abb generator circuit-breaker systems

ABB Power Transmission

Generator Circuit-Breaker Systems HEC, HGC

Data and Dimensions

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ApplicationThe Generator Circuit-Breaker System typeHEC and HGC has been developed as a sy-stem suitable for application in all types of po-wer plants. The HEC and HGC Generator Circuit-Breaker

System is also suitable for retrofitting in exi-sting power plants, when these are moderni-sed, extended and/or automated. It is availa-ble for both indoor and outdoor application.

ContentsApplication 3 Characteristics 3 Modular design concept 4 Equipment options 5 Standards and quality 5Generator circuit-breaker 5Disconnector 8 Earthing switch 9 Starting switch 9 Manual short-circuiting connection 9Short-circuiting-/braking switch 10Current transformer 10

Voltage transformer 11 Surge arrester 11 Surge capacitor 11 Terminals 12 Phase enclosure 12 Control and supervision 12 Tests 13 Transport to site 13 Site erection and commissioning 13 Maintenance 13Technical data and dimensions 14

3-phase system with a SF6 circuit-breaker and disconnector in series with the circuit-breaker, in single-phase enclosures, sup-plied fully ensembled on a common frame,with operating mechanisms, supervisoryand control equipment.

Additional components as earthing swit-ches, starting switch (for starting of gastur-bines), short-circuiting connection either

permanent with switch (for braking) or to be mounted manually (for power plant protec-tion setting), current- and voltage transfor-mers, surge capacitors, surge arrester, all integrated and mounted in the phase enclo-sures, can be provided.

The phase distance can be selected to suit the busbar spacing in the power plant.

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Characteristics

Standards and qualityThe Generator Circuit-Breaker System typeHEC and HGC fulfil the requirements of all re-levant standards, i.e. IEEE (ANSI) StdC37.013 and IEC 60694, IEC 60129, IEC60044-1/2, IEC 60099-4, IEC 60358, IEC60529, IEC 61166.

ABB High Voltage Technologies Ltd. is conti-nuously endeavoured to improve its quality-assurance-system; this has been recentlynew assessed by The Swiss Association forQuality and Management Systems with theSQS-certificate ISO 9001 / ISO 14001.


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View into one pole of circuit-breaker type HGC 3

As required by the plant layout, individual compo-nents can be deleted from the standard execution.The standard execution can be extended by the following optional items:• Short-circuiting connection - either permanently

fitted with switch (for braking), or to be manually mounted (for power plant protection setting)

• Surge arrester on transformer side.

Modular design conceptThe standard design includes:• SF6 circuit-breaker and disconnector• Earthing switches on one or both sides• Current transformers on one or both sides with

up to three cores per current transformer (depen-ding on the class)

• One or two voltage transformers on one or both sides with one or two secondary windings

• Starting switch for (reduced voltage) starting thegas turboset via SFC (Static Frequency Converter)

• Surge capacitors on both sides.


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1 Generator circuit-breaker2 Disconnector3, 4 Earthing switches5 Starting switch for gas turbines7 Braking switch (HEC only)

or manual short-circuiting connection

9 -12 Voltage transformers13,14 Current transformers15 Surge arrester16,17 Surge capacitors19 System enclosure20 Earthing link

Generator circuit-breaker Interrupting chamber

Within the interrupting chamber SF6 gas is used forboth arc extinguishing and internal insulation. The ex-ternal insulation is air. For the interruption a combination of the self-existin-guishing and the puffer principle is used, a design op-timised to achieve a significant reduction in operatingenergy. This self-pressurising principle allows high breakingcapacities as well as almost overvoltage-free interrup-tion of small (inductive) currents. Separate contact systems for breaking and for conti-nuous current carrying are used. This avoids wear /erosion of the continuous current contacts and ensurestrouble-free current carrying even after a large numberof operations.

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Equipment options


Interrupting chamber of the circuit-breaker type HEC 3. On theright the terminal is visible, while on the left a concentric ringof spring loaded contact fingers can be seen. This ring formsthe fixed contact which accepts the cylindrical moving contactof the disconnector.The circuit-breaker contacts are operated by a shaft passingfrom below, through the vertical support insulator.


