Chapter 11 - Electrical Installations

11.1 General

11.1.1 Electrical installations should be such that:

• .1 all electrical auxiliary services necessary for maintaining the craft in normal operation and habitable conditions will be ensured without recourse to the emergency source of electrical power;

• .2 electrical services essential for safety will be ensured under various emergency conditions; and

• .3 the safety of passengers, crew and craft from electrical hazards will be ensured.

The System Safety Assessment (SSA) should include the electrical system, taking into account the effects of electrical failure on the systems being supplied. In cases where faults can occur without being detected during routine checks on the installations, the analysis should take into account the possibility of faults occurring simultaneously or consecutively.

11.1.2 The electrical system should be designed and installed so that the probability of the craft being at risk of failure of a service is extremely remote.

11.1.3 Where loss of a particular essential service would cause serious risk to the craft, the service should be fed by at least two independent circuits both fed in such a way that no single failure in the electrical supply or distribution systems would affect both supplies.

11.1.4 The securing arrangements for heavy items, i.e. accumulator batteries, should prevent excessive movement during the accelerations according to 3.4.4.

11.1.5 Precautions should be taken to minimise risk of supplies to essential and emergency services being interrupted by the inadvertent or accidental opening of switches or circuit-breakers.

11.1.6 Electronic equipment essential for propulsion and attitude control purposes should be approved and installed according to a recognized IEC Standard.

11.2 Main Source of Electrical Power

11.2.1 A main source of electrical power of sufficient capacity to supply all those services mentioned in 11.1.1 should be provided. The main source of electrical power should consist of at least two generating sets supplying two main switchboards.

11.2.2 The capacity of these generating sets should be such, that in the event of any one generating set being stopped or failing in the ground effect mode, it will still be possible to supply those services necessary to provide the normal operational conditions of propulsion, attitude control in ground effect and safety. Minimum comfortable conditions of habitability should also be ensured which include at least adequate services for cooking, heating or cooling, domestic refrigeration, mechanical ventilation, and sanitary and fresh water.

11.2.3 The arrangements of the craft's main source of electrical power should be such that the services referred to in 11.1.1.1 can be maintained regardless of the speed of the propulsion machinery.

11.2.4 One source of power independent from the main propulsion plant should be capable of providing the electrical services necessary to start the main propulsion plant from dead craft condition.

11.2.5 Where charging units or converters constitute an essential part of the electrical supply system required by this section, the system should be so arranged as to ensure the same continuity of supply as is stated in 11.2.2.

11.2.6 A main electric lighting system, which should provide illumination throughout those parts of the craft normally accessible to and used by passengers and crew should be supplied from the main source of electrical power.

11.2.7 The two main switchboards should be located in a dry space with a minimum risk of fire.

11.2.8 The connection of generating sets and any other duplicated equipment should be equally divided between the two switchboards. The generators should operate in single operation. Equivalent arrangements may be permitted to the satisfaction of the Administration.

11.2.9 Separation and duplication of electrical supply should be provided for duplicated consumers of essential services. During normal operation the systems may be connected to the same power-bus, but facilities for easy separation should be provided. Each system should be able to supply all equipment necessary to maintain the control of propulsion, steering, stabilization, navigation, lighting and ventilation, and allow starting of the largest essential electric motor at any load. Automatic load-dependent disconnection of non-essential consumers may be allowed.

11.3 Emergency Source of Electrical Power

11.3.1 A self-contained emergency source of electrical power should be provided.

11.3.2 The emergency source of electrical power, any associated transforming equipment, transitional source of electrical power, emergency switchboard and emergency lighting switchboard should be located above the waterline in the final condition of damage as referred to in chapter 1, operable in that condition and readily accessible.

11.3.3 The location of the emergency source of electrical power and any associated transforming equipment, the transitional source of emergency power, the emergency switchboard and the emergency electrical lighting switchboards in relation to the main source of electrical power, any associated transforming equipment and the main switchboard should be such as to ensure that a fire or other casualty in spaces containing the main source of electrical power, any associated transforming equipment, will not interfere with the supply, control, and distribution of emergency electrical power. As far as practicable, the space containing the emergency source of electrical power, any associated transforming equipment, the transitional source of emergency electrical power and the emergency switchboard should not be contiguous to the boundaries of main machinery spaces or those spaces containing the main source of electrical power, any associated transforming equipment, or the main switchboard.

