L V CIRCUIT BREAKERS
PART 1 -GENERAL
1.01 RELATED DOCUMENTS:
A. Drawings and general provisions of Contract, including General and
Supplementary Conditions and Division-1 Specification sections, apply to
the work of this section.
B. Division-16 "Basic Electrical Materials and Methods" and other sections
apply to work of this section.
C. Division-16 "Switchboards" and "Panelboards" sections.
D. Division-16 "LV Wires and Cables" Section, work required in conjunction
with CB protective devices; not work of this section.
1.02 SUMMARY:
A. Extent of Low Voltage (L V) circuit-breaker ( CB ) work is indicated by
drawings and schedules.
B. Types of circuit breakers in this section include the following:
1. Power Air Circuit Breakers, (P ACB's).
2. Moulded case circuit breakers (MCCB's).
3. Miniature Circuit Breakers (MCB's).
4. Moulded case switch (MCS)
1.03 SUBMITTALS:
A. Product Data: submit manufacturer's product data including frame size
(continuous Current rating), short circuit interrupting ratings, special and
regular ) features of mounting, trip rating and illustrated relay features etc. as
required '- by the Engineer and installation instructions for each type of
circuit breaker.
B. Wiring Diagrams: submit wiring diagrams for circuit breakers and
accessories showing connections to electrical power feeders and associated
equipment. Differentiate between portions of wiring which are
manufacturer-installed and portions which are field-installed.
C. Certification: submit certified type test and routine factory test data, which
indicates current-interrupting ratings for each circuit breaker.
D. Protection coordination: submit complete network study showing proper
selection of circuit breakers characteristic time-current curves that will
achieve discrimination under fault conditions between downstream and
up-stream circuit breakers to and including Power Company's source
protection at the substations.
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1.04 QUALITY ASSURANCE:
A. Manufacturer's Qualifications: firms regularly engaged in manufacture of
circuit breakers of types, ratings, and capacities required, whose products
have been in satisfactory use in similar service for not less than 5 years.
B. Installer's Qualifications: firm with at least 3 years of successful installation
experience on projects utilizing circuit-breaker devices similar to those
required for this project.
E. Codes and Standards:
1. Electrical Code Compliance: comply with applicable local electrical code
requirements of the authority having jurisdiction, as applicable to
construction and installation of circuit breakers.
2. IEC Compliance: comply with IEC 947-2 for power and molded-case
circuit breakers, and IEC 898 for miniature circuit breakers.
3. Testing Laboratory Compliance: comply with applicable Testing
Authority: requirements in country of origin, which apply to construction
and installation of circuit breakers of types specified.
1.05 DELIVERY STORAGE AND HANDLING:
A. Deliver circuit breakers and components in factory-fabricated type containers
or wrappings, which properly protect devices from damage.
B. Store circuit breakers in original packaging and protect from weather and
construction traffic. Wherever possible, store indoors; where necessary to
store outdoors, store above grade and enclose with watertight wrapping.
C. Handle circuit breakers carefully to prevent physical damage to CBs and,
components. Do not install damaged CBs; remove from site and replace
damaged devices with new.
PART 2- PRODUCTS
2.01 MANUFACTURERS:
A. Available Manufacturers: subject to compliance with requirements,
regulations, specification, and drawings.
2.02 CIRCUIT BREAKERS:
A. General: except as otherwise indicated, provide circuit breakers and ancillary
components, of types, sizes, ratings and electrical characteristics indicated,
which comply with manufacturer's standard design,. materials, components,
.and construction in accordance with published product information, and as
required for a complete installation which shall be subject to approval or
rejection of the Engineer.
B. Power Air Circuit Breakers (PACBs) , Insulated Case.
1. Type: encased in steel structure, air ventilated, air break for normal
operation at maximum temperature within enclosure at point of
application, tested to approved standards. manually operated :or normal
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functions, and 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.
2. Construction: manually and electrically operated, as shown on the
Drawings, with two-step spring charged, stored energy mechanism,
quick-make, quick break type, electrically and mechanically trip-free, 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 automatically recharged upon closing. 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
Safety feature is to allow discharging stored energy without closing
circuit breaker. Circuit breaker is to have arc quenching device on each
pole and replaceable arcing contacts.
3. Control power for electrically charged, CB and/or for shunt and
undervoltage trip devices, where required, is to be l20V ac obtained from
in-built MDB control power transformer, connected and fused on
bus-side.
4. Rating: 3 or 4 pole, 750V rated insulation voltage 600 V rated operational
voltage, with continuous current rating (frame size) as shown on the
Drawings, ranging between 400 A and 4000 A (400, 800, 1200, 1600,
2000, 2500 3000, and 4000 A), fully rated (100%) for service under worst
- site conditions. Breakers are to be rated for a symmetrical rms service
short-circuit breaking capacity as shown on the Drawings, to IEC 947-2,
sequence II (rated service short-circuit breaking capacity) at specified
voltage and frequency, to meet IEC 947- 2, sequence I, II, III and IV tests,
utilization category B, tested in an enclosure substantially the same as the
enclosure in which they are to be installed.
5. Trip unit: to be totally enclosed, programmable, solid state device,
interchangeable for compatible frame sizes, pluggable into front of circuit
breaker, tamper-proof and with transparent, sealable cover. Trip unit is to
measure sinusoidal and non- sinusoidal current wave forms (fundamental
to thirteenth harmonic) by continuously sampling each phase through out
every cycle. 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 current setting (0.5 -1.0 times trip unit rating) with
adjustable long-time delay, short-time pick-up and short-time delay, earth
fault pick-up and time delay instantaneous over current pick-up. Current
setting range is to be by means of replaceable trip-units 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 10% to
60% of normal current rating of the circuit breaker and a maximum of
1200A, with adjustable time delay between 0.1 and 0.5 seconds. Short
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time delay is to. be adjustable in steps, 2 -9 times current setting, with
pre-settable or adjustable time band having maximum delay of 0.3 to 0.5
seconds. Instantaneous trip is to be adjustable in steps at least 2 -13 times
the trip unit rating. Over-ride protection is to allow full sensitivity up to
interrupting capacity of circuit breaker.
6. Trip Unit Status Display: is to indicate in words the status of normal
breaker operation, long time over current pick up, instantaneous time over
current trip, short time over current trip, ground fault trip. Unit shall have
integral resetabel counter to count long time, short time, instantaneous
and ground fault trips.
7. 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.
8. Circuit breaker accessories are to include the following:
a. padlocking or keylocking provisions for all positions (disconnected, test,
connected, closing blocking, open).
b. overload, short-circuit, ground fault trip LEDS.
c. trip indicator and reset button .
d. operations counter e.
e. on/off pilot lights
f. shunt trip coil and colsing solenoid for remote control.
9. Auxiliary Contacts: to include N.O. and N.C. contacts on switchgear as
required, plus 2 N.O. and 2 N.C. spare contacts.
