IEC TS 60815-1:2025
(Main)Selection and dimensioning of high-voltage insulators intended for use in polluted conditions - Part 1: Definitions, information and general principles
Selection and dimensioning of high-voltage insulators intended for use in polluted conditions - Part 1: Definitions, information and general principles
IEC TS 60815-1:2025 is applicable to the selection of insulators, and the determination of their relevant dimensions, to be used in outdoor high-voltage systems with respect to pollution. For the purposes of this technical specification series, the insulators are divided into the following broad categories, each dealt with in a specific part as follows:
- IEC TS 60815-2 – Ceramic and glass insulators for AC systems;
- IEC TS 60815-3 – Polymer insulators for AC systems;
- IEC TS 60815-4 – Insulators for DC systems.
This document provides general definitions, gives methods for the evaluation of site pollution severity (SPS) and outlines the principles to arrive at an informed judgement on the probable behaviour of a given insulator in certain pollution environments. The general principles described are applicable to both AC and DC systems. However, the applicability part mainly refers to AC. More information about DC can be found in IEC TS 60815-4.
This document is applicable to all types of external insulation, including insulation forming part of other apparatus. The term "insulator" is used hereafter to refer to any type of insulator.
The objective of this technical specification series is to:
- understand and identify parameters of the system, application, equipment and site influencing the pollution behaviour of insulators,
- understand and choose the appropriate approach to the design and selection of the insulator solution, based on available data, time and resources.
- characterise the type of pollution at a site and determine the site pollution severity (SPS) value and the SPS class,
- determine the reference unified specific creepage distance (RUSCD) of "reference" insulator based on the SPS class,
- select candidate insulators and determine corrections to apply to RUSCD to arrive at the USCD of the "candidate" insulators by taking into account their specific properties (notably their shed profiles), conditions of the site, the application and the type of system,
- evaluate the relative advantages and disadvantages of the possible solutions, using HTM or non-HTM insulators,
- assess the need and merits of "hybrid" solutions or mitigative measures.
The IEC 60815 series does not deal with the effects of ice and snow on polluted insulators.
CIGRE documents form a useful complement to this technical specification for those wishing to study in greater depth the performance of insulators under pollution.
This second edition cancels and replaces the first edition of IEC TS 60815‑1 published in 2008. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) In the Scope, it is clarified that this specification is applicable to AC and DC conditions while it mainly refers to AC conditions. Detailed application indications refer to AC only. The RUSCD is determined based on the SPS class of reference insulators, and this document does not deal with the effects of ice and snow on polluted insulators;
b) Some terms and definitions are modified or introduced in this document, such as RUSCD, creepage factor, average diameter, SPS value and SPS class, hydrophobicity transfer and HTM, etc.;
c) Clause 5 is re-organized and revised regarding input parameters for the selection and dimensioning of insulators, including system requirements and environmental conditions;
d) Clause 6 "Determination of site pollution severity (SPS) class" is re-organized and re-written. A distinction was made between SPS value and SPS class. The measurement of pollution that is made on the de-energized reference insulator is valid for AC only;
e) A new pollution class, extremely heavy class f, is added. It is applicable only to the special situations of extremely heavy pollution when the RUSCD of class e cannot meet the requirements. The RUSCD value for class f is not specified;
f) The parameters of reference insulators were defined;
g) The pro
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Standards Content (Sample)
IEC TS 60815-1 ®
Edition 2.0 2025-11
TECHNICAL
SPECIFICATION
Selection and dimensioning of high-voltage insulators intended for use in
polluted conditions -
Part 1: Definitions, information and general principles
ICS 29.080.10 ISBN 978-2-8327-0759-3
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CONTENTS
FOREWORD . 4
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions. 8
3.2 Abbreviated terms . 11
