supplied as an indoor designwithin a boiler house.

SPPA-T3000 plant control system withoperator station integrated in the existingcontrol room.

Power control centres and electricalequipment such as isolated phase bus duct,generator circuit breaker, DC componentsand LV switchgear.

Main and auxiliary transformer. New 345 kV grid connection employing

GIS. New LNG connection including new gas

pressure governor station. The fuel gas isdelivered from the KOGAS terminal pointvia LNG piping, gas filtering, metering andpreheating equipment, to the gas turbine

fuel gas skid. The gas pressure at the terminalpoint to the power plant is >40 bar(g). New cooling water structures. New lifting and circulating water pumps. Extension of ancillary systems such as

demineralised water and chlorination plant.

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The gas turbine (see also pp 23-27)The fully air-cooled model SGT6-8000H gasturbine, like the 50 Hz version, the SGT5-8000H, is a single-shaft machine of single-casing design.

The basic design, adopted from previous gasturbine models, includes the followingfeatures: disc-type rotor with central tie boltand radial serrations; two journal bearingsand one thrust bearing; generator drive atcompressor intake end; and axial exhaustdiffuser

The rotor is supported by two journalbearings and one thrust bearing. The journaland thrust bearing are located at thecompressor side, and the second journalbearing at the exhaust side of the turbine.

The rotor is an assembly of disks, eachcarrying one row of blades, and hollow shaftsections, all held together by a pre-stressedcentral-tie bolt. Hirth serration provides the

alignment of disks and hollow shaft sectionsto allow free radial expansion and contraction,and transmit the generated torque. Theturbine rotor is internally air-cooled.

The platform combustion system (PCS)consists of 12 baskets with air cooledtransitions. The annular arrangementprovides excellent uniformity of exhaust-gastemperature field over the full cross-sectionalarea of the turbine inlet. This is attributable tothe fact that the 12 burners in the PCS form acontinuous ring, thus eliminating hot and coldspots. The ultra low NOx technologysuppresses thermal NOx formation withoutthe need for injection of steam or water.

The generatorThe two-pole SGen6-2000H generator hasdirect radial hydrogen cooling for the rotorwinding and indirect hydrogen cooling for thestator winding. The hydrogen filled generatorcasing is of pressure-resistant and gas-tightconstruction and is equipped with two endshields. The hydrogen cooler is divided intofour sections, two arranged at each generatorend.

The three-phase winding inserted in thestator core slots is a two-layer transposed-bardesign. The winding is vacuum pressureimpregnated together with the stator core. Thehigh-voltage insulation employs a provenproprietary epoxy-mica system.

The generator rotor shaft is a vacuum-castforging and has two end-shield sleevebearings. The hydrogen is circulated in thegenerator interior in a closed circuit by axialflow fans arranged on the rotor shaft journals.A gas system contains all necessaryequipment for filling, removal and operationof the generator with purging gas, hydrogenor air.

A static (thyristor based) excitation system,including transformer, is used to take theexcitation current from the auxiliary powersystem. A start-up frequency converter isprovided for start-up of the turbine generatorunit. The generator acts as a motor in theconverter mode to start the gas turbine setwithout an additional rotating prime mover.

Features of the generator include highefficiency and low maintenance costs.

Steam turbineThe tandem-compound steam turbinecomprises one combined HP/IP casing andone double-flow low-pressure casing, with allcomponents being standardised modules.

With the compact design of the HP/IPturbine, hot steam conditions are confined to

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the middle of the casing. On the other handthe glands at the casing ends are in regions ofrelatively cool steam conditions. Temperaturedecay is much slower when compared to adesign with individual turbine casings.Consequently, the start-up times of such acompact turbine are significantly shorter,saving precious fuel.

The design also requires less space, leadingto savings with respect to the civil structures.

The main feature of the LP turbine is thedouble shell inner casing, which can bedisplaced axially by means of pushrods. Thedifferential expansion between rotor andcasings is thus minimised under all operatingconditions.

ClutchTo support flexible operation as well as thestart-up procedure for the single-shaftcombined cycle plant a self-synchronousclutch (SSS) is installed between the generatorand steam turbine.

With the gas turbine only driving thegenerator (during start-up) and the steamturbine at rest, the clutch is disengaged.

Then, the steam turbine is accelerated andat the instant the steam turbine speedovertakes the generator, the relay clutch isengaged and transfers the steam turbinetorque.

Condensing plantThe condenser is a box type surfacecondenser. The steam space is of a rectangularcross section in order to achieve optimumutilisation of the enclosed volume for thenecessary condensing surface, formed oftitanium tubing. The condenser is installedlaterally at the LP turbine and forms anintegral part of it.

