Section 2 System level requirements

2.1.1 All electrical equipment supplied from the main and emergency sources of electrical power and electrical equipment for Mobility systems, Ship Type systems, and emergency services supplied from d.c. sources of electrical power is to be so designed and manufactured that it is capable of operating satisfactorily under normally occurring variations of voltage and frequency.

2.1.2 Unless specified otherwise, a.c. electrical equipment is to operate satisfactorily with the following simultaneous variations, from their nominal value, when measured at the consumer input terminals:

1. voltage:

   permanent variations +6%, -10%

   transient variations due to step changes in load ±20%

   recovery time 1,5 seconds

2. frequency:

   permanent variations ±5%

   transient variations due to step changes in load ±10%

   recovery time 5 seconds

   A maximum rate of change of frequency not exceeding ±1,5 Hz per second during cyclic frequency fluctuations.

2.1.3 Unless specified otherwise, the total harmonic distortion (THD) of the voltage waveform at any switchboard or section-board is not to exceed 8 per cent of the fundamental for all frequencies up to 50 times the supply frequency and no voltage at a frequency above 25 times supply frequency is to exceed 1,5 per cent of the fundamental of the supply voltage. THD is the ratio of the rms value of the harmonic content to the rms value of the fundamental, expressed in per cent and may be calculated using the expression:

where

2.1.4 Where a higher value of THD is specified, all installed equipment and systems are to be designed for the higher specified limit. This relaxation on the limit is to be documented in the harmonic distortion calculation report.

2.1.5 Unless specified otherwise, d.c. electrical equipment is to operate satisfactorily with the following simultaneous variations, from their nominal value, when measured at the consumer input terminals:

1. When supplied by d.c. generator(s) or a rectified a.c. supply:

   	Voltage tolerance (continuous)	±10%
   	Voltage cyclic variation deviation	5%
   	Voltage ripple	10%
   	(a.c. rms over steady state d.c. voltage)

2. When supplied by batteries:

   1. Equipment connected to the batteries during charging: Voltage tolerance +30%, -25%;

   2. Equipment not connected to batteries during charging: Voltage tolerance +20%, -25%.

Different voltage variations as determined by the charging/discharging characteristics, including ripple voltage from the charging device, may be considered. When battery chargers/battery combinations are used as d.c. power supply systems, adequate measures are to be taken to keep the voltage within the specified limits during charging, boost charging and discharging of the battery.

2.1.6 Where the electrical class notation ELS is to be assigned, see Vol 2, Pt 9, Ch 1, 3 Quality of power supplies – ELS notation.

2.1.7 Where weapons or other combat systems may degrade the quality of power supplies, relevant details are to be advised to LR and to the prime contractor in order that the consequences may be established.

2.2.1 Electrical propelling machinery and associated equipment together with equipment for services essential for the propulsion and safety of the ship are to be constructed in accordance with the relevant requirements of this Chapter.

2.2.2 The design and installation of all equipment is to be such that risk of fire due to its failure is minimised. It is, as a minimum, to comply with a National or International Standard revised where necessary for ambient conditions.

2.2.3 Electrical equipment is to be suitable for its intended purpose in all conditions in which it is expected to operate. Equipment is to be designed and constructed in accordance with agreed specified standards. The design and construction is to take account of both functional and environmental requirements. For details of marine environmental conditions, reference should be made to Annex B of IEC 60092: Electrical installations in ships - Part 101: Definitions and general requirements.

2.2.4 Laser light sources for optical fibre systems are to be constructed in accordance with IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements. Acceptance of alternative standards will be subject to consideration by LR.

2.2.5 Optical fibre communication systems are to be constructed in accordance with IEC 60825-2, Safety of laser products – Part 2: Safety of optical fibre communication system. Acceptance of alternative standards will be subject to consideration by LR.

2.2.6 For areas susceptible to deluge or submersion, cable entries are to prevent water ingress. In general, cable entries are to be in accordance with IEC 60092-101, Electrical Installations in Ships – Part 101: Definitions and General Requirements.

2.2.7 Where equipment intended for Mobility or Ship Type systems requires a controlled environment, an alternative means is to be provided to maintain the required environment in the event of a failure of the normal cooling system. Failure of the cooling system is to initiate an alarm. Duplication of the equipment requiring cooling can be provided instead of an alternative means of cooling, providing that the duplicated equipment is fed from an alternative, independent cooling system.

