Section
7 Switchgear and controlgear assemblies
7.1 General requirements
7.1.1 Switchgear
and controlgear assemblies and their components are to comply with
the following standards, as appropriate for the nominal voltage, and
amended where necessary for ambient temperature and other environmental
conditions:
-
IEC 61439: Low-voltage
switchgear and controlgear assemblies(relevant parts);
-
IEC 62271-200:High-voltage
switchgear and controlgear Part 200: AC metal-enclosed switchgear
and controlgear for rated voltages above 1 kV and up to and including
52 kV;
-
IEC 62271-201: High
voltage switchgear and controlgear Part 201: AC insulation-enclosed
switchgear and controlgear for rated voltages above 1 kV and up to
and including 52 kV;
-
IEC 60092-503: Electrical installations in ships Part 503:
Special features AC supply systems with voltages in the range of above 1 kV
up to and including 36 kV;
-
IEC 60255: Measuring
relays and protection equipment; or
-
an acceptable and
relevant National Standard.
In addition, the requirements of Pt 16, Ch 2, 7.2 Busbars to Pt 16, Ch 2, 7.19 Disconnectors and switch-disconnectors are to be complied with.
7.2 Busbars
7.2.1 Busbars
and their connections are to be of copper or aluminium, all connections
being so made as to inhibit corrosion/oxidation between current-carrying
mating faces, which may result in poor electrical contact giving rise
to over-heating. Busbars and their supports are to be designed to
withstand the mechanical stresses which may arise during short-circuits.
A test report or calculation to verify the short-circuit withstand
strength of the busbar system is to be submitted for consideration
when required.
7.2.2 The maximum
permissible temperature rise for bare conductors is 45°C. A test
report or calculation to verify the rated current assigned to the
busbar system is to be submitted for consideration when required.
7.3 Circuit-breakers
7.3.1 Circuit-breakers
are to comply with one of the following standards amended where necessary
for ambient temperature:
-
IEC 60947-2: Low-voltage
switchgear and controlgear Part 2: Circuit-breakers;
or
-
IEC 62271-100: High-voltage
switchgear and controlgear Part 100: Alternating current circuit-breakers; or
-
an acceptable and
relevant National Standard.
Type test reports to verify the characteristics of a circuit-breaker
are to be submitted for consideration when required.
7.3.2 Circuit-breakers
are to be capable of isolation.
7.3.3 Circuit-breakers
are to be of the trip free type and, where applicable, be fitted with
anti-pumping control.
7.3.4 High-voltage circuit-breakers
are to be of the withdrawable type or with equivalent means or arrangements
permitting safe maintenance whilst the busbars are live.
7.3.5 Where
the means of setting adjustable protection characteristics are not
durably marked and locked in position and cannot be visually inspected
(e.g. electronic storage), the settings of characteristics are to
be recorded and a copy of the records included in the details retained
on board, see
Pt 16, Ch 2, 6.1 General 6.1.4.
7.3.6 Air circuit-breakers
for essential or emergency services and rated at 800A and above are
to have a cumulative count kept of the switching operations of the
electrical contacts. This count, along with the manufacturers
details for the circuit-breaker, including the maximum number of switching
operations for the electrical contacts, is to be retained on board.
These details are to be made available to the Surveyor on request.
7.4 Contactors
7.4.1 High-voltage
contactors are to comply with one of the following standards amended
where necessary for ambient temperature.
-
IEC 62271-106:High-voltage
switchgear and controlgear Part 106: Alternating current contactors,
contactor-based controllers and motor-starters; or.
-
an acceptable and
relevant National Standard.
Type test reports to verify the characteristics of a contactor
are to be submitted for consideration when required.
7.4.2 High-voltage contactors
are to be of the withdrawable type or with equivalent means or arrangements
permitting safe maintenance whilst the busbars are live.
7.5 Creepage and clearance distances
7.5.1 The shortest
distances between conductive parts and between conductive parts and
earth, in air or along the surface of an insulating material, are
to be suitable for the rated voltage having regard to:
- the nature of the insulating material;
- the transient over voltages developed by switching and fault conditions;
and
- the environment into which the assembly will be installed.
