IEC GUIDE 111:2004

Electrical high-voltage equipment in high-voltage substations - Common recommendations for product standards

Horizontal publication giving guidance for the harmonization of product and system standards within substations where the highest voltage for equipment is higher than 1 kV. Contains recommendations for common specifications for all HV substation product standards, each of which is augmented by the technical background specific to each TC, which naturally retains freedom in its technical choices. For use by TCs involved in high-voltage (HV) substation systems, such as TCs 13, 14, 17, 20, 22, 28, 32, 33, 36, 37, 38, 57, 95 and 99.

General Information

• Status: Published
• Publication Date: 20-Jul-2004
• ICS: 29.020 - Electrical engineering in general
• ICS: 29.240.10 - Substations. Surge arresters
• Technical Committee: SMB - STANDARDIZATION MANAGEMENT BOARD
• Current Stage: PPUB - Publication issued
• Start Date: 15-Sep-2004
• Completion Date: 21-Jul-2004

Relations

• Replaced By: IEC GUIDE 111-1:2023 - Electric equipment for high-voltage substations - Common recommendations for product and system standards - Part 1: AC (alternating current)
• Effective Date: 05-Sep-2023
• Revises: IEC GUIDE 111:1998 - Electrical high-voltage equipment in high-voltage substations - Common clauses for product standards
• Effective Date: 05-Sep-2023

Overview

IEC Guide 111:2004 - Electrical high‑voltage equipment in high‑voltage substations provides horizontal guidance to harmonize product and system standards for equipment used in substations where the highest voltage for equipment is greater than 1 kV. It is intended mainly for conventional AC substation equipment but also gives guidance for HV power‑electronic equipment where possible. The Guide helps technical committees, standards authors, manufacturers and utilities align requirements for safety, performance, testing and environmental exposure across different HV product standards.

Key topics and requirements

The Guide defines common recommendations to be referenced in product standards. Major topics include:

• Environmental conditions - recommended normal and special conditions (e.g. ambient temperature categories, solar radiation, altitude, humidity, icing and pollution considerations) to ensure consistent design expectations across HV equipment.
• Ratings - guidance on highest voltage for equipment, rated insulation levels, rated frequency, rated currents and short‑circuit withstand values.
• Design and construction - common rules on insulation media, earthing, low‑voltage parts, marking, degrees of protection (IP code), creepage distances, fire hazard, noise and electromagnetic compatibility (EMC).
• Tests - harmonized approach for type, routine, sample, special and commissioning tests to ensure interoperable verification of HV equipment.
• Safety and lifecycle - electrical, mechanical, thermal and operational safety aspects; environmental impact and end‑of‑life considerations.
• Procurement and documentation - guidance on information to be supplied with enquiries, tenders and orders and a list of drawings/test specimen identification (Annex A).

Practical applications and who uses it

IEC Guide 111 is a reference for:

• IEC technical committees (TCs) developing product standards for HV substations (e.g., TC 13, 14, 17, 20, 22, 28, 32, 33, 36, 37, 38, 57, 95, 99).
• Standards writers and policy makers seeking harmonized clauses for substation equipment.
• Manufacturers and designers specifying design, testing and marking for switchgear, transformers, busbars and other HV equipment.
• Utilities, system integrators and procurement teams who need consistent tender specifications and interoperability between substation components.
• Test laboratories and certification bodies applying common test methods and acceptance criteria.

Related standards

Guide 111 recommends referencing horizontal and supporting documents such as:

• IEC 60060 (high‑voltage test techniques), IEC 60071 (insulation coordination), IEC 60529 (IP code), IEC 60721 (environmental classification), IEC 61000 series (EMC) and others cited in the Guide.

Using IEC Guide 111 improves consistency, reduces costly over‑ or under‑standardization, and helps ensure that HV substation equipment meets unified expectations for performance, safety and environmental resilience.