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a Circuit-breaker CLOSED

b Initiation of opening movement, (transfer of current from the main contacts to the arcing contacts)

c Separation of arcing contacts with interruption of small currentssupported by puffer action

d Separation of arcing contacts with interruption of large currents –supported by the thermal effect of thecurrent arc itself to build up the pressure in the heating volume

e Circuit-breaker OPEN

Hydraulic spring drive

The hydraulic spring operating mechanism combinesthe advantages of a hydraulic operating mechanismwith those of a spring energy storage system. Energystorage is accomplished with the aid of a disk springassembly, with the advantages of high long-term sta-bility, reliability and non-influence of temperaturechanges. Tripping of the operating mechanism andenergy output are based on proven design elementsof the hydraulic operating technique, such as controlvalves and hydraulic cylinders.

The operating mechanism is based on the so-calleddifferential piston principle (between the larger pistonhead side area and the smaller piston rod side area).For the closing operation the piston head side is iso-lated from the low pressure and simultaneouslyconnected to the high pressure oil volume. As long asthe pressure is maintained, the piston remains in theCLOSED position. A pressure controlled mechanicalinterlock prevents movement of the piston to theOPEN position in case of a pressure drop.

Mode of operation of the interrupting chamber of the HEC 3-6 circuit-breaker

High pressureLow pressure

1 Breaker operating rod2 Energy storage device

1 Terminals2 Cylindrical coil3 Fixed arcing contact4 Moving arcing contact5 Fixed main contacts6 Moving main contact7 Puffer8 Heating volume9 Gas compartment

Schematic diagram of the hydraulic spring operatingmechanism

View of the hydraulic spring operating mecha-nism with cover removed

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SF6 gas density monitoring system

The breaking capacity of an SF6 circuit-breakerand the dielectric withstand level across its opencontacts is dependent upon the density of the SF6gas. Under the condition of constant volume thegas density is independent of the gas temperature,while the pressure varies with the temperature. It istherefore more practical to measure and use thegas density rather than the pressure for circuit-breaker supervisory purposes.

Schematic diagram of the SF6 gas density monitor

1 Pressure connection 4 Reference gas volume 2 SF6 gas volume of 5 Actuating rod

the circuit-breaker 6 Microswitch3 Metallic bellows

P/t-diagram for SF6 gas, with operating cha-racteristics of the gas density monitor for theSF6 circuit-breaker

The functional principle of the density monitor is shown in below diagram. The density monitor ope-rates according to the reference-volume-densityprinciple. The density of the gas in the circuit-brea-ker chamber is compared with the density of thegas in a sealed reference gas volume. When thegas density drops below the specified value, thedensity monitor signals the loss of SF6 gas in se-veral steps.It is mounted on the crankcase of the middle pole.Since the gas volumes of the three breaker polesare connected via the refilling pipe only one SF6gas density monitor per breaker is required to su-pervise the gas density.

A non-return valve between pump and high-pressu-re oil volume prevents pressure loss in the event ofa pump outage. The hydraulic system is hermetical-ly sealed against atmosphere (no corrosion). Themechanically operated position indicator providesreliable indication of the circuit-breaker position.

The drive operates all three breaker poles simulta-neously by mechanical linkages, thus keeping theswitching time difference between the poles to a mi-nimum.

For the opening operation, the piston head side isisolated from the high pressure and simultaneous-ly connected to the low pressure oil volume.

The charging state of the spring disk assembly iscontrolled by switching elements, actuating thepump motor to immediately maintain the oil pres-sure. For emergency use or maintenance, chargingof the spring disk assembly and tripping is possi-ble locally. The fully integrated construction has nohydraulic pipe connections of any kind.



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SF6 circuit-breaker pole type HEC 3 and its disconnector, shown installed in its phase enclosure. The disconnector on the left, is shown withits moving contact stopped in an intermediate position between closed and open. The terminals on both ends are formed with silver platedmulti contact surfaces to fit the flexible connectors to the bus bars.

Besides the drive of the circuit-breaker, other operating me-chanisms, as for disconnector, earthing switch, starting switchare shown.The operating mechanisms for disconnector and all switchesare identical. They incorporate a driving motor and gearing, amechanical semaphore, key locking and an electrical auxilaryswitch.

The yellow sticker shows the differentoperation modes of the key locking sche-me of the individual motor operating me-chanisms, which all of them operate in thesame way.

DisconnectorThe switchgear concept provides a disconnector fitted in series with the circuit-breaker. It is placed on theout- going side of circuit-breaker and within the same enclosure.

The disconnector is a tubular telescopic unit, with the moving contact tube on the circuit-breaker side and thefixed contact on the terminal side. This layout provides easy access and simplifies maintenance.