Each assembly type is to be subjected to an impulse voltage
test in accordance with its constructional Standard or, alternatively,
the minimum distances for bare conductive parts in switchgear and
controlgear assemblies given in Table 2.7.1 Minimum clearance
distances are to be used.
Table 2.7.1 Minimum clearance
distances
Nominal voltage (V)
|
Minimum clearance distance (mm)
|
Verified assemblies, see Note 2
|
Non-verified assemblies
|
Main
switchboards
|
Other
switchgear and controlgear
|
Main
switchboards and other switch and controlgear
|
≤ 250
(see Note 1)
|
8
|
8
|
15
|
≤690
(see Note 1)
|
8
|
8
|
20
|
≤1000 (see Note
1)
|
8
|
8
|
25
|
<3,300
|
32
|
26
|
55
|
<6600
|
60
|
50
|
90
|
<11,000
|
100
|
80
|
120
|
≤15,000
|
See Note 3
|
See Note 3
|
160
|
≤22,000
|
See Note 3
|
See Note 3
|
220
|
≤33,000
|
See Note 3
|
See Note 3
|
320
|
≤35,000
|
See Note 3
|
See Note 3
|
360
|
Note
2 For the verification requirements for a
verified assembly refer to IEC 61439-2.
|
7.5.2 For assemblies
with a rated voltage of up to and including 1kV, the requirement of Pt 16, Ch 2, 7.5 Creepage and clearance distances 7.5.1 may be met by complying with
IEC 60092-302 Electrical installations in ships Part
302: Low-voltage switchgear and controlgear assemblies.
-
Table 2.7.1 Minimum clearance
distances and Table 2.7.2 Minimum creepage distances indicate the minimum clearance
and creepage distances normally allowed.
- For assemblies installed in spaces where the environmental conditions
are in excess of pollution degree 3 (that is conductive pollution
occurs or dry, non-conductive pollution occurs which is expected to
be conductive due to condensation) as defined in IEC 61439-1, Low-voltage
switchgear and controlgear assemblies Part 1: General requirements; the clearance distances for non-verified assemblies are to
be used.
- A minimum creepage distance of 16 mm is permitted for assemblies
verified in accordance with the requirements of IEC 61439-2, Low-voltage
switchgear and controlgear assemblies Part 2: Power switchgear
and controlgear assemblies.
- An alternative relevant National or International Standard may
be used when an acceptable justification is submitted as part of the
documentation required by Pt 16, Ch 2, 1.3 Documentation required for supporting evidence 1.3.4.
7.5.3 For assemblies with a rated voltage above 1kV, the requirement of Pt 16, Ch 2, 7.5 Creepage and clearance distances 7.5.1 may be met by complying with IEC 60092-503
Electrical installations in ships Part 503: Special features AC supply systems
with voltages in the range of above 1 kV up to and including 36 kV.
An alternative relevant National or International Standard may
be used when an acceptable justification is submitted as part of the
documentation required by Pt 16, Ch 2, 1.3 Documentation required for supporting evidence 1.3.4.
Table 2.7.2 Minimum creepage distances
Nominal voltage (V)
|
Minimum creepage distance (mm)
|
Main
switchboards
|
Other
switchgear and controlgear
|
≤ 250
(see Note 1)
|
20
|
20
|
≤690
(see Note 1)
|
25
|
25
|
≤1000 (see Note
1)
|
35
|
35
|
<3,300
|
48
|
See Note 2
|
<6,600
|
90
|
70
|
<11, 000
|
150
|
120
|
≤15, 000
|
See Note 2
|
See Note 2
|
≤35, 000
|
See Note 2
|
See Note 2
|
|
7.6 Degree of protection
7.6.1 Low voltage
assemblies where the rated voltage between conductors or to earth
exceeds 55 V a.c. or 250 V d.c. are to be of the deadfront or enclosed
type. High-voltage assemblies are to be of the enclosed type.