Standards Content (Sample)

INTERNATIONAL
GUIDE
ELECTROTECHNICAL
COMMISSION
Second edition
2004-07
Electrical high-voltage equipment
in high-voltage substations –
Common recommendations
for product standards
Reference number
INTERNATIONAL
GUIDE
ELECTROTECHNICAL
COMMISSION
Second edition
2004-07
Electrical high-voltage equipment
in high-voltage substations –
Common recommendations
for product standards
© IEC 2004 – 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, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
PRICE CODE
S
Commission Electrotechnique Internationale
International Electrotechnical Commission
ɆɟɠɞɭɧɚɪɨɞɧɚɹɗɥɟɤɬɪɨɬɟɯɧɢɱɟɫɤɚɹɄɨɦɢɫɫɢɹ
For price, see current catalogue

– 2 – Guide 111 ¤ IEC:2004(E)
CONTENTS
FOREWORD.4
INTRODUCTION.5
1 Scope.6
2 Reference documents.6
3 Guidance for the “Normative references” clause in product standards.8
4 Guidance for the “Definitions” clause in product standards .8
5 Environmental conditions.8
5.1 General.8
5.2 Normal environmental conditions .9
5.3 Special environmental conditions .10
6 Ratings.11
6.1 General.11
6.2 Highest voltage for equipment.11
6.3 Rated insulation levels.12
6.4 Rated frequency.12
6.5 Rated current.12
6.6 Rated short-time withstand current.12
6.7 Rated peak withstand current.12
6.8 Rated duration of short circuit .13
6.9 Rated supply voltage of auxiliary and control circuits .13
6.10 Rated supply frequency of auxiliary and control circuits .13
7 Design and construction.13
7.1 Requirements for liquids and gases in equipment.13
7.2 Earthing of equipment.14
7.3 Low-voltage part of equipment .14
7.4 Marking.14
7.5 Degrees of protection by enclosures .15
7.6 Creepage distances.15
7.7 Fire hazard.15
7.8 Noise level.15
7.9 Electromagnetic compatibility (EMC) .15
7.10 Mechanical stresses on terminals .16
7.11 Interfaces.16
8 Tests.16
8.1 General.16
8.2 Type tests.17
8.3 Routine tests.18
8.4 Special tests.18
8.5 Sample tests.18
8.6 Commissioning tests.18
9 Rules for transport, storage, erection, operation and maintenance.19

Guide 111 ¤ IEC:2004(E) – 3 –
10 Safety.19
10.1 General.19
10.2 Electrical aspects.19
10.3 Mechanical aspects.19
10.4 Thermal aspects.19
10.5 Operation aspects.19
11 Effects of product standards on the natural environment .20
12 Guide for the selection of equipment according to use.20
13 Information to be given with enquiries, tenders and orders .20
Annex A Identification of test specimens .21
Table 1 – Normal environmental conditions .9
Table 2 – Special environmental conditions .10
Table 3 – DC supply voltage.13
Table 4 – Auxiliary contact classes.14
Table A.1 – List of drawings to be submitted by manufacturer.21

– 4 – Guide 111 ¤ IEC:2004(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ELECTRICAL HIGH-VOLTAGE EQUIPMENT
IN HIGH-VOLTAGE SUBSTATIONS –
COMMON RECOMMENDATIONS FOR PRODUCT STANDARDS
FOREWORD
This second edition of IEC Guide 111 has been prepared in accordance with Annex A of Part 1
of the ISO/IEC Directives by an ad hoc group of the Standardization Management Board set up
to harmonize characteristics for substation standards.
It constitutes a technical revision of the first edition, published in 1998. This edition has been
amended to express more clearly the guidance being provided to product committees and
contains corrected and completed technical material and references.
The text of this guide is based on the following documents:
Approval document Report on voting
C/1325/DV C/1334/RV
Full information on the voting for the approval of this Guide can be found in the report on voting
indicated in the above table.
Guide 111 ¤ IEC:2004(E) – 5 –
INTRODUCTION
This Guide is for use by technical committees (TCs) involved in high-voltage (HV) substation
systems, such as:
TC 13, TC 14, TC 17, TC 20, TC 22, TC 28, TC 32, TC 33, TC 36, TC 37, TC 38, TC 57,
TC 95, TC 99.
It is of paramount importance that the IEC, through this Guide, finds a way to overcome the
lack of consistency and unnecessary discrepancies between standards within one system,
even though a few discrepancies might be justified in certain cases according to the specificity
of a given product or situation.
Furthermore, the cost of over-standardization of one component when the nearest linked
component is under-standardized should be considered. The supplementary cost does not in
any way increase the reliability of the system as a whole.
Since the same external stresses (climatic, electrical, mechanical) apply to all the components
of the substations, the consistency of their technical features is vital.
Hence, standards will deal more and more with the same essential requirements for safety,
environmental impact, end of life, availability and integration of systems. All product standards
for a single system have to fulfil these requirements with the same degree of responsibility.
The aim of this Guide is to provide common rules for HV substation equipment.

