federal electricity & water authority water directorate...

WAM

Client: FEDERAL ELECTRICITY AND WATER AUTHORITY (FEWA) Project: STANDARD SPECIFICATIONS FOR WATER WORKS

Engineer WATER DIRECTORATE / ASSET MANAGEMENT DEPARTMENT

Title: Technical Terms / Chapter-4 / Engineering Specifications / B-Electrical System

ES03-LOW VOLTAGE [LV] SWITCHGEARS

Office:

DUBAI Order:

Document: MWA_PRO07/WAM-04-ES03 Rev:

OCT/2014 sheet: 1 of: 19

Federal Electricity & Water Authority

Water Directorate

Asset Management Department

STANDARD SPECIFICATIONS

FOR WATER WORKS

TECHNICAL TERMS

Chapter – 4

Engineering Specifications

[B-Electrical System]


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Office: DUBAI Order: Document:

MWA_PRO_07/WAM-04-ES03 rev: OCT/2014 sheet: 2 of: 19


TABLE OF CONTENTS

1. GENERAL

2. APPLICABLE STANDARDS AND GENERAL REQUIREMENTS

3. CAPACITIES, RATINGS, SIZES, QUANTITIES AND MATERIALS

4. DESIGN CONSIDERATION

4.1 System Variations

4.2 Performance Requirements

4.3 Temperature Rise

5. LV POWER DISTRIBUTION SYSTEM EQUIPMENT CONFIGURATION

5.1 Main Distribution Board

5.2Sub-Distribution Boards – AC Supply

5.3DC Distribution Boards

6. LV SWITCHGEAR AND MCC

6.1Construction

6.2 Interchangeability

6.3 Arcing Faults

6.4Bus-bars

6.5Bus Ducts

6.6Earthing

7. EQUIPMENT/DEVICES

7.1 Switchgear/MCC Feeders and Starters

7.1 Circuit Breakers

7.1 Motor Starters

7.1 Contacts, Plugs and Sockets

7.1 Moulded Case Circuit Breakers

7.1 Miniature Circuit Breakers

7.1 Contactors

7.1 Fuses

7.1 Residual Current Circuit Breakers

7.1 Keys and Key Cabinets

8. CONTROL AND PROTECTION FOR L.V. SWITCHGEAR/MCC

8.1 Relays

8.2 Interlocks

8.3 Control

9. CONTROL SUPPLY

10. AUXILIARY SWITCHES

11. SPARE CAPACITY

12. RATING PLATES AND NAMEPLATES

13. TESTS AND INSPECTION

13.1 Tests in the Manufacturer’s works

13.2 Tests at Site

14. PACKING AND SHIPMENT

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1. GENERAL

The scope of these specifications is for design, manufacture, testing at manufacturer works, supply, erection, testing, commissioning, performance and reliability confirmation, warranty confirmation of the complete LV Power distribution system and motor control centers (AC & DC) which are required for the plant/equipment being provided under the scope of this tender contract.

The scope of work and the equipment to be provided shall be as given in Chapter-2, Specific

Requirements of the Project of this Volume-2 and the performance guarantees and technical particulars given in Volume-3, Technical Schedules and Drawings.

It is not intended here to describe the design, arrangement or installation, or to specify each and

every component required for the completeness of the equipment or to select each material for safe and reliable operation of the proposed equipment. In general the equipment shall be complete in all respect with its components and accessories.

2. APPLICABLE STANDARDS AND GENERAL REQUIREMENTS

The LV power distribution system and LV motor control centers shall be designed, manufactured, tested, installed and commissioned in accordance with the latest revision of applicable IEC-439 or equivalent standard. Unless otherwise stated in these specifications, the general requirements shall be in accordance with the General Specifications Chapter-3 of this Volume-2 and shall be applicable to all the equipment of the similar type and size.However codes, standards and reference documents are listed below.

IEC Standards . Standard voltages IEC 60038

. Standard current ratings IEC 60059

. Preparation of documents used in electro technology IEC 61082

. General requirements Part 1

. Function oriented diagrams Part 2

. Connection diagram, tables and lists Part 3

. Location and installation documents Part 4

. Index Part 6

. Graphical symbols for diagrams(Part 1 to 13) IEC 60617

. Low voltage switchgear and control gear (Part 1 to 7) IEC 60947

. LV fuses (Part 1 to 4) IEC 60269

. Identification of equipment terminals and of termination of certain designated conductors, including general rules for an alphanumeric system IEC 60445 . Low voltage switchgear and control gear assemblies (Part 1 to 5) EC 60439 . Identification of conductors by colours or numericals IEC 60446

. Class 0.5, 1 and 2 alternating-current watt-hour meters IEC 60521 . Classification of degrees of protection provided by enclosures IEC 60529 . Insulation Coordination within low voltage systems (Part 1 to 3) IEC 60664

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Copy of any relevant standards other than specified above should be included in the vendor documentation

3. CAPACITIES, RATINGS, SIZES, QUANTITIES AND MATERIALS The capacities, ratings, sizes, quantities and materials specified in chapter-2, specific requirements of project and in this specification are to be considered as the minimum requirement to be provided. It is the responsibility of the contractor/manufacturer to determine the required capacities, ratings, sizes and quantities and select the appropriate material based on the guidelines given in the following specifications.