7.6.2 Where
switchboards or section boards are required to comply with Pt 16, Ch 2, 5.2 Essential services 5.2.2, barriers are to be installed
to provide protection for the independent sections against contamination
due to the products of arcing, which may result in a fault.
7.6.3 Segregation
between low-voltage and high-voltage circuits and equipment installed
within common assemblies is to be in accordance with IEC 62271-1: High-voltage
switchgear and controlgear Part 1: Common specifications.
7.7 Distribution boards
7.7.1 Distribution
boards are to be suitably enclosed unless they are installed in a
cupboard or compartment to which only authorised persons have access
in which case the cupboard may serve as an enclosure. See
Pt 16, Ch 2, 7.16 Position of switchboards 7.16.4.
7.8 Earthing of high-voltage switchboards
7.8.1 High-voltage
switchboards are to be provided with suitable means to earth isolated
circuits so that they are discharged and so maintained that they are
safe to touch.
7.8.2 Protective
shutters associated with withdrawable parts are to be clearly marked
to indicate the incoming and outgoing circuits and bus tie connections.
The colour coding shall be as follows:
- Incoming (busbar side) red;
- Outgoing (Circuit side) yellow; and
- Bus ties red
7.9 Fuses
7.9.1 Fuses
are to comply with one of the following standards amended where necessary
for ambient temperature.
-
IEC 60269: Low-voltage
fuses(all parts);
-
IEC 60282-1: High-voltage
fuses Part 1: Current-limiting fuses;
-
acceptable and relevant
National Standard for enclosed current-limiting fuses.
Type test reports to verify the characteristics of a fuse are
to be submitted for consideration when required.
7.10 Handrail or handles
7.10.1 All
main and emergency switchboards are to be provided with an insulated
handrail or insulated handles suitably fitted on the front of the
switchboard. Where access to the rear is required, a horizontal insulated
handrail is to be suitably fitted on the rear of the switchboard.
7.11 Instruments for alternating current generators
7.11.1 For
alternating current generators not operated in parallel, each generator
is provided with at least one voltmeter, one frequency meter, and
one ammeter with an ammeter switch to enable the current in each phase
to be read, or an ammeter in each phase. Generators above 50 kVA are
also to be provided with a wattmeter.
7.11.2 For
alternating current generators operated in parallel, each generator
is to be provided with a wattmeter, and one ammeter with an ammeter
switch to enable the current in each phase to be read, or an ammeter
in each phase.
7.11.3 For
parallelling purposes, two voltmeters, two frequency meters and two
synchronising devices, of which one at least is to be a synchroscope
or a set of lamps are to be provided. One voltmeter and one frequency
meter are to be connected to the busbars, the other voltmeter and
frequency meter are to be switched to enable the voltage and frequency
of any generator to be measured. Where the electrical power requirement
to maintain the ship in a normal operational and habitable condition
is usually supplied by two or more generators operating in parallel,
the two synchronising devices are to be independent of each other, see also
Pt 16, Ch 2, 2.2 Number and rating of generators and converting equipment 2.2.1.
7.11.4 The
indicators and displays required by Pt 16, Ch 2, 7.11 Instruments for alternating current generators 7.11.1 are to be located and arranged such that they may
be viewed at a single operating position. Where manual paralleling
is provided, generators are to have controls to adjust their voltage
and frequency located at the single operating position. Access to
voltage adjustment is to be restricted, such that it can only be used
by authorised personnel to avoid accidental operation.
7.11.5 Where
the indications of voltage, frequency, current and power are displayed
digitally, the indications are to be separately displayed.
7.12 Instrument scales
7.12.1 The
upper limit of the scale of every voltmeter is to be approximately
120 per cent of the nominal voltage of the circuit, and the nominal
voltage is to be clearly indicated.
7.12.2 The
upper limit of the scale of every ammeter is to be approximately 130
per cent of the normal rating of the circuit in which it is installed.
Normal full load is to be clearly indicated.
7.12.3 Kilowatt
meters for use with alternating current generators which may be operated
in parallel are to be capable of indicating 15 per cent reverse power.