10. Trip Unit: is to have inputs from conventional potential transformers for
every phase. Current sensors transformers for every phase. Current
sensors shall be encased in epoxy filled plastic housing to protect against
damage and moisture and shall be integrally mounted in breakers.
11. Neutral Current Transformer: is to be provided on the neutral conductor
of each main, tie or outgoing circuit having earth fault protection. Rating
and characteristics of the neutral current transformer are to be suitable for
proper operation of the earth fault protection system.
12. Electrical Interlock: if electrical interlock is required between power air
circuit breakers, the mechanical closing button of the circuit breaker is to
be disabled in the connect position and an additional electrical push
button is to be provided for closing of the circuit breaker through the
breaker's shunt close coil. The electrical interlock is to be provided on
both the shunt trip and close coils of the circuit breaker through key
system in order to perform simultaneous tripping and inhibit closing
functions on the interlocked breaker.
C. Moulded Case Circuit Breakers (MCCBs):
1. Type: totally enclosed, moulded case, constructed from high quality, high
temperature resistant tropicalized, moulded insulating materials designed
for normal operation at 70°c within enclosure to approved standards,
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provided with quick-make, quick break, trip free switching mechanism,
operated by front toggle type handle mechanism for manual operation of
main contacts in addition to automatic operation under overcurrent
conditions. Tripping to be indicated by handle automatically assuming a
middle position between manual on and off positions. Multi-pole breakers
are to have common integral trip bar for simultaneous operation of all
poles. Ampere rating is to be clearly visible. All terminals are to be box
lug or clamp type with set screws, suitable for copper or Aluminum
conductors contacts. Contacts are to be non-welding silver alloy with arc
quenching metallic .devices of approved construction. Cable terminals
are to be solder less anti-turn box lug or clamp type with set screws
suitable for copper or aluminum cables
2. Circuit Breaker Trip Units: unless otherwise specified or shown on the
Drawings, circuit breakers below 400 A frame size, are to be non-current
limiting thermal-magnetic type, having bi-metallic inverse time delay,
overcurrent element for small overloads and instantaneous magnetic
overcurrent trip element for operation under short-circuit conditions on'
each pole. Circuit breaker 160 A and larger are to have adjustable.
Instantaneous trips. Circuit breakers 400 A and larger are to have
electronic trip unit.
3. Switching Mechanism: quick-make, quick-break type, with positive
trip-free operation so that contacts cannot be held closed against excess
currents under manual or automatic operation. Contacts are to be nonwelding
silver alloy with approved arc-quenching devices of metallic grid
construction.
4. Thermal overcurrent trips are to be compensating type to allow for
ambient temperature higher at breaker than at protected circuit or device.
Compensation is to be applicable between 25 and 55 deg. C. In case of
adjustable thermal settings, range of adjustment is not to exceed
maximum trip rating shown on the Drawings/Schedules.
5. Trip current rating (Amps) indicates nominal maximum rating at which
overload element is set to operate.
6. MCCB's For MDBs: non-current limiting, type, 750 V rated insulation.
voltage, 600V.a.c. and 250V dc. rated operational voltage, utilization
Category B, fully rated ( 100% ) with continuous duty at site conditions,
and with frame size and interrupting capacity to IEC 947-2, sequence II
(rated service short-circuit breaking capacity), and maximum trip rating
as shown on Drawings. Circuit breakers at specified voltage and
frequency are to meet IEC 947-2 test sequences I, II, III and IV. Frame
sizes. normally selected are to be in accordance with Tables at end of this
section of the Specification, with Service short circuit capacities at 50%
of indicated ultimate breaking capacities.
7. MCCB's application for LPs, PPs & DP's are to be of same characteristics
as described above for the MCCB's for MDB's, except their short circuit
interrupting capacity which is to be in compliance with Sequence III to
IEC 1: 947-2 (ultimate .rating). Preferred ratings of MCCB s are as shown
In the tables at end of this section.
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8. Tripped Position: when tripped automatically by overcurrent condition,
operating mechanism of circuit breaker is to assume an intermediate
position clearly indicated by the handle between on and off positions.
9. Interchangeable Trips: circuit breakers 250 A frame and larger are to
interchangeable trip unit type.
10. Sealing: circuit breakers with non-interchangeable trip units are to be
sealed. Circuit breakers with interchangeable trip units are to have trip
unit covers sealed to prevent tampering.
11. Electronic trip units, applicable to circuit breakers 400 A frame size and
larger, are to be solid state with long time delay settings between 0.5 and
1.0 times maximum trip rating, short time delay range of 3 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
built into trip unit where specified, adjustable between 0.2 and 0.6 of
normal phase current pick-up with maximum time-delay of 0.2 seconds,
with integral current transformers. Push-to-trip button is to be provided
on cover for testing the trip unit.
12. Accessories: circuit breakers are to be designed to accommodate standard
attachments including shunt-trip, under- voltage release, combined
auxiliary and alarm switches, and electrical operator to any circuit breaker
of rating (frame size) l00 A and over. Padlocking and key-lock devices
are to be provided where shown on the Drawings.
13. Residual Current Operated Earth Leakage Trip Devices (RCDs): provide
add-on or built-in earth leakage accessories, where required and as shown
on the Drawings. Protection against earth leakage current, in addition to
overcurrent and short-circuit protection, is to be in accordance with the
Regulations. Trip current sensitivity on breakers for branch circuits is to
be 30 mA maximum; and for main breakers trip ratings are to be as shown
on the Drawings or as specified in Section Earth-fault Protection “Circuit
breakers are to include current transformer with tripping coil assembly,
test button and trip free mechanism to ensure circuit breaker cannot be
held closed against earth faults.
D. Miniature Circuit Breakers (MCBs)
1. Type: thermal magnetic non-adjustable type, tested in accordance with
IEC 898 or BS3871,Part l.
2. Voltage Rating: 440 V rated insulation voltage and 250 rated operational
voltage.
3. Minimum Short-Circuit Breaking Capacities are to be as follows:
100 A MCB : 10, 15 kA 20 or 25 kA at 230/400 V a.c. as required in the
panelboards schedule drawing
4. Construction: MCB's are to be tropicalized for operation at ambient,
temperatures up to 70 deg. C within panelboard enclosure and humidities
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up to 100%, and are to be constructed from high quality , high
temperature, moulded insulating materials. Guaranteed duties and
characteristics are to be submitted for temperatures above 40 deg. C.
MCBs and combinational devices are to be modular, of unified profile
and mounted to a standard DIN rail.
5. Operation: under overload conditions, thermal tripping is to provide close
protection of insulated conductors. Under short-circuit conditions,
magnetic trip is to operate at 5 -10 times normal rated current (type 3
characteristic) unless otherwise indicated. .Magnetic operation is to be in
the current limiting region and opening time is not to exceed 5 milliseconds.
