IEC 61892-3:1999
(Main)Mobile and fixed offshore units - Electrical installations - Part 3: Equipment
Mobile and fixed offshore units - Electrical installations - Part 3: Equipment
This part of IEC 61892 contains provisions for the electrical equipment in electrical installations of mobile and fixed units, including pipelines, pumping or "pigging" stations, compressor stations and exposed location single-buoy moorings, used in the offshore petroleum industry for drilling, production, processing and for storage purposes.
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Standards Content (Sample)
INTERNATIONAL IEC
STANDARD
61892-3
First edition
1999-02
Mobile and fixed offshore units –
Electrical installations –
Part 3:
Equipment
Unités mobiles et fixes en mer –
Installations électriques –
Partie 3:
Matériel
Reference number
Numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series.
Consolidated publications
Consolidated versions of some IEC publications including amendments are
available. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the
base publication, the base publication incorporating amendment 1 and the base
publication incorporating amendments 1 and 2.
Validity of this publication
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology.
Information relating to the date of the reconfirmation of the publication is available
in the IEC catalogue.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is to be found at the following IEC sources:
• IEC web site*
•
Catalogue of IEC publications
Published yearly with regular updates
(On-line catalogue)*
• IEC Bulletin
Available both at the IEC web site* and as a printed periodical
Terminology, graphical and letter symbols
For general terminology, readers are referred to IEC 60050: International Electro-
technical Vocabulary (IEV).
For graphical symbols, and letter symbols and signs approved by the IEC for
general use, readers are referred to publications IEC 60027: Letter symbols to be
used in electrical technology, IEC 60417: Graphical symbols for use on equipment.
Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols
for diagrams.
* See web site address on title page.
INTERNATIONAL IEC
STANDARD
61892-3
First edition
1999-02
Mobile and fixed offshore units –
Electrical installations –
Part 3:
Equipment
Unités mobiles et fixes en mer –
Installations électriques –
Partie 3:
Matériel
IEC 1999 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
XB
International Electrotechnical Commission
For price, see current catalogue
– 2 – 61892-3 IEC:1999(E)
CONTENTS
Page
FOREWORD . 5
INTRODUCTION . 6
Clause
1 Scope. 7
2 Normative references. 7
3 Definitions. 9
4 Generators and motors. 12
4.1 General. 13
4.2 Performance characteristics. 13
4.3 Voltage regulation of generators. 13
4.4 Generators for special purposes. 15
4.5 Parallel operation of general service generators – DC generators . 15
4.6 Parallel operation of general service generators – AC generators . 15
4.7 Control and excitation of generators . 16
4.8 Mechanical features (generators and motors) . 17
4.9 Lubrication (generators and motors) . 18
4.10 Prime movers. 18
4.11 Cyclic irregularity. 19
4.12 Lubrication (prime movers). 19
4.13 Running speed. 20
4.14 Testing. 20
4.15 Degree of protection provided by enclosures . 20
4.16 Rating plates. 20
5 Transformers for power and lighting . 24
5.1 General. 24
5.2 Winding arrangement. 24
5.3 Terminals. 24
5.4 Cooling arrangements. 24
5.5 Voltage regulation. 25
5.6 Parallel operation. 25
5.7 Temperature-rise limits. 25
5.8 Tests. 25
6 Switchgear and controlgear assemblies . 25
6.1 General. 25
6.2 Definitions. 25
6.3 Classification of assemblies . 25
6.4 Electrical characteristics of assemblies . 25
6.5 Information to be given regarding the assemblies . 25
6.6 Environmental conditions. 27
6.7 Design and construction. 27
6.8 Test specifications. 34
6.9 Switchgear and controlgear in the range above 1 kV up to and including 15 kV . 36
61892-3 IEC:1999(E) – 3 –
Clause Page
7 Semiconductor convertors. 39
