Section 7 Electrical power circuits and equipment

7.1.1 In addition to this section, the electrical installation is to comply with the relevant sections of Vol 2, Pt 9 Electrotechnical Systems.

7.1.2 Short circuit protection, an overload alarm and, in the case of polyphase circuits, an alarm to indicate single phasing are to be provided for each main and auxiliary motor circuit. Protective devices are to operate at not less than twice the full load current of the motor or circuit protected and are to allow excess current to pass during the normal accelerating period of the motors.

7.1.3 Where steering gear motor circuits are supplied by converters, consideration will be given to arrangements that provide an equivalent level of safety, reliability, availability and indication to those specified in Vol 2, Pt 6, Ch 1, 7.1 Electric power circuits, electric control circuits, monitoring and alarms 7.1.2, provided that a technical justification is submitted.

7.1.4 The alarms required by Vol 2, Pt 6, Ch 1, 7.1 Electric power circuits, electric control circuits, monitoring and alarms 7.1.2 are to be provided on the bridge and in the main machinery space or control room from which the main machinery is normally controlled.

7.1.5 Indicators for running indication of each main and auxiliary motor are to be installed on the navigating bridge and at a suitable main machinery control position.

7.1.6 A low-level alarm is to be provided for each power actuating system hydraulic fluid reservoir to give the earliest practicable indication of hydraulic fluid leakage. Alarms are to be given on the navigation bridge and in the machinery space where they can be readily observed.

7.1.7 Two exclusive circuits are to be provided for each electric or electrohydraulic steering gear arrangement consisting of one or more electric motors.

7.1.8 Each of these circuits is to be fed from the main switchboard. One of these circuits may pass through the emergency switchboard.

7.1.9 One of these circuits may be connected to the motor of an associated auxiliary electric or electrohydraulic power unit.

7.1.10 Each of these circuits is to have adequate capacity to supply all the motors which can be connected to it and which can operate simultaneously.

7.1.11 These circuits are to be separated throughout their length as widely as is practicable.

7.1.12 Where specified and agreed, in ships of category NS3, if an auxiliary steering gear is not electrically powered or is powered by an electric motor primarily intended for other services, the main steering gear may be fed by one circuit from the main switchboard. Consideration would be given to other protective arrangements than described in Vol 2, Pt 6, Ch 1, 7.1 Electric power circuits, electric control circuits, monitoring and alarms 7.1.2, for such a motor primarily intended for other services.

7.1.13 For a ship fitted with multiple steering systems, Vol 2, Pt 6, Ch 1, 7.1 Electric power circuits, electric control circuits, monitoring and alarms 7.1.6 to Vol 2, Pt 6, Ch 1, 7.1 Electric power circuits, electric control circuits, monitoring and alarms 7.1.10 are to be applied to each of the steering systems.

7.2.1 Electric control systems are to be independent and separated as far as is practicable throughout their length.

7.2.2 Each main and auxiliary electric control system which is to be operated from the navigating bridge is to comply with the following:

1. It is to be served with electric power by a separate circuit supplied from the associated steering gear power circuit, from a point within the steering gear compartment, or directly from the same section of switchboard busbars, main or emergency, to which the associated steering gear power circuit is connected.

2. Each separate circuit is to be provided with short circuit protection only.