33kv breaker spec

1. TECHNICAL PARTICULARS OF 33KV INDOOR TYPE VCB AND SWITCHGEAR PANEL

1 SYSTEM DETAILS kV 33

1.1 Rated system voltage kV 36

1.2 Earthing of system neutral solid

1.3 System frequency Hz 50

2 INSULATION LEVEL (at site altitude)

2.1 Lightning impulse voltage withstand level, positive and negative polarity

kVp 170

2.2 Switching impulse voltage withstand level of insulation to ground, positive and negative polarity

drywet

kVpkVp

--

2.3 Power frequency withstand voltage

drywet

kVkV

7070

2.4 Voltage below which corona shall not be visible kV -

2.5 Maximum radio interference voltage level measured at 1.1 times Us/3 at 1 MHz

µV -

2.6 Minimum creepage to earth over insulation on rated service voltage (to IEC 815) mm

/kV25

3. SWITCHGEAR DETAILS

ItemNo Description Particulars

kV 36.3

3 TYPE OF SWITCHGEAR

3.1 Type of switchgear

GIS or Open terminalOpen terminal

3.2 Installation Indoor Indoor

4 SHORT TIME CURRENT CAPACITY

4.1 All equipment 3 seconds kA 25

4.2 Maintenance earthing devices, 3 seconds

kA 25

5 CIRCUIT BREAKER

5.1 Normal current rating A 1250

5.2 Fault rating

5.2.1 Making current kAp

62..5

5.2.2 Breaking current (symmetrical) kA 25

5.2.3 Breaking current (asymmetrical)

% DC/kAp IEC 56

5.2.4 Breaking current under out of phase conditions

kA 6.25

5.2.5 Rated line charging current A 10

5.2.6 Rated cable charging current A 50

5.2.7 Rated inductive current A 1 to 10 - 50 - 100 - 200

5.2.8 Maximum overvoltage factor on any switching duty

pu <2.0

5.3 Operating sequence


5.3.1 Normal 0-10 s - CO-3 min - CO

5.3.2 Auto re-closing 0-0.3 s - CO-3 min - CO

5.3.3 Delayed three phase auto re-close cycle adjustable dead time range s 2-30

6.1 High speed single phase auto re-close cycle adjustable dead time s

-

6.2 Number of closing operations under out of synchronous conditions

(2.0 pu) 2

6.3 Transient recovery voltage

6.4 First phase to clear factor 1.5

6.5 Recovery voltage parameter for 3 phase unearthed terminal fault IEC 56

6.6 Short line fault parameter IEC 56

6.7 Surge impedance for short line fault test

ohms

-

6.8 Minimum voltage to earth when switching capacitive currents, (1.4 times rated phase to earth voltage)

kV 29

6.9 Voltage across circuit breaker under out of phase switching conditions

pu 2

6.10 Electro mechanical performance

6.11 Maximum total break time throughout complete rating, ie trip coil initiation to final arc extinction ms 50


6.12 Maximum time interval between closure of first and last phase of three phase circuit breakers

ms 1

6.13 Maximum time interval between closure of interrupters of one phase of the circuit breaker

ms -

6.14 Maximum time interval between opening of first and last phase of three phase circuit breaker ms 10

6.15 Maximum time interval between opening of interrupters of one phase of the circuit breaker

ms -

kV 36.3

6.6 Insulation level (IEC 694)

6.6.1 Lightning impulse withstand (1.2/50 wave) - positive and negative

a. To earth, closed contacts

b. Across, open contacts

kVp

kVpkVp + kVACp

6. 6.2 Switching impulse withstand (250/ 2500 wave) - positive and negative

a. To earth, closed contacts

b. Across, open contacts

kVp

kVpkVp + kVACp

6.6.3 Power frequency withstand

a. To earth, closed contacts - 1 minute

Dry/wet

kV

kV

70


b. Across, open contacts - 1 minute

80

6.7 Ancillary equipment

6.7.1 Number of trip coils required 2

6.7.2 Number of closing coils required

1

6.7.3 Degree of protection IP 56

1.1. 13.1 General

Circuit breakers shall be of three pole air break design, horizontal draw out type in accordance with IEC 947-2. In particular, evidence shall be provided of the performance when switching currents in the critical current range. They shall be capable of the ratings specified in the Schedules, when mounted in the switchboard.

Circuit breakers shall be fitted with trip-free, spring-operated mechanisms of the independent manually operated type and be provided with making and over current release facilities. A push-button shall be provided to trip the breaker electrically.

