Section 4 Main source of electrical power

4.1.1 The main source of electrical power is to comply with the requirements of this section without recourse to the emergency source of electrical power.

4.2.1 Under seagoing conditions, the number and rating of service generating sets and converting sets, such as transformers and semi-conductor converters, when any one generating set or converting set is out of action, are:

1. to be sufficient to ensure the operation of electrical services for Mobility systems, Ship Type systems, and habitable conditions. See Vol 2, Pt 4, Ch 5, 4.3 Power requirements 4.3.5 for electric propulsion systems;

2. to have sufficient reserve capacity to permit the starting of the largest motor without causing any motor to trip, stall or any device to fail due to excessive voltage drop on the system;

3. to be capable of providing the electrical services necessary to start the main propulsion machinery from a dead ship condition. The emergency source of electrical power may be used to assist if it can provide power at the same time to those services required to be supplied by Vol 2, Pt 9, Ch 2, 5 Emergency and alternative sources of electrical power

4.2.2 The arrangement of the ship’s main source of power is to be such that the operation of electrical services for Mobility systems, Ship Type systems, and habitable conditions can be maintained regardless of the speed and direction of the propulsion machinery shafting.

4.2.3 Arrangements are to be provided to prevent overloading of the generating set(s) supplying the electrical power that is/are required to maintain the ship in a normal operational and habitable condition. On loss of electrical power, arrangements are to be made for a standby generator set to be started, connected to the switchboard and Mobility systems and Ship Type systems restarted in as short a time as is practicable. These load control, starting and restart functions may be achieved by the actions of suitably trained personnel but in ships with UMS notation the arrangements are to be automatic, see also Vol 2, Pt 9, Ch 4, 4.9 Load management.

4.3.1 The starting arrangements of the generating sets prime movers are to comply with the requirements of Vol 2, Pt 2, Ch 1, 9 Starting arrangements as applicable.

4.3.2 When the emergency source of electrical power is required to be used to restore propulsion from a dead ship condition, the emergency generator is to be capable of providing initial starting energy for the propulsion machinery within 30 minutes of the dead ship condition. The emergency generator capacity is to be sufficient for restoring propulsion in addition to supplying those services in Vol 2, Pt 9, Ch 2, 5 Emergency and alternative sources of electrical power. See Vol 2, Pt 2, Ch 1, 9 Starting arrangements for dead ship condition starting arrangements.

4.4.1 The governing accuracy of the generating sets prime movers is to meet the requirements of Vol 2, Pt 2, Ch 1, 7.3 Auxiliary and emergency engine governors and Vol 2, Pt 2, Ch 1, 7.4 Additional requirements for auxiliary engine governors for naval vessels.

4.4.2 The maximum electrical step load switched on or off is not to cause the frequency variation of the electrical supply to exceed the parameters given in Vol 2, Pt 9, Ch 1, 2.1 Quality of power supplies (QPS)..

4.5.1 Generators and generator systems, having the ship's propulsion machinery as their prime mover but not forming part of the ship's main source of electrical power may be used whilst the ship is at sea to supply electrical services required for normal operational and habitable conditions provided that the requirements of Vol 2, Pt 9, Ch 2, 4.5 Main propulsion driven generators not forming part of the main source of electrical power 4.5.2 to Vol 2, Pt 9, Ch 2, 4.5 Main propulsion driven generators not forming part of the main source of electrical power 4.5.4 are satisfied.

4.5.2 Within the declared operating range of the generators and/or generator system, the specified voltage and frequency variations of the Rules are to be met.

4.5.3 Where there is remote control of the propulsion machinery, arrangements are to ensure that Mobility machinery power supplies are maintained during manoeuvring conditions in order to prevent a blackout situation.

4.5.4 In addition to the requirements of Vol 2, Pt 9, Ch 2, 4.2 Number and rating of generators and converting equipment 4.2.3, arrangements are to be fitted to automatically start and connect one of the generators forming the main source of power should the frequency variations exceed those permitted by the Rules.