molded case circuit breakers .pdf

MAJARRAH BUSINESS COMPLEX

6th October

MOULDED CASE CIRCUIT BREAKERS FEB. 2014. REV. 01 16478

PAGE 1 OF 7

SECTION 16478

MOULDED CASE CIRCUIT BREAKERS

PART 1 - GENERAL

1.1 RELATED DOCUMENTS

A. Drawings and general provisions of Contract, including General and special Conditions and Division-1 (General requirements), apply to work of this section.

B. General Provisions for Electrical Work, Section 16010, apply to work of this section.

C. The requirements of this section apply to moulded case circuit breakers solid state type specified elsewhere in these specifications.

D. Low voltage switchgear assemblies main distribution boards. Section 16425.

E. Distribution boards section 16470.

F. Testing and commissioning section 16950.

1.2 DESCRIPTION OF WORK

A. Work includes providing all materials, equipment, accessories, services and tests

necessary to complete and make moulded case circuit breakers ready for operation in

accordance with Drawings and Specifications.

1.3 QUALITY ASSURANCE

A. Manufacturers: Firms regularly engaged in the manufacture of moulded case circuit

breakers solid state type whose products have been in satisfactory use in similar

service for not less than 5 years. produced by a manufacturer listed as an Acceptable

Manufacturer in this section.

B. Standards Compliance: Comply with requirements of applicable local codes, IEC 60947-2, IEC 60947-4, IEC 60947-4-1 and Standards pertaining to moulded case circuit

breakers solid state type (adjustable for long time , short time and instantaneous

protection features).

C. In case of conflict among the referenced standards and codes, the more stringent

provision will govern.

1.4 SUBMITTALS

A. Product Data: Submit manufacturer's data for all types of moulded case circuit breakers, including solid state type.

PART 2 - PRODUCTS

2.1 GENERAL REQUIREMENTS

A. DEFINITIONS

The definitions of terms and symbols used in this Specification are those used in IEC

60947-2.

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B. STANDARDS

Moulded case circuit-breakers solid state type, all MCCB's shall comply with IEC

60947-2 plus any additional requirements of this Specification.

All MCCB's shall be equipped with solid state release (adjustable for long time and

short time and/or instantaneous protection depends on the selectivity achievements

features).

Breakers of 1000A rating and above shall be provided with ground fault protection as

per NEC requirements.

C. GENERAL

Minimum short-circuit capacities of circuit breakers shall be as indicated on the

drawings.

All MCCB's connected in one electrical circuit shall be selected to ensure full

discrimination up to and including the prospective short-circuit, and earth fault

currents as specified on drawings and Schedules for prospective earth fault currents the

disconnection times shall not exceed 5s.

All MCCBs should be rated at service short circuit entrance level for all incoming and outgoing.

All circuit breakers in one electrical circuit shall be fully selective and coordinated, if

selectivity coordination study is failed for any reason, contractor is responsible to add

or change any number of breakers, relays, such that the selectivity coordination shall be

fully achieved with no extra cost to the owner.

2.2 CONSTRUCTION

A. MANUFACTURE

MCCB's shall be manufactured with double insulation of the front face, insulating

auxiliary components from the main power poles thereby allowing as far as reasonable

the fitting of auxiliary units on site without full isolation of the unit.

B. CURRENT RATINGS

Rated currents, rated service short-circuit breaking capacities and trip release settings

shall be as specified in cable installation schedules and on drawings.

Current ratings as specified in the schedules and drawings are for interrupted duty at

220/380V in the final installed location on site under full load operating conditions of

the complete installation, i.e. taking account of heat produced by other devices and the

ambient temperature, physical situation, enclosure, position and attitude of the MCCB.

The appropriate de-rating factors shall be applied to manufacturer's standard ratings

when selecting MCCB's to meet the specified ratings.

MCCB's shall be suitable for operation in both the horizontal and vertical mounting

position without detrimental effect on operation or rating.

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C. TRIPPING CHARACTERISTICS

Details of tripping characteristics shall be provided for each type of MCCB. The

details shall include manufacturer's full current discrimination tables showing overload

and short-circuit discrimination and, additionally, a full set of overlay transparency

discrimination curves or software program to enable discrimination settings to be

checked.

D. TEST CERTIFICATES

Complete certificates shall be provided for each type of MCCB, stating the service and

ultimate short-circuit capacities.

E. CONTACTS

The contact arrangement of current-limiting MCCB's where applicable shall be such

that the current-limiting contacts are in series with the main contacts and remain closed

in normal operation, including time delayed over current tripping.