The steam dome, shell, hotwell, and thewater boxes are steel fabrications. Thecondenser is fixed to the foundation beneath,with thermal expansion accommodated bymeans of Teflon pads.

The double flow LP turbine outer casing isconnected to the condenser via the steamdome. The steam dome is welded to theexhaust casing of the turbine with the resultthat the LP turbine cylinder and the condenserform one unit.

Two water ring pumps with air jets (ELMOunits) are installed for evacuation. Duringnormal operation, only one pump is inoperation. To shorten the evacuation timeduring start up both pumps can be put intooperation.

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The heat recovery steam generator (HRSG) islocated downstream of the gas turbine diffuserand as already mentioned produces steam inthree pressure stages: high pressure;intermediate pressure; and low pressure.

The exhaust gas flows horizontally throughthe HRSG.

The plant features advanced steamconditions, with 150 bar and 585C in the HPstage at the steam turbine nozzle.

The HP steam generator is of the Bensontype, with a once-through evaporator in theHP section, and natural circulation, drum-type evaporators in the IP and LP sections.

A condensate preheater is integrated into theHRSG. This arrangement contributes toincreasing the efficiency of the combined cycleplant by using exhaust gas energy to preheatthe condensate before it passes towards thefeed water pump and into the LP system.

The boiler casing is made of steel plate asdictated by the prevailing exhaust gastemperatures. The HRSG is of the coldcasing design with inside insulation.

The HRSG is equipped with an outlet ductand steel stack at the end. The stack is fittedwith a damper and a silencer.

The top-supported heating surfaces consistmainly of finned tubes, which are suspendedfrom a support structure.

The heat recovery steam generator isdesigned to be located indoors and iscontained in a boiler house, which alsoencloses the main working platforms.

Each steam stage consists of an economiser(HP and IP), evaporator and superheater. Thefeedwater is heated in the economiser almostup to boiling temperature and fed into thesuperheater (HP section) or in the drum (IPsection). From the IP drum, water is fed intothe evaporator, where a portion is evaporated.The resulting water-steam mixture flows backto the drum where it is separated. Thesaturated steam is fed to the IP superheaterwhere it is superheated up to main steam outlettemperature.

The HP evaporator system is of the Bensonforced flow design, so an HP drum is notneeded. Instead a combined separator/watervessel is employed.

During start-up and low load, a mixture ofwater and steam from the evaporator isintroduced to the separator. Within theseparator, the two phase flow is separated intowater (fed to the water vessel) and steam(routed to the super-heaters).

In the LP system, the condensate preheaterheats the condensate to approximately theboiling temperature of the LP system. The LPfeed water therefore goes directly from thecondensate preheater to the LP drum.

The HP steam is fed to the HP section of thesteam turbine. The steam expands in the HPturbine and is fed back as cold reheat steam tothe HRSG. There it is mixed with thesuperheated IP steam, superheated further inthe reheater and then fed to the intermediatepressure section of the steam turbine.

The HP and IP steam temperature iscontrolled by attemperation control.

The generated LP steam is fed to theconnection line from the outlet of theintermediate to the LP section of the steamturbine and the entire steam flow is completelyexpanded to vacuum in the LP steam turbine.

8BUFSoTUFBNDZDMFFor redundancy reasons the watersteamcycle is furnished with 2 x 100% maincondensate pumps and 2 x 100% feedwaterpumps. The feedwater pumps are equippedwith Voith variable speed couplings.

A 2 x 50% condensate polishing plant isincluded. This is to prevent potential pollutantconcentration, thus reducing corrosion andscaling/fouling in the turbine and superheaterareas.

The turbine exhaust steam is condensed bya seawater cooled condenser. The condensateand demineralised water accumulated in thecondenser hotwell is discharged by one of the2 x 100% condensate extraction pumps to thecondensate preheating system. Onecondensate extraction pump operates duringfull load operation and a stand-by pump isready to cut in automatically in case of failureof the operating pump. Deaeration of thecondensate is mainly performed in thecondenser under vacuum.

The condensate extraction pump deliversthe condensate from the condenser hotwell tothe LP drum and to the suction side of thefeedwater pumps via the condensate preheaterof the HRSG.

The condensate quality required for properoperation of the once through type heatrecovery steam generator is ensured by thecondensate polishing plant. Depending on thecondensate quality the entire or only a part ofthe condensate mass flow can be supplied by the2 x 50% condensate polishing pumps to thecondensate polishing plant. The treatedcondensate is directly discharged to the suctionside of the condensate extraction pumps.