6. Ratings: preferred rated currents are to be 6, 10, 10,20,25, 32,40, 50,63,
80 and l00 A, calibrated at 45 deg. C, available as 1, 2, 3 and 4-pole circuit
breakers. Derating above 45 d.eg. .C is not to exceed 1% per deg. C, and
loading is not to exceed 70% of circuit breaker rating.
7. Residual current devices for earth leakage protective circuit breakers may
be add-on devices, or built-in and integral with the standard miniature
circuit breaker. Non-adjustable sensitivities of 10 mA, 30 mA, 100 mA
and .300 mA are to be available for all ratings of 2-pole and 4-pole circuit
breakers.
8. Auxiliaries, where required or shown on the Drawings, are to include
alarm switch, auxiliary switch, shunt trip, under voltage trip and similar
units which are to be modular additions to the circuit breakers.
E. Moulded Case Switch (MCS).
1. Moulded Case Switch: non-automatic on/off switching device of equal
construction to equivalent circuit breaker, having no overcurrent or fault
protective elements, but marked with maximum current withstand and
voltage rating.
F. Motor Circuit-Protector.
1. Magnetic only type circuit breaker with adjustable current sensing trip
coil in each of the 3-poles to provide short circuit protection, manually
operated for normal switching functions and automatically operated
under short circuit Conditions.
2. Motor Circuit Protector: to be a recognized component under UL 489
and comply with the applicable requirement of IEC 947-2.
3. Rating is to be 750V rated insulation voltage and 600V rated operational
voltage with continuous current rating selectable between 3 A and 400 A
as shown on drawings. fully rated for service under worst site conditions
and with trip settings between 3 and 10 times continuous ratings. Motor
circuit protectors to be rated for a service short circuit breaking capacity
as required at the motor control centre. Back-up fuses may be added for
short circuit protection; coordinated with the magnetic trip element to
effect tripping of all poles of the circuit breaker, where short circuit
currents are above the normal magnetic tripping range indicated. Fuses
are to be of the current limiting type.
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2.03 CONTACTORS AND REMOTE CONTROL RELAYS:
A. GENERAL
1. Mechanically or magnetically held with contacts normally open or normally
closed and/or combination required.
2. Rated for continuous operation with capacities and voltage at 50 Hz, as
indicated on drawings or required.
3. Spring loaded contacts to maintain contact pressure in closed position,
readily replaceable, self-aligning type.
4. Suitable for inductive or non-inductive loads, unless otherwise noted.
5. With arc shields and magnetic blow coils if interrupting duty exceeds 300
ampere.
6. Interrupting capability not less than six times rated full load current.
7. Operating coils voltage: 220 Volts, unless otherwise noted.
B. Mechanically held contactors
1. Single and/or dual coil operation.
2. Positive locking type without the use of latching hooks or magnets.
3. With a manual operator for hand operation giving positive indication of
contactor position.
4. Control Circuit: For 3-wire operation with momentary contact open/close
stations as indicated or required.
2.04 MULTIPLE POLE RELAYS
A. Electrically operated, mechanically held type, with 10 amperes minimum rated
contacts (unless otherwise indicating or required).
B. Open and close coils rated 220 volts or 380 volts, 50 Hz, unless otherwise
indicated or required.
C. Number of poles as indicated on drawings or schedules.
2.05 CENTRALIZED EMERGENCY SYSTEM (CES)
A. The centralized emergency system shall be a computerized system for the
control of self-contained emergency exit luminaries via a periodically and
automatically testing the luminaries system efficiency.
B. The system shall be remotely controlled using PC and printer and shall be
linked to the BMS.
C. The system shall include a microprocessor unit to perform the following:-
- Control system operation.
- Controls programmed events.
- Tests operation of lamps.
- Tests operation of control circuits.
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- Record data and events.
- Charging/Discharging status.
D. The microprocessor unit shall include a set of batteries to allow it to continues
running the system during the electricity failure (black –out).
E. The system shall check the autonomy of the luminaries corresponds to their
rated autonomy.
2.06 INSTRUMENTS
A. GENERAL REQUIREMENTS
1. All electrical indicating instruments shall be the product of a single
manufacturer.
2. All ammeters and voltmeters shall be digital type.
3. All instruments shall be flush mounted.
B. COMMON SPECIFICATIONS
1. STANDARD IEC 60051.
2. ADMISSIBLE OVER LOADS
a. Voltage : 1.2 rated Voltage Continuously
-2 rated voltage For 2 seconds
b. Current -2 in continuously
- 10 in for 10 seconds.
- 40 in for 2 seconds
3. DIELECTRIC STRENGTH: 2 KV.r.m.s. for 1 min
4. OPERATING TEMPERATURE : - 10OC to 60OC
5. DIGITAL PANEL METERS
Consists of:
a. 3 ½ DIGIT SERIES Display for Ammeters and 3 ½ DIGIT for Ammeters
and Frequency meters.
b. ANALOG SECTION:
The conversion between the magnitude to be measured and the input to
the digital section made from high accuracy components.
c. DIGITAL SECTION:
An analog/digital converter is used with dual slope integration and
automatic zero correction and shall have thermal stability from 0 to 60OC
and Linearity error is under 0.05%
d. DIMENSIONS
For all shall be (96x48mm).
C. AMMETER AND VOLTMETER SWITCHES
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1. On 3-phase, 5-wire system, ammeter switches shall have four operating
positions marked 'R', 'Y', 'B' and 'N', and an 'OFF' position, and shall
enable the single ammeter to read, in sequence, the currents in each of the
three operating positions marked 'R', 'Y' and 'B' and an "OFF" position.
Ammeter switches shall be connected so that the associated current
transformers are short-circuited when they are not connected to the
ammeter.
2. On 3-phase, 5-wire, systems, voltmeter switches shall have six operating
positions, marked 'R', 'Y' , 'Y-B', 'B-R'-'R-N','Y-N'-'B-N', and an 'OFF'
position, and shall enable the single voltmeter to read, in sequence, each
of the three line voltages and each of the three phase-to-neutral voltages.
On 3-wire systems, voltmeter switches shall have three operating
positions marked 'R-Y', 'Y-B' and 'B-R' and an 'OFF' position.
3. Voltmeter switches shall have 'break-before-make-contacts.
2.07 CURRENT TRANSFORMERS (CTS)
A. GENERAL REQUIREMENTS
1. All CTs shall have an Accuracy Class Designation according to the
following:
- Tariff metering.
Accuracy Class Designation 0.5.
- Non-tariff metering.
Accuracy Class Designation 1.0.
- Switchgear indicating instruments.
Accuracy Class Designation 1.0.
- Motor Starter ammeters.
Accuracy Class Designation 3.0.
- Protection (over current, UEF).
Accuracy Class Designation 3.0.
- Protection (over current, UEF).
Accuracy Class Designation 10p
- Protection (UEF)
Accuracy Class Designation X
2. Unless otherwise specified in the schedules or drawings, the CTs are
required for use under service conditions not more onerous than those set
out in IEC, standards.