If the evaluated requirements are higher than the minimum requirement, if specified in chapter-2, specific requirements of the project of the volume-2, or in the following specifications then the required capacity/ratings/size/quantities/equipment shall be provided. If the evaluated requirements are less than the minimum requirements, then the minimum requirements shall be complied.

Any discrepancy in capacities, rating, sizes, quantities and materials specified at Chapter-2, specific requirements of the projects in the following specifications, then the requirements given at specific requirement of the project shall prevail. Similarly any discrepancy in capacities, ratings, sizes, quantities and materials specified in the following specifications and in Chapter-3 General Specifications, then the requirements given in this specification shall prevail.

4. DESIGN CONSIDERATION The distribution boards and MCC's shall be of a standard, well tested and proven design which ensures maximum safety to personnel, maximum service reliability and economic operation for an operational lifetime of at least 30 years. Design and construction shall be simple and well laid-out and shall provide good accessibility to components and parts. Even under extreme conditions of major short circuit or maloperation there shall be no danger to persons in the vicinity of the assembly. The electrical system for all low voltage boards and MCC's shall be 3 phase and neutral, 4- wire solidly earthed. Unless otherwise specified in the scope of work and in the drawings (including SLDS) all incomers, and buscoupler shall be mutually interlocked mechanically and electrically, the neutral conductor size shall be the same size as the phase conductors. All the distribution boards and their associated equipment shall have their designed and test voltages as per the applicable IEC standards and shall withstand the following short circuit currents :

a) Main Distribution Board

Voltage class - 1 KV

Symmetrical short circuit - 50 KA b) Sub-Distribution Boards – AC Supply

Voltage class - 1KV

Symmetrical short circuit - 50 KA

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c) DC Distribution Boards

Voltage class - 1KV

Fault level - According to Battery fuses

The normal current rating of LV distribution boards shall be according to the capacity of the feeding transformers. That for MCC’s and sub-distributions shall be according to their loads in the worst operating conditions plus a margin of at least 30% for future use. All distribution boards and MCC’s shall have duplicate supply connected to two different upstream bus sections. 4.1 System Variations All equipment and components of the LV distribution boards and MCC's shall be capable of continuous operation at their full current and voltage ratings and without detriment or malfunction at system continuous deviation of up to and including the following percentages of the normal values.

- Voltage ± 10% - Frequency ± 5%

4.2 Performance Requirements All components shall be capable of withstanding the dynamic, thermal and dielectric stresses resulting from prospective short-circuit currents without damage or injury of personnel.

4.3 Temperature Rise The temperature rise of the LV distribution board and motor control centre shall not Exceed temperatures indicated in IEC 60947.

5. LV POWER DISTRIBUTION SYSTEM EQUIPMENT CONFIGURATION According to its denomination, each individual switchboard feeder respective section shall contain the following main equipment as a minimum. Actual number of the feeders and devices shall generally comply with the requirements and single line diagrams.

5.1 Main Distribution Board

a) Incoming feeder

Two numbers

Circuit breaker, 4 pole,motorized,withdrawable.

Overload protection.

Short circuit protection

Earth fault protection.

Phase sequence(direction of rotation) monitoring on primary side.

Under/over voltage monitoring on primary side.

Voltage indications for each phase on primary side .

Push buttons on MCC. BREAKER ON ,BREAKER OFF.

Selector switch; OFF,MCC,DCS,locable.

Voltmeter with selector for phase-phase and phase-neutral voltage indication on primary side.

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Surge arrester on primary side

CTs for each phase.

Three (3) ammeters with maximum demand indication on yellow phase for incoming feeder.

One (1) current transducer

Two (2) voltage transformers (for incomers only)

One (1) voltmeter with selector switch (for incomers only)

One (1) voltage transducer (for incomers only)

One (1) set of control and monitoring devices

One of each KWh, KVArh, meters for incoming line or with multifunction measurement and display device on secondary side; phase voltages, phase currents, kw, kvar, kwh, kvarh, power factor frequency. KWH meter shall be of non resettable type.

Temperature controlled cubicle heating and ventilation.

Interface signals to the DCS ; PHASE FAULT OVER/UNDER VOLTAGE, TRIP,ON,OFF

Interface signals from the DCS;ON/OFF COMMAND.

