3.6 MAIN DISTRIBUTION BOARDS
PART.1 GENERAL
3.6.1.1 DESCRIPTION OF WORK
- Main distribution board(s) (DP-MM) & (DP-EMM) for low voltage (LV
3.6.1.2 STANDARDS:
Switchgear and control gear are to be type tested assemblies comply, as a minimum, with IEC 439-1 Assemblies of Switchgear and Control Gear for voltages not exceeding 1000V a.c. and 1200 V d.c. Circuit breakers are to comply with IEC 947 as specified. Other components, where not otherwise specified, are to comply with the relevant IEC standards.
3.6.1 EQUIPMENT DATA:
Submit for approval detailed description of main distribution boards and major components supported by manufacturer's catalogues ,indicating compliance with the Standards, equipment characteristics, details of construction ,operating data, dimensions and weights......etc. Give details of miscellaneous items including incoming and outgoing feeder terminal arrangement, connections at bus bars, isolating means, earthing means, interlocks, control devices, indicating and metering instruments etc.
3.6.1.4 TESTS AND CERTIFICATES:
Provide complete certified manufacturer's type and routine test records, in accordance with the Standards.
3.6.1.5 SHOP AND CONSTRUCTION DRAWINGS
Submit drawings for approval including, but not limited to, the following:
- Plans and elevations with indication of built-on equipment exact dimensions and weights
- Arrangement of boards inside rooms allocated, indicating spaces and clearances
- Arrangement of equipment inside board
- One-line diagram of power system showing current ratings of switchgear and busbars and types and locations of protective gear (relays, instruments, CTs, VTs etc.)
- Schematic and elementary diagrams of control circuits
- Foundation details, grouting holes, installation details
- Arrangement of incoming and outgoing feeders, terminal fittinings instruments, busbar connections etc.
3.6.1.6 TECHNICAL LITERATURE:
Submit the following for approval prior to placing orders for equipment manufacture:
Schedule of circuit breakers application, indicating type, range features and characteristics, short circuit ratings, time-current curves, etc.
Method of setting of protective devices for overload, short-circuit and earth-fault currents as coordinated with upstream and downstream systems based on the specific coordination curves of protective devices used and specific calculated prospective short-circuit currents at the various points
3.6.1.7 SPARE PART
Provide as recommended by manufactures, for possible emergency replacement and/or for one year's maintenance, including, but not limited to the following
- One set of fixed and moving contacts for every type of replaceable (consumable) contact set
- One operating motor and/or coil for each type of electrically operated circuit-breaker
- two sets of each type of indicating lights, fuses, LEDs etc
3.6.1.8 TOOLS AND INSTRUMENTS :
Provide tools and instruments required for routine inspection and maintenance and testing of circuit breakers and protective devices as appropriate for type of switchgear supplied
3.6.1.8 APPROVED MANUFACTURES:
Obtain main distribution board from one of the following:
ABB (Egypt (
Schnider Group (Egypt
PART 2 MAIN DISTRIBUTION BOARDS AND ACCESSORIES
3.6.2.1 GENERAL REQUIREMENS
Main distribution boards are to be dead-front type, metal enclosed, multi cubicle, floor mounted, free standing, 600V class of service switchboards, with draw-out switchgear manually and electrically operated, as shown on the single line diagram, with matching vertical sections to form a continuous integral and rigid structure.
3.6.2.2 GENERAL CONSTRUCTION:
Rigidly framed and bolted with electro-galvanized sheet steel enclosures, minimum thickness 2 mm, phosphatized, primed with rust inhibiting primer and finished with thermal polymerized polyester epoxy powder coating, grey color (RAL 7703 or ANSI 61) to approval.
Switchgear is to be vermin, dust and rodent proof, with IP31protection to IEC 144 for indoor installations, and is to have adequate lifting means and base-frames and be capable of being moved and rolled into position and directly bolted to floor without additional sills.
3.6.2.2.1. VENTILATION:
Compartments are to be ventilated, where required, by approved methods complying with the Standards.
3.6.2.2.2 FASTENINGS:
Between structural members are to be bolted.
3.6.2.2.3 EXTENSION:
Of structure and busbars is to be possible at either end of switchboard.
3.6.2.2.4 ARRANGEMENT:
Is to permit incoming and outgoing busbars and cables to enter enclosure as indicated on the Drawings and connect at respective terminals without inconvenience to installation or maintenance.
3.6.2.2.5 REMOVING CIRCUIT BREAKERS:
Suitable arrangements and equipment are to be provided for extracting, lifting and unloading switchgear from enclosures as appropriate for type of switchgear.
