GB/T 18814-2024 Small craft - Electrical systems - Alternating and direct current installations
1 Scope
This document specifies the requirements for the design, construction and installation of the following types of DC and AC electrical systems, installed on small craft either individually or in combination:
a) extra-low-voltage direct current (DC) electrical systems that operate at nominal potentials of 50 V DC or less;
b) single-phase alternating current (AC) systems that operate at a nominal voltage not exceeding AC 250 V.
This document does not cover the following:
——electrical propulsion systems of direct current less than 1500 V DC, single-phase alternating current up to 1000 V AC, and three-phase alternating current up to 1000 V AC, which are addressed by ISO 16315;
——any conductor that is part of an outboard engine assembly and that does not extend beyond the outboard engine manufacturers supplied cowling;
——three-phase AC installations that operate at a nominal voltage not exceeding 500 V AC, which are addressed by IEC 60092-507.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 7010:2019 Graphical symbols - Safety colours and safety signs - Registered safety signs
ISO 8846:1990 Small craft - Electrical device - Protection against ignition of surrounding flammable gases
ISO 10240:2022 Small craft - Owner’s manual
IEC 60309-2:2021 Plugs, fixed or portable socket-outlets and appliance inlets for industrial purposes - Part 2: Dimensional compatibility requirements for pin and contact-tube accessories1)
IEC 60529:1989 Degrees of protection provided by enclosures (IP code)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
craft’s ground/earth
protective grounding
connection, provided for safety purposes, that is established by a conducting connection with the common ground/earth (potential of the earth's surface)
3.2
equipotential bonding conductor
normally non-current-carrying conductor used to put various exposed conductive parts of direct current electrical devices and extraneous conductive parts at a substantially equal potential
3.3
engine negative terminal
terminal on the engine, starter or solenoid to which the negative battery cable is connected
3.4
main grounding
earthing point
main point that provides connection for the DC negative conductor, AC protective grounding conductor and bonding conductor to the craft's ground that is established by a conducting connection with the common ground
Note: It can include any conductive part of the wetted surface of the hull in permanent contact with the water, depending on the overall system design.
3.5
overcurrent protection device
device designed to interrupt the circuit when the current flow exceeds a predetermined value for a predetermined time
Example: A fuse or circuit breaker.
3.6
residual current device
RCD
electro-mechanical switching device or association of devices designed to make, carry and break currents under normal service conditions and to cause the opening of contacts when the residual current attains a given value under specified conditions
Note: RCDs serve to reduce the risk of injury to people from electrical shock hazard, and damage to equipment from leakage of stray currents to earth or to other circuits.
3.7
polarization transformer
transformer that automatically orientates the neutral and active (phase) conductors in the system in the same polarity orientation as the polarized system of the craft
3.8
isolation transformer
transformer installed in the shore power supply circuit on a craft to electrically isolate all the normally live conductors and the protective conductor on the craft from the AC system conductors of the shore power supply
3.9
neutral conductor
conductor intentionally maintained at ground potential and capable of contributing to the transmission of electrical energy
3.10
protective conductor
protective grounding conductor
conductor, not normally carrying current, used for some measure of protection against electric shock, for electrically connecting any of the following parts of electrical equipment to the craft's ground/earth and to the shore AC grounding conductor through the shore power cable:
a) exposed conductive parts of electrical equipment;
b) extraneous conductive parts;
c) the main grounding terminal;
d) earth electrode(s);
e) the earth point of a source, or an artificial neutral
3.11
live conductor
conductor or conductive part intended to be energized in normal use, including a neutral conductor
3.12
active (phase) conductor
conductor that is maintained at a difference of potential from the neutral conductor or protective conductor
Note: In a system that does not include a neutral or protective conductor, all conductors are considered active conductors.
3.13
ignition-protected equipment
designed and constructed to give protection against ignition of surrounding flammable gases
Note: The protection against ignition of surrounding flammable gases is covered in ISO 8846:1990.
3.14
system voltage
nominal voltage supplied to the craft from a power source
3.15
exposed conductive part
conductive part of electrical equipment, which can be touched and which is not normally live, but which can become live under fault conditions
3.16
panel board
switchboard
assembly of devices for the purpose of controlling and/or distributing electrical power
Note: It can include devices such as circuit breakers, fuses, switches, instruments, and indicators.
3.17
polarized system
system in which the live conductors (active and neutral) are connected in the same relation to all terminals on devices or receptacles (socket outlets) in a circuit
3.18
fully insulated two-wire DC system
system in which both positive and negative poles remain isolated from the ground.
Note: Some systems can use a momentary ground connection for engine starting purposes and can remain isolated. e.g. not connected to the water through a metallic hull, the propulsion system or earthed through the AC protective conductor.
3.19
self-limiting
device whose maximum output is restricted to a specified value by its magnetic or electrical characteristics
3.20
two-wire DC system with negative ground
system in which the DC negative is connected to the ground
3.21
shore power appliance inlet
fitting designed for mounting on a craft, of a shrouded male type, to connect to the female connector on the craft end of the shore power cable in order to make the electrical connection for transmission of electrical energy
3.22
trip-free circuit breaker
mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of overload or short circuit, and which is designed so that the resetting means cannot be manually held in place to override the current-interrupting mechanism
