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Section 2 Design Principles

201. General principles

1. All electrical systems and equipment are to be constructed and installed in such a way that they are serviceable and perform satisfactorily under the design conditions specified for the submersible. The operating parameters of electrical equipment are to conform to the requirements stated in Pt 6 of Rules for the Classification of Steel Ships.

2. The following items of electrical equipment on submersibles also count as essential consumers:

(1) Battery charging equipment

(2) Battery room ventilators; Acid circulation and cooling system

(3) Equipment for monitoring and treating breathing air.

(4) Steering gears

202. Materials and insulation

1. The materials used in the construction of electrical machines, cables and apparatus are to be re- sistant to moist and salty sea air, seawater and oil vapours. They may not be hygroscopic and are to be flame retardant and self-extinguishing. The requirement that they should be flame retardant does not apply to winding insulations.

2. Materials with high tracking resistance are to be used for the supports of live parts.

3. Leakage paths and air gaps are to be calculated in conformity in accordance with recognized standard. Generator circuit-breakers, pressure hull wall penetrations, under water plug connectors and appliances directly connected to the busbars are to be designed for the next higher nominal in- sulation rating.

4. Materials and insulations for electrical equipment used in water are to be agreed with the Society in each instance.

203. Supply systems

1. Approved supply systems are:

(1) Direct current and single-phase alternating current: 2 conductors insulated from the vehicle hull

(2) Three-phase alternating current: 3 conductors insulated from the vehicle hull

2. Networks with an earthed neutral are not permitted in submersibles.

204. Voltages and frequencies

The use of the following standard voltages and frequencies is recommended.

(1) The maximum permissible voltages are 500 V:

(a)

for permanently installed power systems

(b) for permanently installed control current circuit

(c)

for power systems connected by socket outlets, provided they do not need to be handled

(d) for heating and galley equipment.

(2) The maximum permissible voltages are 250 V:

(a)

for lighting systems and sockets for direct current and single-phase alternating current

(b) mobile appliances with double insulation and/or protective isolating transformers

(c)

machinery control and monitoring systems, vehicle, control systems and vehicle safety systems.

(3) The maximum permissible voltages are 50 V (protective low voltage):

(a)

for mobile appliances used in confined conditions in damp spaces, upper decks, stores, ma-

chinery spaces and similar service spaces, where these appliances and/or fitted with protective isolating transformers.

are not double insulated

205. Protective measures

1. All electrical equipment is to be protected in accordance with

Classification of Steel Ships unless otherwise stated below.

Pt 6

of Rules for the

2. The minimum classes of protection stated in class of protection is to be maintained for

Table 1.12.1 are to be applied in submersibles. The the equipment as installed, even when in operation

(heeling position). In this context, the provision of shielding to be a protective measure.

at the point of installation is deemed

Table 1.12.1 The minimum classes of protection

3. Protective conductors

(1) The following points are to be observed in relation to the use of protective conductors:

(a) The protective conductors are to take the form of an additional cable, additional conductor

or additional core in the connecting cable; cable shields or sheaths may not be used as pro- tective conductors.

(b) A conductor which is live in normal operation may not at the same time be used as a pro- tective conductor and may not be connected with the latter to the hull.

(c)

The cross-section of the protective conductor is to be equal to at least half that of the prin-

cipal conductors. However, with cross-sections of 16 mmË and under, its cross-section is to be equal to that of the principal conductors. The minimum cross-section of separately laid protective conductors is 4 mmË. In the vehicle's propulsion network, the dimensional design

of the protective conductors is to be based on the maximum short-circuit currents of the equipment concerned, the maximum break times of the relevant protective elements and a

maximum temperature rise of the protective conductor of 90°C

(d) Machines and appliances mounted on insulated vibration dampers are to be earthed with mo- bile cables or conductors or braided copper leads.

(e)

(f)

The protective conductor is to be connected to the hull in a position where it can easily be checked.

The superstructure or the hull of the vehicle, as the case may be, is to be provided in an

easily accessible position with means of connection in the form of a connecting plate with M 12 stud bolts to which protective conductors can be connected without the use of tools when the vehicle is in harbour or in dock.

(g) The connection described under (f) also serves as a protective lightening conductor when in dock.

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