7.12.4 Where
the indications provided by the instrumentation required by Pt 16, Ch 2, 7.11 Instruments for alternating current generators are displayed digitally, nominal
voltage, over voltage, over current and reverse power indications
are to be indicated by an appropriate means. The information provided
is to be clearly visible and immediately available.
7.12.5 In general,
indications provided by instrumentation which are displayed digitally
are not to change more frequently than twice per second.
7.13 Labels
7.13.1 The identification of individual circuits and their devices is to be made
on labels of durable material. The ratings of fuses and settings of protective devices
are also to be indicated. The warning of the presence of electric arc-flash hazards is
also to be shown. Section and distribution boards are to be marked with the rated
voltage.
7.14 Protection
7.15 Wiring
7.15.1 Insulated
wiring connecting components are to be stranded, flame retardant and
manufactured in accordance with a relevant and acceptable National
Standard.
7.16 Position of switchboards
7.16.1 An unobstructed
space not less than 1 m wide is to be provided in front of switchboards
and section boards. When switchboards and section boards contain withdrawable
equipment the unobstructed space is to be not less than 0,4 m wide
with this equipment in its fully withdrawn position.
7.16.2 Where
necessary, the space at the rear of switchboards and section boards
is to be ample to permit maintenance and in general not less than
0,6 m except that this may be reduced to 0,5 m in way of stiffeners
or frames.
7.16.4 So far
as is practicable, pipes are not to be installed directly above or
in front of or behind switchboards, section boards and distribution
boards. If such placing is unavoidable, suitable protection is to
be provided in these positions, see
Pt 15, Ch 2, 2.5 Testing after installation.
7.16.5 For
switchgear and controlgear assemblies, for rated voltages above 1
kV, arrangements are to be made to protect personnel in the event
of gases or vapours escaping under pressure as the result of arcing
due to an internal fault. Where personnel may be in the vicinity of
the equipment when it is energised, this may be achieved by an assembly
that has been tested in accordance with Annex A of IEC 62271- 200
- 2011: High-voltage switchgear and controlgear Part
200: AC metal-enclosed switchgear and controlgear for rated voltages
above 1 kV and up to and including 52 kV and qualified for
classification IAC (internal arc classification).
7.17 Switchboard auxiliary power supplies
7.17.1 Where
the operation of a protective device relies upon a power supply, an
alarm is to be provided to indicate failure of the power supply, unless
its failure causes automatic tripping of the protected circuit.
7.18 Testing
7.18.1 Tests
in accordance with Pt 16, Ch 2, 7.18 Testing 7.18.2 are
to be satisfactorily carried out on all assemblies, complete or in
sections, at the manufacturer's premises, and a test report issued
by the manufacturer.
7.18.3 Calibration
of protective devices and indicating instruments is to be verified
by means of current and/or voltage injection.
7.18.4 Demonstration
of the satisfactory operation of protection circuits, control circuits
and interlocks by means of simulated functional tests.
7.18.5 For
switchgear and controlgear assemblies, for rated voltages above 1
kV, type tests are to be carried out, in accordance with Annex A of
IEC 62271-200 -2011: High-voltage switchgear and controlgear
Part 200: AC metal-enclosed switchgear and controlgear for
rated voltages above 1 kV and up to and including 52 kV and IAC (internal arc classification) assigned, to verify that
the assembly will withstand the effects of an internal arc occurring
within the enclosure at a prospective fault level equal to, or in
excess of, that of the installation.
7.19 Disconnectors and switch-disconnectors
7.19.1 Disconnectors,
switch-disconnectors and their components are to comply with one of
the following standards, amended where necessary for ambient temperature
and other environmental conditions:
-
IEC 60947-3:Low-voltage
switchgear and controlgear Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units;
-
IEC 62271-102:High-voltage
switchgear and controlgear Part 102: Alternating current disconnectors
and earthing switches;
-
Acceptable and
relevant National Standard.
Type test reports to verify the characteristics of a disconnector
or switch-disconnector are to be submitted for consideration when
required.
|