Section 2 Performance requirements

2.1.1 The electrical system design maximum and minimum operating voltage and input frequency together with acceptable limits of excursions are to be specified by the system designer.

2.1.2 The system designer is to specify for each of the vessels possible operating modes:

• the type of each electrical power source used to supply the distribution system, such as a.c. generators, d.c. generators, converter, batteries, fuel cells and photovoltaics;
• the operating mode of each electrical power source such as constant voltage, constant current or variable voltage; and
• the configuration of the electrical distribution system, including, but not limited to, the earthing and protection strategies to be used.

2.1.3 The supply of electrical power sufficient for the correct operation of electrical services for essential equipment and habitable conditions is to be ensured:

• during all reasonably foreseeable normal and abnormal operating and fault conditions;
• irrespective of the direction of the propulsion shaft rotation;
• without any requirement to revert to emergency supplies.

2.1.4 The choice of materials and components of construction, as well as the design, location and ship installation, are to be made according to the environmental, maintenance and operating conditions in order to ensure the continued function of the equipment during all normal and reasonably foreseeable abnormal conditions and to reduce the risk of:

• injury to crew and passengers;
• damage to the equipment the system is contained within or adjacent equipment and systems;
• damage to adjacent equipment and systems;
• damage to the ship;

Where applicable, equipment and components are to be selected from the list of LR type approved products. See Pt 6, Ch 1, 1.3 Control, alarm and safety equipment 1.3.2 and Pt 6, Ch 1, 2.13 Programmable electronic systems - Additional requirements for essential services and safety critical systems 2.13.3 of the Rules for Ships.

2.1.5 Alternative or redundant systems are to be provided to ensure that the supply of essential services is not disrupted by the unavailability of the largest generator or convertor.

2.1.6 Electrical equipment is to be used within its designed operating parameters, such as current, voltage, power, charging rate, energy storage etc. to prevent:

• a hazard occurring; and
• the equipment affecting safety functions.

Additional supporting evidence for verification is to be submitted on request.

2.1.7 Facilities are to be provided to restore essential services from a dead ship condition as required by Pt 6, Ch 2, 2.2 Number and rating of generators and converting equipment 2.2.1 of the Rules for Ships.

2.1.8 Where semi-conducting equipment is arranged to distribute electrical power to consumers of a lower voltage of supply, arrangements are to be provided to ensure the lower voltage distribution consumers are not subjected to voltage variations, including fast transients, outside their safe operating regions.

2.1.9 In the event of failure of the main source of electrical power, means to ensure sufficient electrical power to supply the emergency consumers are to be provided within the time specified in accordance with SOLAS 1974 as amended.

2.1.10 All electrical equipment supplied from the main and emergency sources of electrical power and electrical equipment for essential and emergency services are to be so selected that they are capable of operating satisfactorily under the variations of voltage and ripple frequencies which may be present in the system.

2.1.11 Systems employing loads characterised by constant power characteristics connected to the d.c. bus through a converter are to be evaluated with respect to the instability they can cause to the distribution system. See also Ch 1, 4.3 Functional description 4.3.1.

2.1.12 Arrangements for the isolation and switching of distribution circuits are to be provided which shall enable safe isolation of faults and for maintenance. See also Ch 1, 5.3 Isolation and switching 5.3.2.

2.1.13 The continuity of supply to essential and emergency safety systems is to be ensured, in accordance with SOLAS 1974 as amended.

2.1.14 Suitable means to detect insulation breakdown with respect to earth of equipment and distribution systems which alert the Operator are to be provided.

2.1.15 Effective means, suitably located, are to be provided to protect every part of a system as necessary from excess current to prevent danger in accordance with Pt 6, Ch 2, 6 System design – Protection of the Rules for Ships.

2.1.16 Suitable arrangements for the protection of electrical equipment from the effects of both mechanical and electrical overload are to be provided in accordance with Pt 6, Ch 2, 6 System design – Protection of the Rules for Ships.

2.1.17 Means are to be provided to protect personnel from electric shock and arc flash during maintenance of the electrical distribution system and any of its connected equipment.