11.3.4 Distribution systems should be so arranged that the feeders from the main and emergency sources be separated both vertically and horizontally as widely as practicable.

11.3.5 The emergency source of electrical power may be either a generator or an accumulator battery, which should comply with the following:

• .1 Where the emergency source of electrical power is a generator, it should be:

  • .1 driven by a suitable prime mover with an independent supply of fuel having a flash point which meets the provisions of 6.1.1.2.2;

  • .2 started automatically upon failure of the electrical supply from the main source of electrical power and should be automatically connected to the emergency switchboard. Those services referred to in 11.4 should then be transferred to the emergency generating set. The automatic starting system and the characteristic of it be such as to permit the emergency generator to carry its full rated load as quickly as is safe and practicable, subject to a maximum of 15 s; and

  • .3 provided with a transitional source of emergency electrical power according to 11.4; and

• .2 Where the emergency source of electrical power is an accumulator battery, it should be capable of:

  • .1 carrying the emergency electrical load without recharging while maintaining the voltage of the battery throughout the discharge period within 12% above or below its nominal voltage;

  • .2 automatically connecting to the emergency switchboard in the event of failure of the main source of electrical power; and

  • .3 immediately supplying at least those services specified in 11.4.

11.3.6 The emergency switchboard should be installed as near as is practicable to the emergency source of electrical power.

11.3.7 Where the emergency source of electrical power is a generator, the emergency switchboard should be located in the same space unless the operation of the emergency switchboard would thereby be impaired.

11.3.8 No accumulator battery fitted in accordance with this section should be installed in the same space as the emergency switchboard. An indicator should be mounted in a suitable space at the craft's operating compartment to indicate when the batteries constituting either the emergency source of electrical power or the transitional source of emergency electrical power referred to in 11.3.5.1.3 are being discharged.

11.3.9 The emergency switchboard should be supplied during normal operation from one main switchboard by an interconnection feeder which should be adequately protected at the main switchboard against overload and short circuit and which should be disconnected automatically at the emergency switchboard upon failure of the main source of electrical power. A manual switchover to the other main switchboard must be possible.

11.3.10 In order to ensure ready availability of the emergency source of electrical power, only emergency circuits should be fed by the emergency switchboard.

11.3.11 The emergency generator and its prime mover and any emergency accumulator battery should be so designed and arranged as to ensure that they will function at full rated power when the craft is upright and when the craft has a list or trimming in accordance with 8.1.1.12, including any damage cases considered in chapter 1, or is in any combination of angles within those limits.

11.3.12 Where accumulator batteries are installed to supply emergency, back up or engine start-up services, provisions should be made to charge them in situ from a reliable onboard supply. Charging facilities should be designed to permit the supply of services, regardless of whether battery is on charge or not. Means should be provided, by which the batteries on board can be checked before each journey (e.g. minimum allowable voltage at a laid down load). The risk of overcharging or overheating the batteries should be minimised. Means for efficient air ventilation should be provided. A total number of two battery systems and two chargers for all battery services except for radio installations should be sufficient.

11.3.13 For unassisted craft, the emergency electrical power available should be sufficient to supply all the services that are essential for safety in an emergency. The emergency source of electrical power should be capable, having regard to starting currents and the transitory nature of certain loads, of supplying simultaneously at least the following services for the periods specified hereinafter, if they depend upon an electrical source for their operation:

• .1 for a period of 12 h, emergency lighting:

  • .1 at the stowage positions of life-saving appliances;

  • .2 at all escape routes, such as alleyways, stairways, exits from service spaces, embarkation points, etc.;

  • .3 in the passenger compartments;

  • .4 in the machinery spaces and main emergency generating spaces including their control positions;

  • .5 in control stations; and

  • .6 at the stowage positions for any fireman's outfits provided in accordance with chapter 6;

• .2 for a period of 12 h:

  • .1 the navigation lights, and other lights required by the International Regulations for Preventing Collisions at Sea, 1972, in force;

    .2 electrical internal communication equipment for announcements for passengers and crew required during evacuation;

    .3 fire detection and general alarm system and manual fire alarms; and

    .4 remote control devices of fire-extinguishing systems, if electrical;