7.1 General. 39
7.2 Cooling arrangements. 39
7.3 Accessibility. 39
7.4 Service conditions. 39
7.5 Application. 39
7.6 Nameplate. 40
7.7 Convertor transformers. 40
8 Secondary cells and batteries. 40
8.1 General. 40
8.2 Types of battery . 40
8.3 Construction and assembly . 40
8.4 Crates and trays. 41
8.5 Location. 41
8.6 Nameplates. 41
8.7 Charging facilities. 41
8.8 Ventilation of secondary battery compartments. 42
9 Luminaires. 42
9.1 General. 42
9.2 Construction. 42
9.3 Temperature and temperature rise . 43
9.4 Standard types of lampholders . 43
9.5 Exposure to mechanical damage. 44
9.6 Discharge lamp luminaires operating at voltages below 250 V. 44
9.7 Discharge lamp luminaires operating at voltages above 250 V . 44
9.8 Searchlights and arc lamps . 45
9.9 Portable luminaires. 45
9.10 Marking. 45
10 Heating and cooking appliances . 45
10.1 General. 45
10.2 General requirements. 45
10.3 Special requirements for galley appliances . 48
10.4 Special requirements for space-heating appliances . 48
11 Trace and surface heating. 49
11.1 General. 49
11.2 Construction. 49
11.3 Protection. 49
11.4 Protection against mechanical damage. 49
11.5 Installation in hazardous areas . 49
12 Communication. 49
12.1 General. 49
12.2 Safety requirements. 50
12.3 Other requirements. 50
12.4 Safety and maintenance. 50
– 4 – 61892-3 IEC:1999(E)
Clause Page
13 Underwater systems and appliances. 50
13.1 General. 50
13.2 Fixed diving systems . 50
13.3 Temporary diving systems . 50
14 Control and instrumentation. 51
14.1 General. 51
14.2 General requirements. 51
14.3 Environmental and supply conditions and testing . 51
14.4 Adjustments. 57
14.5 Accessibility. 57
14.6 Replacement. 57
14.7 Non-interchangeability. 57
14.8 Cooling air. 57
14.9 Mechanical load on connectors. 57
14.10 Mechanical features of cabinets. 57
14.11 Shock and vibration absorbers. 57
14.12 Internal wiring. 57
14.13 Cable connections. 58
14.14 Rodent protection . 58
14.15 Sensors. 58
14.16 Computer-based systems . 58
15 Accessories . 61
15.1 General. 62
15.2 Enclosures. 62
15.3 Switches. 62
15.4 Socket outlets and plugs. 62
Annex A (informative) Bibliography . 64
Table 1 – Limits of cyclic irregularity . 19
Table 2 – Limits of temperature rise of air-cooled machines based on an ambient
temperature of 50 °C . 21
Table 3 – Dielectric tests . 23
Table 4 – Clearance and creepage distances for non type-tested assemblies . 29
Table 5 – Correspondence between the nominal voltage of the supply system
and the test voltage for type-tested assemblies at sea level. 38
Table 6 – Standard types of lampholders . 43
Table 7 – Temperature limits of exposed parts. 47
Table 8 – Variations from nominal values. 53
Table 9 – Type tests, test procedures and severities . 54
61892-3 IEC:1999(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_________
MOBILE AND FIXED OFFSHORE UNITS –
ELECTRICAL INSTALLATIONS –
Part 3: Equipment
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61892-3 has been prepared by IEC technical committee 18:
Electrical installations of ships and of mobile and fixed offshore units.
The text of this standard is based on the following documents:
FDIS Report on voting
18/859/FDIS 18/864/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annex A is for information only.
A bilingual version of this standard may be issued at a later date.
IEC 61892 consists of the following parts, under the general title Mobile and fixed offshore
units – Electrical installations
Part 1: General requirements and conditions
Part 2: System design
Part 3: Equipment
Part 4: Cables
Part 5: Mobile units
Part 6: Installation
Part 7: Hazardous areas
– 6 – 61892-3 IEC:1999(E)
INTRODUCTION
IEC 61892-3 forms part of a series of International Standards intended to ensure safety in the
design, selection, installation, maintenance and use of electrical equipment for the generation,
storage, distribution and utilization of electrical energy for all purposes in offshore units which
are used for the purpose of exploration or exploitation of petroleum resources.