Mechanical interlock with 1st incoming feeder and coupling feeder(2out of 3 logic) and vice versa

Electrical interlock with 2nd incoming feeder ,coupling feeder and emergency Incoming feeder if available, emergency feeder on when both incoming Feeders are off and vice versa.

Mechanical interlock with incoming feeders,2 out of 3 logic ( for coupling feeder) .

Electrical interlock with incoming feeders ; bus coupler only on when one of the incoming feeders is off ( for coupling feeder)

b) Bus coupling feeder

One number

Circuit breaker, 4 pole,motorized,withdrawable.




Voltage indications for each phase on primary and secondary side.



CTs for each phase.

Three (3) ammeters with maximum demand indicatior



Interface signals to the DCS ; FAULT /TRIP, ON, OFF

Interface signals from the DCS; ON/OFF COMMAND.

Mechanical interlock with incoming feeders, 2 out of 3 logic.

Electrical interlock with incoming feeders ; bus coupler only on when one of the incoming feeders is off.

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c) Emergency incoming feeder

One number

Circuit breaker, 4 pole, motorized, withdrawable.




Phase sequence (direction of rotation) monitoring on primary side.

Under/over voltage monitoring on primary side.

Voltage indications for each phase on primary side.

Push buttons on MCC. BREAKER ON, BREAKER OFF.

Selector switch; OFF, MCC, DCS, locable.

Voltmeter with selector for phase-phase and phase-neutral voltage indication on primary side.

Surge arrester on primary side

CTs for each phase.




Interface signals to the DCS ; PHASE FAULT, OVER/UNDER VOLTAGE, TRIP, ON, OFF


Electrical interlock with incoming feeders and emergency coupling feeders; emergency feeder only on when emergency bus coupler off and both incoming feeders off.

d) Emergency coupling feeder

One number

Circuit breaker, 4 pole, motorized, withdrawable.




Voltage indications for each phase on primary and secondary side.



CTs for each phase.




Interface signals to the DCS ;FAULT/ TRIP,ON,OFF


Mechanical interlock with emergency incoming feeder.

Electrical interlock with incoming feeder and emergency incoming feeder ; emergency feeder on and emergency bus coupler off.

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e) Outgoing Feeder

One (1) load switch with fuses or circuit breaker with instantaneous over current protection.

One (1) current transformer for feeders rated 63A and above.

One (1) ammeter for feeders rated 63A and above.

One (1) current transducer for sub-distribution feeder For smaller ratings the above load switch with fuses shall be replaced by m.c.b. with electro-magnetic release and collective reconnected fuses.

f) Measuring Section

Three (3) HRC fuses with fuse monitoring

Two (2) potential transformers in V-connection

One (1) miniature circuit breaker

One (1) voltmeter with selector switch

One (1) voltage monitoring relay

One (1) voltage transducer

g) AC Motor Feeders LV motor feeders up to 30 KW capacity shall be equipped as follows:

HRC fuses/circuit breaker 3 pole.

With two (2) auxiliary contacts for alarm and tripping or circuit breaker with instantaneous over current protection.

Contactor

Adjustable thermal overload and phase failure protection.

One (1) set of control and monitoring devices.

All motors above 3 KW shall be provided with an ammeter having a compressed overload scale, unless otherwise approved. Separate ON and OFF indicating lamps shall be provided for all motor feeders. Emergency stop push button shall be provided near each of the motors, on dedicated supports.

LV motor feeders above 30 KW capacities shall be equipped as follows:

Circuit breaker with drive for remote control

Motor protection relay covering

Thermal protection


Instantaneous earth fault protection

Stall protection

Power supply supervision and detection of negative phase Sequence.

One (1) current transformer

One (1) ammeter


One (1) set of control and monitoring devices

h) Valve Motor Feeder

Three (3) HRC fuses with individual fuse monitoring

Two (2) contactors

One (1) thermal overload protection device

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One (1) set of control and monitoring devices i) General

Remote control of all motor control centers from DCS for desalination plants & boilers.

Position indication of all feeders on DCS.

Common alarm auxiliary supply failure MCB trip, fuse blown on DCS.

Trip alarm for feeders and motors on DCS.

5.2 Sub-Distribution Boards – AC Supply

a) Incoming Feeder

One (1) manual operated circuit breaker with electro-magnetic and thermal release /MCCB and ELCB for lighting panel.

ELCB for power circuit .

ELCB for energy stations/power plug points.

One (1) Shunt

One (1) ammeter

Three (3) phase indication lamps b) Outgoing Feeder

One (1) outgoing miniature circuit breaker

If the connected load is above 10 amps - thermal over current release.

If the connected load is above 20 amps – electromagnetic and thermal over current release.

