Section 7 Switchgear and controlgear assemblies

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:

1. IEC 61439: Low-voltage switchgear and controlgear assemblies (relevant parts);

2. 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;

3. 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;

4. 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;

5. IEC 60255: Measuring relays and protection equipment; or

6. an acceptable and relevant National Standard.

In addition, the requirements of Pt 6, Ch 2, 7.2 Busbars to Pt 6, Ch 2, 7.19 Disconnectors and switch-disconnectors are to be complied with.

7.2.1 Busbars and their connections are to be of copper or aluminium, all connections being so made as to inhibit corrosion/oxidisation between current-carrying mating faces, which may result in poor electrical contact giving rise to overheating. 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 For bare conductors, where no precautions are taken against surface oxidisation, the temperature rise limit at rated normal current is not to exceed 45°C. Where suitable precautions are taken against surface oxidisation, e.g. by using silver, nickel or tin coated terminations, a temperature rise limit not exceeding 60°C is permitted. Where the busbar temperature rises are above 45°C it is to be ensured that there is no adverse effect on equipment adjacent to and/or connected to the busbars and that the temperature rise limits of any materials in contact with the busbars are not exceeded. A test report or calculation to verify the rated current assigned to the busbar system is to be submitted for consideration when required.

7.3.1 Circuit-breakers are to comply with one of the following standards amended where necessary for ambient temperature:

1. IEC 60947-2: Low-voltage switchgear and controlgear – Part 2: Circuit-breakers; or

2. IEC 62271-100:High-voltage switchgear and controlgear – Part 100: Alternating current circuit-breakers; or

3. 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 6, Ch 2, 6.1 General 6.1.4.

7.3.6 Air circuit-breakers for essential or emergency services and rated at 800 A and above are to have a cumulative count kept of the switching operations of the electrical contacts. This count, along with the manufacturer’s 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.

7.4.1 High-voltage contactors are to comply with one of the following standards amended where necessary for ambient temperature:

1. IEC 62271-106: High-voltage switchgear and controlgear – Part 106: Alternating current contactors, contactor-based controllers and motor-starters; or

2. 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.

7.5.1 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.

7.5.2 For assemblies with a rated voltage of up to and including 1kV, the requirement of Pt 6, 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 6, 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 6, 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.

• 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 main switchboards rated at above 1kV, a minimum clearance distance of 25 mm is required for busbars and other bare conductors.

An alternative relevant National or International Standard may be used when an acceptable justification is submitted as part of the documentation required by Pt 6, Ch 2, 1.3 Documentation required for supporting evidence 1.3.4.

7.5.4 Suitable shrouding or barriers are to be provided in way of connections to equipment, where necessary, to maintain the minimum distances in Table 2.7.1 Minimum clearance distances.

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 6, 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.

7.7.1 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 6, Ch 2, 7.16 Position of switchboards 7.16.4.

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

7.9.1 Fuses are to comply with one of the following Standards amended where necessary for ambient temperature:

1. IEC 60269 (all parts): Low-voltage fuses ;

2. IEC 60282-1: High-voltage fuses – Part 1: Current-limiting fuses;

3. 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.

7.10.1 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.

7.11.1 For alternating current generators not operated in parallel, each generator is to be 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 paralleling 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 6, 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 6, Ch 2, 7.11 Instruments for alternating current generators 7.11.1 to Pt 6, Ch 2, 7.11 Instruments for alternating current generators 7.11.3 are to be located and arranged such that they may be viewed at a single operating position. Where manual paralleling is provided, it is to be possible to adjust voltage and frequency at this position; 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 will generally 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.

7.12.1 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 6, 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.

7.13.1 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.

7.14.1  See Pt 6, Ch 2, 6 System design – Protection.

7.15.1 Insulated wiring connecting components are to be stranded, flame retardant and manufactured in accordance with a relevant and acceptable National Standard.

7.16.1 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.

7.16.3 The spaces defined in Pt 6, Ch 2, 7.16 Position of switchboards 7.16.1 and Pt 6, Ch 2, 7.16 Position of switchboards 7.16.2 are to have non-slip surfaces. Where access to live parts within switchboards and section boards is normally possible the surface is, in addition, to be electrically insulated.

7.16.4 So far as is practicable, pipes are not 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 5, Ch 13, 2 Construction and 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).

7.17.1 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.

7.18.1 Tests in accordance with Pt 6, Ch 2, 7.18 Testing 7.18.2to Pt 6, Ch 2, 7.18 Testing 7.18.4are 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, see also Pt 6, Ch 2, 1.4 Surveys 1.4.2.

7.18.2 A high voltage test, see Pt 6, Ch 2, 21 Testing and trials.

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.

7.19.1 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:

1. IEC 60947–3: Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors, switch-disconnectors and fuse-combination units;

2. IEC 62271-102: High-voltage switchgear and controlgear – Part 102: High-voltage alternating current disconnectors and earthing switches;

3. 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.