– 6 – Guide 111 ¤ IEC:2004(E)
ELECTRICAL HIGH-VOLTAGE EQUIPMENT
IN HIGH-VOLTAGE SUBSTATIONS –
COMMON RECOMMENDATIONS FOR PRODUCT STANDARDS
1 Scope
IEC Guide 111 is a horizontal publication which gives guidance for the harmonization of
product and system standards within substations where the highest voltage for equipment is
higher than 1 kV. It primarily addresses conventional a.c. equipment which is found in high-
voltage (HV) substations in most cases.
This Guide contains recommendations for common specifications for all HV substation product
standards, each of which is augmented by the technical background specific to each TC, which
naturally retains freedom in its technical choices.
Where HV power electronic equipment is part of an HV substation, for example, HVDC or SVC,
economics and technology dictate a deviation from common clauses as standardized for a.c.
equipment. However, when developing product standards for HV power electronic equipment
for use in HV substations, the common recommendations of this Guide should be adopted as
far as possible.
Clearly, any specification in this guide which is inapplicable to a certain type of product,
because of that product's inherent characteristics, for example, should not be taken into
account when writing standards for that type of product.
2 Reference documents
IEC 60027-1, Letter symbols to be used in electrical technology – Part 1: General
IEC 60038, IEC standard voltages
IEC 60059, IEC standard current ratings
IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60068 (all parts), Environmental testing
IEC 60068-2-18, Environmental testing – Part 2-18: Tests – Test R and guidance: Water
IEC 60068-2-75, Environmental testing – Part 2-75: Tests – Test Eh: Hammer tests
IEC 60071-1, Insulation co-ordination – Part 1: Definitions, principles and rules
IEC 60071-2, Insulation co-ordination – Part 2: Application guide
IEC 60216 (all parts), Electric insulating materials – Properties of thermal endurance
IEC 60296, Specification for unused mineral insulating oils for transformers and switchgear
IEC 60376, Specification and acceptance of new sulphur hexafluoride
IEC 60417 (all parts), Graphical symbols for use on equipment