5.3 DC Distribution Boards

a) DC Incoming feeder

One (1) circuit breaker with electro-magnetic and thermal over current release.

One (1) shunt

One (1) ammeter

One (1) DC transducer

One (1) set of control monitoring devices b) DC Motor Feeder

Two (2) HRC fuses with individual fuse monitoring

One (1) main contactor with thermal over current release

One (1) starting resistor with start-up contactor combination

One (1) shunt

One (1) ammeter

One (1) set of control and monitoring devices c) DC Outgoing feeder from Main to Sub-distribution

Two (2) HRC fuses with individual fuse monitoring

One (1) load switch of adequate size

One (1) shunt for feeders rated 100 A and above

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One (1) ammeter - do –

One (1) DC Current transducer - do –

Blocking diodes d) DC Outgoing Feeder

One (1) circuit breaker with electro-magnetic and thermal over current release, if necessary with individual or collective fuses.

e) DC Measuring Section

One (1) miniature circuit breaker

One (1) voltage monitoring relay

One (1) voltmeter

One (1) DC voltage transducer

One (1) earth fault monitoring device with all required accessories.

Busbars earthing shall be achieved through the use of portable earthing devices attached via the circuit breaker plug orifice, in conjunction with a voltage-checking device.

6. LV SWITCHGEAR AND MCC 6.1 Construction The switchgears and motor control centers shall be of the indoor, completely enclosed (protection class IP41) two section or three section single bus-bar metal clad type with horizontal draw out switching units. They shall be dust and vermin proof with robust and rigid construction. These shall be of self-supported, freestanding, flush-fronted design having extension facilities in both directions. Each complete switchgear equipment shall be capable of carrying a through fault current equivalent to its specified breaking capacity. Each part of the complete switchgear equipment shall also be capable of carrying continuously the rated current specified for circuit breakers, contactors, bus bars and other fixed portions without damage or over heating of any part. In determining the load current performance of tiered cubicles it shall be assumed that all circuits are carrying their rated currents. The temperature rise of any portion shall not, unless otherwise approved, exceed the limits imposed by the relevant standards without the need to adopt forced cooling.

The construction shall be such that the various components of the switchgear are segregated electrically from each other, it shall be possible to gain access to the circuit breaker and the cable box chamber in any cubicle without having to take the busbars out of service after earthing of conductive elements. The lay-out of the operational front and the location of the components of the assembly shall be arranged in a logical and systematic sequence and standardized throughout. Each feeder compartment shall be of form 4 type. The front of the LV distribution boards shall be provided with a plastic or equivalent line mimic diagram illustrating the main circuit and its components Alphanumeric notation, generally in accordance with IEC 60445, shall be used for identification and marking of phases, conductors and terminals. The system of construction for the LV distribution

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boards and motor control centres shall be a factory-built assembly of a standard, well tested design. Interchangeable standardized components shall be used where feasible. It is preferred that spare compartments can be equipped to the maximum rating of the unit. Electrical cubicles shall be constructed of braced rolled steel section, with recessed panels, and substantial mounting frames for mounting of power and control cables. All main steel work shall be made of minimum 2 mm thick steel sheets. The cubicles shall be complete with all locks, cable end boxes, colour coded busbars, internal wiring, terminal boards and accessories.Hinged doors and bolted panels shall be provided. The opening angle of the doors shall be locked at about 100 deg. The terminal blocks, relays and instruments shall be so located as to be safely accessible while the equipment is in service. Suitable interlocks shall be provided for preventing access to live parts. Floor openings under cubicles, panels, desks etc. shall be covered and/or sealed by the contractor so as to obtain fireproof and vermin proof installation.All secondary wiring shall be arranged and protected so as to prevent it being damaged by arcing or by mechanical effects. All required base frames, anchors etc. shall be provided. The individual unit compartments shall be such as to obtain different zones fully insulated from each other.The fixed primary plug in contacts shall be protected by automatically closing shutters if the corresponding switchgear/MCC elements are removed. All faults occurring in any of the individual sections are to be restricted to that area and - except for busbar faults - shall not cause shut down of any other unit of the board other than the faulty unit itself. Insulating barriers, bus supports, mounted covers etc. shall be of non-hygroscopic, non-inflammable synthetic resin or other approved material. If required, pressure relief devices shall ensure that impermissible pressures created during heavy switching operations prevent destructions or deformations of the relevant cubicle. Special means shall be provided for connection of the bus ducts coming from the transformers. Circuit breakers less than 63 A may group wise be mounted on one draw out unit, with common short circuit protection for the subject mcbs.

