Generator Circuit-Breaker SystemsHECS, HEC 7/8

Data and Dimensions

2 ABB 3ABB

2 ABB 3ABB

Contents

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

Surge arrester 10Surge capacitor 10Terminals 11Phase enclosure 11Control and supervision 11Tests 12Transport to site 12Site erection and commissioning 12Maintenance and overhaul 12Dimensions 13Technical data 14

Application

The Generator Circuit-Breaker System type HECS and HEC 7/8 has been developed as a system suitable for application in all types of power plants.The HECS and HEC 7/8 Generator Circuit-Breaker

Systems are also suitable for retrofitting in existing power plants, when these are modernised, extended and/or automated. It is available for both indoor and outdoor application.

Characteristics

• 3-phase system with a SF6 circuit-breaker and dis-connector in series with the circuit-breaker, in sin-gle-phase enclosures, supplied fully assembled on a common frame, with operating mechanisms, super-visory and control equipment.

• Additional components as earthing switches, start-ing switch (for starting of gas-turbines), current- and voltage transformers, surge capacitors, surge arrester, all integrated and mounted in the phase enclosures, can be provided. Additionally the earthing switch on the breaker side of the HECS Generator Circuit-Breaker System (if equipped with an optional short-

circuiting bar) can be used as a short-circuiting link during power plant protection setting, whereas the HEC 7/8 for this purpose can be equipped with a short circuiting connection which is either manually mounted or motor operated.

• The phase distance can be selected to suit the bus-bar spacing in the power plant.

Standards and quality

The Generator Circuit-Breaker System type HECS and HEC 7/8 fulfil the requirements of all relevant stand-ards, i.e. IEEE (ANSI) Std C37.013 and IEC 60694, IEC 62271-102, IEC 60044-1/2, IEC 60099-4, IEC 60358, IEC 60529, IEC 61166.

ABB High Voltage Products is continuously endeav-oured to improve its quality-assurance-system; this has been recently new assessed by The Swiss Association for Quality and Management Systems with the SQS-certificate ISO 9001 / ISO 14001.

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Modular design concept

The standard design includes:

• SF6 circuit-breaker and disconnector

• Earthing switches on one or both sides (for HECS: on breaker side also optional available with short-circuit bar to be used as short-circuiting link)

• Current transformers on one or both sides with up to three cores per current transformer (depending on the class)

• Voltage transformers on one or both sides with one or two secondary windings

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

• Surge capacitors on both sides.

As required by the plant layout, individual compo-nents can be deleted from the standard execution. The standard execution can be extended by the fol-lowing optional items:

• For HECS: Short-circuiting connection - either in connection with generator side earthing switch, or to be manually mounted (for power plant protection setting)

• For HEC 7/8: Short-circuiting connection - either permanently fitted with switch, or to be manually mounted (for power plant protection setting)

• Surge arrester on transformer side.

View into one pole of circuit-breaker type HECS-130L

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Equipment options

1 Generator circuit-breaker

2 Line disconnect switch

3 Earthing switch

4 Starting switch for SFC connection

5 Manual short-circuiting connection (by removal of cover)

6 Surge capacitor

7 Current transformers

8 Voltage transformers

9 Surge arrester

10 Motor-operated short circuiting link (only HECS with generator side earthing switch)

Generator circuit-breaker

Interrupting chamber

Within the interrupting chamber SF6-gas is used for both arc extinguishing and internal insulation. The external insulation is air.For the interruption a combination of the self-extin-guishing and the puffer principle is used, a design optimised to achieve a significant reduction in operat-ing energy.This self-pressurising principle allows high breaking capacities as well as almost overvoltage-free interrup-tion of small (inductive) currents.Separate contact systems for breaking and for continu-ous current carrying are used. This avoids wear / ero-sion of the continuous current contacts and ensures trouble-free current carrying even after a large number of operations.