2.2.8 Assessment of performance parameters, such as accuracy, repeatability, etc. are to be in accordance with an acceptable specialised naval standard, national or international standard, e.g. IEC 60051, Direct acting indicating analogue electrical measuring instruments and their accessories.

2.2.9 Special consideration will be given to arrangements that comply with a relevant and acceptable specialised Naval, National or International Standard, such as IEC 60092-504, Electrical Installation on Ships – Special Features: Control and Instrumentation.

2.2.10 All electrical equipment is to be constructed or selected and installed such that:

1. live parts cannot be inadvertently touched, unless they are supplied at the safety voltage specified in Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding 2.4.2.(h);

2. it does not cause injury when handled or touched in the normal manner; and

3. it is unaffected by any water, steam or oil and oil vapour to which it is likely to be exposed.

Where not exposed to direct liquid spray, electrical equipment having, as a minimum, the degrees of protection as specified in IEC 60092-201 for the relevant location will satisfy these requirements. For high voltage electrical equipment, the degrees of protection as specified in IEC 60092-503 Electrical installations in ships – Part 503: Special features AC supply systems with voltages in the range of above 1kV up to and including 36kV for the relevant location will satisfy these requirements.Where the equipment may be exposed to direct liquid spray the degree of protection is not to be less than IPX4. Where the equipment may be exposed to possible liquid immersion, the degree of protection is not to be less than IPX7.

2.2.11 Switchboards, section boards and distribution boards supplying Mobility or Ship Type systems, and emergency services, as well as cables from the respective generators to and between these boards, are to be arranged to avoid areas of high fire risk and elevated temperatures, for example, in close proximity to incinerators and boilers.

2.2.12 Electrical equipment, as far as is practicable, is to be located:

1. such that it is accessible for the purpose of maintenance and survey;

2. clear of flammable material;

3. in spaces adequately ventilated to remove the waste heat liberated by the equipment under full load conditions, at the ambient conditions specified in Vol 2, Pt 9, Ch 1, 2.3 Ambient reference and operating conditions;

4. where flammable gases cannot accumulate. If this is not practicable, electrical equipment is to be of the appropriate ‘safe type’, see Vol 2, Pt 9, Ch 5, 4 Electrical equipment for use in explosive gas atmospheres or in the presence of combustible dusts;

5. where it is not exposed to the risk of mechanical injury or damage from water, steam or oil.

2.2.13 Equipment design and the choice of materials are to reduce the likelihood of fire, ensuring that:

1. where the electrical energised part can cause ignition and fire, it is contained within the bounds of the enclosure of the electrotechnical product;

2. the design, material(s) and construction of the enclosure minimises, as far as is practicable, any internal ignition causing ignition of adjacent materials; and

3. where surfaces of the electrotechnical products can be exposed to external fire, they do not, as far as practicable, contribute to the fire growth.

2.2.14 Insulating materials and insulated windings are to be oil resistant to tracking, moisture, sea air, oil and oil vapour unless special precautions are taken to protect them.

2.2.15 The minimum creepage and clearance distances provided for electrical connections, terminals and similar bare live parts are to be in accordance with a relevant International or National Standard for the equipment or apparatus concerned. In cases where the rated voltage is outside that given in the Standard or where no Standard is available, the minimum creepage and clearance distances provided are to be in accordance with Vol 2, Pt 9, Ch 3, 5.7 Creepage and clearance distances. Details of alternative proposals including supporting design rationale and demonstration may be submitted for consideration.

2.2.16 Studs, screw-type of spring-type clamp terminations, satisfactory for the normal operating currents and voltages, are to be provided in electrical equipment for the connection of external cable, or bus-bar conductors, as appropriate, see also Vol 2, Pt 9, Ch 3, 8.15 Electric cable ends. There is to be adequate space and access for the terminations.

2.2.17 The design of equipment is to enable ease of access to all parts requiring inspection or replacement in service.

2.2.18 Equipment is not to remain live through the control circuits and/or pilot lamps when switched off by the control switch. This does not apply to synchronising switches and/or plugs. Where equipment such as anti-condensation heaters is fed from a supply separate from the main supply, isolation arrangements are to be provided.