This standard also incorporates and co-ordinates, as far as possible, existing rules and forms a
code of interpretation, where applicable, of the requirements of the International Maritime
Organization, and constitutes a guide for future regulations which may be prepared and a
statement of practice for offshore unit owners, constructors and appropriate organizations.
This standard is based on equipment and practices which are in current use, but it is not
intended in any way to hamper development of new or improved techniques.
The ultimate aim has been to produce a set of International Standards exclusively for the
offshore petroleum industry.
In this part of IEC 61892, references are made to other parts of the standard, which are still in
preparation. Footnotes are attached to such references. A footnote indicates which current
standard should be used until the part in preparation is published.
61892-3 IEC:1999(E) – 7 –
MOBILE AND FIXED OFFSHORE UNITS –
ELECTRICAL INSTALLATIONS –
Part 3: Equipment
1 Scope
This part of IEC 61892 contains provisions for electrical equipment in electrical installations of
mobile and fixed units, including pipelines, pumping or "pigging" stations, compressor stations
and exposed location single-buoy moorings, used in the offshore petroleum industry for drilling,
production, processing and for storage purposes.
It applies to equipment in all installations, whether permanent, temporary, transportable or
hand-held, to a.c. installations up to and including 15 000 V and d.c. installations up to and
including 1 000 V.
This standard does not apply to the electrical installations in rooms used for medical purposes
or in tankers.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61892. At the time of publication, the editions indicated
were valid. All normative documents are subject to revision, and parties to agreements based
on this part of IEC 61892 are encouraged to investigate the possibility of applying the most
recent editions of the normative documents indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 60034-1:1996, Rotating electrical machines – Part 1: Rating and performance
IEC 60044-1:1996, Instrument transformers – Part 1: Current transformers
IEC 60050(441):1984, International Electrotechnical Vocabulary (IEV) – Chapter 441: Switchgear,
controlgear and fuses
IEC 60056:1987, High-voltage alternating-current circuit-breakers
IEC 60065:1998, Audio, video and similar electronic apparatus – Safety requirements
IEC 60076-1:1993, Power transformers – Part 1: General
IEC 60076-2:1993, Power transformers – Part 2: Temperature rise
IEC 60076-3:1980, Power transformers – Part 3: Insulation levels and dielectric tests
IEC 60076-3-1:1987, Power transformers – Part 3: Insulation levels and dielectric tests –
Section 1: External clearances in air
IEC 60076-5:1976, Power transformers – Part 5: Ability to withstand short-circuit
IEC 60092-101:1994, Electrical installations in ships – Part 101: Definitions and general
requirements
– 8 – 61892-3 IEC:1999(E)
IEC 60092-201:1994, Electrical installations in ships – Part 201: System design – General
IEC 60092-401:1980, Electrical installations in ships – Part 401: Installation and test of
completed installation
IEC 60092-504:1994, Electrical installations in ships – Part 504: Special features – Control and
instrumentation
IEC 60092-505:1984, Electrical installations in ships – Part 505: Special features – Mobile
offshore drilling units
IEC 60146-1-1:1991, Semiconductor convertors – General requirements and line commutated
convertors – Part 1-1: Specifications of basic requirements
IEC 60146-1-2:1991, Semiconductor convertors – General requirements and line commutated
convertors – Part 1-2: Application guide
IEC 60146-1-3:1991, Semiconductor convertors – General requirements and line commutated
convertors – Part 1-3: Transformers and reactors
IEC 60146-2:1974, Semiconductor convertors – Part 2: Semiconductor self-commutated
convertors
IEC 60146-3:1977, Semiconductor convertors – Part 3: Semiconductor direct d.c. convertors
(d.c. chopper convertors)
IEC 60265-1:1998, High-voltage switches – Part 1: High-voltage switches for rated voltages
above 1 kV and less than 52 kV
IEC 60282 (all parts), High-voltage fuses
IEC 60298:1990, AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV
and up to and including 52 kV
IEC 60309 (all parts), Plugs, socket-outlets and couplers for industrial purposes
IEC 60364-4-41:1992, Electrical installations of buildings – Part 4: Protection for safety –
Chapter 41: Protection against electric shock
IEC 60439-1:1992, Low-voltage switchgear and controlgear assemblies – Part 1: Type-tested