Interrupting chamber of the circuit-breaker type HECS-100L. On the left the terminal is visible. The circuit-breaker contacts are operated by a shaft passing from below, through the vertical support insulator.

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Mode of operation of the interrupting chamber of the HECS circuit-breaker systems

Schematic diagram of the hydraulic spring operating mechanism

High pressure 1 Breaker operating rodLow pressure 2 Energy storage device

View of the hydraulic spring operating mechanism

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 cur-rents supported by puffer action

d Separation of arcing contacts with interruption of large cur-rents – supported by the thermal effect of the current arc itself to build up the pressure in the heating volume

e Circuit-breaker “OPEN”

1 Terminals

2 Cylindrical coil

3 Fixed arcing contact

4 Moving arcing contact

5 Fixed main contacts

6 Moving main contact

7 Puffer

8 Heating volume

9 Gas compartment

Hydraulic spring drive

The hydraulic spring operating mechanism combines the advantages of a hydraulic operating mechanism with those of a spring energy storage system. Energy storage is accomplished with the aid of a disk spring assembly, with the advantages of high long-term sta-bility, reliability and non-influence of temperature changes. Tripping of the operating mechanism and energy output are based on proven design elements of the hydraulic operating technique, such as control valves and hydraulic cylinders.

The operating mechanism is based on the so-called differential piston principle (between the larger pis-ton head side area and the smaller piston rod side area). For the closing operation the piston head side is isolated from the low pressure and simultaneously connected to the high pressure oil volume. As long as the pressure is maintained, the piston remains in the “CLOSED” position. A pressure controlled mechani-cal interlock prevents movement of the piston to the “OPEN” position in case of a pressure drop.

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For the opening operation, the piston head side is iso-lated from the high pressure and simultaneously con-nected to the low pressure oil volume.

The charging state of the spring disk assembly is con-trolled by switching elements, actuating the pump motor to immediately maintain the oil pressure. For emergency use or maintenance, charging of the spring disk assembly and tripping is possible locally. The fully integrated construction has no hydraulic pipe connections of any kind.

A non-return valve between pump and high-pres-sure oil volume prevents pressure loss in the event of a pump outage. The hydraulic system is hermeti-cally sealed against atmosphere (no corrosion). The mechanically operated position indicator provides reli-able indication of the circuit-breaker position.

The drive operates all three breaker poles simulta-neously by mechanical linkages, thus keeping the switching time difference between the poles to a mini-mum.

SF6-gas density monitoring system

The breaking capacity of an SF6 circuit-breaker and the dielectric withstand level across its open contacts is dependent upon the density of the SF6-gas. Under the condition of constant volume the gas density is inde-pendent of the gas temperature, while the pressure varies with the temperature. It is therefore more practi-cal to measure and use the gas density rather than the pressure for circuit-breaker supervisory purposes.

The functional principle of the density monitor is shown in below diagram. The density monitor oper-ates according to the reference-volume-density princi-ple. The density of the gas in the circuit-breaker cham-ber is compared with the density of the gas in a sealed reference gas volume. When the gas density drops below the specified value, the density monitor signals the loss of SF6-gas in several steps.It is mounted on the crankcase of the middle pole. Since the gas volumes of the three breaker poles are connected via the refilling pipe only one SF6-gas den-sity monitor per breaker is required to supervise the gas density.

SF6-gas density indication and filling connection

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

Schematic diagram of the SF6-gas density monitor

1 Pressure connection2 SF6-gas volume of the

circuit-breaker3 Metallic bellows

4 Reference gas volume5 Actuating rod6 Microswitch

Rated filling density 40.7 kg/m3

Alarm density 36.1 kg/m3

Blocking density 34.7 kg/m3

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Disconnector

The switchgear concept provides a disconnector fitted in series with the circuit-breaker. It is placed on the out-going side of circuit-breaker and within the same enclosure.The disconnector is a tubular telescopic unit, with the moving contact on the terminal side and fixed contact tube on the circuit-breaker 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 inspection window in the side wall (HECS) or in the cover (HEC 7/8) of the enclosure. The moving contact is motor driven.