• .3 for a period of 4 h on intermittent operation:

  • .1 the daylight signalling lamps, if they have no independent supply from their own accumulator battery; and

  • .2 the craft's whistle, if electrically driven;

• .4 for a period of 12 h:

  • .1 the navigational equipment as recommended in chapter 12;

  • .2 essential electrically powered instruments and controls for propulsion machinery, if alternate sources of power are not available for such devices;

  • .3 the firefighting systems recommended in 6.1.6;

  • .4 the emergency bilge pump and all equipment essential for the operation of electrically powered remote controlled bilge valves as recommended in chapter 9; and

  • .5 craft radio facilities and other loads as set out in 13.12.2; and

• .5 for a period of 12 hours, any essential power drives for directional control devices including those required to direct thrust forward and astern.

11.3.14 For assisted craft, the emergency source of power should be capable of supplying simultaneously the following services:

• .1 for a period of 5 h emergency lighting:

  • .1 at the stowage positions of life-saving appliances;

    .2 at all escape routes, such as alleyways, stairways, exits from accommodation and service spaces, embarkation points, etc;

    .3 in the public spaces;

    .4 in the machinery spaces and main emergency generating spaces, including their control positions;

    .5 in control stations; and

    .6 at the stowage positions for any firemen's outfits fitted in accordance with chapter 6;

• .2 for a period of 5 h;

  • .1 main navigation lights, except for "not under command" lights;

  • .2 electrical internal communication equipment for announcements for passengers and crew required during evacuation;

  • .3 fire-detection and general alarm system and manual fire alarms; and

  • .4 remote control devices of fire-extinguishing systems, if electrical;

• .3 for a period of 4 h of intermittent operation:

  • .1 the daylight signalling lamps, if they have no independent supply from their own accumulator battery; and

  • .2 the craft's whistle, if electrically driven;

  .4 for a period of 5 h:

  • .1 craft radio facilities and other loads as set out in chapter 13; and

  • .2 essential electrically powered instruments and controls for propulsion machinery, if alternate sources of power are not available for such devices;

  .5 for a period of 12 h, the "not under command" lights; and

  .6 for a period of 10 min, power drives for directional control devices, including those required to direct thrust forward and astern, unless there is a manual alternative acceptable to the Administration as complying with 4.2.3.

11.3.15 Transitional source of emergency electrical power

The transitional source of emergency electrical power recommended in 11.3.5.1.3 may consist of an accumulator battery suitably located for use in an emergency which should operate without recharging while maintaining the voltage of the battery throughout the discharge period within 12% above or below its nominal voltage and be of sufficient capacity and so arranged as to supply automatically in the event of failure of either the main and emergency source of electrical power at least the following services, if they depend upon an electrical source for their operation for a period of 30 min, the load specified in 11.3.14.1 to 11.3.14.3.

11.3.16 The provisions of 11.3.15 may be considered satisfied without the installation of a transitional source of emergency electrical power if each of the services recommended by that paragraph have independent supplies, for the period specified, from accumulator batteries suitably located for use in an emergency. The supply of emergency power to the instruments and controls of the propulsion and direction systems should be uninterruptible.

11.3.17 Provisions should be made for the periodic testing of the complete emergency system, including the emergency consumers recommended in 11.3.13 or 11.3.14 and 11.3.15, and should include the testing of automatic starting arrangements.

11.3.18 Distribution systems should be so arranged that fire in any main vertical zone will not interfere with services essential for safety in any other such zone. This provision will be met if main and emergency feeders passing through any such zone are separated both vertically and horizontally as widely as is practicable.

11.4 Starting Arrangements for Generating Sets

11.4.1 The generating sets should be capable of being readily started in their cold condition at a temperature of 0°C. If this is impracticable, or if lower temperatures are likely to be encountered, provisions should be made for heating arrangements to ensure ready starting of the generating sets.

11.4.2 The main generating set (emergency generator set) should be equipped with starting devices with a stored energy capability of at least six (three) consecutive starts. The source of stored energy should be protected to preclude critical depletion by the automatic starting system. A second source of energy should also be provided for an additional six (three) starts.