In the open position of the disconnector the isolating air distance can be clearly seen through an inspectionwindow in the cover of the enclosure. The moving contact is motor driven.

The operating mechanism is a compact sub-as-sembly, including the motor, auxilary switch, reduc-tion gear box and coupling flanges in one unit.Key locking in the positions “Close” and “Open” isa standard facility. An additional locking preventsmotor operation while the disconnector is beingmanually operated. Mechanically driven positionindicator is provided in a readily visible position anda crank handle is provided for manual operation.


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Earthing switchThe earthing switch can be provided on either oneor both sides of the system. The switch and itsconnections are designed for protective earthingpurposes, i.e. it is rated for the full fault current buthas no current making or continuous carrying ca-pacity. Design is of a blade type with the hinge pointconnected to the enclosure and the fixed contactto the current path. The earthing connection is ma-de via the system enclosure, which is earthed atone end to the busbar enclosure. The movingcontact is motor driven.


Breaker type HECEarthing switch or starting switch shown in closed position.

Starting switchThe starting switch can be provided on the gene-rator side of the system. The starting switch and itsconnections have been designed for the voltage,current and current-duration occurring during theSFC (Static Frequency Converter) start-up periodof the gas turboset. The design is of a blade typewith the fixed contacts at the current path and thehinge point isolated from the enclosure. High vol-tage cables can be connected to this. The movingcontact is motor driven.

Manual short-circuiting connectionThe manual short-circuiting connection can be provided for the use between the circuit-breaker and the dis-connector of the system. This arrangement has been designed for installations where the short-circuiting faci-lity is only rarely used. The short-circuiting connection is built for the voltage, current and current duration oc-curring during the testing and adjustment of the power plant protection system.The cover of each of the phase enclosures has to be removed to allow the fitting of the short-circuiting busbars.


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Short-circuiting-/braking switchThe short-circuiting-/braking switch (HEC 3-6only) can be provided between the circuit-breaker and the disconnector of the system.The short-circuiting-/braking switch and itsconnection between phases have been deve-loped to expedite the testing and adjustmentof the power plant protection system, respec-tively for the use as an electrical brake toshut-down the generator set. Closure of the switch establishes an unear-thed three phase short-circuit, which thencan be switched to the generator terminals byclosure of the circuit-breaker.The design of the switch is of a sliding typewith the moving contact isolated from the en-closure and the fixed contact connected tothe current path. The actual short-circuiting connection bet-ween the phases is established external tothe enclosure and being insulated from theenclosure (2000V), and is protected againstinadvertently touching.The moving contact is motor driven.As an additional feature, a link can be provi-ded with which the short-circuit connectioncan be connected to the phase enclosure i.e.,to earth. This link can only be fitted manually.

Braking switch contacts - shown in closed position - establish via integra-ted buses a connection between the three phases. Braking switch and busis isolated from the enclosure. The contacts of the braking switch are normally motor operated, but canalso be operated by means of a hand crank. The operating mechanism ismounted on the braking switch housing.

Current transformerA ring core current transformer can be provi-ded on either one or both sides of the breakersystem. Depending on the class up to threecores per current transformer can be accom-modated, depending on output and class re-quired. The secondary windings are perma-nently wired back to terminal blocks in thecontrol cubicle.

Ring core current transformers with up to 3 cores per transformer can bemounted at each end of each phase enclosure.


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Surge capacitorSurge capacitors are fitted on both sides of the breakersystem, to provide additional protection against overvol-tages and to support arc extinction in the circuit-breakerby TRV limitation. The surge capacitors are fitted outside the phase enclo-sure with only the porcelain bushings protruding into thephase enclosure.

Surge arresterA surge arrester can be fitted on thetransformer side, to provide protectionfor transformer and generator againstovervoltages. Standard is an ABB me-tal-oxide surge arrester of the POLIMrange with silicon housing. Metal-oxideresistors have a highly non-linear resi-stance characteristic. At service volta-ge a predominantly capacitive currentof <1mA flows. Any voltage increaseleads to a rapid increase of the current,thereby limiting any further rise in thevoltage. When the voltage decreases,the condition reverts to its essentialnon-conducting state. Metal-oxide sur-ge arresters are characterised by theresidual voltage, i.e. the voltage duringthe passage of an impulse current.

Voltage transformerSingle-phase, cast resin voltage transformers can be provided on either one or both sides of the breaker sy-stem. Up to two voltage transformers can be fitted at each side and each voltage transformer can be suppliedwith one or two secondary windings, depending on the class and output power required. The secondary win-dings are permanently wired back to terminal blocks in the control cubicle.