View through the inspection window of HECS to assure that the disconnect switch is in the open position.

The operating mechanism is a compact subassembly, including the motor, auxilary switch, reduction gear box and coupling flanges in one unit.Key locking in the positions “CLOSE” and “OPEN” is a standard facility. An additional locking prevents motor

The sticker shows the different operation modes of the key locking scheme of the individual motor operating mechanisms, which all of them operate in the same way.

The operating mechanisms, as for disconnector, earthing switch, starting switch are shown, the operating mechanisms for disconnec-tor and all switches are identical and integrated in the pole frame. They incorporate a driving motor and gearing, a mechanical sema-phore, key locking and an electrical auxilary switch.

operation while the disconnector is being manually operated. Mechanically driven position indicator is provided in a readily visible position and a crank han-dle is provided for manual operation.

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Breaker type HECSEarthing switch in closed position.

Short-circuiting connection

For the HEC 7/8 there is either a manual short circuiting connection or an electrical operated short-circuiting switch available.The manual short-circuiting connection can be provided for the use between the circuit-breaker and the disconnec-tor of the system. This arrangement has been designed for installations where the short-circuiting facility is only rarely used. The short-circuiting connection is built for the volt-age, current and current duration occurring during the test-ing 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 busbar.

The short-circuiting switch can be provided between the circuit-breaker and the disconnector of the system. The short-circuiting switch and its connection between phases have been developed to expedite the testing and adjust-ment of the power plant protection system. Closure of the switch establishes an unearthed three phase short-circuit, which then can be switched to the generator terminals by closure of the circuit-breaker.The design of the switch is of a sliding type with the mov-ing contact isolated from the enclosure and the fixed con-tact connected to the current path.The actual short-circuiting connection between the phases is established external to the enclosure and being insulated

from the enclosure (2000 V), and is protected against inadvertently touching.The moving contact is motor driven. As an additional fea-ture, a link can be provided with which the short-circuit connection can be connected to the phase enclosure i.e., to earth. This link can only be fitted manually.

For the HECS there is also a manual short circuiting con-nection available which needs to be connected between the circuit breaker and the disconnector. The cover of each of the phase enclosures has to be removed to allow the fitting of the short-circuiting busbar.

Alternatively there is a motor operated short-circuiting connection available for the HECS. If a motor operated short-circuit connection is required, the three poles of the earthing switch on the breaker side are linked together to a common bar, which is connected by a copper bracket to the enclosure of the middle phase and thereby ground-ed. By removing this bracket (to be done manually) and closing of the earthing switch an unearthed three phase short-circuit is established. The closing of the earthing switch can be done motor operated (local/remote switch in position local) while the generator is de-excited and the residual voltage of the generator does not exceed 350 V.

Earthing switch

The earthing switch can be provided on either one or both sides of the system. The switch and its connections are designed for protective earthing purposes, i.e. it is rated for the full fault current but has no current making or continu-ous carrying capacity.Design is of a blade type with the hinge point connected to the enclosure and the fixed contact to the current path. The earthing connection is made via the system enclosure, which is earthed at one end to the busbar enclosure. The moving contact is motor driven.

Starting switch

The starting switch can be provided on the generator side of the system. The starting switch and its connections have been designed for the voltage, current and current-duration occurring during the SFC (Static Frequency Converter) start-up period of the gas turboset. The design is of a blade type with the fixed contacts at the current path and the hinge point isolated from the enclosure. High voltage cables can be connected to this. The moving contact is motor driven.

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Current transformer

A ring core current transformer can be provided on either one or both sides of the breaker system. Depending on the class up to three cores per current transformer can be accommodated, depending on output and class required. The secondary windings are permanently wired back to terminal blocks in the control cubicle.