3.6.2.2.6 SPARE AND SPACE POSITIONS:
Are defined as follows:
spare position : fully equipped enclosure switchgear
space position : fully equipped enclosure ready to receive switchgear.
3.6.2.2.7 BUSBARS:
To be site rated for normal current as shown on the Drawings with 10% higher than main circuit breaker frame size, and braced for a symmetrical rms short-circuit duty equal or higher than main circuit breaker duty, for one second, unless otherwise specified or shown on drawings. Busbars are to be copper of sufficient size to limit temperature rise to the allowable insulation or equipment temperature ratings in contact, and to a maximum of 40 deg. C above an average ambient temperature of 40 deg. C outside enclosure. Connections and bus work are to be bolted with copper alloy hardware, and are to be accessible for inspection and maintenance. Contact surfaces are to be electro-silver plated.
3.6.2.2.8 CONNECTIONS:
From busbar to switchgear are to be rated to carry full continuous current rating of switchgear frame and are to be insulated.
3.6.2.2.9 FULL SIZE NEUTRAL:
Is to be continuous through all sections. Neutral bus is to be insulated and separate from earth bus and connected to it with removable links.
3.6.2.2.10 EARTH BUS:
To extend full length of board, firmly fixed to each section in accordance with the Regulations and Standards, complete with two main earthing lugs; one at each end, and the required number of feeder protective earth connectors.
3.6.2.3 SWITCHBOARD TYPE:
Switchboard(s) to be of the following type(s):
- Front and\or rear accessible aligned with fixed or with drawable main circuit breaker section (CB type as shown in schedules) and fixed group mounted MCCB distribution section(s).
3.6.2.4 WITHDRAWABLE METAL ENCLOSED CIRCUIT BREAKER SECTION:
Is to consist of compartmented unit(s), stationary part with rear busbar and cable connection compartments and front draw-out circuit breaker assembly. Partitions between sections are to be bolted steel plate. Partitions between compartments are to be tough solid insulating removable bolted barriers. Each unit is to have a hinged lockable front door with grip-handle and door mounted instrumentation.
3.6.2.4.1 DRAWOUT CIRCUIT BREAKER ASSEMBLY:
Is to be equipped with disconnecting contacts, wheels and interlocks to prevent connecting or disconnecting circuit breaker when in the 'open' position, and closing circuit breaker while racking into any of the three positions; connect, test, disconnect. Racking mechanism and rail assemble are to be an approved worm and lever mechanism. It is to be possible to close the unit door with breaker in any of the three positions and when removed. An external position indicator is to be provided. Fixed disconnecting primary contacts are to be accessible and replaceable from the front and are to be silver plated copper. Moving primary disconnect contacts are to consist of self-aligning silver plated spring pressure finger-cluster copper contacts fitted on line and load studs of circuit breaker.
3.6.2.5 FRONT ACCESSIBLE FIXED GROUP-MOUNTED MCCB DISTRIBUTION SECTIONS:
Are to rear align with main section(s) and be of uniform depth, with all devices removable from the front, and mounted on a panel board type base. Construction is to allow all connections and maintenance to be made without rear access. Cables are to be accommodated in extra wide vertical gutters. Sides, top and rear are to be covered with removable screw-on plates having formed edges all around. Front plates are to be sectionalized and removable, covered by trims, and secured by self-tapping screws.
3.6.2.6 AIR CIRCUIT BREAKERS (A .C. B. )
(A TYPE ) :
Encased in high strength, high temperature resistant, molded plastic insulating materials, for continuous normal operation at 100% rated current at ambient temp. 40oC outside the Panel All should be category B as per IEC 947-2 to allow max. selectivity. Manually operated for normal functions, automatically tripped under over current conditions. Trip power is to be derived from main power circuit, with sufficient tripping energy to reliably trip circuit breaker. Fixed mounted circuit breaker is to be rear connected.
3.6.2.6.1 CONSTRUCTION:
Manually or manually and electrically operated, as shown on the single line diagram, with two-step spring charged stored energy mechanism, quick- make, quick-break type, electrically and mechanically trip-free operation to prevent maintaining circuit breaker closed against over current condition whether under manual or automatic operation. Electrically operated circuit breakers are to have integrally mounted, spring charging motor mechanism. Both manually or manually and electrically operated circuit breakers are to have mechanical built-in charging lever and are to include open and close direct acting push buttons. Stored energy provision is to allow open-close-open sequence of operation without use of external energy. As safety feature is to allow discharging stored energy without closing circuit breaker.