Dependent upon the rated voltage, the voltage transformers are fitted on the samesupport frame as the surge arrester, or on the side panel of the phase enclosure.

Surge capacitors are installed in such a manner that only theirporcelain bushings protrude into the phase enclosure.



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TerminalsThe current path of the system is connected to the busbar current path by bolted flexible, laminated or stran-ded connectors. In order to avoid detrimental tensile stresses to the terminals, resulting from electro-dynamic forces of a short-circuit current, the flexible connectors must be supported at the midpoint by a ring having the same diameteras the terminals. These rings reduce the contraction of the flexible connectors and the subsequent tensile for-ces on switchgear components, under short-circuit current conditions.

Control and supervisionAll control and supervisory apparatuses aremounted in the control cubicle. The controlcubicle is placed on the operating mechanism side of the system above the operating me-chanisms of the circuit-breaker, disconnectoretc., but is not mechanically connected withthe common frame of the breaker system. Upon request, the control cubicle can also beplaced at the opposite side. An active mimic diagram is provided with theactual position indications and the integratedlocal control of the circuit-breaker and allother switching apparatuses.It is mounted in a swing panel behind theglass window of the front panel of the controlcubicle.In the control cubicle there are also installed alocal / remote change-over switch and coun-ters for C-O operations of the circuit-breakerand pump startings of the circuit-breaker drive.

Phase enclosureThe phase enclosures are designed to carrythe induced reverse current, flowing throughthe isolated phase busbar enclosures. Thusthe external magnetic field and its influence tothe equipment is minimised. As standard, thephase enclosure is welded onto the busbarenclosure, ensuring continuity of the phaseenclousure characteristics. On the otherhand, the phase enclosures effectively elimi-nate any possibilty of accidental contact withlive components. In order to avoid pollutiondue to ingress of dust and/or moisture, thephase enclosures are made airtight to with-stand also a small internal overpressure. Win-dows are provided in the phase enclosuresnear to the disconnector, earthing switchesand starting switch, to allow visually checkingof the position of each of them. Phase enclosures and control cubicle of GCB system type HEC 7/8

Note: The flexible connectors are not part of the scope of supply of the GCB system, usually they are supplied by the IPB supplier.


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TestsType testsThe performance of the generator circuit-breakersystem was fully tested by the High Power Labora-tory of KEMA/Netherlands in accordance to thestandard IEEE C37.013 with regard to the interrup-ting capability.

Further type tests were carried out with all of therelated components within the system to provecontinuous current capability, dielectric strength,long term endurance, noise level etc. and verify theliability and compliance with the requirements ofthe relevant IEC-standards.

Routine testsAfter production, but prior to dispatch, the systemis subject to an extensive test program, as:• Design and visual checks• Dielectric tests on the main circuit

Transport to siteThe entire system is fully assembled and tested together with all its ancillary equipment in the factory.

Site erection and commissioningSite erection requires a well prepared foundation.Due to the fact, that the system is delivered as a single, fully assembled, wired and tested unit, thetime, required for erection, testing and commissio-ning is extremely short. The only substantial site work is the welding of the

MaintenanceRemoval of the phase enclosure top covers provi-des easy access to the active components of eachphase, including the instrument transformers, sur-ge capacitors and surge arrester. Maintenance canbe scheduled based on service time, number of C/O-operations or number of current interrupti-ons. The contact erosion can be measured without opening the interrupting chamber with the

• Dielectric tests on auxiliary and control circuits• Measurements of the resistance of the main

circuit• Mechanical operation tests• Timing tests and recording the switching

times and movement of breaker contacts• Functional tests of individual components• Leakage test of phase enclosures• SF6 gas leakage test.

It is hence dispatched from the factory and trans-ported to site as a single unit.

enclosures onto the busbar enclosures, the moun-ting of the flexible high-current connections, theconnecting of the electrical supply cables and theperforming of the commissioning tests.

DRM-methode (Dynamic Resistance Measure-ment), which has been specifically developed forgenerator circuit-breakers by ABB High VoltageTechnologies Ltd. This allows to optimise the ser-vice intervals also for frequent switching of higherservice currents. The DRM-Measurement systemcan be ordered separately.


Note: Exception - control cubicle according to ANSI standard.