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

Voltage transformer

Single-phase, cast resin voltage transformers can be provided on either one or both sides of the breaker system. Up to three voltage transformers or two volt-age transformers and one surge arrester can be fitted at each side and each voltage transformer can be sup-plied with one or two secondary windings, depending on the class and output power required. The second-ary windings are permanently wired back to terminal blocks in the control cubicle.

The voltage transformers are fitted on the side panel of the phase enclosure.

The surge arrester is fitted on the side panel of the phase enclosure.

Surge capacitor are installed in such a manner that only their porce-lain bushings protrude into the phase enclosure.

Surge arrester

A surge arrester can be fitted on the transformer side, to provide protection for transformer and generator against overvoltages. Standard is an ABB metal-oxide surge arres-ter of the POLIM range with silicon housing. Metal-oxide resistors have a highly non-linear resistance characteristic. At service voltage a predominantly capacitive current of < 1mA flows. Any voltage increase leads to a rapid increase of the current, thereby limiting any further rise in the voltage. When the voltage decreases, the condition reverts to its essential non-conducting state. Metal-oxide surge arresters are characterised by the residual voltage, i.e. the voltage during the passage of an impulse current.

Surge capacitor

Surge capacitors are fitted on both sides of the breaker system, to provide additional protection against over-voltages and to support arc extinction in the circuit-breaker by TRV limitation.The surge capacitors are fitted outside the phase enclosure with only the porcelain bushings protruding into the phase enclosure.

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Terminals

The current path of the system is connected to the busbar current path by bolted flexible, laminated or stranded 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 diameter as the terminals. These rings reduce the con-

traction of the flexible connectors and the subsequent tensile forces on switchgear components, under short-circuit current conditions.

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

Phase enclosures and control cubicle of GCB system type HECS-130L

Mimic board of the control cubicle

Phase enclosure

The phase enclosures are designed to carry the induced reverse current, flowing through the isolated phase bus-bar enclosures. Thus the external magnetic field and its influence to the equipment is minimised. As standard, the phase enclosure is welded onto the busbar enclosure, ensuring continuity of the phase enclosure characteristics. On the other hand, the phase enclosures effectively elimi-nate any possibilty of accidental contact with live compo-nents. In order to avoid pollution due to ingress of dust and/or moisture, the phase enclosures are made airtight to withstand also a small internal overpressure. Windows are provided in the phase enclosures near to the disconnec-tor, earthing switches and starting switch, to allow visually checking of the position of each of them.

Control and supervision

All control and supervisory apparatuses are mounted in the control cubicle. The control cubicle is placed on the operating mechanism side of the system above the operating mechanism of the circuit-breaker and is not mechanically connected with the common frame of the breaker system.An active mimic diagram is provided with the actual position indications and the integrated local control of the circuit-breaker and all other switching apparatuses.It is mounted in the door panel behind the glass door of the control cubicle.In the control cubicle there are also installed a local/remote change-over switch and counters for C-O oper-ations of the circuit-breaker and pump startings of the circuit-breaker drive.

Phase enclosures and control cubicle of GCB system type HEC 7/8

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Tests

Type tests

The performance of the generator circuit-breaker sys-tem was fully tested by the High Power Laboratory of KEMA/Netherlands in accordance to the standard IEEE C37.013 with regard to the interrupting capability.

Further type tests were carried out with all of the related components within the system to prove con-tinuous current capability, dielectric strength, long term endurance, noise level etc. and verify the liability and compliance with the requirements of the relevant IEC-standards.

Routine tests

After production, but prior to dispatch, the system is subject to an extensive test program, as:

• Design and visual checks

• Dielectric tests on the main circuit

• 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.

Transport to site

The entire system is fully assembled and tested togeth-er with all its ancillary equipment in the factory.

Note: Exception - control cubicle according to ANSI standard.

It is hence dispatched from the factory and transported to site as a single unit.