Each individual enclosure accommodating LV equipment which is liable to suffer from internal condensation due to atmospheric or load variations shall be fitted with heating devices suitable for electrical operation at 240 volts AC 50 Hz single phase, of sufficient capacity to raise the internal temperature by about 5 deg. C above the ambient temperature. These heaters shall be controlled automatically by adjustable hygrostats. The electrical apparatus so protected shall be designed so that the maximum permitted rise in temperature is not exceeded if the heaters are energized while the apparatus is in operation. Where heaters are fitted, a suitable terminal box and main switch, with indicating lamp, shall be provided and mounted in an accessible position. All such equipment, whether fitted with a heating device or not, shall be provided with suitable drainage and shall be free from pockets in which moisture can collect. All instruments, relays, control and selector switches, indicating lamps, push buttons and trip levers shall be flush mounted and located at convenient heights in the front of the switchgear board.

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All steel work shall be rust proofed by immersion in a phosphate solution followed by at least two coasts of synthetic primer and two coats of air-drying steel paint for the exterior and interior surfaces. Extra amount of the same paint, sufficient for one final finish coat, shall be made available and applied to all steel work not incorporated in the factory made cubicle, after erection and before commissioning.

All outside surface shall be primed, filled where necessary and given not less than two applications of synthetic undercoat. The exterior finish shall consist of lacquer of the colour RAL 7032 This painting shall be scratch proof and resistant to perspiration from the operator’s hands. The painting shall be of such quality that damage of the paint during transport or erection can be easily repaired at site with paint furnished with the panels/desk by the contractor. 6.2 Interchangeability Electrically identical components shall be of one type and make. Withdrawable sub-assemblies containing one or more components with identical functions and capacities shall be mechanically interchangeable. Withdrawable sub-assemblies with identical functions but of different capacities might be mechanically interchangeable provided the sub-assembly can be adapted easily for its new capacity.

6.3 Arcing Faults Measures shall be taken to prevent the occurrence of internal arcing faults in accordance with the IEC requirements. The design and construction of the LV distribution boards and motor control centres shall be such as to provide the highest possible degree of personnel protection against radiation, overpressure and hot gases

6.4 Bus-bars Busbars shall be made of high conductivity electrolytic copper conductors suitably protected against corrosion and rigidly supported on approved type of insulators, and shall, unless otherwise specified, comply with the requirements of the latest relevant approved standard specifications. Access to the busbars shall be possible only by removing bolted covers. Opening the back or front of any circuit breaker cubicle shall not expose the busbars. Those connections to the busbars laying outside the busbars compartment shall be isolated, insulated or shrouded to eliminate the hazard of accidental contact while working on other parts of the switchgear. Busbars shall be capable of withstanding all electrical, mechanical and thermal stresses they may be subjected to under normal or prevailing short circuit conditions. Provisions shall be made for expansion and contraction of the busbars resulting from temperature variations. Insulated coloured busbars are preferred.Clearances between live parts and to earth shall be in accordance with the latest relevant approved standard specifications.

Main and auxiliary busbars shall be covered with insulating sleeves or moulded plastic form pieces to safely prevent internal busbar faults and spreading of arcs. All joints shall be properly silver-plated.

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6.5 Bus Ducts

433V bus ducts, wherever used for LV main incoming line, shall be supplied with 3 phase and neutral insulated busbars made of same size copper conductor section mounted inside steel or aluminium sheet metal enclosure of protection class IP54. Bus ducting, where it passes through walls, shall have provision for weather sealing. Where bus ducting is located outdoors, it shall be weather and dust protected to IP55. Each bus ducting shall be equipped with silica gel breather. Where necessary, expansion joints shall be provided in the run of the bus ducting.

Sunshade shall be provided for outdoor part of the bus duct. The maximum temperatures at full

load continuous running at 50C ambient temperature shall not exceed 85C for conductor and 65 for enclosure. In case of bus duct connection between transformer and LV switchgear, fully rated flexible connection links shall be used. The bus duct shall be designed to follow shortest route. The bus duct cover and conductors shall be suitably designed to accommodate thermal expansions at extreme possible temperature conditions. The bus duct shall be designed to withstand thermal and dynamic stresses under normal load or 50 kA symmetrical short circuit for 3 seconds.

The voltage and current rating of the bus duct shall be a) Rated voltage - 433 V AC, 4 wire, 50 Hz b) Max. system voltage - 660V c) Power frequency withstand voltage - 2.5 KV d) Nominal current rating - As per transformer capacity e) Symmetrical short circuit current (3 sec.) - 50 kA (rms) f) Asymmetric short circuit current - 125 kA (peak)

All busbars including neutral shall be segregated by metal partitions. The bus duct shall be provided with manual condensate drain valve at its lowest point.

Busbar compartments shall be provided with suitably rated space heaters to prevent condensation.

The heaters shall have built in protection against over temperature and shall be controlled by humidistat.