3. CTS shall be designed either for measurement or for protection and shall
not be used in a dual-purpose role serving both instruments and protective
gear.
4. Unless otherwise specified, all CTs shall have 5A secondary windings.
5. So far as it is practicable, all CTs shall be of the ring type. Wound primary
CTs will only be accepted when the rated primary current is so low as to
make the ring type impracticable.
6. One side of the secondary of each CT shall be connected to earth at one
point via a bolted removable link.
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7. For mattering circuits, either, a proprietary front of panel CT test block or
special "shorting" terminals within the panel shall be provided for test
purposes.
8. All CTs whether of the ring type or the wound primary type, for use at
voltages exceeding 1000V shall be epoxy resin encapsulated.
Where dual-ratio CTs are specified, they shall be provided with two
separate secondary windings capable of being connected in series or in
parallel to give the required ratio.
9. All CTs shall be provided with a rating plate bearing the information as
stated in IEC, DIN/VDE standards. All CTs shall be installed in
accessible location. The secondary connections shall be brought out by
means of insulated leads, and made off on a suitable terminal block
–mounted in a readily accessible position.
Magnetization curves and/or type test Certificates shall be provided for
all CTs associated with protection devices.
10. Evey CT shall have a rated burden at least 50% greater than the total
burden of the instruments, relays, and/or other apparatus which is to
serve.
2.08 VOLTAGE TRANSFORMERS
A. GENERAL REQUIREMENTS
1. Voltage transformers shall be of the type, rating, and voltage ratio
specified in the schedules or drawings.
2. All voltage transformers shall have an Accuracy Class Designation
according to the following table:
- Metering : Accuracy Class Designation 1.0
- Switchgear indicating instruments: Accuracy Class Designation 1.0
- Motor starter voltmeters : Accuracy Class Designation 3.0
- Protection : Accuracy class Designation 3P
3. Unless other specified in the schedules or drawings, the voltage
transformers are required for use under service conditions not more than
those set out in IEC, standards.
4. Voltage transformers designed for a primary voltage not exceeding
4000V shall be the air insulated type, with the windings encapsulated in
epoxy resin or other suitable synthetic material.
5. Unless otherwise specified, all voltage transformers shall be designed for
a secondary output voltage of 110V.
6. Each voltage transformer shall have a rated burden at least 50% greater
than the total burden of the apparatus or instruments which it is to serve.
7. The insulation resistance of each voltage transformer shall be indelibly
marked on the shipping/dispatch label.
2.09 DIGITAL MULTI – METER (DMM)
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A. GENERAL
1. DMM is an instrument for measuring and metering electrical values for
three phase, low voltage balanced or unbalanced electrical networks.
2. DMM will has a front panel keys and LCD displays all the parameters and
use the functions provided to measure electrical values and measure
energy consumption.
B. MEASUREMENT:
1. Instantaneous and maximum current over a programmable period (8 to 30
minutes).
2. Phase to neutral and phase to phase voltage.
3. Frequency (HZ).
4. Instantaneous and maximum active power (P) over a programmable period
(8 to 30 min.), reactive power(s).
5. Power factor (PF).
C. ENERGY METERING
1. Active KWH.
2. Reactive KV arch.
D. DMM will be provided with link protocol for using with DEMS.
PART 3 -EXECUTION
3.01 EXAMINATION:
C. Examine areas and conditions under which circuit breakers are to be installed
and evaluate conditions detrimental to proper completion of the Work. Do not
proceed with the Work until unsatisfactory conditions have been corrected in
an acceptable manner.
3.02 INSTALLATION OF CIRCUIT BREAKERS:
A. Install circuit breakers and accessories as indicated, in accordance with
manufacturer's written instructions and with recognized industry practices to
ensure that protective devices comply with requirements. Comply with
requirements of Local Regulations and Standards, and applicable approved or
recommended "Standard of 1nstallation” pertaining to installation of circuit
breakers and general wiring practices.
B. Coordinate with other work, including electrical wiring work, switchboards,
panelboards as necessary to interface installation of circuit breaker work with
other work.
C. Fasten circuit breakers without causing mechanical stresses, twisting or
misalignment being exerted by clamps, supports, or cabling.
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D. Set field-adjustable circuit breakers for trip settings as indicated in
accordance with an approved system coordination scheme, subsequent to
installation of Units.
E. Tighten electrical connectors and terminals, including screws and bolts, in
accordance with equipment manufacturer's published torque tightening
values for equipment connectors. Where manufacturer's torquing
requirements are not indicated, tighten connectors and terminals to comply
with tightening torques of compatible standards.
3.03 ADJUST AND CLEAN:
A. Inspect circuit-breaker operating mechanisms for malfunctioning and, where
necessary, clean and adjust units for free mechanical movement.
3.04 EARTHING
A. Provide equipment earthing connections for circuit breakers as indicated.
Tighten connectors to comply with tightening torques specified in
manufacturers standards or compatible international standards to assure
permanent and effective earthing.
3.05 FIELD QUALITY CONTROL:
A. Upon completion of installation and after circuitry has been energized,
demonstrate capability and compliance of system with requirements. Where
possible, correct malfunctioning units on site, then retest to demonstrate
compliance; otherwise, remove and replace with new units, and proceed with
retesting. Testing and retesting at no cost to Employer.
B. Circuit Breakers: tests are to include operation of every circuit breaker
manually. Check automatic operation of selected circuit breakers, as required
by the Engineer, by applying necessary short-circuit, overload and earth
leakage current for tripping circuit breaker as applicable and compare with
manufacturer's data/characteristic curves. Measure and report ambient.
temperature inside enclosure.
1. Primary Injection Tests: provide primary injection 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.
2. Instantaneous. Trip Elements: test instantaneous trip by high current
primary injection, using high-current primary Injection test-sets and
report all readings.
3.06 MCCB PREFERRED RATINGS:
A. 'Frame size is defined as maximum continuous current rating of circuit
breaker which corresponds with its maximum trip range listed below and
which is to be related to minimum acceptable short-circuit interrupting
ratings, based on fully rated interrupting duties: normal duty (N), high break
(H), or current limiting, (L), as specified/shown on drawings.
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B. Frame sizes are generally to be selected with minimum interrupting
capacities at specified voltages and rated frequency, in accordance with the
following table:
Trip range frame
Size (amperes)
Minimum Symm. Rms rated
breaking capcity (ultimate in KA)
Rating
Volts (a.c.)
N H L
TABLE 1
Thermal-magnetic
16-100 (1P) 14 --- --- 230
16-100 (2,3 P) 25 50- --- 400
16-150 (2,3,4 P) 35 65 100 400
70-250 (2,3,4 P) 35 65 100 400
Electronic
16-400 (2,3,4P) 35 65 100 400
250-400 (2,3,4P) 35 65 100 400
400-800 (2,3P) 40 65 100 400
800-1250 (2,3P) 50 65 100 400
END OF SECTION 16476
PART 1 -GENERAL
1.01 RELATED DOCUMENTS:
A. Drawings and general provisions of Contract, including General and
Supplementary Conditions and Division-1 Specification sections, apply to
the work of this section.