11.4.3 The stored energy of the emergency generating set should be maintained at all times, as follows:

• .1 electrical and hydraulic starting systems should be maintained from the emergency switchboard;

• .2 compressed air starting systems may be maintained by the main or auxiliary compressed air receivers through a suitable non-return valve or by an emergency air compressor which, if electrically driven, is supplied from the emergency switchboard; and

• .3 all of these starting, charging and energy storing devices should be located in the emergency generator space. These devices should not be used for any purpose other than the operation of the emergency generating set. This does not preclude the supply to the air receiver of the emergency generating set from the main or auxiliary compressed air system through the non-return valve fitted in the emergency generator space.

11.5 Steering and Attitude Control

11.5.1 Where steering and/or attitude control of a craft is essentially dependent on the continuous availability of electric power, it should be served by at least three independent circuits, two of which should be fed from the main switchboards and one from the emergency source of electric power including the transitional source, both located in such a position as to be unaffected by fire or flooding affecting the main source of power. Failure of either supply should not cause any risk to the craft or passengers during switching to the alternative supply and such switching arrangements should meet the provisions in 4.2.6. These circuits should be provided with short circuit protection and an overload alarm.

11.5.2 Protection against excess current may be provided, in which case it should be for not less than twice the full load current of the motor or circuit so protected, and should be arranged to accept the appropriate starting current with a reasonable margin. Where three-phase supply is used, an alarm should be provided in a readily observed position in the craft's operating compartment that will indicate failure of any one of the phases.

11.5.3 Where such systems are not essentially dependent on the continuous availability of electric power but at least one alternative system, not dependent on the electric supply, is installed, then the electrically powered or controlled system may be fed by a single circuit protected in accordance with 11.5.2.

11.5.4 The provisions of chapters 4 and 15 for power supply of the directional control systems and stabilization systems of the craft should be met.

11.6 Precautions Against Shock, Fire and Other Hazards of Electrical Origin

11.6.1 Exposed metal parts of electrical machines or equipment which are not intended to be live but which are liable under fault conditions to become live should be earthed unless the machines or equipment are:

• .1 supplied at a voltage not exceeding 55 V direct current or 55 V, root-mean-square between conductors; auto-transformers should not be used for the purpose of achieving this voltage; or

• .2 supplied at a voltage not exceeding 250 V by safety isolating transformers supplying only one consuming device; or

• .3 constructed in accordance with the principle of double insulation.

11.6.2 All electrical apparatus should be so constructed and so installed as not to cause injury when handled or touched in the normal manner.

11.6.3 Main and emergency switchboards should be so arranged as to give easy access, as may be needed, to apparatus and equipment, without danger to personnel. The sides and the rear and, where necessary, the front of switchboards should be suitably guarded. Exposed live parts having voltages to earth exceeding a voltage to be specified by the Administration should not be installed on the front of such switchboards. Where necessary, non-conducting mats or gratings should be provided at the front and rear of the switchboard.

11.6.4 When a distribution system, whether primary or secondary, for power, heating or lighting, with no connection to earth is used, a device capable of continuously monitoring the insulation level to earth and of giving an audible and visual indication of abnormally low insulation values should be provided. For limited secondary distribution systems the Administration may accept a device for manual checking of the insulation level.

11.6.5 Cables and wiring

11.6.5.1 Power cables and control or communication cables as well as cables of each main supply and emergency supply should be installed on separated cable runs. Power and control cables for emergency consumers should be fire-resistant when they pass through fire risk areas. Where, for safety reasons, a system has duplicated supply and/or control cables, the cable routes should be placed as far apart as possible. All metal sheaths and armour of cables should be electrically continuous and should be earthed.

11.6.5.2 All electric cables and wiring external to equipment should be at least of a halogen-free flame-retardant type and should be so installed as not to impair their original flame-retarding properties. Where necessary for particular applications, the Administration may permit the use of special types of cables such as radio frequency cables, which do not comply with the foregoing.

11.6.5.3 Cables and wiring serving essential or emergency power, lighting, internal communications or signals should, so far as practicable, be routed clear of machinery spaces and their casing and other high fire risk areas. Where practicable, all such cables should be run in such a manner as to preclude their being rendered unserviceable by heating of the bulkheads that may be caused by a fire in an adjacent space.