and partially type-tested assemblies
IEC 60466:1987, AC insulation-enclosed switchgear and controlgear for rated voltage above
1 kV and up to and including 38 kV
IEC 60519 (all parts), Safety in electroheat installations
IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)
IEC 60533:1977, Electromagnetic compatibility of electrical and electronic installations in ships
IEC 60617 (all parts), Graphical symbols for diagrams
IEC 60669 (all parts), Switches for household and similar fixed-electrical installations
61892-3 IEC:1999(E) – 9 –
IEC 60865-1:1993, Short-circuit currents – Calculation of effects – Part 1: Definitions and
calculation methods
IEC 60884 (all parts), Plugs and socket-outlets for household and similar purposes
IEC 60906 (all parts), IEC system of plugs and socket-outlets for household and similar purposes
IEC 61131 (all parts), Programmable controllers
IEC 61131-1:1992, Programmable controllers – Part 1: General information
IEC 61131-2:1992, Programmable controllers – Part 2: Equipment requirements and tests
IEC 61346-1:1996, Industrial systems, installations and equipment, and industrial products –
Structuring principles and reference designations – Part 1: Basic rules
IEC 61363-1:1998, Electrical installations of ships and mobile and fixed offshore units – Part 1:
Procedures for calculating short-circuit currents in three-phase a.c.
IEC 61892-6:1999, Mobile and fixed offshore units – Electrical installations – Part 6: Installation
IEC 61892-7:1997, Mobile and fixed offshore units – Electrical installations – Part 7: Hazardous
areas
ISO 6592:1985, Information processing – Guidelines for the documentation of computer-based
application systems
ISO 8528-5:1993, Reciprocating internal combustion engine driven alternating current
generating sets – Part 5: Generating sets
3 Definitions
For the purpose of this part of IEC 61892, the following definitions apply.
3.1
computer-based system
system that consists of one or more programmable electronic devices with the connections,
peripherals and software necessary to automatically carry out specified functions
NOTE – The following types of programmable devices could form part of a computer system: mainframe, mini-
computer, micro-computer, programmable logic controller.
3.2
convertor
a set of equipment, static or rotating, to convert one type of electric current to another type,
different in nature, voltage and/or frequency
3.3
distribution board
switchgear or controlgear assembly for the control and distribution of electrical power to final
subcircuits
– 10 – 61892-3 IEC:1999(E)
3.4
double insulation
insulation comprising both basic insulation and supplementary insulation
3.5
electric surface heating
heat generated in the surface layer of a body to be heated by electrical means in order to raise
or maintain its temperature
3.6
electric surface heating device
resistive or skin effect device designed to produce a defined output at a declared voltage and
temperature, and terminated in a manner suitable for connection to the electricity supply
3.7
electric surface heating systems
system of electric surface heating devices together with any controls, thermal insulation and
protective cladding designed to meet a specified electric surface heating requirement
3.8
electromagnetic compatibility (EMC)
ability of an equipment or system to function satisfactorily in its electromagnetic environment
without introducing intolerable electromagnetic disturbances to anything in that environment
3.9
emergency switchboard
switchgear and controlgear assembly which is normally supplied by the main switchboard but
which, in the event of failure of the main electrical power supply system, is directly supplied by
the emergency source of electrical power or the transitional source of emergency power and is
intended to distribute and control electrical energy to the emergency services for all electrical
consumers essential to the safety of the crew, contractors, visitors and the unit under
emergency conditions
3.10
expert system
intelligent knowledge-based system that is designed to solve a problem using information that
has been compiled from some form of human expertise
3.11
extra-low voltage (safety voltage)
voltage which does not exceed 50 V a.c. r.m.s. between conductors, or between any conductor
and earth, in a circuit isolated from the supply by means such as safety isolating transformers,
or convertors with separate windings; a voltage which does not exceed 50 V d.c. between
conductors, or between any conductor and earth, in a circuit which is isolated from higher
voltage circuits.
