IEC PAS 63108:2017

IEC PAS 63108 ®
Edition 1.0 2017-05
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
Electrical installations in ships – Primary DC distribution – System design
architecture
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IEC PAS 63108 ®
Edition 1.0 2017-05
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
Electrical installations in ships – Primary DC distribution – System design

architecture
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 47.020.60 ISBN 978-2-8322-4400-5

– 2 – IEC PAS 63108:2017  IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 General requirements . 8
4.1 General . 8
4.2 Acceptance of substitutes or alternatives . 9
4.3 Provisions for maximum load . 9
4.4 Additions and alterations . 9
4.5 Environmental conditions . 9
4.6 Power supply system characteristics . 9
4.6.1 General . 9
4.6.2 DC distribution systems limits . 9
4.7 Mechanical protection . 9
4.8 Enclosures . 9
5 System design . 10
5.1 General . 10
5.2 Power quality . 10
5.3 Combined AC and DC distribution systems . 10
5.4 Black-out start up and start from dead ship condition . 10
5.5 DC distribution systems . 10
5.6 AC distribution systems . 10
5.7 Shore powered charging systems . 10
5.8 Short-circuit currents in combined AC and DC systems . 11
5.8.1 General . 11
5.8.2 Short-circuit current in DC systems . 11
5.9 System studies and calculations . 11
5.10 Protection . 11
5.10.1 General . 11
5.10.2 Fixed and variable speed AC generator protection . 12
5.10.3 Battery circuits . 12
5.10.4 Safety barriers for energy storage systems . 12
5.10.5 Protection against electric shock . 13
5.11 Protection of interconnection to shore . 13
6 Sources of electrical power . 13
6.1 General . 13
6.2 AC power generation with variable speed . 13
6.3 DC power generation with variable speed . 14
6.4 Various DC power sources . 14
6.5 Load sharing . 14
6.6 Transient operation . 14
7 Power distribution systems . 14
7.1 General . 14
7.2 AC distribution systems . 14
7.3 DC distribution systems . 14

7.4 DC distribution systems feeding AC distribution systems . 15
8 Equipment . 15
8.1 General . 15
8.2 Generators . 15
8.3 DC assemblies . 15
8.3.1 General . 15
8.3.2 Cooling . 15
8.3.3 Individual circuits . 16
9 Control systems . 17
9.1 General . 17
9.2 Control architecture . 17
9.3 Automatic control of vessel energy systems . 17
9.3.1 General . 17
9.3.2 Initiation of start-commands . 18
9.3.3 Transfer of start-command . 18
9.3.4 Events and indications . 18
9.3.5 Automatic reconnection to dead DC distribution system . 18
9.3.6 Automatic load sharing . 18
10 Installation . 18
11 Testing, verification and documentation . 19
11.1 General requirements . 19
11.2 Factory acceptance test . 19
11.3 On-board testing (site testing) . 19
11.4 Documentation . 19
Bibliography . 20

– 4 – IEC PAS 63108:2017  IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSTALLATIONS IN SHIPS –

Primary DC distribution – System design architecture

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
A PAS is a technical specification not fulfilling the requirements for a standard, but made
available to the public.
IEC PAS 63108 has been processed by IEC technical committee 18: Electrical installations of
ships and of mobile and fixed offshore units.
The text of this PAS is based on the This PAS was approved for
following document: publication by the P-members of the
committee concerned as indicated in
the following document
Draft DPAS Report on voting
18/1560/DPAS 18/1574/RVDPAS
Following publication of this PAS, which is a pre-standard publication, the technical committee
or subcommittee concerned may transform it into an International Standard.

This PAS shall remain valid for an initial maximum period of 3 years starting from the
publication date. The validity may be extended for a single period up to a maximum of
3 years, at the end of which it shall be published as another type of normative document, or
shall be withdrawn.
– 6 – IEC PAS 63108:2017  IEC 2017
INTRODUCTION
The majority of existing distribution systems of ships are AC systems with electric power
generated by fixed speed generator sets and a fixed frequency and voltage for the distribution
system. This is also reflected by the current parts of the IEC 60092 series. The ship owners
are facing new environmental regulations and are asking for more flexible solutions to meet
the new market demands. It is acknowledged that the maritime industry is developing new
innovative power and distribution solutions enabling reduced emissions to air, as well as
reduced fuel consumption. Next generation of distribution systems involves use of a variety of
power sources and DC distribution architecture. Novel concepts for design and operation of
electrical systems with energy storage and advanced control of main and emergency power
sources, including essential load services such as propulsion systems have evolved. These
energy systems combine a wide range of technologies that will improve the fuel and emission
profiles and performance of ship operations.
The primary DC distribution system exploit new and radical approaches for system
design/configuration, operation and control compared to conventional solutions for power
generation and distribution systems.
This PAS intends to describe these solutions. A new IEC International Standard is scheduled
to replace this PAS.
The main intention with this PAS is to set design and test criteria to power systems with
primary DC distribution. Semiconductor devices used as breaker shall fulfil requirements for
breaking current and isolation according to IEC 60947-2 and IEC 60947-3.