3.6.2.6.2 RATING:
For breaker higher than 1600A frame size as shown in SLD 3P, 600V, with continuous current rating as shown on the single line diagram.(SLD) Breaker are to be rated for symmrical rms service S.C breaking capacity = 100% of the ultimate S.C B.C. as per EC 947.2.
3.6.2.3.6 TRIP UNIT:
To be totally enclosed, solid state device, measuring true r.m.s values ,interchangeable for compatible frame sizes, pluggable into front of circuit breaker, tamper-proof and with transparent, sealable cover. Trip unit is to be direct-acting trip device, current transformer operated, with flux transfer shunt trip that requires no external power. It is to have adjustable ampere setting (0.5 - 1.0 times sensor rating) with adjustable long-time delay, short-time pick-up and short-time delay, earth-fault pick-up and time delay and over-ride instantaneous discriminator. Current setting range is to be by replaceable elements within the maximum frame size rating. Once removed, circuit breaker is to remain in the trip-free position. Earth-fault trip is to be adjustable, range up to maximum of 1200 A, with adjustable time delay between 0.1 and 0.5 seconds. Short time delay is to be adjustable in steps, 2 - 10 times sensor rating, with settable or adjustable time band having maximum fixed delay of 0.2 seconds. Selective over-ride protection is to allow full sensitivity up to interrupting capacity of circuit breaker.
3.6.2.6.4 POSITION INDICATORS:
To be positive with trip indication target. Target indicator is to be mechanical and is to give indication even when control power has been lost.
3.6.2.6.4. CIRCUIT-BREAKER ACCESSORIES:
Are to include the following: -
Padlocking or key locking provisions for all positions disconnected, test, and connected, closing blocking, open
- Overload, short-circuit, ground fault trip LEDS
- Trip indicator and reset button
- see single line diagrams.
AUXILIARY CONTACTS:
To include N.O. and N.C. contacts on switchgear as required, plus three N.O. and three N.C. spare contacts
3.6.2.6.5 MOULDED CASE CIRCUIT BREAKERS MCCBs:
Are to be generally of the thermal-magnetic adjustable type for ratings below 250- 630 A frame size unless otherwise indicated on the Drawings. MCCBs 800 A and larger are to be electronic solid-state trip type with true r.m.s short circuit.
3.6.2.6.5.1 CONSTRUCTION:
Totally enclosed molded case, constructed from high quality, high temperature resistant, tropicalized molded insulating materials, for continuous normal operation at 100% rated current at ambient temp 40 oC outside the enclosure, provided with quick make, quick-break, trip-free switching mechanism, manually operated by front toggle type handle and automatically tripped under over current conditions. Multi-pole breakers are to have a common integral trip bar for simultaneous operation of all poles. Contacts are to be non-welding silver alloy with arc quenching metallic devices of approved construction. Cable terminals are to be anti-turn box lug or clamp type with set screws.
Circuit breakers are to include on each pole a bi-metallic inverse time-delay over current trip element for small overloads and instantaneous magnetic over current trip elements for operation under short-circuit conditions. Circuit breakers 250 A
3.6.2.6.5.2 THERMAL MAGNETIC:
frame size and larger are to be equipped with adjustable instantaneous trips.
3.6.2.6.5.3 THERMAL OVERCURRENT TRIPS:
Are to be ambient temperature compensated to allow for ambient temperature higher at breaker than at protected circuit or device. Compensation is to be applicable between 25 and 50 deg. C. In case of adjustable thermal settings, range of adjustment is not to exceed maximum trip rating shown on the Drawings.
3.6.2.6.5.4 ELECTRONIC TRIPS:
For circuit breakers 800 A frame size and larger, are to have solid state trip units with long time delay settings at least between 0.4 and 1.0 times maximum trip rating, short time delay range of 2 to 10 times maximum trip rating with a maximum clearing time of 0.2 seconds, and instantaneous protection adjustable from 5 to 10 times continuous rating. Solid state trip units are to be insensitive to changes in ambient temperature
Between -20 and +55 deg. C. Earth fault protection is to be added to the trip unit where specified, and is to be adjustable between 0.2 and 0.6normal phase current pick-up with maximum time delay of 0.2 seconds, and is to be suitable for connection to an external current sensor. Push-to-trip button is to be provided on cover for testing the trip unit.
3.6.2.6.5.5 TRIPPED POSITION:
When tripped automatically by over current condition, operating mechanism of circuit breakers are to assume an intermediate position clearly indicated by the handle between ON and OFF positions.
3.6.2.6.5.6 INTERCHANGEABLE TRIPS:
All circuit breakers are to have interchangeable trip units.