NOTE 1 – Consideration should be given to the reduction of the limit of 50 V under certain conditions, such as wet
surroundings, exposure to heavy seas or powerful water jets where direct contact with live parts is involved.
NOTE 2 – The voltage limit should not be exceeded, either at full load or no load, but it is assumed, for the purpose
of this definition, that any transformer or convertor is operated at its rated supply voltage.
NOTE 3 – Information about protection by extra-low voltage is given in IEC 60364-4-41.
61892-3 IEC:1999(E) – 11 –
3.12
heating cable
cable, with or without a shield or a metallic sheath, intended to give off heat for heating purposes
3.13
invertor
convertor for conversion from d.c. to a.c
3.14
low-voltage switchgear and controlgear assemblies
combination of one or more low-voltage switching devices together with associated control,
measuring, signalling, protective, regulation equipment, etc., completely assembled under the
responsibility of the manufacturer with all the internal electrical and mechanical inter-
connections and structural parts
3.15
main switchboard
switchgear and controlgear assembly which is directly supplied by the main source of electrical
power and is intended to distribute and control electrical energy to the unit’s services
3.16
non-type-tested low-voltage switchgear and controlgear assemblies (NTTA)
low-voltage switchgear and controlgear assembly which does not belong to 3.17 or 3.28.
3.17
partially type-tested low-voltage switchgear and controlgear assemblies (PTTA)
low-voltage switchgear and controlgear assembly, containing both type-tested and non-type-
tested arrangements provided that the latter are derived (e.g. by calculation) from type-tested
arrangements which have complied with the relevant tests
3.18
rectifier
convertor for conversion of a.c. to d.c.
3.19
reinforced insulation
single insulation system applied to live parts, which provides a degree of protection against
electric shock equivalent to double insulation under the conditions specified in the relevant
IEC standard.
NOTE – The term ”insulation system” does not imply that the insulation must be one homogeneous piece. It may
comprise several layers which cannot be tested singly as supplementary or basic insulation
3.20
resistive device
electric surface heating device of either the trace heating unit type or the surface heating unit type
3.21
ripple-free
conventionally defined for sinusoidal ripple voltage as a ripple content of not more than 10 %
r.m.s.; the maximum peak value does not exceed 140 V for a nominal 120 V ripple-free d.c.
system and 70 V for a nominal 60 V ripple-free d.c. system
– 12 – 61892-3 IEC:1999(E)
3.22
(secondary) cell (Syn. (rechargeable) cell)
an assembly of electrodes and electrolyte which constitutes the basic unit of a secondary battery
3.23
section boards
switchgear and controlgear assembly for controlling and distributing the supply of electrical
power to other section boards, distribution boards or final subcircuits
3.24
self-commutated convertor
convertor in which the commutating voltages are supplied by components within the convertor
NOTE – Included, for example, are converters in which the commutating voltages are built up within the
semiconductor devices (as in transistors and in thyristors which can be turned off by the gate) or in which they are
supplied outside the semiconductor devices by means of capacitors. Excluded are convertors requiring special
characteristics from the load to commutate.
