Ships’ electrical power network systems
protected from damages caused by
short-circuit current other than
three-phase symmetrical current
Presenter: Daniel Czarkowski
Polski Rejestr Statków S.A.
Electrical and Automation Department
Gdańsk, POLAND
Conference “Aeronautics and surface transport days”
11-12 April 2005, Warsaw
© 2005 PRS S.A.
Short-circuit current
The short-circuit current analysis is a
fundamental requirement of the classification
societies. Although the short-circuit condition is
an abnormal operating state. The calculations
are essential to ensure that ships electrical
system is designed assuming safety at see.
Why do we need to calculate it?
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A simple formula
I=10xG+4*M
I short-circuit current
G sum of generator full load current
M sum of running motor current
If so simple, why to complicate it?!
© 2005 PRS S.A.
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Source of fire
1.Fault of a cable insulation or a poor conductor cause higher
current which is a source of heat that damages an insulation.
2.Destroyed insulation causes one phase short-circuit to the
ship’s hull that changes into two or even three-phase shortcircuit.
3.High temperature caused by an arc is a source of fire.
4.A fire protection system usually detects smoke after a while.
The delay might be too long to save human lives or, certainly,
the main board equipment.
5.Arc short circuits and asymmetrical currents that occur on the
main board are not considered by designers and classification
societies while the currents are usually lower than these
calculated according to IEC 61363.
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Scope of IEC 61363-1:1998
Electrical installations of ships and of mobile and fixed
offshore units – Part 1: Procedures for calculating
short circuit currents in three-phase a.c.
“The calculation procedures are for a three-phase
symmetrical short-circuit condition i.e. three-phase,
or shorted to the ship’s hull and for which the shortcircuit occurs on all three poles simultaneously.”
“The calculation of short-circuit currents resulting from
asymmetric short-circuit conditions can lead to higher
aperiodic components of the short circuit and is not
considered in this standard.”
Asymmetrical current is not considered!
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Scope of IEC 60909-0:2001
Short-circuit currents in three-phase a.c. systems –
Part 0: Calculation of currents
This standard covers:
line-to-earth short circuit, occurring in a solidly earthed
neutral system or an impedance earthed neutral
system.
This standard does not cover:
a single line-to-earth fault, occurring in an isolated
neutral earthed system or a resonance earthed neutral
system.
© 2005 PRS S.A.
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Scope of IEC 60909-3:2003
Short-circuit currents in three-phase a.c. systems – Part 3:
Currents during two separate simultaneous line-to-earth short
circuits and partial short-circuit currents flowing through earth
This standard covers:
a) currents during two separate simultaneous line-to-earth short
circuits in isolated neutral or resonant earthed neutral systems;
b) partial short-circuit currents flowing through earth in case of
single line-to-earth short circuit in solidly earthed or lowimpedance earthed neutral systems.
This standard does not cover: short-circuit currents in the
electrical installations on board ships or aeroplanes.
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Aim of the project
The aim is to fulfil the gap that exists in
IEC 61363 that stems from the requirements
set forth after analysis of main boards damaged
by short-circuit currents.
Thank you for your attention
Any further questions please contact me:
d.czarkowski@prs.pl
© 2005 PRS S.A.
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