11.6.5.4 Where cables which are installed in hazardous areas introduce the risk of fire or explosion in the event of an electrical fault in such areas, special precautions against such risks should be taken to the satisfaction of the Administration.

11.6.5.5 Cables and wiring should be installed and supported in such manner as to avoid chafing or other damage.

11.6.5.6 Terminations and joints in all conductors should be so made as to retain the original electrical, mechanical, flame-retarding and, where necessary, fire-resisting properties of the cable.

11.6.6.1 Each separate circuit should be protected against short circuit and against overload, except as permitted in section 11.5 or where the Administration may exceptionally otherwise permit. For supplies with 400 cycles the impedance of the circuits should be observed.

11.6.6.2 The rating or appropriate setting of the overload protective device for each circuit should be permanently indicated at the location of the protective device.

11.6.6.3 When the protective device is a fuse it should be placed on the load side of the disconnect switch serving the protected circuit.

11.6.7 Lighting fittings should be so arranged as to prevent temperature rises which could damage the cables and wiring, and to prevent surrounding material from becoming excessively hot.

11.6.8 All lighting and power circuits terminating in a bunker or cargo space should be provided with a multiple-pole switch outside the space for disconnecting such circuits.

11.6.9.1 Accumulator batteries should be suitably housed, and compartments used primarily for their accommodation should be properly constructed and efficiently ventilated.

11.6.9.2 Electrical or other equipment, which may constitute a source of ignition of flammable vapours, should not be permitted in compartments likely to contain such vapours.

11.6.10 The following additional provisions from .1 to .7 should be met, and provisions from .8 to .13 should be met also for non-metallic craft:

• .1 The electrical distribution voltages throughout the craft may be either direct current or alternating current and should not exceed:

  • .1 500 V for power, cooking, heating, and other permanently connected equipment; and

  • .2 250 V for lighting, internal communications and receptacle outlets.

• .2 For electrical power distribution earthed systems with non hull-return are acceptable. Where applicable, the provisions of 6.1.4.2.6.3 or 6.1.4.2.6.4 should also be met.

• .3 Effective means should be provided so that voltage may be cut off from each and every circuit and sub-circuit and from all apparatus as may be necessary to prevent danger.

• .4 Electrical equipment should be so designed that the possibility of accidentally touching live parts, rotating or moving parts as well as heated surfaces which might cause burns or initiate fire is minimised.

• .5 Electrical equipment should be adequately secured. The probability of fire or dangerous consequences arising from damage to electrical equipment should be reduced to an acceptable minimum.

• .6 The rating or appropriate setting of the overload protective device for each circuit should be permanently indicated at the location of the protection device.

• .7 Where it is impracticable to provide electrical protective devices for certain cables supplied from batteries, e.g. within battery compartments and in engine starting circuits, unprotected cable runs should be kept as short as possible and special precautions should be taken to minimise risk of faults, e.g. use of single core cables with additional sleeve over the insulation of each core, with shrouded terminals.

• .8 In order to minimise the risk of fire, structural damage, electrical shock and radio interference due to lightning strike or electrostatic discharge, all metal parts of the craft should be bonded together, in so far as possible in consideration of galvanic corrosion between dissimilar metals, to form a continuous electrical system, suitable for the earth return of electrical equipment and to connect the craft to the water when water-borne. The bonding of isolated components inside the structure is not generally necessary, except in fuel tanks.

• .9 Each refuelling point should be provided with a means of bonding the fuelling equipment to the craft.

• .10 Metallic pipes capable of generating electrostatic discharges, due to the flow of liquids and gases, should be bonded so as to be electrically continuous throughout their length and should be adequately earthed.

• .11 Primary conductors provided for lightning discharge currents should have a minimum cross section of 50 mm² in copper or equivalent surge carrying capacity in aluminium.

• .12 Secondary conductors provided for the equalisation of static discharges, bonding or equipment, etc., but not for carrying lightning discharges should have a minimum cross-section of 5 mm² copper or equivalent surge current carrying capacity in aluminium.

• .13 The electrical resistance between bonded objects and the basic structure should not exceed 0.05 Ohm, except where it can be demonstrated that a higher resistance will not cause a hazard. The bonding path should have sufficient cross-sectional area to carry the maximum current likely to be imposed on it without excessive voltage drop.