B. Division-16 "Basic Electrical Materials and Methods" and other sections
apply to work of this section.
C. Division-16 "Switchboards" and "Panelboards" sections.
D. Division-16 "LV Wires and Cables" Section, work required in conjunction
with CB protective devices; not work of this section.
1.02 SUMMARY:
A. Extent of Low Voltage (L V) circuit-breaker ( CB ) work is indicated by
drawings and schedules.
B. Types of circuit breakers in this section include the following:
1. Power Air Circuit Breakers, (P ACB's).
2. Moulded case circuit breakers (MCCB's).
3. Miniature Circuit Breakers (MCB's).
4. Moulded case switch (MCS)
1.03 SUBMITTALS:
A. Product Data: submit manufacturer's product data including frame size
(continuous Current rating), short circuit interrupting ratings, special and
regular ) features of mounting, trip rating and illustrated relay features etc. as
required '- by the Engineer and installation instructions for each type of
circuit breaker.
B. Wiring Diagrams: submit wiring diagrams for circuit breakers and
accessories showing connections to electrical power feeders and associated
equipment. Differentiate between portions of wiring which are
manufacturer-installed and portions which are field-installed.
C. Certification: submit certified type test and routine factory test data, which
indicates current-interrupting ratings for each circuit breaker.
D. Protection coordination: submit complete network study showing proper
selection of circuit breakers characteristic time-current curves that will
achieve discrimination under fault conditions between downstream and
up-stream circuit breakers to and including Power Company's source
protection at the substations.
2
1.04 QUALITY ASSURANCE:
A. Manufacturer's Qualifications: firms regularly engaged in manufacture of
circuit breakers of types, ratings, and capacities required, whose products
have been in satisfactory use in similar service for not less than 5 years.
B. Installer's Qualifications: firm with at least 3 years of successful installation
experience on projects utilizing circuit-breaker devices similar to those
required for this project.
E. Codes and Standards:
1. Electrical Code Compliance: comply with applicable local electrical code
requirements of the authority having jurisdiction, as applicable to
construction and installation of circuit breakers.
2. IEC Compliance: comply with IEC 947-2 for power and molded-case
circuit breakers, and IEC 898 for miniature circuit breakers.
3. Testing Laboratory Compliance: comply with applicable Testing
Authority: requirements in country of origin, which apply to construction
and installation of circuit breakers of types specified.
1.05 DELIVERY STORAGE AND HANDLING:
A. Deliver circuit breakers and components in factory-fabricated type containers
or wrappings, which properly protect devices from damage.
B. Store circuit breakers in original packaging and protect from weather and
construction traffic. Wherever possible, store indoors; where necessary to
store outdoors, store above grade and enclose with watertight wrapping.
C. Handle circuit breakers carefully to prevent physical damage to CBs and,
components. Do not install damaged CBs; remove from site and replace
damaged devices with new.
PART 2- PRODUCTS
2.01 MANUFACTURERS:
A. Available Manufacturers: subject to compliance with requirements,
regulations, specification, and drawings.
2.02 CIRCUIT BREAKERS:
A. General: except as otherwise indicated, provide circuit breakers and ancillary
components, of types, sizes, ratings and electrical characteristics indicated,
which comply with manufacturer's standard design,. materials, components,
.and construction in accordance with published product information, and as
required for a complete installation which shall be subject to approval or
rejection of the Engineer.
B. Power Air Circuit Breakers (PACBs) , Insulated Case.
1. Type: encased in steel structure, air ventilated, air break for normal
operation at maximum temperature within enclosure at point of
application, tested to approved standards. manually operated :or normal
3
functions, and 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.
2. Construction: manually and electrically operated, as shown on the
Drawings, with two-step spring charged, stored energy mechanism,
quick-make, quick break type, electrically and mechanically trip-free, 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 automatically recharged upon closing. 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
Safety feature is to allow discharging stored energy without closing
circuit breaker. Circuit breaker is to have arc quenching device on each
pole and replaceable arcing contacts.
3. Control power for electrically charged, CB and/or for shunt and
undervoltage trip devices, where required, is to be l20V ac obtained from
in-built MDB control power transformer, connected and fused on
bus-side.
4. Rating: 3 or 4 pole, 750V rated insulation voltage 600 V rated operational
voltage, with continuous current rating (frame size) as shown on the
Drawings, ranging between 400 A and 4000 A (400, 800, 1200, 1600,
2000, 2500 3000, and 4000 A), fully rated (100%) for service under worst
- site conditions. Breakers are to be rated for a symmetrical rms service
short-circuit breaking capacity as shown on the Drawings, to IEC 947-2,
sequence II (rated service short-circuit breaking capacity) at specified
voltage and frequency, to meet IEC 947- 2, sequence I, II, III and IV tests,
utilization category B, tested in an enclosure substantially the same as the
enclosure in which they are to be installed.
5. Trip unit: to be totally enclosed, programmable, solid state device,
interchangeable for compatible frame sizes, pluggable into front of circuit
breaker, tamper-proof and with transparent, sealable cover. Trip unit is to
measure sinusoidal and non- sinusoidal current wave forms (fundamental
to thirteenth harmonic) by continuously sampling each phase through out
every cycle. 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 current setting (0.5 -1.0 times trip unit rating) with
adjustable long-time delay, short-time pick-up and short-time delay, earth
fault pick-up and time delay instantaneous over current pick-up. Current
setting range is to be by means of replaceable trip-units 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 10% to
60% of normal current rating of the circuit breaker and a maximum of
1200A, with adjustable time delay between 0.1 and 0.5 seconds. Short
4
time delay is to. be adjustable in steps, 2 -9 times current setting, with
pre-settable or adjustable time band having maximum delay of 0.3 to 0.5
seconds. Instantaneous trip is to be adjustable in steps at least 2 -13 times
the trip unit rating. Over-ride protection is to allow full sensitivity up to
interrupting capacity of circuit breaker.
6. Trip Unit Status Display: is to indicate in words the status of normal
breaker operation, long time over current pick up, instantaneous time over
current trip, short time over current trip, ground fault trip. Unit shall have
integral resetabel counter to count long time, short time, instantaneous
and ground fault trips.
7. 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.
8. Circuit breaker accessories are to include the following:
a. padlocking or keylocking provisions for all positions (disconnected, test,
connected, closing blocking, open).
b. overload, short-circuit, ground fault trip LEDS.
c. trip indicator and reset button .
d. operations counter e.
e. on/off pilot lights
f. shunt trip coil and colsing solenoid for remote control.
9. Auxiliary Contacts: to include N.O. and N.C. contacts on switchgear as
required, plus 2 N.O. and 2 N.C. spare contacts.