6.6 Earthing

Each circuit shall be provided with the ability to earth the cable by means of a device having a making capacity and short time rating equal to that of the circuit breaker. This may be achieved by means of integral earthing via the circuit breaker for earthing purposes, or by means of an earth switch installed within the switchboard and located between the circuit breaker and cable box.

Busbar earthing shall be achieved through the use of portable earthing devices attached via the

circuit breaker plug orifice in conjunction with a voltage-checking device. An earthing bar shall run the full length of the switchboards and to be connected to main earthing

system.

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7. EQUIPMENT/DEVICES 7.1. Switchgear/MCC Feeders and Starters

All circuit breakers, fused load switches, motor starters and other switching devices shall be of the

with draw able type or plug-in module type. If required, the metal surfaces of the cubicle walls adjacent to the switchgear are to be protected by fireproof insulating material. Where two or more starters or feeders are contained in the same cubicle, they are to be separated by barriers of steel sheet or fire proof insulating material. Each panel shall combine in tier form all respective control gears with their main incoming and outgoing power feeders. If capacitor banks are used for power factor correction separate suitable circuit breaker shall be provided.

The control gears and switching devices shall be suitably rated and controlled according to the

electrical and mechanical performance and duties they are assigned for. They shall be of the continuously rated pattern generously de-rated to comply with the site conditions and requirements.

The units shall have clearly marked service and test positions. A mechanical interlock shall be

provided to prevent withdrawal of the unit unless the power circuit has been interrupted. The unit shall, further more, positively be locked in the test position before it is manually released for complete withdrawal. The test position shall permit local and remote closing and tripping of the relevant switchgear with the power contacts not energized i.e. removed from the load circuit.

Each switchgear room shall be furnished with a switching unit transportation carriage of which the

height is adjustable to the respective installation heights. Moulded case circuit breakers and miniature circuit breakers may be used if they are properly

selected to stand the maximum assigned short circuit current level and proved by the contractor.

7.2. Circuit Breakers Air circuit breaker shall meet the requirements of IEC 947-3.2. It shall be motorized, with draw able

type with DC shunt trip and mechanical hand trip devices. The circuit breaker phases shall be separated by barriers of approved heat resisting, non-tracking insulating material. Suitable insulating barriers shall be provided between incoming and out going bus bars of the circuit breaker. The breakers shall be provided with main and isolating contacts and with suitable arcing contacts, magnetic arc quenching devices, arc chutes, etc.

The C.B.’s spring charging motor shall be of the totally enclosed type, with class F insulated

winding.Spring release closing mechanism shall be effected by means of a DC solenoid coil and by means of a mechanical pull out handle. Tripping shall be effected by means of DC solenoid shunt trip coil and by means of a mechanical push button.

The closing mechanism only may be of the AC solenoid coil operated and latched type. The closing

solenoid coil rated voltage shall be 220/240 Volts, 50 Hz. It shall be possible to 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.

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Where heaters are provided, these shall be permanently connected. Where two-stage heaters are provided, one stage shall be permanently connected and the other switched.

Means for locking shall be provided for the doors of each mechanism housing. Means shall be provided to prevent pumping while the closing circuit remains energized should the

breaker either fail to latch or be tripped during closing due to the operation of a protective device.

7.3. Motor Starters L.V. Contactors shall be of the air break type with arc shields, class AC-3 according to IEC

standards. Butt contacts of the rolling, self cleaning type shall preferably be utilized and all portions likely to suffer from arcing shall be easily removable.

All motor starters and their associated apparatus must be capable of operating without overheating

for a period of five minutes if the supply voltage falls, for that period, to 75 percent of the normal at normal frequency. Means shall be provided to prevent pumping.

Circuit breakers shall be of the trip-free type with a driving mechanism composed of spring loaded,

energy storing closing and tripping device.

7.4. Contacts, Plugs and Sockets The fixed power contacts shall be self-aligning type and shall have shutters, which automatically

close upon withdrawal of the circuit breaker. The withdrawal of big circuit breakers shall be accomplished by means of a crank, with as little effort as possible.

The contact surfaces of the power contacts, plugs and sockets shall be silver plated and their

design shall take into consideration the severe dust conditions of the site. They shall be amply sized and sufficiently strong to withstand maximum prevailing short circuits and carry continuously their normal rated currents without damage or overheating of any kind.

The control circuits shall be provided with plugs and sockets.

7.5. Moulded Case Circuit Breakers

Moulded case circuit breakers (MCCBs) shall be of the thermal/magnetic type to IEC 947-2, with quick make and quick break, trip free mechanisms which prevent the breaker being held in against over loads or faults. Tripping arrangement shall be such as to ensure simultaneous opening of all phases. Arc extinction shall be by de-ionizing arc chutes.