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Technical data and dimensions

Generator circuit-breaker system type

General:• Rated maximum voltage 25.3 25.3 kV• Rated frequency 50/60 50/60 Hz• Rated continuous current 50Hz 12/13 12/13 kA, rms• Rated continuous current 60Hz 11,5/12,5 11,5/12,5 kA, rms • Rated insulation level:

• Rated power frequency withstand voltage• to earth and across circuit-breaker/switch contacts 60 60 kV, rms• across isolating distance of disconnector 70 70 kV, rms

• Rated lightning impulse withstand voltage• to earth and across circuit-breaker/switch contacts *) 125 125 kV, peak• across isolating distance of disconnector 145 145 kV, peak

Circuit-Breaker:• Rated peak withstand current 300 360 kA, peak• Rated short-time withstand current 100 120 kA, 3s • Rated short-circuit making current 300 360 kA, peak• Rated short-circuit breaking current 100 120 kA, rms• Rated operating sequence CO -30min - CO• Rated interrupting time 60 60 ms

Disconnector:• Rated peak withstand current 300 360 kA, peak• Rated short-time withstand current 100 120 kA, 3s • Operating time 2 2 s

Earthing Switch:• Rated peak withstand current 300 360 kA, peak• Rated short-time withstand current 100 120 kA, 1s • Operating time 2 2 s

Dimension drawing HEC 3-6

HEC 3/4 HEC 5/6

*) On request BIL = 150 kV peak possible

TRANSFORMER SIDE

GENERATOR SIDE


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General:• Rated maximum voltage 30 30 kV, rms• Rated frequency 50/60 50/60 Hz• Rated continuous current 24/22 28/26 kA • Rated insulation level:

• Rated power frequency withstand voltage• to earth and across circuit-breaker/switch contacts 80 80 kV, rms• across isolating distance of disconnector 88 88 kV, rms

• Rated lightning impulse withstand voltage• to earth and across circuit-breaker/switch contacts 150 150 kV, peak• across isolating distance of disconnector 165 165 kV, peak

Circuit-Breaker:• Rated peak withstand current 600 600 kA, peak• Rated short-time withstand current 200 200 kA/3s • Rated short-circuit making current 440 440 kA, peak• Rated short-circuit breaking current 160 160 kA, rms• Rated operating sequence CO -30min - CO• Rated interrupting time 53 53 ms

Disconnector:• Rated peak withstand current 600 600 kA, peak• Rated short-time withstand current 200 200 kA/3s • Operating time 2 2 s

Earthing Switch:• Rated peak withstand current 440 440 kA, peak• Rated short-time withstand current 160 160 kA, 1s • Operating time 2 2 s

Dimension drawing HEC 7/8

HEC 7 HEC 8

TRANSFORMER SIDE

GENERATOR SIDE


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General:• Rated maximum voltage 21 kV, rms• Rated frequency 50/60 Hz• Rated continuous current 7,7/7,5 kA • Rated insulation level:

• Rated power frequency withstand voltage• to earth and across circuit-breaker/switch contacts 60 kV, rms• across isolating distance of disconnector 70 kV, rms

• Rated lightning impulse withstand voltage• to earth and across circuit-breaker/switch contacts 125 kV, peak• across isolating distance of disconnector 145 kV, peak

Circuit-Breaker:• Rated peak withstand current 190 kA, peak• Rated short-time withstand current 63 kA/3s • Rated short-circuit making current 190 kA, peak• Rated short-circuit breaking current 63 kA, rms• Rated operating sequence CO -30min -CO

• Rated interrupting time 55 ms

Disconnector:• Rated peak withstand current 190 kA, peak• Rated short-time withstand current 63 kA/3s • Operating time 2 s

Earthing Switch:• Rated peak withstand current 190 kA, peak• Rated short-time withstand current 63 kA, 1s • Operating time 2 s

Dimension drawing HGC 3

HGC 3

TRANSFORMER SIDE

GENERATOR SIDE


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HGI 2

HGC-3 (HGI 3)

Un = 24-30kV

HEC 3-8

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ABB Power Transmission

28’000 A

Range of ABB generator circuit-breaker systems

Un = 17.5kV

Un = 21kV

In pursuance of our policy of continuing product improvement, equipment described in this publication is subject to change without notification.


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Notes:


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ABB High Voltage Technologies LtdDivision AG High Current SystemsP.O.Box 85468050 Zurich /SwitzerlandPhone: +41 (0)1 318 3424Fax: +41 (0)1 318 1644Internet: http://www.abb.com/ch

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ABB Generator Circuit-Breaker Systems worldwide


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abb generator circuit-breaker systems

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