3.25
semiconductor device
device whose essential characteristics are due to the flow of charge carriers within a semi-
conductor
3.26
skin effect device
electric surface heating device of the skin effect heater type
3.27
software
program, procedures and associated documentation pertaining to the operation of a computer
system and including both the application (user) program and the operating system (firmware)
program
3.28
type-tested low-voltage switchgear and controlgear assembly (TTA)
low-voltage switchgear and controlgear assembly conforming to an established type or system
without deviations likely to significantly influence the performance from the typical assembly
verified to be in accordance with this standard
3.29
valve-regulated battery cell
a secondary cell which is closed under normal conditions but which has an arrangement which
allows the escape of gas if the internal pressure exceeds a predetermined value. The cell
cannot normally receive addition to the electrolyte
3.30
vented (secondary) battery cell (Syn. open (secondary) cell)
a secondary cell having a cover provided with an opening through which gaseous products may
escape
NOTE – The opening may be fitted with a venting system.
61892-3 IEC:1999(E) – 13 –
4 Generators and motors
4.1 General
The provisions of this clause are applicable to all rotating machines rated at 750 W or more for
use in offshore units. It also applies to excitation machines and includes relevant requirements
for prime-mover driving generators. Requirements particular to electrical propulsion machines
1)
are given in IEC 61892-5
All electrical machines shall comply with the relevant requirements of IEC 60034-1 and also
with the additional requirements included in this standard.
4.2 Performance characteristics
4.2.1 Temperature rise
The limits of temperature rise shall be in accordance with table 2, which is based on
IEC 60034-1.
NOTE – When a rotating machine is connected to a supply system with harmonic distortion, the rating of the
machine must allow for the increased heating effect of the harmonic loading.
4.2.2 Unbalance load on three-wire d.c. generators
Unless otherwise specified, all three-wire d.c. generators shall be designed for a current
unbalance of 25 %.
4.3 Voltage regulation of generators
4.3.1 General
The inherent voltage regulation of a general service generator shall be designed in relation to
the speed regulation and governing of the prime movers as outlined below.
NOTE – "General service" means that supplying motors and other consumers are a part of the normal distribution
system of the unit. Consumers such as propulsion motors and other special consumers, for which other governing
characteristics can be accepted or are required, are not considered part of the general service.
4.3.2 DC generators
4.3.2.1 Shunt or stabilized shunt-wound generators
Shunt or stabilized shunt-wound generators rated at 50 kW and above shall comply with the
following requirements:
a) when the voltage has been set at full load to its rated value, the removal of the load shall
not cause a permanent increase of the voltage greater than 15 % of the rated voltage;
b) when the voltage has been set either at full load or at no load, the voltage obtained at any
value of the load shall not exceed the no-load voltage.
4.3.2.2 Compound-wound generators
Compound-wound generators rated at 50 kW and above shall be so designed in relation to the
governing characteristics of the prime-mover that, with the generator at full-load operating
temperature and starting at a 20 % load with voltage within 1 % of the rated voltage, it gives at
full load a voltage within 1,5 % of the rated voltage.
________
1)
In preparation. Before IEC 61892-5 is published, see IEC 60092-101.
– 14 – 61892-3 IEC:1999(E)
The average of ascending and descending voltage regulation curves between 20 % load and
full load shall not vary by more than 3 % from the rated voltage.
4.3.2.3 Other types of generators
Generators required to have characteristics not covered by 4.3.2.1 and 4.3.2.2 shall be subject
to special consideration.
4.3.2.4 Automatic voltage regulation for d.c. service generators
General service generators which are of the shunt type shall be provided with automatic
voltage regulators.
4.3.3 AC generators
The excitation system of a.c. generators rated 50 kW and above, and complying with 4.7.4,
shall also comply with the requirements given below.
4.3.3.1 Steady conditions: tolerance of voltage and waveform
Each a.c. generator for general service driven by its prime-mover, whose governor charac-
teristics comply with 4.10.3, shall be provided with an excitation system capable of maintaining
the voltage under steady conditions within ±2,5 % of the rated voltage for all loads between
zero and rated load at the rated power factor. These limits may be increased to ±3,5 % for
emergency sets (see 4.3.3.4).
When the generator is driven at rated speed, giving its rated voltage and rated symmetrical
load, the tolerance of waveform shall not exceed the values listed below:
– total harmonic distortion: 5 %
– single harmonic: 3 %
NOTE – Attention is drawn to the possibility that under certain operating conditions the power factor may be less
than the rated value, and that this can affect the voltage regulation.