ELECTRICAL INSTALLATIONS IN SHIPS –

Primary DC distribution – System design architecture

1 Scope
This PAS specifies the requirements of primary DC distribution systems and interconnected
installations.
The requirements of this PAS establish general principles for
• operations, without degrading unit and human safety, capable of a reduced environmental
footprint,
• existing and new power generating units, new DC distribution concepts for electrical
power, energy storage and advanced control of a total power balance, including
semiconductor converters (AC to DC, DC to DC and DC to AC power converters) and
dynamic load controllers, and
• relevant system studies and calculations demonstrating a protection philosophy as needed
for necessary selectivity, segregation methods and equipment.
This PAS also gives guidelines for integration of energy sources of different nature and
suitable ways to identify locations of such installations.
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.
IEC 60034 (all parts), Rotating electrical machines
IEC 60092 (all parts), Electrical installations in ships
IEC 60092-101:1994, Electrical installations in ships – Part 101: Definitions and general
requirements
IEC 60092-101:1994/AMD1:1995
IEC 60092-301, Electrical installations in ships – Part 301: Equipment – Generators and
motors
IEC 60092-302, Electrical installations in ships – Part 302: Low-voltage switchgear and
controlgear assemblies
IEC 60092-352, Electrical installations in ships – Part 352: Choice and installation of electrical
cables
IEC 60092-401, Electrical installations in ships – Part 401: Installation and test of completed
installation
IEC 60364-4-41, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock

– 8 – IEC PAS 63108:2017  IEC 2017
IEC 60533, Electrical and electronic installations in ships – Electromagnetic compatibility
(EMC) – Ships with a metallic hull
IEC 60947-2, Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
IEC 60947-3, Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units
IEC 61557-8, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500
V d.c. – Equipment for testing, measuring or monitoring of protective measures – Part 8:
Insulation monitoring devices for IT systems
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE Other relevant terms and definitions can be found in IEC 60092-101 and other parts of the
IEC 60092 series.
3.1
shore power charging system
Note 1 to entry: Definition under consideration
3.2
DC bus
DC distribution system which interconnects DC loads and power sources
3.3
DC assembly
cabinet with modules interconnected with DC bus for loads and power sources
3.4
energy management system
EMS
system controlling, monitoring and protecting energy sources and loads to ensure safe
operation
3.5
battery management system
BMS
system protecting battery, controlling battery charging and/or discharging, and monitoring
battery conditions (i.e. state of charge, cell temperature etc.)
Note 1 to entry: The definition is under consideration.
4 General requirements
4.1 General
Attention is drawn to the requirements of the International Convention for the Safety of Life at
Sea. Clause 4 contains conditions and requirements which are common to all apparatus and
installations within the scope of this PAS.

Semiconductor devices used as breaker shall fulfil requirements for breaking current and
isolation according to IEC 60947-2 and IEC 60947-3.
4.2 Acceptance of substitutes or alternatives
Where in this PAS any special type of apparatus, construction or arrangement is specified,
the use of any other apparatus, construction or arrangement is admissible, provided it fulfils
the requirements of the original apparatus.
4.3 Provisions for maximum load
All components and systems shall be of such size as to be capable of carrying, without their
respective ratings being exceeded, the current which can normally flow through them. They
shall be capable of carrying anticipated overloads and transient currents, for example the
capacitor inrush currents, without operational degradation.
4.4 Additions and alterations
An addition or alteration, temporary or permanent, shall not be made to an existing installation
until it has been definitely ascertained that the ratings and the condition of existing
accessories, conductors, switchgear, etc. affected are adequate for the new situation.
Special attention is taken to those factors affecting the existing system design such as
current-carrying capacity, maximum fault current level, harmonic content, power quality and
proper discrimination of the protective devices.
4.5 Environmental conditions
Electrical equipment shall operate satisfactorily under various environmental conditions. The
environmental conditions of IEC 60092 (all parts) shall apply.
4.6 Power supply system characteristics
4.6.1 General
NOTE The use of primary DC distribution are characterized by
• DC-grids including various sources of power and consumers with power electronic controllers forming
operational interfaces, with high dynamics,
• fast response times and small reaction times and inductances in DC-grid systems compared to conventional
AC-grid systems, and
• voltage sourced converters, diode bridges, etc., which will create special fault mitigation scenarios by their
ability to block in one direction, and lead in the opposite direction.
4.6.2 DC distribution systems limits
When batteries are used as power supply systems, adequate measures should be taken to
keep the voltage within the specified limits during charging, quick charging, gas-charging and
discharging of the battery.
4.7 Mechanical protection
Electrical equipment shall be placed so that, as far as practicable, it is not exposed to risk of
mechanical damage according to IEC 60092-101 and IEC 60092-352.
Safety barriers shall be established in design and arrangement of energy sources.
4.8 Enclosures
Enclosures shall comply with the degrees of protection in IEC 60092-302.

– 10 – IEC PAS 63108:2017  IEC 2017
5 System design
5.1 General
The design of the electrical system shall be in accordance with relevant parts of the
IEC 60092 (series) and IEC 60533, with the additional requirements of this PAS.
5.2 Power quality
Harmonic voltage distortion levels in AC parts of ship systems shall be in line with
requirements in IEC 60092 (all parts). For DC systems the frequency amplitudes and voltage
pulses due to switching of semiconductor devices will vary depending on the load conditions
and voltage conditions. All connected devices to the DC bus-bar shall be able to operate
normally under any operating conditions with the actual voltage and curre
...