The breaker shall be provided with `OPEN'. `CLOSE', `SERVICE', `TEST' and `SPRING CHARGED' position indicators and shall be provided with the necessary number of auxiliary contacts for interlocking, indication and tripping purposes plus two spare.

Each incoming circuit shall be provided with thermal overload relays and short circuit protection relays; they shall also be provided with an undervoltage relay to trip breaker in the event of a supply failure.

There shall be `SERVICE', `TEST' and fully withdrawn positions for the breakers. It shall be possible to close the door in ‘TEST’ position.

Movement of a circuit breaker between ‘SERVICE’ and ‘TEST’ positions shall not be possible unless it is in ‘OPEN’ position. Attempted withdrawal of a closed circuit breaker shall not trip the cir-cuit breaker.

Closing of a circuit breaker shall not be possible unless it is in ‘SERVICE’, ‘TEST’ or fully withdrawn positions.

A breaker of particular rating shall be prevented from insertion in a cubicle of a different rating.

Circuit breakers shall be provided with electrical anti-pumping and trip free feature.

Means shall be provided to slowly close the circuit breaker in withdrawn position if required for inspection and setting of contacts. In service position slow closing shall not be possible.

Circuit breakers shall be provided with the following mechanism as specified in the Bill of Material.

All relays and timers in protective circuits shall be flush mounted on panel front with connections from the inside. They shall have transparent dust tight covers removable from the front. All protective relays shall have a drawout construction for easy replacement from the front. They shall either have built-in test facilities, or shall be provided with necessary test blocks and test switches located immediately below each relay. Auxiliary relays and timers may be furnished in non-drawout cases.

All AC relays shall be suitable for operation at 50 Hz with 110 volts VT secondary and 1A or 5A CT secondary.

All protective relays and timers shall have at least two potential free output contacts. Relays shall have contacts as required for protection schemes. Contacts of relays and timers shall be silver faced and shall have a spring action. Adequate numbers of terminals shall be available on the relay cases for applicable relaying schemes.

All protective relays, auxiliary relays and timers shall be provided with hand reset operation indicators (flags) for analysing the cause of operation.

All relays shall withstand a test voltage of 2kV (rms) for one minute.

Motor starters shall be provided with three element, ambient temperature compensated, time lagged, hand reset type terminal overload relays with adjustable settings. The setting ranges shall be properly selected to suit the motor ratings. These relays shall have a separate black coloured hand reset push button mounted on compartment door and shall have at least one changeover contact.

All fuse protected, contactor controlled motors shall have single phasing protection, either as a distinct feature in the overload relays (by differential movement of bi-metallic strips), or as a separate device. The single phasing protection shall operate with 80% of the set current flowing in two of the phases

2. SCOPE

This technical specification is applicable to circuit breakers (AIS) for use on 36kV,rated system voltages corresponding to the nominal system voltages of 33kV, 50 Hz systems for all substation layout configurations.

Circuit breakers are to be supplied complete with pole control cabinets where the type of circuit breaker requires them, local control cabinets, foundation bolts, support structures, piping, fittings, pipe supports for inter pole, pipe work, pumps for hydraulic mechanisms and compressed air plant for pneumatic mechanisms.

The circuit breaker assembly includes provision of all inter pole and pole to control cabinet cabling and all cable accessories such as ferrules, glands and terminals.

The circuit breaker shall conform in all respects to high standards of engineering, design, workmanship and the latest revisions of relevant standards at the time of offer and Purchaser shall have the power to reject any work or material, which, in his judgement, is not in full accordance therewith.

3. STANDARDS

All circuit breakers and associated equipment shall comply with the latest editions of the relevant Indian Standards (IS), International Electro-Technical Commission (IEC) standards and any other standard mentioned as here under.

STANDARD TITLE

IEC 56/IS 13118 General requirements HV open terminal circuit breakers above 1000 V.

IEC 694/IS 12729 General requirements (common specifications) for switchgear and control gear for voltages exceeding 1000 V.

IEC 427/IS 13516 Method of synthetic testing of high voltage alternating current circuit breakers.

IEC 56/IS 9135 Guide for testing of circuit breakers with respect to out-of-phase switching.

IEC 144/IEC 529/IS 13947

Degree of protection provided by enclosure (IP Code).

IEC 1233 High voltage alternating current circuit breaker inductive load switching.

IEC 17A (Sect) 438 High voltage alternating current circuit breaker capacitive current switching.

IEC 815 Guide for the selection of insulators in respects of polluted condition.

IEC 71/IS 3716/IS 2165

Application guide for insulation co-ordination.