MCCBs shall be fitted with adjustable thermal releases and instantaneous magnetic release. The

thermal over current release shall be of the inverse definite minimum time type. This shall be designed to provide satisfactory discrimination with other protective equipment. Earth leakage protection shall also be provided.

The mechanism shall have three positions, “ON” / “OFF’” and “tripped” and shall have clear

indications. To reset from the “tripped” position the mechanism shall first pass into the “Off” position. MCCBs shall have the facility to be locked in the “Off” position.

The circuit breakers shall have the facility to initiate an alarm in the event of an automatic trip. MCCBs shall be of 4 pole or 2 pole construction as required.

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The MCCB characteristics shall be coordinated with the upstream LV board incomer/bus coupler for selective and fast fault clearance, the details shall be submitted for approval by the Ministry.

The number of MCCBs, rating shall be based on load requirement and to the approval of the

Ministry and the distribution, in general, be made by providing separate MCCBs for each load like outgoing feeder for lighting distribution, oil treatment plant, AC/ventilation, battery charger, other distribution boards etc. At least 20% spares of approved rating on each section shall be provided.

7.6. Miniature Circuit Breakers

Miniature circuit breakers shall conform to or relevant IEC or equivalent standard or any other internationally approved standard.

Circuit breakers shall be of the thermal/magnetic type conforming to relevant IEC or equivalent standard with quick make and quick break trip free mechanisms, which prevent the breaker being held in against over loads or faults.

Tripping arrangements shall be such as to ensure simultaneous opening of all phases. Arc

extinction shall be by de-ionizing arc chutes.The dolly shall have three positions, “on”, “off” and “tripped”. To reset from the “tripped position the dolly shall first pass into the “off” position.

MCBs on the main switchboard shall have facilities for locking in the “off” position.The rupturing

capacity of the MCB shall not be less than that of the switchboard itself, or if this is not the case MCCBs of adequate fault withstand and fault breaking capacity shall be provided.

The number of MCBs, rating etc. shall be based on the individual load requirement and subject to

the approval of the Ministry/Engineer.

7.7. Contactors Contactors for controlling supplies to the sub distribution shall be of the 3-phase type with neutral

links. The contactors shall be provided with electrical closing and hold on coils and the no-volt release provided with a time delay feature adjustable between 0 and 5 seconds.

When in the “standby supply” position, the contactors shall automatically revert to the ‘Normal

supply’ position as soon as such supply is restored. The contactors shall be provided with indicating lamp coloured amber to indicate when the

contactors are in the standby position and with clearly indicated ‘Normal’ and ‘standby’ mechanical indications visible with the distribution board door in the closed position.

7.8. Fuses Fuses shall be of the HRC cartridge type for operation at a prospective fault level of 50 KA and

conforming to IEC 269. The mounting of the fuses shall be such that they can be readily withdrawn and replaced whilst the associated bus bars and circuits are alive.

7.9. Residual current circuit breakers

Residual current breakers shall comply with the requirements of BS 4293 and shall be complete with current transformer, ON/OFF switch, test button and trip free mechanism. Each shall be of suitable rating and sensitivity for its application.

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7.10. Keys and Key Cabinets Key interlocked switches shall be provided with an approved lock for locking in the neutral position.

A similar lock shall be provided for each selector switch for locking the switch in any of its positions. Approved means shall be provided for locking the cubicle doors, live terminal shutters etc.The locks

or pad lock shall be coordinated for the different applications and shall be supplied with three keys. A standard key cabinet shall be provided in each switch room for storing the keys. Each key shall

have identification label and a label above the key-hanging hook inside the cabinet. 6 Master keys with similar cabinet to be provided in the control room.

8. CONTROL AND PROTECTION FOR L.V. SWITCHGEAR/MCC 8.1 Relays

The relays shall be dust proof with removable glass covers and external resetting devices, unless otherwise specified relays shall be of the hand resetting type with hand reset flag having seal-in operation. The relays shall provide easy access for testing and setting purposes.

All protective relays shall be mounted on their anticipated breaker panels.Control contacts shall be suitable for 110 Volts D.C.

The relays shall have sufficient contacts and/or auxiliary relay contacts to perform all the tripping,

inter tripping, interlocking, indication and alarm functions required. Spare contacts ( 2 N.O. + 2 N.C) shall be provided for the Owner’s use.

Each relay and its place on the cubicle shall have the same identifying mark shown on the

appropriate wiring diagrams. Panel meters and control switches shall be fixed at levels not higher than 2 and 1.8 meters respectively.

All meters, indicators, switches and the other different kinds of exposed components shall be fixed

flush to the panel front surfaces, plane and displayed in symmetrical form with reasonably large free spacing.

Closing of the circuit breakers and contactors shall be possible between 80% and 110% of the

rated control voltage. Holding of contactors must safely be effected by at least 70% of the rated control voltage. Tripping devices shall operate at 50% - 120 % of the rated control voltage.