2.2.19  The operation of all electrical equipment and the lubrication arrangements are to be efficient under such conditions of vibration and shock as arise in normal practice. This requirement excludes military aspects that are required to be defined by Vol 2, Pt 1, Ch 3, 4.9 Military requirements

2.2.20 All nuts and screws and clamping devices used in connection with current-carrying, supporting and working parts are to be provided with means to ensure that they cannot work loose by vibration and shock as arise in normal practice.

2.2.21 To allow ease of access, connectors are to be spaced far enough apart to permit connection and disconnection. At test points, adequate clearance is to be provided between connection points and controls to provide access for testing.

2.2.22 Conductors and equipment are to be placed at such a distance from the magnetic compasses, or are to be so disposed, that the interfering magnetic field is negligible when circuits are switched on and off.

2.2.23 Where electrical power is used for propulsion, the equipment is to be so arranged that it will operate satisfactorily in the event of partial flooding by bilge water above the tank top up to the bottom floor plate level under the normal angles of inclination given in Vol 2, Pt 9, Ch 1, 2.3 Ambient reference and operating conditions for Mobility systems, see Vol 2, Pt 7, Ch 2, 4 Drainage of machinery spaces. This requirement excludes military aspects that are required to be defined by Vol 2, Pt 1, Ch 3, 4.9 Military requirements.

2.2.24 Cables for emergency alarms and their power sources are to be in accordance with Vol 2, Pt 9, Ch 1, 2.5 Operation under fire conditions.

2.2.25 Electrical equipment and cables for emergency alarms are to be so arranged that the loss of alarms in any one area due to localised fire, collision, flooding or similar damage is minimised, see Vol 2, Pt 9, Ch 1, 2.8 Labels, signs and noticesand Vol 2, Pt 9, Ch 1, 2.5 Operation under fire conditions.

2.3.1 Reference is to be made toVol 2, Pt 1, Ch 3, 4.4 Ambient reference conditions, Vol 2, Pt 1, Ch 3, 4.5 Ambient operating conditions and Vol 2, Pt 1, Ch 3, 4.6 Inclination of ship for the requirements concerning: Ambient reference conditions and Ambient operating conditions, with regards to the rating of Mobility and/or Ship Type electrical equipment for classification of restricted and unrestricted service conditions, and satisfactory operating conditions of machinery Mobility and/or Ship Type systems.

2.3.2 Where electrical equipment is installed within environmentally controlled spaces, the ambient temperature for which the equipment is suitable for operation at its rated capacity may be reduced to a value not less than 35°C provided:

• the equipment is not for use for emergency services and is located outside of machinery space(s);
• temperature control is achieved by at least two cooling units so arranged that in the event of loss of one cooling unit, for any reason, the remaining unit(s) is (are) capable of satisfactorily maintaining the design temperature;
• the equipment is able to be initially set to work safety within a 45°C ambient temperature until such a time that the lesser ambient temperature may be achieved; the cooling equipment is to be rated for a 45°C ambient temperature;
• alarms are provided, at a continually attended control station, to indicate any malfunction of the cooling units.

2.3.3 Where equipment is to comply with Vol 2, Pt 9, Ch 1, 2.3 Ambient reference and operating conditions 2.3.2, it is to be ensured that electrical cables for their entire length are adequately rated for the maximum ambient temperature to which they are exposed along their length.

2.3.4 Equipment used for cooling and maintaining the lesser ambient temperature in accordance with Vol 2, Pt 9, Ch 1, 2.3 Ambient reference and operating conditions 2.3.2 are considered Mobility or Ship Type systems and are to satisfy the requirements of Vol 2, Pt 9, Ch 3, 4.2 Essential services 4.2.1.

2.4.1 Except where exempted by Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding 2.4.2, all non-current carrying exposed metal parts of electrical equipment and cables are to be earthed for personnel protection against electric shock. Bonding is to give a substantially equal potential and a sufficiently low earth fault loop impedance to ensure correct operation of protective devices.