4 Proposed approaches for the selection and dimensioning of an insulator . 12
4.1 Introductory remark . 12
4.2 Approach 1 . 12
4.3 Approach 2 . 12
4.4 Approach 3 . 12
4.5 Comparison of the three approaches . 12
5 Input parameters for the selection and dimensioning of insulators . 14
5.1 Introductory remark . 14
5.2 System requirements . 15
5.3 Environmental conditions . 16
5.3.1 Identification of types of pollution . 16
5.3.2 General types of environments . 17
5.3.3 Pollution severity parameters . 18
6 Determination of site pollution severity (SPS) class . 19
6.1 General . 19
6.2 Evaluation methods of the site pollution severity and their degree of
confidence . 19
6.3 SPS value and evaluation methods . 21
6.4 SPS class and determination methods . 22
6.4.1 SPS class . 22
6.4.2 Methods for determination of SPS class . 23
7 General guidance for insulation selection and dimensioning . 26
7.1 General description of the process . 26
7.2 General guidance on materials . 27
7.3 General guidance on shed profiles . 27
7.4 Considerations on creepage distance and insulator length . 30
7.5 Considerations for exceptional or specific applications or environments . 30
7.5.1 Hollow insulators . 30
7.5.2 Arid areas . 31
7.5.3 Proximity effects . 32
7.5.4 Orientation. 32
7.5.5 Maintenance and mitigative methods . 32
7.5.6 Cold energisation, wet switching of circuit breaker interrupter heads . 32
Annex A (informative) Flowchart representation of the design approaches . 33
Annex B (informative) Pollution flashover mechanisms . 36
B.1 Description of the pollution flashover mechanism under type A pollution . 36
B.2 Description of the pollution flashover mechanism under type B pollution . 37
B.2.1 Conductive fog . 37
B.2.2 Bird streamers . 37
B.3 The pollution flashover mechanism on hydrophobic surfaces . 37
Annex C (normative) Measurement of ESDD and NSDD . 39
C.1 Introductory remark . 39
C.2 Necessary equipment to measure pollution degree . 40
C.3 Pollution collection methods for ESDD and NSDD measurement . 40
C.3.1 General remark. 40
C.3.2 Procedure using a swab technique . 40
C.3.3 Procedure using washing technique (cap and pin insulators) . 41
C.4 Determination of ESDD and NSDD. 41
C.4.1 ESDD calculations . 41
C.4.2 NSDD calculations . 43
C.5 Chemical analysis of pollutants . 44
Annex D (normative) Evaluation of type B pollution severity . 45
D.1 Introductory remark . 45
D.2 Evaluation of SES for type B pollution by leakage current measurement . 45
D.2.1 Measurement of surface conductivity . 45
D.2.2 Measurement of surface leakage currents . 45
D.2.3 Calibration by a salt fog test . 45
D.3 Evaluation of SES for type B pollution by measurement of insulator flashover
stress . 46
D.4 How to estimate SPS for type B pollution . 46
Annex E (normative) Directional dust deposit gauge measurements . 47
E.1 Introductory remark . 47
E.2 Measurement procedure . 48
E.3 Correction for climatic influences . 49
Annex F (normative) Use of laboratory test methods . 50
Annex G (normative) Deterministic and statistical approaches for artificial pollution
test severity and acceptance criteria . 51
G.1 General remark . 51
G.2 Deterministic approach . 51
G.3 Statistical approach . 52
Annex H (informative) Example of a questionnaire to collect information on the
behaviour of insulators in polluted areas . 55
H.1 General information . 55
H.2 System data/requirements (see 5.2) . 55
H.3 Environmental and pollution conditions (see 5.3) . 55
H.4 Insulator parameters . 56
H.5 Details of incidents . 57
Annex I (informative) Form factor. 58
Annex J (informative) Correspondence between specific creepage distance and
USCD . 59
Bibliography . 60
Figure 1 – Type A site pollution severity – Relation between ESDD/NSDD and SPS
class for the reference cap and pin insulator for AC condition . 24
Figure 2 – Type A site pollution severity – Relation between ESDD/NSDD and SPS
class for the reference long rod insulator for AC condition . 24
Figure 3 – Type B site pollution severity – Relation between SES and SPS class for
reference cap and pin insulators for AC condition . 25
Figure 4 – Type B site pollution severity – Relation between SES and SPS class for
reference long rod insulator for AC condition . 25
Figure A.1 – Flowchart of Approach 1 . 33
Figure A.2 – Flowchart of Approach 2 . 34
Figure A.3 – Flowchart of Approach 3 . 35
Figure C.1 – Insulator strings for measuring ESDD and NSDD . 39
Figure C.2 – Wiping of pollutants on insulator surface. 41
Figure C.3 – Value of factor b . 42
Figure C.4 – Relation between σ and Sa . 43
Figure C.5 – Procedure for measuring NSDD . 44
Figure E.1 – Directional dust deposit gauges . 47
Figure G.1 – I
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