10. Trip Unit: is to have inputs from conventional potential transformers for
every phase. Current sensors transformers for every phase. Current
sensors shall be encased in epoxy filled plastic housing to protect against
damage and moisture and shall be integrally mounted in breakers.
11. Neutral Current Transformer: is to be provided on the neutral conductor
of each main, tie or outgoing circuit having earth fault protection. Rating
and characteristics of the neutral current transformer are to be suitable for
proper operation of the earth fault protection system.
12. Electrical Interlock: if electrical interlock is required between power air
circuit breakers, the mechanical closing button of the circuit breaker is to
be disabled in the connect position and an additional electrical push
button is to be provided for closing of the circuit breaker through the
breaker's shunt close coil. The electrical interlock is to be provided on
both the shunt trip and close coils of the circuit breaker through key
system in order to perform simultaneous tripping and inhibit closing
functions on the interlocked breaker.
C. Moulded Case Circuit Breakers (MCCBs):
1. Type: totally enclosed, moulded case, constructed from high quality, high
temperature resistant tropicalized, moulded insulating materials designed
for normal operation at 70°c within enclosure to approved standards,
5
provided with quick-make, quick break, trip free switching mechanism,
operated by front toggle type handle mechanism for manual operation of
main contacts in addition to automatic operation under overcurrent
conditions. Tripping to be indicated by handle automatically assuming a
middle position between manual on and off positions. Multi-pole breakers
are to have common integral trip bar for simultaneous operation of all
poles. Ampere rating is to be clearly visible. All terminals are to be box
lug or clamp type with set screws, suitable for copper or Aluminum
conductors contacts. Contacts are to be non-welding silver alloy with arc
quenching metallic .devices of approved construction. Cable terminals
are to be solder less anti-turn box lug or clamp type with set screws
suitable for copper or aluminum cables
2. Circuit Breaker Trip Units: unless otherwise specified or shown on the
Drawings, circuit breakers below 400 A frame size, are to be non-current
limiting thermal-magnetic type, having bi-metallic inverse time delay,
overcurrent element for small overloads and instantaneous magnetic
overcurrent trip element for operation under short-circuit conditions on'
each pole. Circuit breaker 160 A and larger are to have adjustable.
Instantaneous trips. Circuit breakers 400 A and larger are to have
electronic trip unit.
3. Switching Mechanism: quick-make, quick-break type, with positive
trip-free operation so that contacts cannot be held closed against excess
currents under manual or automatic operation. Contacts are to be nonwelding
silver alloy with approved arc-quenching devices of metallic grid
construction.
4. Thermal overcurrent trips are to be compensating type to allow for
ambient temperature higher at breaker than at protected circuit or device.
Compensation is to be applicable between 25 and 55 deg. C. In case of
adjustable thermal settings, range of adjustment is not to exceed
maximum trip rating shown on the Drawings/Schedules.
5. Trip current rating (Amps) indicates nominal maximum rating at which
overload element is set to operate.
6. MCCB's For MDBs: non-current limiting, type, 750 V rated insulation.
voltage, 600V.a.c. and 250V dc. rated operational voltage, utilization
Category B, fully rated ( 100% ) with continuous duty at site conditions,
and with frame size and interrupting capacity to IEC 947-2, sequence II
(rated service short-circuit breaking capacity), and maximum trip rating
as shown on Drawings. Circuit breakers at specified voltage and
frequency are to meet IEC 947-2 test sequences I, II, III and IV. Frame
sizes. normally selected are to be in accordance with Tables at end of this
section of the Specification, with Service short circuit capacities at 50%
of indicated ultimate breaking capacities.
7. MCCB's application for LPs, PPs & DP's are to be of same characteristics
as described above for the MCCB's for MDB's, except their short circuit
interrupting capacity which is to be in compliance with Sequence III to
IEC 1: 947-2 (ultimate .rating). Preferred ratings of MCCB s are as shown
In the tables at end of this section.
6
8. Tripped Position: when tripped automatically by overcurrent condition,
operating mechanism of circuit breaker is to assume an intermediate
position clearly indicated by the handle between on and off positions.
9. Interchangeable Trips: circuit breakers 250 A frame and larger are to
interchangeable trip unit type.
10. Sealing: circuit breakers with non-interchangeable trip units are to be
sealed. Circuit breakers with interchangeable trip units are to have trip
unit covers sealed to prevent tampering.
11. Electronic trip units, applicable to circuit breakers 400 A frame size and
larger, are to be solid state with long time delay settings between 0.5 and
1.0 times maximum trip rating, short time delay range of 3 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
built into trip unit where specified, adjustable between 0.2 and 0.6 of
normal phase current pick-up with maximum time-delay of 0.2 seconds,
with integral current transformers. Push-to-trip button is to be provided
on cover for testing the trip unit.
12. Accessories: circuit breakers are to be designed to accommodate standard
attachments including shunt-trip, under- voltage release, combined
auxiliary and alarm switches, and electrical operator to any circuit breaker
of rating (frame size) l00 A and over. Padlocking and key-lock devices
are to be provided where shown on the Drawings.
13. Residual Current Operated Earth Leakage Trip Devices (RCDs): provide
add-on or built-in earth leakage accessories, where required and as shown
on the Drawings. Protection against earth leakage current, in addition to
overcurrent and short-circuit protection, is to be in accordance with the
Regulations. Trip current sensitivity on breakers for branch circuits is to
be 30 mA maximum; and for main breakers trip ratings are to be as shown
on the Drawings or as specified in Section Earth-fault Protection “Circuit
breakers are to include current transformer with tripping coil assembly,
test button and trip free mechanism to ensure circuit breaker cannot be
held closed against earth faults.
D. Miniature Circuit Breakers (MCBs)
1. Type: thermal magnetic non-adjustable type, tested in accordance with
IEC 898 or BS3871,Part l.
2. Voltage Rating: 440 V rated insulation voltage and 250 rated operational
voltage.
3. Minimum Short-Circuit Breaking Capacities are to be as follows:
100 A MCB : 10, 15 kA 20 or 25 kA at 230/400 V a.c. as required in the
panelboards schedule drawing
4. Construction: MCB's are to be tropicalized for operation at ambient,
temperatures up to 70 deg. C within panelboard enclosure and humidities
7
up to 100%, and are to be constructed from high quality , high
temperature, moulded insulating materials. Guaranteed duties and
characteristics are to be submitted for temperatures above 40 deg. C.
MCBs and combinational devices are to be modular, of unified profile
and mounted to a standard DIN rail.
5. Operation: under overload conditions, thermal tripping is to provide close
protection of insulated conductors. Under short-circuit conditions,
magnetic trip is to operate at 5 -10 times normal rated current (type 3
characteristic) unless otherwise indicated. .Magnetic operation is to be in
the current limiting region and opening time is not to exceed 5 milliseconds.