8.2 Interlocks The basic interlocking principles for the power supply systems are listed below:

All incoming feeders of a distribution board or a section of such board shall be interlocked against each other or against the bus coupler, if provided, to achieve two out of three logic system.

Paralleling of important distribution boards being provided with two in feeds or with one in feed and one bus coupler to another in feed shall be possible for a few seconds if the bus coupler of the respective M.V. distribution is in the closed position. In such case one of the two relevant feeder circuit breakers shall be subsequently switched off (manual operations) or the bus coupler of the L.V. distribution shall be tripped automatically after the preset period.

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Tripping of any protection device in one of two feeder circuits (for example 11 kv transformer feeder protection, transformer buchholz or oil temperature tripping, but not the L.V. incomer protection) shall automatically trip the defective circuit and connect the second feeder circuit (provided its 11 KV breaker is closed) via the L.V. incoming breaker or the bus coupler, whatever is applicable. This system shall be applied on double feed switchboards supplying consumers, which are indispensable for the plant operation.

8.3 Control The control of different feeders shall be as required and approved by the Engineer.

9. CONTROL SUPPLY

Generally all signal, monitoring and protection circuits as well as shunt-trips of circuit breakers shall be fed by unit D.C. All other circuits may be controlled by A.C. Also, contactor operating circuits shall be controlled by A.C. with the contactor solenoid preferably designed for D.C. with a pre-connected rectifier bridge. All aforesaid circuits shall individually be protected by means of miniature circuit breakers with position monitoring. A.C. control circuits shall be derived from the relevant bus-bar system via supervised main fuses and the above mentioned individual MCBs a maximum of 10 consumers may be connected to one MCB.

10. AUXILIARY SWITCHES

Where appropriate, each item of plant is to be equipped with all necessary auxiliary switches, contactors and mechanism for indication, protection, metering, control, interlocking, supervision and other services. All auxiliary switches are to be wired up to a terminal board on the fixed portion of the plant, whether they are in use or not in the first instance.

All auxiliary switches and mechanisms are to be mounted in approved accessible positions clear of

the operating mechanisms and are to be protected in an approval manner. The contacts of all auxiliary switches shall be strong and shall have a positive wiping action when closing.

11. SPARE CAPACITY

All boards and MCC’s shall have 20% spare equipped outgoing and motor feeders of each type and size (minimum one feeder). All panels shall still have minimum 10% of inside spares room when commissioning is finished.

Each distribution board shall additionally be provided with at least 10% empty compartments of

each type completely wired as spare. Such compartments shall be closed by steel panels/doors.

12. RATING PLATES AND NAMEPLATES

Distribution boards shall have a rating plate permanently fixed in the front of the equipment giving at least the following information:

- Rated voltage and frequency. - Rated SC capacity and current capacity of busbars. - Standard to which equipment conforms. - Year of manufacture. - Purchaser's tag no.

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- Manufacturer's name, type and serial number. - Weight.

All components (switching devices, contactors protection relays, instruments etc.) shall be fitted with a rating plate in accordance with the relevant IEC requirements. All functional units shall be clearly labelled to identify the service. All relays, meters, switches etc. shall be labelled in accordance with the wiring diagrams. Labels inscribing "CAUTION LIVE PARTS INSIDE" shall be fixed on the doors.

Rating plates shall be made of corrosion-resistant metallic material and have indelible inscriptions in the language specified in the requisition. Enamelled plates are not acceptable. Each panel shall be provided with nameplates, mounted on the front of a non-removable part.

13. TESTS AND INSPECTION 13.1 Tests in the Manufacturer’s works

At least the following tests shall be performed in the manufacturer’s workshop on the individual apparatus and on the complete installation, respectively, all in accordance with IEC Standards:

Visual inspection

Power frequency H.V. tests

Dielectric tests of the auxiliary circuits

Functional tests of the control circuits

Check of the operational sequence

Check of the denominations.

13.2 Tests at Site The complete switchgear and - as far as reasonable - the individual apparatus shall be tested on

site as follows:

Visual inspection

Dielectric test/High voltage test.

Functional and sequence test

Setting and functional test of protection devices (primary injection method)

13. PACKING AND SHIPMENT

LV distribution boards and MCC's shall be packed in wooden type seaworthy crates having sufficient strength to withstand normal ship handling and transport or be fixed mounted in containers.

The crates shall be marked with FEWA's name and address, order number, type of equipment, hoisting points, etc.Enclosed with the board, the following documents shall be included in suitable wrapping:

- Electrical schematic diagram - Electrical wiring diagram - General arrangement drawing - Foundation plan including foundation loadings - Operation and maintenance manual.

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