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COMBINED CYCLE

A connection from the demineralised waterdistribution system is installed for fillingof thepump discharge side and pressurising thecondensate system during standstill.Downstream a line for the injection cooling

of the intermediate pressure and low pressurebypass stations branches off.The feedwater is routed downstream of the

HRSG condensate preheater in separatesuction lines to the feedwater pumps via astrainer located upstream of each pump. Anautomatic recirculation check valve for thepump minimum flow requirement is locateddownstream of each feedwater pump. Theminimum flow is returned to the condensatepreheating systemupstreamof the condensatepreheater.TheHP pump discharge lines are connected

to a commonheader,which delivers feedwaterto the HP part of the HRSG. IP feedwater istapped from a specific pump stage. Thetapping lines are connected to a commonheader, which delivers the feedwater to the IPpart of the HRSG.Another tapping point of the feedwater

pump is used to recirculate feedwater via acommon header to the condensate preheatingsystem.Under normal operating conditions,

feedwater is discharged by one of the twofeedwater pumps via the HP/IP economisersof theHRSG into theHP evaporator and intothe IP drum. The other pump is in stand-by.In case of failure of the operating feedwaterpump, the standby pump cuts inautomatically.The HP, IP and LP steam generated in the

HRSG is fed to the steam turbine via therelated steam piping system. The expandedHP steam is fed back to the boiler via the coldreheat line and is mixed with the superheatedIP steam. All of the IP steam is superheatedfurther in the reheater and fed to the IP sectionof the steam turbine.In order to achieve short start-up times and

to control turbine trips a turbine bypasssystem isprovided.Thebypass systemconsists

of the HP bypass connected to the cold reheatas well as the IP and LP bypass, both dumpedto the condenser, and with relatedattemperation systems. The bypass controlvalves are equipped with hydraulic drives.A fuel gas preheating system preheats the

fuel gas to approximately 215C in order toincrease the efficiency of the power plant.Accordingly, IP feedwater is extracted fromthe IP economiser and routed via the fuel gaspreheater to the condensate preheating systemupstream of theHRSG condensate preheater.Downstreamof the fuel gaspreheater amass

flow control valve is provided to control thefuel gas temperature at the outlet of the fuelgas preheater. To guarantee a sufficient massflow through the preheater at part load andduring preheater start-up conditions and tolimit the temperature gradient at the preheatera recirculation pump is installed. This pumpreturns cold condensate from the outlet of thepreheater to the inlet via a recirculationcontrol valve.Auxiliary steam is supplied to the seal steam

system of the steam turbine and to theevaporators of theHRSG forwarming duringplant standstill.The auxiliary steam piping system receives

saturated steam either from the LPdrum steam header or

from the auxiliary boiler of the existing unitsdependingon the operationmodeof the plant.During normal combined cycle operation theauxiliary steam is delivered from the LP steamgenerating system.The coolingwater systemconsists of 2 x 50%

seawater lift pumps, 2 x 50% circulating waterpumps as well as a 1 x 100 % seawater coolingpump.The circulating water system absorbs the

heat from the steam surface condenser of thesteam turbine, and transfers this heat to theseawater.Also, there is an additional seawater cooling

pump which enables holding of vacuum andremaining cooling of the closed cooling watercoolers during shortdowntimes of the powerplant without the maincooling water pumpsrunning. The service coolingwater system

Schematic process diagram

Cutaway of Bugok 3

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COMBINED CYCLE

absorbs the heat from the closed coolingwatersystem.The closed cooling water system, equipped

with plate type heat exchangers, cools theequipment andcomponents of the gas turbine,the steam turbine and the water/steam cycle.

Electrical systemThe generator is connected to the generatortransformer via an isolated phase busduct. Agenerator circuit breaker is installed betweenthe generator and the tee-off connections tothe unit auxiliary transformer, excitationtransformer and static frequency convertertransformer.The low voltage transformers and large

motors are supplied from the medium voltageswitchgear.AnemergencyACsupply system isprovided

ensuring the supply of AC power to essentialloads in case of complete loss of the main ACpower system.The uninterruptible power supply consists

of 220 V DC battery and chargers, 125 V DCbattery and chargers, 24 V DC (220/24 VDC/DC converters) and 460 V AC (inverter),208/120 V AC (inverter) systems.The 220 V DC and 125V DC system

provides power for designated consumers (eg,emergency oil pumps, protection, controlvoltage, inverter infeed).The 220VDC and 125VDC system consists

of 2 x 100% battery chargers connected viaindividual fuses to one 100% battery. Onebattery charger is supplied from the normalAC system, the other one is supplied from theemergency diesel AC bus. The battery has anadequate capacity to supply the emergencyloads for 1 hour.The 24VDCsystem is powered via 2 x 100%

redundantDC/DCconverters. Their in-feed istaken fromthe220VDCbattery system.Mainconsumers of 24 V DC are the DCS cabinets.The main control and monitoring functions

of the electrical equipment are integrated intotheDCS in order tominimise the required localcontrolandmonitoringactivities.Also themainautomatics and interlocks are realised in theDCS. Safety relevant interlocks, eg, groundingswitches and protection, are hardwired.The DCS system automatic control