2.4.2 The following parts may be exempted from the requirements of Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding 2.4.1:

1. lamp-caps, where suitably shrouded;

2. shades, reflectors and guards supported on lampholders or light fittings constructed of, or shrouded in, non-conducting material;

3. metal parts on, or screws in or through, non-conducting materials, which are separated by such material from current-carrying parts and from earthed non-current carrying parts in such a way that in normal use they cannot become live or come into contact with earthed parts;

4. apparatus which is constructed in accordance with the principle of double insulation;

5. bearing housings which are insulated in order to prevent circulation of current in the bearings;

6. clips for fluorescent lamps;

7. cable clips and short lengths of pipes for cable protection;

8. apparatus supplied at a safety voltage not exceeding 55 V direct current or 55 V, root mean square, between conductors, or between any conductor and earth in a circuit isolated from the supply. Autotransformers are not to be used for the purpose of achieving the alternating current voltage;

9. apparatus or parts of apparatus which although not shrouded in insulating material is nevertheless otherwise so guarded that it cannot be touched and cannot come in contact with exposed metal.

2.4.3 Where extraneous-conductive parts (i.e. parts not forming part of the electrical installation and liable to introduce an electric potential) are not bonded by separate earthing conductors, details are to be submitted that demonstrate that a permanent, metal-to-metal connection of negligible impedance, which will not degrade due to corrosion or vibration, will be achieved.

2.4.4 Armouring, braiding and other metal coverings are to be effectively earthed. Where the armouring, braiding and other metal coverings are earthed at one end only, they are to be adequately protected and insulated at the unearthed end with the insulation being suitable for the maximum voltage that may be induced. See Vol 2, Pt 9, Ch 5, 4.9 Cable and cable installation 4.9.2 for earthing of cables in hazardous zones or spaces.

2.4.5 The electrical continuity of all metal coverings of cables throughout the length of the cable, particularly at joints and tappings, is to be ensured.

2.4.6 Earthing conductors are to be of copper or other corrosion-resistant material and be securely installed and protected where necessary against damage and also, where necessary, against electrolytic corrosion. Connections are to be so secured that they cannot work loose under vibration. It is recommended that earthing conductors carrying RF currents should be solid strip, not braid, to minimise the impedance.

2.4.7 The nominal cross-section areas of copper earthing conductors for electrical equipment are, in general to be equal to the cross-section of the current-carrying conductor up to 16 mm², with a minimum of 1,5 mm². Above this figure they are to be equal to at least half the cross-section of the current-carrying conductor with a minimum of 16 mm².

2.4.8 The nominal cross-sectional areas of copper earthing conductors for amouring, braiding and other metal coverings of cables are, in general, to be equal to the equivalent cross-section of the armouring, braiding and other metal coverings with a minimum of 1,5 mm².

2.4.9 Earthing conductors of materials other than copper are to have a conductance not less than that specified for an equivalent copper earthing conductor.

2.4.10 The connection of the earthing conductor to the hull of the ship is to be made in an accessible position, and is to be secured by a screw or stud of a diameter appropriate for the size of the earthing conductor, but not less than 6 mm which is to be used for this purpose only. Bright metallic surfaces at the contact areas are to be ensured immediately before the nut or screw is tightened and, where necessary, the joint is to be protected against electrolytic corrosion. The connection is to remain unpainted.

2.4.11 Bonding straps for the control of static electricity are required for refuelling tanks and piping systems, for flammable products and solids liable to release flammable gas and/or combustible dust, which are not permanently connected to the hull of the ship either directly or via their bolted or welded supports and where the resistance between them and the hull exceeds 1MΩ.

2.4.12 Where bonding straps are required for the control of static electricity, they are to be robust, that is, having a cross-sectional area of at least 10 mm², and are to comply with Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding 2.4.6 and Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding 2.4.10.

2.5.1 As a minimum, the following emergency services and their emergency power supplies are required to be capable of being operated under fire conditions:

• Emergency fire pump.
• Control and power systems to power-operated fire doors and status indication for all fire doors.
• Control and power systems to power-operated watertight doors and their status indication.
• Emergency lighting.
• Fire and general emergency alarms.
• Fire detection systems.
• Fire-extinguishing systems and fire-extinguishing media release alarms.
• Fire safety stops, see also Vol 2, Pt 9, Ch 5, 4.9 Cable and cable installation 4.9.2.
• Low location lighting, see also Vol 2, Pt 9, Ch 6, 4.6 Escape route or low location lighting (LLL) 4.6.3
• Crew and embarked personnel address systems.