Contacts shall be arranged so that normal current is carried by low-resistance silver

alloy or other non-welding material while arcing is handled by tungsten contacts.

Multi-set contact MCCB's shall be arranged using one set of contacts for thermal

current and other for arc interruption.

F. TERMINALS

Terminals shall be sized to accommodate the size and type of cable of incoming and

outgoing circuits as specified in the schedules or drawings. MCCB's shall be provided

complete with terminal shields.

Terminals shall be arranged for direct connection to busbars, front or rear as required

by the switchboard design.

All poles of multi-pole circuit-breakers shall be constructed so that contacts open,

close and trip simultaneously. It shall not be possible for one or more poles to be

closed while another remains open and vice-versa.

G. OPERATING MECHANISMS

Operating mechanisms shall be over-center, quick-make, quick-break type having

operation in which speed of operation of the breaker is independent of the operator.

All hand-operated circuit breakers shall be fitted with rotary action handles only in the

main distribution boards. The handles shall be lockable in open position.

Where motor operated MCCB's are specified in the schedules or drawings, the motors,

the clutches shall be as scheduled. Direct action operating handles shall be provided

for local operation.

Where solenoid operated MCCBs are specified in the schedules or drawings, the

operating voltage shall be as scheduled. Separate solenoids shall be provided for

opening and closing operations. Built-in push buttons shall be provided for local

operation.

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Indication of the "ON", "OFF" and "TRIPPED" conditions shall be provided not only

by the position of the handle but also by means of a colored band, or line which shall

be visible when the circuit-breaker is on but not when it is off or tripped.

The "TRIPPED" condition shall be indicated by the handle assuming a mid-point

position between "ON" and "OFF" It shall not be possible to manually place the handle

in the tripped position.

Indication shall be provided to confirm that all main contacts have separated.

H. ENCLOSURES

Moulded case covers and non-interchangeable trip elements shall be permanently

sealed at works to prevent tampering, but the trip elements may be changed/Adjusted

and re-sealed on site by using suitable tools.

All internal components of MCCB's shall be replaceable on site.

MCCB's shall be certified as satisfying the leakage current testes called for in IEC

60947-2 with regards to safety isolation.

MCCB's used for motor starting shall satisfy the Type 2 coordination requirements

called for in IEC 60947-2.The MCCB and the starter shall preferably be of the same

manufacture, and in all cases shall be tested together and certified as satisfying the co-

ordination requirements.

All MCCB's shall be of the same manufacture and those of like kind shall be of the

same type. This requirement applies to loose or individually mounted MCCB's as well

as to those incorporated within assemblies such as control panels, switchboards and

distribution boards.

I. PROTECTION MECHANISMS

Each pole shall provide inverse time over current protection and adjustable high set

instantaneous tripping and in accordance to item 2.1 (B) above. All poles shall be

tripped simultaneously if one detects a fault.

Trip units of ratings up to and including 250A shall be built in. Trip units above 250A

shall be replaceable.

Tripping mechanisms shall be selective limiting type to obtain discrimination or by

interconnection with other MCCB trip units.

All adjustable trips shall be visible and adjustable from the front with the breaker in

position. Adjustments to trip settings shall be made to all poles simultaneously by

means of a common adjustment mechanism.

J. OPERATING FACILITIES

Facilities shall be provided for the use of a hand-held tester for on-site testing of all

operational features.

Where specified in the schedules/drawings, earth leakage trips, shunt trips,

undervoltage trips and remote operation shall be provided. These accessories shall all

be factory assembled and tested.

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Energy based limiting MCCB's which require replacement of the current limiters after

operatic shall not be re-settable until such replacement has been made.

2.3 AUXILIARY CONTACTS

A. Auxiliary contacts shall be provided where specified in the schedule or drawings,

auxiliary contacts shall operate simultaneously with the main breaker contacts.

2.4 INSPECTION AND TEST PROCEDURES

The tests to be carried out shall include but not necessarily be limited to:-

1. Visual and Mechanical Inspection

1. Inspect physical and mechanical condition.

2. Inspect anchorage and alignment.

3. Prior to cleaning the unit, perform as-found tests, if required.

4. Clean the unit.

5. Operate the circuit breaker to insure smooth operation.

6. Inspect bolted electrical connections for high resistance using one of the

following methods:

1. Use of low-resistance ohmmeter.

2. Verify tightness of accessible bolted electrical connections by

calibrated torque-wrench method in accordance with

manufacturer's published data.