SEALING:
Non-interchangeable trip circuit-breakers are to have sealed covers. Circuit-breakers with interchangeable trips are to have trip unit covers sealed to prevent tampering.
3.6.2.6.5.6 CIRCUIT BREAKER RATINGS:
Breakers are to be non-limiter type and to be rated for symmetrical r.m.s service short circuit breaking capacity 100% of the ultimate short circuit breaking capacity as per IEC-947-2.
3.6.2.6.5.7 ACCESSORIES:
Circuit-breakers are to be designed to accommodate electrical operator, control and interlocking functions, under-voltage release, shunt-trip coils, alarm and auxiliary switches, padlocking devices, key-lock devices, and are to be equipped with such accessories as required on drawings.
3.6.2.7 METERING INSTRUMENTS
3.6.2.7.1 GENERALLY:
Instruments are to be housed in enameled, square, metal cases for flush installation with scales and markings protected and sealed. Accuracy of instruments is to be within 2% unless otherwise specified.
3.6.2.7.2 VOLTMETERS:
Moving iron type, with centre zero adjuster, range 1.25 times nominal system voltage, 90 deg. angle, size 760 x 760 mm.
3.6.2.7 .3 VOLTMETER SELECTOR SWITCH:
7-position rotary type.
3.6.2.7 .4 AMMETERS:
Moving iron type, with center zero adjuster, of range 2 times nominal circuit amperage, 90 deg. angle, size 760 x 760 mm.
3.6.2.7.5 AMMETER SELECTOR SWITCH:
4-position rotary type.
3.6.2.7.6 CURRENT TRANSFORMER (CT) :
Indoor dry type, rated secondary current 5 A. Rated primary current, core size and accuracy are to be determined in accordance with nominal current of plant protected, short-circuit level and burden.
3.6.2.7.7 VOLTAGE TRANSFORMER (VT):
Provide VT's where required, complete with primary and secondary fuses and disconnecting device.
3.6.2.8 WIRING
3.6.2.8.1 ARRANGEMENT:
Wiring is to be modularly and neatly arranged on master terminal boards with suitable numbering strips and appropriate cartridge type fuses where required.
3.6.2.8.2 CONNECTIONS:
Are to be made at front of terminal board and with no live metal exposed.
3.6.2.8.3 METAL CASES:
Of instruments, control switches, relays etc. are to be connected, by bare copper conductors not less than 2.5 mm2 section, to nearest earthing bar.
3.6.2.8.4 CONTROL WIRING:
PVC insulated 85 deg. C. 600 V grade, and PVC sheathed for multi-core cables.
3.6.2.8.5 FERRULES:
Wires are to be fitted with numbered ferrules of approved type at each termination.
3.6.2.9 MISCELLANEOUS
3.6.2.9.1 ANTI-CONDENSATION HEATERS:
Are to be provided in switchboard with disconnect switch and pilot lamp.
3.6.2.9.2 SCHEMATIC AND WIRING DIAGRAM:
Is to be provided suitably located within each cubicle.
PART3 FIELD AND INSTALLATION WORK
INSTALLATION
3.3.6.1 EQUIPMENT BASES:
Ensure that concrete bases and foundations provided for installation of equipment are constructed in accordance with the approved shop and construction drawings and equipment manufacturers' drawings and that holes for fixing bolts and provisions for passage of cables etc. are provided as required.
3.3.6.2 BUILT-IN ITEMS:
Ensure that equipment supports, fixings and the like, and sleeves for passage of feeders and cables which are to be built into concrete foundations, bases, cable trenches or building structure are provided as and when required and that they are properly installed.
3.3.3.6 INSTALL EQUIPMENT:
On concrete bases etc., and assemble completely plumb and level, before grouting in holding-down bolts.
3.3.6.4 SUPPORTS AND TERMINATIONS:
Install all incoming and outgoing cable supports, cable ends and termination fittings required for power and control cables.
3.3.6.5 SET RELAYS:
In accordance with manufacturer's instructions and in accordance with an approved scheme.
3.3.6.6 MAKE GOOD:
Damaged painted surfaces, clean and apply rust-inhibiting prime coat and two finishing coats of approved enamel upon delivery of equipment to site and as required by the Engineer.
PART4 INSPECTION AND TESTS ON SITE
3.6.4.1 INSPECT EQUIPMENT:
Upon delivery to Site and report any damage to the Engineer.
3.6.4.2 INSPECT AND CHECK SWITCHGEAR:
For completeness, component ratings, types, sizes, and wiring connections. Check phasing of busbars, contacts and clearances.