Guide 111 ¤ IEC:2004(E) – 7 –
IEC 60480, Guide to the checking of sulphur hexafluoride (SF ) taken from electrical equipment
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60664-1, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
IEC 60694, Common specifications for high-voltage switchgear and controlgear standards
IEC 60695, Fire hazard testing
IEC 60721 (all parts), Classification of environmental conditions
IEC 60721-1, Classification of environmental conditions – Part 1: Environmental parameters
and their severities
IEC 60721-2-2, Classification of environmental conditions – Part 2-2: Environmental conditions
appearing in nature – Precipitation and wind
IEC 60721-2-4, Classification of environmental conditions – Part 2-4: Environmental conditions
appearing in nature -- Solar radiation and temperature
IEC 60721-2-6, Classification of environmental conditions – Part 2-6: Environmental conditions
appearing in nature – Earthquake vibration and shock
IEC 60826, Loading and strength of overhead transmission lines
IEC 60867, Insulating liquids – Specifications for unused liquids based on synthetic aromatic
hydrocarbons
IEC 60943, Guidance concerning the permissible temperature rise for parts of electrical
equipment, in particular for terminals
IEC 61000-6-5, Electromagnetic compatibility (EMC) – Part 6-5: Generic standards – Immunity
for power station and substation environments
IEC 61180-1, High-voltage test techniques for low-voltage equipment – Part 1: Definitions, test
and procedure requirements
IEC 62155: Hollow pressurized and unpressurized ceramic and glass insulators for use in
electrical equipment with rated voltage greater than 1 000 V
CISPR 11, Industrial scientific and medical (ISM) radio-frequency equipment – Electromagnetic
disturbance characteristics – Limits and methods of measurement
CISPR 18-2, Radio interference characteristics of overhead power lines on high-voltage
equipment – Part 2: Methods of measurement and procedure for determining limits
IEC Guide 109, Environmental aspects – Inclusion in electrotechnical standards
ISO 1996-1, Acoustics – Description and measurement of environmental noise – Part 1: Basic
quantities and procedures
– 8 – Guide 111 ¤ IEC:2004(E)
3 Guidance for the “Normative references” clause in product standards
The use of horizontal publications is of the utmost importance for the harmonization process.
Strong reasons are needed to depart from the recommendations of horizontal publications,
and, in all cases, it is necessary to explain the reason for any discrepancy.
Within the fields concerned, the essential horizontal documents to be taken into account and to
be mentioned in the normative references clause of each standard are the following:
• field of definitions: International Electrotechnical Vocabulary (IEC 60050);
• field of voltage: IEC 60038;
• field of current: IEC 60059;
• field of insulation: IEC 60060, IEC 60071, IEC 60815 and IEC 61180;
• field of temperature rise: IEC 60216 and IEC 60943;
• field of degrees of protection: IEC 60529;
• field of environment: IEC 60664, IEC 60721, IEC 61166, IEC 60376, IEC 60296, IEC 60867
and IEC Guide 109;
• field of electromagnetic compatibility (EMC): IEC Guide 107; horizontal publications in the
IEC 61000 series; CISPR 11, 18, 22 and 24;
• field of safety: IEC Guide 104; ISO/IEC Guide 51; ISO 60695 series
• field of mechanical stresses: IEC 60865 and IEC 62155.
4 Guidance for the “Definitions” clause in product standards
Definitions already in the IEV should always be used. If a definition already in the IEV is not
satisfactory or not clear enough, the difficulty should be referred to TC 1 and solved in
cooperation. New definitions should be discouraged unless absolutely necessary, i.e. no similar
definition exists in publications on a similar subject. A similar definition may be modified with a
reference to the original.
5 Environmental conditions
5.1 General
This clause should be the same for all TCs active in the area of substations. Installations,
including all devices and auxiliary equipment which form an integral part of them, should be
designed for operation under the climatic and environmental conditions listed below. Equipment
product standards should be taken into account.
It is recommended that TCs should use the phrase “environmental conditions” in preference to
“service conditions”.
Guide 111 ¤ IEC:2004(E) – 9 –
5.2 Normal environmental conditions
Table 1 – Normal environmental conditions
Outdoor equipment
Indoor equipment
Upper limit ” 40 ºC
” 40 ºC
and 24 h average ” 35 ºC ” 35 ºC
Ambient air
a)
temperature
and one category: “-5 indoor”: • –5 °C “-10 outdoor”: • –10 °C
or “-15 indoor”: • –15 °C “-25 outdoor”: • –25 °C
or “-25 indoor”: • –25 °C “-40 outdoor”: • –40 °C
b) Solar radiation (clear day, noon) Negligible
” 1 000 W/m
c) Altitude ” 1 000 m ” 1 000 m
” Level II – Medium
Air pollution by dust, salt, smoke,
d) No significant air pollution
corrosive/flammable gas, vapours
(Table 1 of IEC 60071-2)
class 1: ” 1 mm
e) - or class 10: ” 10 mm
Ice coating
or class 20: ” 20 mm
” 34 m/s (correspond to 700 Pa
f) Wind speed -
on cylindrical surfaces)
Relative humidity: 24 h average
” 95 %
g)
Condensation, precipitation 7
Vibration (external to equipment), earth
h) Negligible Negligible
tremors
i) Electromagnetic disturbances According to IEC Guide 107 According to IEC Guide 107
___________
On auxiliary equipment, such as relays and control switches, intended to be used in ambient air temperature
below –5 °C, an agreement between supplier and user is necessary.
Rapid temperature changes should be taken into account.
NOTE 1 Under certain conditions of solar radiation, appropriate measures, for example, roofing, forced
ventilation, etc., may be necessary or derating may be used in order not to exceed the specified temperature
rises.
NOTE 2 Details of global solar radiation are given in IEC 60721-2-4.
NOTE 3 Ultraviolet (UV) radiation can damage some synthetic materials. For more details see IEC 60068.
In regions where icing can occur the resulting load on flexible conductors and on rigid busbars and conductors
should be taken into account.
If local experience or statistics are not available, ice coatings of 1 mm, 10 mm or 20 mm based on criteria given
in IEC 60694 may be assumed. The density of the ice is assumed to be 900 kg/m in accordance with
IEC 60826.
5 Characteristics of wind are described in IEC 60721-2-2.
6 For these conditions, condensation may occasionally occur.
NOTE 1 Condensation can be expected where sudden temperature changes occur in periods of high humidity.
NOTE 2 To avoid breakdown of insulation or corrosion of metallic parts due to high humidity and condensation,
equipment designed for such conditions and tested accordingly should be used.
NOTE 3 Condensation may be prevented by special design of the building or housing, by suitable ventilation
and heating of the station or by the use of dehumidifying equipment.
7 Precipitation in the form of dew, condensation, fog, rain, snow, ice or hoar frost should be taken into account.
NOTE Precipitation characteristics for insulation are described in IEC 60060-1 and IEC 60071-1. For other
properties, precipitation characteristics are described in IEC 60721-2-2.