IEC 71/IEC 694/IS 11182

Guide for evaluation of insulation systems. Common clauses for high-voltage switch gear and control gear standards.

IEC 376/IS 13072 Sulphur hexa-fluoride for electrical purposes.

IEC 233/IS 5621 Hollow insulators for use in electrical equipment (CENELEC doc. EN 560062).

IEC 273/IS 5350 Dimensions of indoor and outdoor porcelain post insulator units for system with nominal voltage greater than 1000 V.

IEC 137/ IS 2099 Bushings for alternating voltages above 1000 V.

IS 4379 Identification of contents of industrial gas cylinders.

IS 7311 Seamless high carbon steel cylinders for permanent and high pressure liquifiable gases.

IEC 157/IS 13032 Miniature circuit breaker boards for voltage up

to and including 1000 V.

IS 2959 / 337 Specification for contactors for voltages not exceeding 1000 V ac or 1200 V dc.

IS 2629/BS 729 Specification for hot dip galvanised coatings on iron and steel articles.

IEC 34/IS 325 Specification for three phase induction motors/rotating electrical machines (motors).

IEC 72 Dimensions and output series for rotating electrical machines.

IS 6005 Code of practise for phosphating.

IEC 227 PVC insulated cables of rated voltages up to and including 450/750V

IEC 617 Graphical symbols for drawings

IS 5 Colours for ready mixed paints and enamels

4. CIRCUIT BREAKER

HV circuit breakers shall be designed and tested in accordance with IEC 56, 17A/474/CD, 694, 529, 427, 1233 and with the requirements of this Specification. All type tests shall be carried out by an independent testing laboratory or witnessed by independent observers.

The design of the circuit breaker shall be such that inspection and replacement of contacts, nozzles and any worn or damaged components can be carried out quickly and with ease. The terminal pads on the circuit breaker shall have silver plating of at least 50 micron thickness.

The circuit breaker shall be suitable for three-phase operation, unless single-phase auto-reclose is specified in Clause 11 of this section. The maximum pole scatter across the three poles shall not exceed 3.3 ms during an opening operation.

The circuit breakers shall be of the Vaccum types, suitable for indoor installations in case of . The inherent design of these circuit breakers shall be such that they shall satisfactorily interrupt all short circuit test duties, including short-line faults and out-of-phase duties and produce very low over voltages (<2.0 pu) on all, capacitive, inductive and reactor current switching circuits. One set of contacts and nozzles shall be capable of successfully interrupting at least twenty, 100 per cent short circuit currents.

The type and profile of the porcelain insulator sheds shall be in accordance with IEC 815 and shall be suitable for the worst environmental conditions specified in the clause 11 of this section. The creepage distance across the interrupting chambers shall be at least equal to the creepage distance to earth and shall be suitable for hot line washing in compliance to latest version of IEC-694.

External parts of the circuit breakers, which are under continuous electrical stress, shall be of hollow porcelain. The creepage and flashover distances of the insulators shall be dimensioned to suit the outdoor service conditions specified in the Schedules. High strength hollow porcelain shall be used on the circuit breaker. It shall be of single length one piece, without any joint and shall comply with IEC 233 and CENELEC document EN 50062. It shall be made of homogeneous material, brown in colour and of high quality smooth finish. It shall withstand the maximum expected dynamic loads (including the seismic) to which the circuit breaker may be subjected during its 40/45 years service life.

The sound pressure levels of the breaker during the mechanical operations shall comply with the local and national health and safety regulations. It shall not exceed 90 dB at 1.2 meters above ground, at a distance of 25 meters from the circuit breaker.

The number of auxiliary switches required may vary for different site conditions in which case, provision shall be made for 30 NO and 30 NC auxiliary switches on each circuit breaker.

Provision shall be made for the connection of an analyser to enable determination of the circuit breaker mechanical operating parameters.

5. INTERUPTING MEDIA

For 36kV class breakers the interrupting media could be either be vacuum. The interrupting media shall confirm the following requirements:

5.1. Vacuum

In vacuum circuit breakers, facilities shall be provided for monitoring the contact erosion and any contact gap. The vacuum bottles shall be easily replaceable and the mechanism shall be conveniently calibrated to permit resetting the contact gap when open

The vacuum circuit breakers poles shall be sealed to prevent contamination of the spaces surrounding the interrupters. The bidders shall be required to demonstrate how this is achieved by supplying technical details along with the bid.

6. CIRCUIT BREAKER OPERATING MECHANISMS

6.1. General

The operating mechanism of the circuit breaker shall be one of the three types: spring, hydraulic or pneumatic. Each mechanism shall be fitted with an anti-pumping device. All working parts in the mechanism shall be of corrosion resistant material. Sealed for life bearings shall be provided in the mechanism and any other bearings which require greasing, shall be equipped with pressure grease fitting.