3.6.4.3 TESTS:
After installation and before handover, carry out all tests required by the governing codes and any other tests the Engineer may require to check compliance of the installation with the Specification, including insulation resistance tests and operational tests.
3.6.4.4 CHECK MAIN AND CONTROL CIRCUITS:
Using 1000 V megger (2000 M-ohm range) for insulation resistance between phases, between phases and earth/enclosure and between neutral and earth.
3.6.4.5 PRIMARY INJECTION TESTS:
Provide portable test equipment to test time-delay characteristics of circuit-breakers by simulating an overload or fault condition. Measure and record all test results and ambient conditions and compare with manufacturer's data.
3.6.4.6 TEST INSTANTANEOUS TRIP ELEMENTS:
By high current primary injection, using high-current primary injection test-sets and report all readings.
3.6.4.7 FUNCTION TEST
Applying the electrical function test including the electrical and mechanical operation in the specification and show in the single line diagrams.
PART 5 MAINS FAILURE AUTOMATIC TRANSFER SWITCH (ATS)
Type wall or floor mounted, galvanized sheet steel cubicle of equal construction to control cubicle, comprising circuit breakers, controls necessary for automatic transfer of power supply from normal source to stand-by source, voltage sensing control relay and time delay relays to signal generator start and stop, auxiliary switches and indicating lights etc. as necessary for the required operation shall be mechanically head type. The interlock should be electrically & mechanically.
OPERATION:
When the voltage and/or frequency of any phase drops below an adjustable setting (60% - 90%) of normal supply, for an adjustable period of 1 - 300 seconds, power failure relay is to actuate engine starting control, whilst normal mains C.B is to open. After an adjustable period (0 - 10 sec) from sensing stabilized rated voltage and frequency of generator at the ATS, the emergency C.B is to close. Upon restoration of normal mains supply to above 95% of rated volt age and/or frequency, for an adjustable preset period of 2 - 10 minutes, emergency C.B. is to open and normal mains contactor is to close.
SELECTOR SWITCH:
Is to have the following positions:
Off : both C.B.S open and remain open
Normal : C.B.S for normal power source closes and remains closed emergency : contactor for stand-by power source closes and remains closed
Auto : automatic transfer as described above
PILOT LIGHTS:
Are to indicate which C.B is on
.
INSTRUMENTS:
Are to include voltmeter and ammeter with selector switches.
WIRING:
Moisture and heat resistant, PVC insulated, stranded copper conductors, modularly and neatly arranged and terminated on master terminal blocks with suitable numbering strips and appropriate cartridge type fuses where required. Flexible wiring is to be used on all hinged/draw-out components METAL CASES: Of instruments, control switches, relays etc. are to be connected by flexible protective conductors, of not less than 2.5 mm2 section to nearest earthing bar or terminal.
EARTHING:
Earthing bar is to be provided for connection of earthing and protective conductors.
FERRULES:
Wire ends are to be fitted with numbered ferrules of approved type at each termination
SPECIFICATION FOR VARIABLE SPEED DRIVE
NOT INCLUDED IN THIS CONTRACT
The variable speed drive shall be used to vary the speed and therefore the flow of the domestic water pumps.
The motor speed variation shall be performed by varying the frequency and voltage. The driving law shall be specially adapted to match the motor available
Torque with the pump torque characteristics (quadratic torque law). Three adjustable skip frequencies shall be available in the speed drive to prevent operating the pump at speeds where mechanical resonance occurs. The variable speed drive controls shall be carried by using 24V static inputs for the logic signals and 0-10V or 4-20 mA for the analog signals.
Alarm signals shall be on a voltage-free relay contact withstanding switching inductive loads of 1,5 A under 250 Vac. Inputs and outputs shall be user configurable to allow for various control schemes to be used. The frequency set point accuracy shall be of 0.05 Hz for 50Hz set point. The analogue outputs shall be configurable 0-20 mA or 4-20 mA with an accuracy of + 0.5% full scale and linearity + 0.1%.
Protections:
The variable speed drive shall be capable of protecting itself and the
Motor against:
Motor overload
Motor phase failure
Internal short-circuits
Phase to phase and phase to ground
Variable speed drive overheating
Loss of supply phase
Supply over voltage and under voltage
Internal short circuits in the Variable Speed Drive.
Performance:
The Variable Speed Drive
the motor nominal current for a period of 60 seconds. The Variable Speed Drive
Environment: The Variable Speed Drive
The variable speed drive shall withstand vibrations and shocks as per IEC 68- 2-6 and IEC 68-2-27.
End Of this Section
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