3. Perform thermographic survey.

7. Inspect operating mechanism, contacts, and arc chutes in unsealed units.

8. Perform as-left tests.

2. Electrical Tests

1. Perform resistance measurements through bolted connections with a low-resistance

ohmmeter, if applicable.

2. Perform insulation-resistance tests on each pole, phase-to-phase and phase-to-

ground with the circuit breaker closed and across each open pole for one minute.

Test voltage shall be in accordance with manufacturers published data.

3. Perform a contact/pole-resistance test.

4. Perform insulation-resistance tests on all control wiring with respect to ground.

Applied potential shall be 500 volts dc for 300 volt rated cable and 1000 volts dc

for 600 volt rated cable. Test duration shall be one minute. For units with solid-

state components, follow manufacturers recommendation.

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5. Perform long-time delay time-current characteristic tests by passing 300 percent

rated primary current through each pole separately.

6. Determine short-time pickup and delay by primary current injection.

7. Determine ground-fault pickup and time delay by primary current injection.

8. Determine instantaneous pickup current by primary injection using run-up or pulse

method.

9. Test functions of the trip unit by means of secondary injection.

10. Perform minimum pickup voltage test on shunt trip and close coils.

11. Verify correct operation of any auxiliary features such as trip and pickup

indicators, zone interlocking, electrical close and trip operation, trip-free, and

antipump function.

3. Test Values

1. Compare bolted connection resistances to values of similar connections.

2. Bolt-torque levels.

3. Microhm or millivolt drop values shall not exceed the high levels of the normal

range as indicated in the manufacturer's published data. If manufacturer's data is

not available, investigate any values which deviate from adjacent poles or similar

breakers by more than 50 percent of the lowest value.

4. Circuit breaker insulation resistance.

5. Control wiring minimum insulation-resistance values should be comparable to

previously obtained results but not less than two megohms.

6. Trip characteristic of breakers shall not exceed manufacturer's published

time-current characteristic tolerance band, including adjustment factors. Circuit

breakers exceeding specified trip time at 300 percent of pickup shall be tagged

defective.

7. Instantaneous pickup values of molded-case circuit breakers shall be within the

tolerances.

8. Minimum pickup voltage on shunt trip and close coils should be comparable to

previously obtained results but not less than two megohms.

2.5 GENERAL INFORMATION

A. The following information shall be provided for each MCCB.

- Voltage and rated insulation voltage.

- Rated current

- Rated operational voltage and rated insulation voltage.

- Number of poles

- Rated service and ultimate short-circuit capacities.

- Method of mounting

- Method of connection

- Protection against external influence

- Current time characteristic curves on log scale.

- The It tripping characteristic curves and the peak let-through currents at prospective

fault levels,

- Rated short time withstand current

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- Rated short-circuit making capacity

2.6 LABELLING

A. On the front of each MCCB a visible label shall be fitted and described as follows:

Labelling shall be marked as follows:

- Rated current and trip setting (for MCCB's with multiple current ratings the

maximum value shall be marked plus, without ambiguity, the value for which the

MCCB has been adjusted)

- Rated voltage

- Manufacturer's name or trade mark

- Type designation, catalogue number or serial number

- Rated short-circuit capacity in amperes

- Reference ambient temperature if different from 30 oC

A label shall be provided, in a clearly visible position on the front of each circuit-

breaker, on which the final commissioned release setting for that circuit-breaker shall

be displayed

2.7 ACCEPTABLE MANUFACTURERS

Refer To The Attached Manufacturer's List.

PART 3 - EXECUTION

3.1 INSPECTION

A. Examine conditions under which moulded case circuit breakers are to be installed and

notify in writing of conditions detrimental to proper completion of the work. Do not

proceed with the work until unsatisfactory conditions have been corrected.

3.2 INSTALLATION

A. Install moulded case circuit breakers as indicated, in accordance with manufacturer's

written instructions, requirements of applicable Standards, and in accordance with

recognized industry practices to ensure that installation complies with requirements

and serves intended function.

B. Coordinate, as necessary to interface installation of moulded case circuit breakers.

3.3 FIELD QUALITY CONTROL

A. Prior to energization of moulded case circuit breakers test devices for continuity of

circuitry and for short circuits. Replace malfunctioning breakers with new breakers

and then demonstrate compliance with requirements.

END OF SECTION 16478

molded case circuit breakers .pdf

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