The mechanism shall fully close the circuit breaker and sustain it in the closed position against the forces of the rated making current and shall fully open the circuit breaker without undue contact bounce at a speed commensurate with that shown by tests to be necessary to achieve the rated breaking capacity in accordance with IEC 56. The mechanism shall be capable of being locked in either the open or closed position. When auto-reclosing is specified, it shall be suitable for multi-shot high speed duty. The mechanism shall be capable of fully closing and opening again after the auto-reclose time interval specified. Evidence shall be submitted to show that the design of the mechanism has given satisfactory service experience in tropical climatic conditions for at least three years.

The mechanism and the connected interrupters shall satisfy the mechanical endurance requirements of IEC 56 and all additional requirements specified herein.

A positively driven open/closed indication device, clearly visible without the necessity to open the mechanism door, shall be provided. The drive for the device shall be positive in both directions.

Means shall be provided to prevent the mechanism from responding to a close signal when the trip coil is energised, or to reclosing from a sustained close signal either after opening due to a trip signal or failure to hold in the closed position. Any relays to accomplish these provisions shall be continuously rated and mounted at the circuit breaker.

Duplicate trip coils with independent trip circuits and phase discrepancy remote indication shall be provided. Trip circuits shall be suitable for trip circuit supervision in both open and closed positions. For single phase mechanisms pole discrepancy scheme shall be an integral feature of circuit breaker control system to detect any discrepancy of one or more phases during an opening or closing operation. In the event of occurrence of a pole discrepancy, the scheme shall apply a trip signal to the circuit breaker with an alarm.

A mechanical open push button shall be provided on the circuit breaker which shall be shrouded and shall be lockable.

The following facilities shall be provided at each circuit breaker local control point:

LOCAL/REMOTE selector switch. The selection of ‘local’ operation shall inhibit the operation of the breaker from any remote source including the protection scheme.

OPEN/NEUTRAL/CLOSE control switch or open and close push buttons. Where push button controls are provided the selector switch shall have a neutral position.

EMERGENCY TRIP DEVICE suitable for manual operation in the event of failure of electrical supplies. The device shall be accessible without opening any access doors and distinctively labelled and protected against inadvertent operation.

For maintenance purposes, means shall be provided for manual operation including the slow closing and opening of those circuit breakers whose moving contacts are mechanically coupled to the direct linkage mechanism. Such operation shall be possible without the necessity of gaining access to the interior of the power unit, and shall not require excessive physical effort.

Mechanical counters, to record the number of closing operations and an indicator to show the close/open position of the circuit breaker shall be provided for each circuit breaker mechanism. Circuit breakers arranged for single-pole operation shall be provided with a counter for each pole.

The operating mechanism control, electrical circuitry, compressor unit, hydraulic pump and all other equipment required for the mechanism shall be housed in an out door type, hot-dip galvanised steel enclosure with IP 55 degree of protection to IS 13947/IEC 529.

The mechanism shall be provided with sufficient stored energy to carry out at least one O-CO operation in the event of power failure to the operating mechanism.

The circuit breaker operating mechanism shall be such that the contacts shall not close automatically upon a low gas pressure.

6.2. Spring mechanism

Provision should be made for remote indication of ‘Spring charged’ and ‘Spring charge fail’ conditions.

The mechanism shall be complete with spring charging motor, closing and opening springs with limit switches for automatic charging and with all necessary accessories to make a complete operating unit.

A spare normally open spring-drive limit switch shall be provided.

It shall be possible to hand charge the operating springs with the circuit breaker in either the open or closed positions. In normal operation, recharging of the operating springs shall commence immediately and automatically upon completion of the closing operation. Closure whilst a spring charging operation is in progress shall be prevented and release of the springs shall not be possible until they are fully charged.

The state of charge of the operating springs shall be indicated by a mechanical device which shows ‘SPRING CHARGED’ when operation is permissible and ‘SPRING FREE’ when operation is not possible. A local manual spring release device shall be provided and arranged to prevent inadvertent operations.

6.3. Pneumatic, pneumatic/spring, hydraulic and hydraulic/spring mechanisms

Operating pressure shall be maintained automatically, a gauge being provided to give indication of the pressure. The pressure gauge shall be suitably damped to ensure that it is not subject to transient pressure oscillations either during pumping or during operation of the circuit breaker.

Pneumatic mechanisms shall be complete with compressed air system and all necessary accessories to make a complete operating unit.