6. Ratings: preferred rated currents are to be 6, 10, 10,20,25, 32,40, 50,63,
80 and l00 A, calibrated at 45 deg. C, available as 1, 2, 3 and 4-pole circuit
breakers. Derating above 45 d.eg. .C is not to exceed 1% per deg. C, and
loading is not to exceed 70% of circuit breaker rating.
7. Residual current devices for earth leakage protective circuit breakers may
be add-on devices, or built-in and integral with the standard miniature
circuit breaker. Non-adjustable sensitivities of 10 mA, 30 mA, 100 mA
and .300 mA are to be available for all ratings of 2-pole and 4-pole circuit
breakers.
8. Auxiliaries, where required or shown on the Drawings, are to include
alarm switch, auxiliary switch, shunt trip, under voltage trip and similar
units which are to be modular additions to the circuit breakers.
E. Moulded Case Switch (MCS).
1. Moulded Case Switch: non-automatic on/off switching device of equal
construction to equivalent circuit breaker, having no overcurrent or fault
protective elements, but marked with maximum current withstand and
voltage rating.
F. Motor Circuit-Protector.
1. Magnetic only type circuit breaker with adjustable current sensing trip
coil in each of the 3-poles to provide short circuit protection, manually
operated for normal switching functions and automatically operated
under short circuit Conditions.
2. Motor Circuit Protector: to be a recognized component under UL 489
and comply with the applicable requirement of IEC 947-2.
3. Rating is to be 750V rated insulation voltage and 600V rated operational
voltage with continuous current rating selectable between 3 A and 400 A
as shown on drawings. fully rated for service under worst site conditions
and with trip settings between 3 and 10 times continuous ratings. Motor
circuit protectors to be rated for a service short circuit breaking capacity
as required at the motor control centre. Back-up fuses may be added for
short circuit protection; coordinated with the magnetic trip element to
effect tripping of all poles of the circuit breaker, where short circuit
currents are above the normal magnetic tripping range indicated. Fuses
are to be of the current limiting type.
8
2.03 CONTACTORS AND REMOTE CONTROL RELAYS:
A. GENERAL
1. Mechanically or magnetically held with contacts normally open or normally
closed and/or combination required.
2. Rated for continuous operation with capacities and voltage at 50 Hz, as
indicated on drawings or required.
3. Spring loaded contacts to maintain contact pressure in closed position,
readily replaceable, self-aligning type.
4. Suitable for inductive or non-inductive loads, unless otherwise noted.
5. With arc shields and magnetic blow coils if interrupting duty exceeds 300
ampere.
6. Interrupting capability not less than six times rated full load current.
7. Operating coils voltage: 220 Volts, unless otherwise noted.
B. Mechanically held contactors
1. Single and/or dual coil operation.
2. Positive locking type without the use of latching hooks or magnets.
3. With a manual operator for hand operation giving positive indication of
contactor position.
4. Control Circuit: For 3-wire operation with momentary contact open/close
stations as indicated or required.
2.04 MULTIPLE POLE RELAYS
A. Electrically operated, mechanically held type, with 10 amperes minimum rated
contacts (unless otherwise indicating or required).
B. Open and close coils rated 220 volts or 380 volts, 50 Hz, unless otherwise
indicated or required.
C. Number of poles as indicated on drawings or schedules.
2.05 CENTRALIZED EMERGENCY SYSTEM (CES)
A. The centralized emergency system shall be a computerized system for the
control of self-contained emergency exit luminaries via a periodically and
automatically testing the luminaries system efficiency.
B. The system shall be remotely controlled using PC and printer and shall be
linked to the BMS.
C. The system shall include a microprocessor unit to perform the following:-
- Control system operation.
- Controls programmed events.
- Tests operation of lamps.
- Tests operation of control circuits.
9
- Record data and events.
- Charging/Discharging status.
D. The microprocessor unit shall include a set of batteries to allow it to continues
running the system during the electricity failure (black –out).
E. The system shall check the autonomy of the luminaries corresponds to their
rated autonomy.
2.06 INSTRUMENTS
A. GENERAL REQUIREMENTS
1. All electrical indicating instruments shall be the product of a single
manufacturer.
2. All ammeters and voltmeters shall be digital type.
3. All instruments shall be flush mounted.
B. COMMON SPECIFICATIONS
1. STANDARD IEC 60051.
2. ADMISSIBLE OVER LOADS
a. Voltage : 1.2 rated Voltage Continuously
-2 rated voltage For 2 seconds
b. Current -2 in continuously
- 10 in for 10 seconds.
- 40 in for 2 seconds
3. DIELECTRIC STRENGTH: 2 KV.r.m.s. for 1 min
4. OPERATING TEMPERATURE : - 10OC to 60OC
5. DIGITAL PANEL METERS
Consists of:
a. 3 ½ DIGIT SERIES Display for Ammeters and 3 ½ DIGIT for Ammeters
and Frequency meters.
b. ANALOG SECTION:
The conversion between the magnitude to be measured and the input to
the digital section made from high accuracy components.
c. DIGITAL SECTION:
An analog/digital converter is used with dual slope integration and
automatic zero correction and shall have thermal stability from 0 to 60OC
and Linearity error is under 0.05%
d. DIMENSIONS
For all shall be (96x48mm).
C. AMMETER AND VOLTMETER SWITCHES
10
1. On 3-phase, 5-wire system, ammeter switches shall have four operating
positions marked 'R', 'Y', 'B' and 'N', and an 'OFF' position, and shall
enable the single ammeter to read, in sequence, the currents in each of the
three operating positions marked 'R', 'Y' and 'B' and an "OFF" position.
Ammeter switches shall be connected so that the associated current
transformers are short-circuited when they are not connected to the
ammeter.
2. On 3-phase, 5-wire, systems, voltmeter switches shall have six operating
positions, marked 'R', 'Y' , 'Y-B', 'B-R'-'R-N','Y-N'-'B-N', and an 'OFF'
position, and shall enable the single voltmeter to read, in sequence, each
of the three line voltages and each of the three phase-to-neutral voltages.
On 3-wire systems, voltmeter switches shall have three operating
positions marked 'R-Y', 'Y-B' and 'B-R' and an 'OFF' position.
3. Voltmeter switches shall have 'break-before-make-contacts.
2.07 CURRENT TRANSFORMERS (CTS)
A. GENERAL REQUIREMENTS
1. All CTs shall have an Accuracy Class Designation according to the
following:
- Tariff metering.
Accuracy Class Designation 0.5.
- Non-tariff metering.
Accuracy Class Designation 1.0.
- Switchgear indicating instruments.
Accuracy Class Designation 1.0.
- Motor Starter ammeters.
Accuracy Class Designation 3.0.
- Protection (over current, UEF).
Accuracy Class Designation 3.0.
- Protection (over current, UEF).
Accuracy Class Designation 10p
- Protection (UEF)
Accuracy Class Designation X
2. Unless otherwise specified in the schedules or drawings, the CTs are
required for use under service conditions not more onerous than those set
out in IEC, standards.