programensures that there isminimalneed formanual intervention in the control of theelectrical system.During start-up, the unit auxiliaries and the

relevant station service loadsare fedby theHVgrid via the generator transformer and unitauxiliary transformer. The generator circuitbreaker is open.The start-up sequence is automated by the

main DCS. The gas turbine is accelerated bythe start-up frequency converter with thegenerator in motor operation and minimumrequired excitation. After reachingsynchronisation conditions and closing thegenerator breaker, the generator takes overthe auxiliary power supply of the unit andprovides power to the network.If theunit is in islandoperation (with theHV

breakeropen), it canbe reconnected to thegridby closing the HV breaker under thesupervision of the synchronisationequipment.During normal operation of the power

plant, the auxiliary power will be provided bythe generator via the unit auxiliarytransformer.

During a normal shutdown, the generatedpower is reduced steadily until the generatorcircuit breaker or the HV circuit breaker canbeopened.Theauxiliarypower is providedviathe respective unit auxiliary transformer fromthe HV grid without interruption.In the case of an emergency shutdown

causedby amain failure in the auxiliary powersupply, the required power for a safe shutdown is provided by the battery and theemergency AC supply system.

Instrumentation and controlThe Bugok 3 combined cycle plant will beequipped with an SPPA-T3000 (SiemensPower Plant Automation Teleperm 3000)distributed control system.The system uses continuous information

flow, consistent data management andstorage, flexible instrumentation and controlconcepts, and uniform humanmachineinterface (HMI) platforms to performnecessary automation, operational control,and data monitoring for the plant.The SPPA-T3000 DCS has a hierarchical

structure. Design features include: a plant-oriented process control structure thatprovides operational functions, combinedwith monitoring and diagnostic capability; aredundant, modular structure capable offuture expansion by adding equipment asrequired; and an open local area network(LAN) structure for interfacing to otherautomation systems and external computernetworks.The SPPA-T3000 DCS consists of a three-

tier architecture based on a server/clientnetworking structure.The 100Mbit Ethernet bus system provides

the communication between thehumanmachine interface, the automationservers and the application server thatprovides all necessary functions for plantengineering, operation monitoring,diagnostics and storing of process data.A basic concept of the system is the use of

what are called embedded componentservices, which means that all process-relevant data is embedded into every singlecomponent. This component-embeddedapproach allows all data to be intrinsicallyavailable for operation, engineering ordiagnostics.An important advantage of this structure is

keeping the user interfaces (thin clients)independent of other applications.

The thin clients present informationregarding engineering, operation, anddiagnostics and standard industrial PCsrunning just a web browser perform this task.The web-based system structure allows the

use of a wide range of hardware such asstandard PCs or notebooks that can run awebbrowser.The server/client structure means that HMI

applications are available at multiplelocations. There is no need for specialhardware or software for engineering andoperation functions.Terminals are identical inaccess capability. Limitations need be definedonly by the authorisation system where theaccess rights are configured. This approachallows for highly flexible configurations for awide range of power plant process controlapplications.The main benefits of the SPPA-T3000

software architecture are: consistent views atany time; only onedatamanagement location;integrated I&C, plant display, alarm,diagnostics and engineering; no codegeneration and separate down-loadingactivities; no subsystems such as engineeringstations, operating stations and diagnosticscomputers.The SPPA-T3000 control system is

functionally and physically distributed and issubdivided into functional areas to create amodular configuration. The functionalseparation is by major systems: gas turbine;steam turbine; heat recovery steam generator;water/steam cycle; and ancillary and auxiliarysystems.

Technology showcaseThe 60 Hz Bugok 3 plant, now underconstruction, will embody some of the mostadvanced features available today incombined cycle technology, producing over415MW on one shaft. The plant is capable ofan efficiency of over 60% (LHV basis), withvery advanced steam conditions. But at thesame time it has immense operationalflexibility, able to hot start in less than 30minutes (hot start on the fly conditions), todeload very quickly and also to provideexcellent frequency response capabilities. TheHRSGwithBenson typeHP stage contributesto the fast cyclingperformancecharacteristics.Overall, Bugok 3 represents an optimal

balance between capital costs, plantperformance and operation & maintenancefactors. MPS

3-tier architecture of the SPPA-T3000

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This article appeared in:Modern Power SystemsSeptember 2011, Page 14 20Copyright 2011 by Modern Power Systems

This reprint is published by:Siemens AGEnergy SectorFreyeslebenstrasse 191058 Erlangen, Germany

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Subject to change without prior notice.The information in this document contains generaldescriptions of the technical options available, whichmay not apply in all cases. The required technicaloptions should therefore be specified in the contract.