Site erection and commissioning

Site erection requires a well prepared foundation. Due to the fact, that the system is delivered as a sin-gle, fully assembled, wired and tested unit, the time, required for erection, testing and commissioning is extremely short.

The only substantial site work is the welding of the enclosures onto the busbar enclosures, the mounting of the flexible high-current connections, the connect-ing of the electrical supply cables and the performing of the commissioning tests.

Maintenance and overhaul

The HECS and HEC 7/8 generator circuit-breaker sys-tems are maintenance-free to a wide extend.Overhaul can be scheduled based on service time, number of C/O-operations or number of current inter-ruptions. Removal of the phase enclosure top covers provides easy access to the active components of each phase, including the instrument transformers, surge capacitors and surge arrester.

The contact erosion can be measured without open-ing the interrupting chamber with the DRM-methode (Dynamic Resistance Measurement), which has been specifically developed for generator circuit-breakers by ABB High Voltage Products. This allows to optimise the service intervals also for frequent switching of higher service currents. The DRM-Measurement system can be ordered separately.

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Dimensions

Type HECS

Type HEC 7/8

14 ABB 15ABB

Generator circuit-breaker system type HECS-80 HECS-100 HECS-130

General:Rated maximum voltage kV 23 25.3 25.3Rated frequency Hz 50/60 50/60 50/60

Rated continuous current 50 Hz S A rms 8500Rated continuous current 50 Hz M A rms 10500 10500Rated continuous current 50 Hz L A rms 13000 13000Rated continuous current 50 Hz XL* A rms 18000 18000

Rated continuous current 60 Hz S A rms 8000Rated continuous current 60 Hz M A rms 10000 10000Rated continuous current 60 Hz L A rms 12000 12000Rated continuous current 60 Hz XL* A rms 17000 17000

Rated insulation level:Rated power frequency withstand voltage to earth and across circuit-breaker/switch contacts kV rms 60 60 60 across isolating distance of disconnector kV rms 70 70 70Rated lightning impulse withstand voltage to earth and across circuit-breaker/switch contacts *) kV peak 125 125 125 across isolating distance of disconnector kV peak 145 145 145

Circuit-breaker:Rated peak withstand current kA peak 220 280 360Rated short-time withstand current kA, 3 s 80 100 130Rated short-circuit making current kA peak 220 280 360Rated short-circuit breaking current kA rms 80 100 130Rated operating sequence CO-30min-CORated interrupting time ms 67 67 67

Disconnector:Rated peak withstand current kA peak 220 280 360Rated short-time withstand current kA, 3 s 80 100 130Operating time s 2 2 2

Earthing Switch:Rated peak withstand current kA peak 220 280 360Rated short-time withstand current kA, 1 s 80 100 130Operating time s 2 2 2

The above data are not limiting values. Additional data on request. We reserve the right to alter data and technical details without notice.

Technical data

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The above data are not limiting values. Additional data on request. We reserve the right to alter data and technical details without notice.

Generator circuit-breaker system type HEC 7 HEC 8

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

Rated insulation level:Rated power frequency withstand voltage to earth and across circuit-breaker/switch contacts kV rms 80 80 across isolating distance of disconnector kV rms 88 88Rated lightning impulse withstand voltage to earth and across circuit-breaker/switch contacts kV peak 150 150 across isolating distance of disconnector kV peak 165 165

Circuit-breaker:Rated peak withstand current kA peak 600 600Rated short-time withstand current kA, 1 s 220 220Rated short-circuit making current kA peak 440 440Rated short-circuit breaking current kA rms 160*) 160*)Rated operating sequence CO-30min-CORated interrupting time ms 56 56

Disconnector:Rated peak withstand current kA peak 600 600Rated short-time withstand current kA, 1 s 220 220Operating time s 2 2

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

*) higher ratings on request

ABB Switzerland LtdHigh Voltage ProductsBrown Boveri Strasse 5CH-8050 Zurich / SwitzerlandPhone: +41 58 58 83424Fax: +41 58 58 81644

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