Section 5 Electric power circuits, electric control circuits, monitoring and alarms

5.1 Electric power circuits

5.1.1 In addition to this section, the control and electrical installation is to comply with Pt 6, Ch 1 Control Engineering Systems and Pt 6, Ch 2 Electrical Engineering.

5.1.2 Short-circuit protection, an overload alarm and, in the case of polyphase circuits, an alarm to indicate single phasing is 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.

5.1.3 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 Pt 5, Ch 19, 5.1 Electric power circuits 5.1.2, provided that technical justification is submitted.

5.1.4 The alarms required by Pt 5, Ch 19, 5.1 Electric power circuits 5.1.2 are to be provided on the bridge and in the main machinery space or control room from which the main machinery is normally controlled.

5.1.5 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.

5.1.6 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.

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

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

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

5.1.10 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.

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

5.1.12 For a ship fitted with multiple steering systems, Pt 5, Ch 19, 5.1 Electric power circuits 5.1.6 to Pt 5, Ch 19, 5.1 Electric power circuits 5.1.11 are to be applied to each of the steering systems.

5.1.13 In ships of less than 1600 gross tonnage, 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 Pt 5, Ch 19, 5.1 Electric power circuits 5.1.2, for such a motor primarily intended for other services.

5.2 Electric control circuits

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

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

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

5.3 Monitoring and alarms

5.3.1 Alarms and monitoring requirements are indicated in Pt 5, Ch 19, 5.3 Monitoring and alarms 5.3.2 and Table 19.5.1 Alarms.

Table 19.5.1 Alarms

Item	Alarm	Note
Rudder position	—	Indication, see Pt 5, Ch 19, 4.1 General 4.1.4
	Failure	See Pt 5, Ch 19, 5.3 Monitoring and alarms 5.3.3
Earthing on AC and DC circuits	Fault	If galvanically isolated from the ship’s network
Data communication	Error	Where the data deviates from expected value, sequence or timing
Steering gear power units, power	Failure	—
Steering gear motors	Overload, Single phase	For alarm and running indication locations,see Pt 5, Ch 19, 5.1 Electric power circuits 5.1.4 and Pt 5, Ch 19, 5.1 Electric power circuits 5.1.5
Control system	Failure	See Pt 5, Ch 19, 5.3 Monitoring and alarms 5.3.3
Control system power	Failure	—
Steering gear hydraulic oil tank level	Low	Each reservoir to be monitored. For alarm locations, see Pt 5, Ch 19, 5.1 Electric power circuits 5.1.6
Auto pilot	Failure	Running indication
Hydraulic oil temperature	High	Where oil cooler is fitted
Hydraulic lock	Fault	Where more than one system (either power or control) can be operated simultaneously each system is to be monitored, see Note
Hydraulic oil filter differential pressure	High	When oil filters are fitted
This alarm is to identify the system at fault and to be activated when (for example): position of the variable displacement pump control system does not correspond with given order; or incorrect position of 3-way full flow valve or similar in constant delivery pump system is detected.

5.3.2 The alarms described in Table 19.5.1 Alarms are to be indicated on the navigating bridge and the additional locations described and are to be in accordance with the alarm system specified by Pt 6, Ch 1, 2.3 Alarm systems, general requirements.

5.3.3 Steering control systems are to be monitored and an audible and visual alarm is to be initiated on the navigation bridge in the event of:

failure of the control system, including command and feedback circuits; or
unacceptable deviation between the rudder order and actual rudder position and/or unacceptable delay in response to changes in the rudder order.