2.5.2 Where cables for the emergency services listed in Vol 2, Pt 9, Ch 1, 2.5 Operation under fire conditions 2.5.1 pass through high fire risk areas, main vertical or horizontal fire zones other than those which they serve, they are to be so arranged that a fire in any of these areas or zones does not affect the operation of the emergency service in any other area or zone. This may be achieved either by:

• cables being of a fire-resistant type complying with Vol 2, Pt 9, Ch 3, 8.5 Construction 8.5.3, and at least extending from the main control/monitoring panel to the nearest local distribution panel serving the relevant area or zone; or
• there being at least two-loops/radial distributions run as widely apart as is practicable and so arranged that in the event of damage by fire at least one of the loops/radial distributions remains operational.

Areas of high fire risk include:

1. Machinery spaces including generator compartments and gas turbine compartments but excluding those spaces which do not contain machinery having a pressure lubrication system and where the storage of combustibles is prohibited.

2. Galleys.

3. Compartments with tanks containing flammable liquids with a flash point lower than 60°C or with a temperature above 32°C.

4. Compartments containing liquid oxygen.

5. Fuel, petrol, oil or lubricant pump spaces.

6. Magazines for munitions and armaments.

2.5.3 Where the cables for the power supplies for the emergency services listed in Vol 2, Pt 9, Ch 1, 2.5 Operation under fire conditions 2.5.1 pass through high fire risk areas, main vertical or horizontal fire zones other than those which they serve, they are to be of a fire resistant type complying with Vol 2, Pt 9, Ch 3, 8.5 Construction 8.5.3, extending at least to the local distribution panel serving the relevant area or zone.

2.5.4 Fire-resistant electrical cables for the emergency services listed in Vol 2, Pt 9, Ch 1, 2.5 Operation under fire conditions 2.5.1, including their power supplies, are to be run as directly as is practicable, having regard to any special installation requirements, for example those concerning minimum bend radii.

2.6.1 Flooding of spaces along the ship bottom that are not fitted with a double bottom is not to result in the loss of the ability to provide electrically operated fire, ship, crew and embarked personnel emergency safety systems outside of the spaces.

2.6.2 Installation of electrical equipment necessary to provide fire, ship, crew and embarked personnel emergency safety systems in spaces along the ship bottom not fitted with a double bottom is to be avoided, wherever practical. Where it is proposed to install electrical equipment, including cabling, necessary to provide fire, ship, crew and embarked personnel emergency safety systems in such spaces, evidence is to be submitted to demonstrate that required emergency services will be available in other spaces in the event of flooding of the space not fitted with a double bottom.

2.7.1 With the exception of dedicated electrical supplies to systems fulfilling military requirements, all other electrical supplies are to comply with these Rules. The Rules are applicable to electrical equipment and systems to the point of isolation of the military system or equipment. The point of isolation is the supply side of the isolating switch, MCCB panel, fuse panel or distribution panel dedicated to the military system or equipment.

2.7.2 Dedicated electrical supply arrangements to military systems are to be in accordance with recognised International/National/specialised naval standards.

2.7.3 Where isolating equipment is used for both military and other services, the Rule requirements are to be applied.

2.7.4 Automatic, hand and emergency changeover switches to military systems on the ship’s supply system are to comply with these Rules.

2.8.1 Labels, signs and notices required by this Chapter are to be positioned in clearly visible locations which will not be obscured.

2.8.2 Labels, signs and notices are to be easy to read under the expected operating conditions. Character height in accordance with Table 1.2.1 Character height and viewing distance will be considered to satisfy this requirement.

2.8.3 Controls, indicators and displays required by this Chapter are to be labelled to indicate their function. Labels are to be positioned in a manner that associates the label with the item being labelled.

2.8.4 Labels, signs and notices are to use short, clear messages. In general, warning signs and notices are to comprise:

• a word signalling the gravity of the risk (e.g. Danger, Warning or Caution)
• a statement of the nature and/or consequence of the hazard, and wherever practical, an instruction giving appropriate behaviour to avoid the hazard.

2.8.5 Electrical equipment that presents an electric arc-flash hazard to personnel is to be clearly marked, see Pt 16, Ch 2, 8.1 General 8.1.1