Hydraulic mechanisms shall be complete with power cylinder, control valves, pressure reservoirs, motor/hand pump set and all necessary accessories to make a complete operating unit.

A lock-out device with provision for remote alarm indication shall be incorporated in each circuit breaker to prevent operation whenever the pressure of the operating medium is below that required for satisfactory subsequent operation at the specified rating. Such facilities shall be provided for the following conditions:

a). Trip lock-out pressure.

b). Close lock-out pressure.

c). Auto re-close lock-out pressure.

Alarm contacts shall be provided to indicate conditions a), b) and c). If two trip systems are specified, then trip lockout shall apply to both systems.

A sudden fall in pressure of the operating medium to a level below which a safe operation is not possible shall not result in slow opening or closing of the circuit breaker contacts. The mechanism shall be locked in position and electrical trip and close signals shall be isolated during this period. On a pneumatic mechanism with unit compressor, the loss of air due to leakage shall not exceed one per cent of the unit receiver volume per hour over the whole guaranteed service life of the mechanism.

Facility shall be provided to enable the available operating energy stored by the mechanism to be determined prior to operating the circuit breaker, together with an alarm in the event of the potential energy falling below a minimum rated level. Facility for hand charging of hydraulic systems shall be provided. Each hydraulic mechanism shall be fitted with a nitrogen leak detector.

Circuit breakers having independent operating mechanisms on each phase shall block tripping, closing, and auto-re-closing of all phases if the operating pressure is below a minimum rated level in one or more of the mechanisms.

Hydraulic oil pipes and joints shall be leak free at up to 1.5 times normal operating pressure.

6.4. Mechanism housing

The heaters provided inside the housing to stop condensation, shall be permanently connected. Where two stage heaters are provided, one stage shall be permanently connected and the other switched.

Mechanism housings shall have an IP55 rating and means for locking shall be provided for each door.

Supplier shall provide all necessary inter-pole cables and cabling from individual poles to the local control cubicle, as well as all cable accessories necessary to achieve proper installation.

The control cabinet shall be provided with 415 V, 3-phase and 240 V, 1-phase ac (50 Hz) and 220 V dc supplies. Separate terminal blocks for terminating circuits of different voltages shall be provided. CT loads shall be terminated on a separate block and shall have provision for short circuiting the CT secondary terminals. All terminals shall be adequately screened, insulated and marked with the phase colour. DANGER notices shall be affixed to the terminal blocks and a danger notice stating the voltages shall be fixed on the inside and outside of the cabinet. The conductors of all current circuits shall be annealed copper of cross sectional area of not less than 4 mm2 and that for potential and control circuits shall not be less than 2.5 mm2 and shall be insulated with PVC to IEC 227.

6.5. Low current switching

The circuit breaker shall produce very low over voltages (< 2.0 pu) on all switching circuits, inductive currents, including shunt reactor (up to 50 MVAr) switching and capacitive current switching. During the low inductive and capacitive current switching duties, there shall be no chopping or virtual current chopping. The circuit breaker shall be re-ignition and re-strike free for all switching duties.

6.6. Capacitive current switching

Capacitive switching tests shall be performed in accordance with IEC 17A/CD/474, clause 6.111.7.C on full pole, preferably by direct test method or alternatively using synthetic method to IEC 427. The test circuits shall simulate the most onerous site conditions.

6.7. Inductive/reactor switching

In addition to the inductive current switching tests, the circuit breaker shall also be tested for shunt reactor switching in accordance with IEC 1233 and 17A/474/CD. Examination of the interrupter after the tests shall not show any evidence of surface tracking or erosion of nozzle.

6.8. Insulation co-ordination

Insulation co-ordination shall be applied in accordance with IEC 71. The Supplier is free to select appropriate rated levels from IEC 71 but will need to provide test evidence to the Purchaser’s Representative’s satisfaction, by means of type tests, to verify that co-ordination of insulation has been achieved.

Insulation co-ordination shall consider the following site conditions:

Atmospheric discharges and lightning strokes.

Switching overvoltages

Fast transient overvoltages

Overvoltages caused by load shedding and switching In and Out of the overhead lines

Resonant overvoltages generated by switching a short section of busbar via an open circuit breaker

Power frequency voltage on one side of the open contact and the transient

Withstand capability of the open contact gap.

6.9. Mechanical endurance

In addition to the requirements of IEC 56, extended mechanical endurance test is required to show that the circuit breaker is capable of at least 10 000 operations in accordance with IEC 17A/474/CD Clause 6.101.2.4.

33kv breaker spec

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