– 10 – Guide 111 ¤ IEC:2004(E)
5.3 Special environmental conditions
When high-voltage equipment is used under conditions different from the normal environmental
conditions given in 5.2, the user’s requirements should refer to the standardized steps given in
Table 2.
Table 2 – Special environmental conditions
Special Notes
environmental
conditions
Very cold climates:
–50 °C to +40 °C
Ambient air
a)
temperature
Very hot climates:
–5 °C to +50 °C
For installation at an altitude higher than 1 000 m above sea level, the
insulation level of external insulation under the standardized reference
atmospheric conditions should be determined by multiplying the
insulation withstand voltages required at the service location by a
factor K in accordance with IEC 60071-2.
a
NOTE 1 For internal pressurized insulation, the dielectric
characteristics are identical at any altitude and no special precautions
need to be taken.
NOTE 2 For low-voltage auxiliary and control equipment, no special
precautions need be taken if the altitude is lower than 2 000 m above
b) Altitude > 1 000 m
sea-level. For higher altitudes, see IEC 60664-1.
NOTE 3 The pressure variation due to altitude is given in IEC 60721.
Regarding this phenomenon, particular attention should be devoted to
the following points:
– thermal exchanges by convection, conduction or radiation;
– efficiency of heating or air-conditioning;
– operating level of pressure devices;
– efficiency of diesel generating set or compressed air station;
– increase of corona effect.
Air pollution by
Level III: heavy, or
dust, salt,
smoke,
Level IV: very heavy
c)
corrosive/
(Table 1 of
flammable gas,
IEC 60071-2)
vapours
In certain regions with frequent occurrence of warm, humid winds, sudden
changes of temperature may occur resulting in condensation, even indoors.
Relative
d)
humidity
In tropical indoor conditions, the average value of relative humidity measured
during a period of 24 h can be 98 %.
Vibration
According to
e) (external to
IEC 60721-2-6
equipment)
Guide 111 ¤ IEC:2004(E) – 11 –
Special Notes
environmental
conditions
Installations situated in a seismic environment should be designed to
take this into account. This should be achieved by applying the
following measures.
a) Any individual equipment
...