3. CTS shall be designed either for measurement or for protection and shall
not be used in a dual-purpose role serving both instruments and protective
gear.
4. Unless otherwise specified, all CTs shall have 5A secondary windings.
5. So far as it is practicable, all CTs shall be of the ring type. Wound primary
CTs will only be accepted when the rated primary current is so low as to
make the ring type impracticable.
6. One side of the secondary of each CT shall be connected to earth at one
point via a bolted removable link.
11
7. For mattering circuits, either, a proprietary front of panel CT test block or
special "shorting" terminals within the panel shall be provided for test
purposes.
8. All CTs whether of the ring type or the wound primary type, for use at
voltages exceeding 1000V shall be epoxy resin encapsulated.
Where dual-ratio CTs are specified, they shall be provided with two
separate secondary windings capable of being connected in series or in
parallel to give the required ratio.
9. All CTs shall be provided with a rating plate bearing the information as
stated in IEC, DIN/VDE standards. All CTs shall be installed in
accessible location. The secondary connections shall be brought out by
means of insulated leads, and made off on a suitable terminal block
–mounted in a readily accessible position.
Magnetization curves and/or type test Certificates shall be provided for
all CTs associated with protection devices.
10. Evey CT shall have a rated burden at least 50% greater than the total
burden of the instruments, relays, and/or other apparatus which is to
serve.
2.08 VOLTAGE TRANSFORMERS
A. GENERAL REQUIREMENTS
1. Voltage transformers shall be of the type, rating, and voltage ratio
specified in the schedules or drawings.
2. All voltage transformers shall have an Accuracy Class Designation
according to the following table:
- Metering : Accuracy Class Designation 1.0
- Switchgear indicating instruments: Accuracy Class Designation 1.0
- Motor starter voltmeters : Accuracy Class Designation 3.0
- Protection : Accuracy class Designation 3P
3. Unless other specified in the schedules or drawings, the voltage
transformers are required for use under service conditions not more than
those set out in IEC, standards.
4. Voltage transformers designed for a primary voltage not exceeding
4000V shall be the air insulated type, with the windings encapsulated in
epoxy resin or other suitable synthetic material.
5. Unless otherwise specified, all voltage transformers shall be designed for
a secondary output voltage of 110V.
6. Each voltage transformer shall have a rated burden at least 50% greater
than the total burden of the apparatus or instruments which it is to serve.
7. The insulation resistance of each voltage transformer shall be indelibly
marked on the shipping/dispatch label.
2.09 DIGITAL MULTI – METER (DMM)
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A. GENERAL
1. DMM is an instrument for measuring and metering electrical values for
three phase, low voltage balanced or unbalanced electrical networks.
2. DMM will has a front panel keys and LCD displays all the parameters and
use the functions provided to measure electrical values and measure
energy consumption.
B. MEASUREMENT:
1. Instantaneous and maximum current over a programmable period (8 to 30
minutes).
2. Phase to neutral and phase to phase voltage.
3. Frequency (HZ).
4. Instantaneous and maximum active power (P) over a programmable period
(8 to 30 min.), reactive power(s).
5. Power factor (PF).
C. ENERGY METERING
1. Active KWH.
2. Reactive KV arch.
D. DMM will be provided with link protocol for using with DEMS.
PART 3 -EXECUTION
3.01 EXAMINATION:
C. Examine areas and conditions under which circuit breakers are to be installed
and evaluate conditions detrimental to proper completion of the Work. Do not
proceed with the Work until unsatisfactory conditions have been corrected in
an acceptable manner.
3.02 INSTALLATION OF CIRCUIT BREAKERS:
A. Install circuit breakers and accessories as indicated, in accordance with
manufacturer's written instructions and with recognized industry practices to
ensure that protective devices comply with requirements. Comply with
requirements of Local Regulations and Standards, and applicable approved or
recommended "Standard of 1nstallation” pertaining to installation of circuit
breakers and general wiring practices.
B. Coordinate with other work, including electrical wiring work, switchboards,
panelboards as necessary to interface installation of circuit breaker work with
other work.
C. Fasten circuit breakers without causing mechanical stresses, twisting or
misalignment being exerted by clamps, supports, or cabling.
13
D. Set field-adjustable circuit breakers for trip settings as indicated in
accordance with an approved system coordination scheme, subsequent to
installation of Units.
E. Tighten electrical connectors and terminals, including screws and bolts, in
accordance with equipment manufacturer's published torque tightening
values for equipment connectors. Where manufacturer's torquing
requirements are not indicated, tighten connectors and terminals to comply
with tightening torques of compatible standards.
3.03 ADJUST AND CLEAN:
A. Inspect circuit-breaker operating mechanisms for malfunctioning and, where
necessary, clean and adjust units for free mechanical movement.
3.04 EARTHING
A. Provide equipment earthing connections for circuit breakers as indicated.
Tighten connectors to comply with tightening torques specified in
manufacturers standards or compatible international standards to assure
permanent and effective earthing.
3.05 FIELD QUALITY CONTROL:
A. Upon completion of installation and after circuitry has been energized,
demonstrate capability and compliance of system with requirements. Where
possible, correct malfunctioning units on site, then retest to demonstrate
compliance; otherwise, remove and replace with new units, and proceed with
retesting. Testing and retesting at no cost to Employer.
B. Circuit Breakers: tests are to include operation of every circuit breaker
manually. Check automatic operation of selected circuit breakers, as required
by the Engineer, by applying necessary short-circuit, overload and earth
leakage current for tripping circuit breaker as applicable and compare with
manufacturer's data/characteristic curves. Measure and report ambient.
temperature inside enclosure.
1. Primary Injection Tests: provide primary injection 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.
2. Instantaneous. Trip Elements: test instantaneous trip by high current
primary injection, using high-current primary Injection test-sets and
report all readings.
3.06 MCCB PREFERRED RATINGS:
A. 'Frame size is defined as maximum continuous current rating of circuit
breaker which corresponds with its maximum trip range listed below and
which is to be related to minimum acceptable short-circuit interrupting
ratings, based on fully rated interrupting duties: normal duty (N), high break
(H), or current limiting, (L), as specified/shown on drawings.
14
B. Frame sizes are generally to be selected with minimum interrupting
capacities at specified voltages and rated frequency, in accordance with the
following table:
Trip range frame
Size (amperes)
Minimum Symm. Rms rated
breaking capcity (ultimate in KA)
Rating
Volts (a.c.)
N H L
TABLE 1
Thermal-magnetic
16-100 (1P) 14 --- --- 230
16-100 (2,3 P) 25 50- --- 400
16-150 (2,3,4 P) 35 65 100 400
70-250 (2,3,4 P) 35 65 100 400
Electronic
16-400 (2,3,4P) 35 65 100 400
250-400 (2,3,4P) 35 65 100 400
400-800 (2,3P) 40 65 100 400
800-1250 (2,3P) 50 65 100 400
END OF SECTION 16476
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