4.3.3.2 Transient conditions
When the generator is driven at rated speed, giving its rated voltage, and is subject to a
sudden change of symmetrical load within the limits of a specified current and power factor, the
voltage shall not fall below 85 % nor exceed 120 % of the rated voltage.
The voltage of the generator shall then be restored to within ±3 % of the rated voltage, for the
main generator set in not more than 1,5 s. For emergency sets these values may be increased
to ±4 % in not more than 5 s respectively (see 4.3.3.4).
In the absence of precise information concerning the maximum values of the sudden loads, the
following conditions shall be assumed: 60 % of the rated current with a power factor of between
0,4 lagging and 0 to be thrown on with the generator running at no load, and then withdrawn
after steady-state conditions have been reached.
NOTE 1 – For the purpose of verifying the above conditions, the generator under test may be driven by a suitable
electric motor at practically constant speed.
NOTE 2 – To achieve satisfactory performance on board a unit, the governor of the prime-mover must restore the
speed to a steady state within the limits specified in 4.10.3 in not more than 3 s.
NOTE 3 – For gas driven machines and turbines, other values may be applicable. Advice can be found in ISO 8528-5.
61892-3 IEC:1999(E) – 15 –
4.3.3.3 Steady short-circuit conditions
Under steady short-circuit conditions, the generator with its excitation system shall be capable
of maintaining a current of at least three times its rated value for a duration of up to 2 s, unless
protection selectivity conditions exist which allow a shorter duration and provided that, in any
case, the safety of the installation is ensured.
4.3.3.4 Emergency generators
Emergency generator sets which are required to meet the same general requirements as in
4.3.3.2 need only maintain the steady-state voltage within 3,5 %, and during transient
conditions to recover their voltage within 4 % in not more than 5 s.
4.4 Generators for special purposes
4.4.1 DC generators
Special purpose d.c. generators, together with their excitation system, shall have such voltage
characteristics as are required.
4.4.2 AC generators
Special purpose a.c. generators and general service generators rated less than 50 kVA,
together with their excitation system, shall have the voltage characteristics agreed upon
between manufacturer and purchaser.
4.5 Parallel operation of general service generators – DC generators
4.5.1 Stability
DC generators which are required to run in parallel shall be stable in operation at all loads from
no load to full load.
4.5.2 Load sharing
The design of d.c. generators and their connections shall be such that, when they operate in
parallel, the individual load on each machine does not normally differ from the theoretical load
(proportional to rating) by more than 12 % of the rated full load of the largest machine, or more
than 25 % of the rating of the individual machine concerned. This requirement applies when the
combined load on the sets is varied between 20 % and 100 % of the combined rating. Such a
load sharing shall not result in overloading the smaller set.
4.5.3 Voltage drop
For each generator of a group required to run in parallel, the voltage drop across the series
fields and its connection to the switchboard (which may incorporate a resistor) shall be ap-
proximately equal.
4.6 Parallel operation of general service generators – AC generators
4.6.1 Reactive load sharing
When a.c. generators are operated in parallel, the reactive load of the individual generating
sets shall not differ from their proportionate share of the total reactive load by more than 10 %
of the rated output of the largest machine, or more than 25 % of the smallest machine where
this value is lower than the former.
NOTE – The alternator design should incorporate sufficient damping in the rotor circuits to avoid power oscillations
and instability when running in parallel.
– 16 – 61892-3 IEC:1999(E)
4.6.2 Load sharing
For a.c. generating sets operating in parallel, the governing characteristics of the prime-movers
shall be such that, within the limits of 20 % and 100 % total load, the load on any generating
set does not normally differ from its proportionate share of the total load by more than 15 % of
the rated output of the largest machine, or more than 25 % of the rating of the individual
machine concerned.
The facilities for adjusting the governor at normal frequency shall be sufficiently accurate to
permit a minimum adjustment of the load on the engi
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