Rotating electrical machines - Part 27-4: Measurement of insulation resistance and polarization index of winding insulation of rotating electrical machines (IEC 60034-27-4:2018)

This part of IEC 60034 provides recommended test procedures for the measurement of
insulation resistance and polarization index of stator and rotor winding insulation of
rotating electrical machines.
This document recommends minimum acceptable values of insulation resistance and
polarization index of winding insulation valid for fully processed low and high voltage AC and
DC rotating electrical machines with a rated power of 750 W or higher.

Drehende elektrische Maschinen - Teil 27-4: Messung des Isolationswiderstands und des Polarisationsindexes der Wicklungsisolierung drehender elektrischer Maschinen (IEC 60034-27-4:2018)

Machines électriques tournantes - Partie 27-4: Mesure de la résistance d'isolement et de l'index de polarisation sur le système d'isolation des enroulements des machines électriques tournantes (IEC 60034-27-4:2018)

La présente partie de l’IEC 60034 fournit des procédures d’essai recommandées pour la mesure de la résistance d’isolement et de l’index de polarisation de l’isolation des enroulements de stator et de rotor des machines électriques tournantes. Ce document recommande des valeurs minimales acceptables pour la résistance d’isolement et l’index de polarisation de l’isolation d’enroulement, applicables pour des machines tournantes à l’état fini, haute et basse tension en courant alternatif et en courant continu d’une puissance assignée de 750 W ou plus.

Električni rotacijski stroji - 27-4. del: Merjenje izolacijske upornosti in indeksa polarizacije izolacije navitja električnih rotacijskih strojev (IEC 60034-27-4:2018)

Ta del standarda IEC 60034 podaja priporočene preskusne postopke za merjenje izolacijske upornosti ter indeksa polarizacije statorske in rotorske izolacije navitja električnih rotacijskih strojev.
Ta dokument priporoča najmanjše sprejemljive vrednosti izolacijske upornosti in indeksa polarizacije izolacije navitja, ki velja za popolnoma obdelane nizko- in visokonapetostne električne rotacijske stroje z izmeničnim in enosmernim tokom ter nazivno močjo najmanj 750 W.

General Information

Status
Published
Publication Date
21-Aug-2018
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
16-Jul-2018
Due Date
20-Sep-2018
Completion Date
22-Aug-2018

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SLOVENSKI STANDARD
SIST EN IEC 60034-27-4:2018
01-oktober-2018

Električni rotacijski stroji - 27-4. del: Merjenje izolacijske upornosti in indeksa

polarizacije izolacije navitja električnih rotacijskih strojev (IEC 60034-27-4:2018)

Rotating electrical machines - Part 27-4: Measurement of insulation resistance and

polarization index of winding insulation of rotating electrical machines (IEC 60034-27-

4:2018)

Drehende elektrische Maschinen - Teil 27-4: Messung des Isolationswiderstands und

des Polarisationsindexes der Wicklungsisolierung drehender elektrischer Maschinen

(IEC 60034-27-4:2018)

Machines électriques tournantes - Partie 27-4: Mesure de la résistance d'isolement et de

l'index de polarisation sur le système d'isolation des enroulements des machines
électriques tournantes (IEC 60034-27-4:2018)
Ta slovenski standard je istoveten z: EN IEC 60034-27-4:2018
ICS:
29.160.01 Rotacijski stroji na splošno Rotating machinery in
general
SIST EN IEC 60034-27-4:2018 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN IEC 60034-27-4:2018
---------------------- Page: 2 ----------------------
SIST EN IEC 60034-27-4:2018
EUROPEAN STANDARD EN IEC 60034-27-4
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2018
ICS 29.160.01
English Version
Rotating electrical machines - Part 27-4: Measurement of
insulation resistance and polarization index on winding insulation
of rotating electrical machines
(IEC 60034-27-4:2018)

Machines électriques tournantes - Partie 27-4: Mesure de la Drehende elektrische Maschinen - Teil 27-4: Messung des

résistance d'isolement et de l'index de polarisation sur le
Isolationswiderstands und des Polarisationsindexes der

système d'isolation des enroulements des machines Wicklungsisolierung drehender elektrischer Maschinen

électriques tournantes (IEC 60034-27-4:2018)
(IEC 60034-27-4:2018)

This European Standard was approved by CENELEC on 2018-02-28. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,

Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 60034-27-4:2018 E
---------------------- Page: 3 ----------------------
SIST EN IEC 60034-27-4:2018
EN IEC 60034-27-4:2018
European foreword

The text of document 2/1880/FDIS, future edition 1 of IEC 60034-27-4:2018, prepared by IEC/TC 2

"Rotating machinery" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC

as EN IEC 60034-27-4:2018.
The following dates are fixed:
(dop) 2018-12-29
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2021-06-29
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice

The text of the International Standard IEC 60034-27-4:2018 was approved by CENELEC as a

European Standard without any modification.
---------------------- Page: 4 ----------------------
SIST EN IEC 60034-27-4:2018
EN IEC 60034-27-4:2018
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60050-411 - International Electrotechnical Vocabulary - -
(IEV) - Chapter 411: Rotating machinery
---------------------- Page: 5 ----------------------
SIST EN IEC 60034-27-4:2018
---------------------- Page: 6 ----------------------
SIST EN IEC 60034-27-4:2018
IEC 60034-27-4
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Rotating electrical machines –
Part 27-4: Measurement of insulation resistance and polarization index of
winding insulation of rotating electrical machines
Machines électriques tournantes –

Partie 27-4: Mesure de la résistance d’isolement et de l’index de polarisation sur

le système d’isolation des enroulements des machines électriques tournantes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.160.01 ISBN 978-2-8322-5252-9

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 7 ----------------------
SIST EN IEC 60034-27-4:2018
– 2 – IEC 60034-27-4:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 8

4 Insulation resistance – components and influence factors .............................................. 10

5 Polarization index .......................................................................................................... 10

6 Measurement ................................................................................................................. 11

6.1 Influences on the measurement of the insulation resistance .................................. 11

6.1.1 General ......................................................................................................... 11

6.1.2 Winding temperature correction ..................................................................... 11

6.2 Measuring equipment ............................................................................................ 12

6.3 Test object and measuring circuit .......................................................................... 13

6.3.1 General ......................................................................................................... 13

6.3.2 Three-phase stator windings .......................................................................... 13

6.3.3 Other windings .............................................................................................. 14

6.4 Measuring voltage................................................................................................. 15

6.4.1 Type and magnitude ...................................................................................... 15

6.4.2 Polarity .......................................................................................................... 15

6.5 Measuring time ..................................................................................................... 15

6.6 Safety ................................................................................................................... 15

6.7 Measurement procedures ...................................................................................... 15

6.7.1 Standard procedure ....................................................................................... 15

6.7.2 Special procedures ........................................................................................ 16

7 Interpretation of measurement results ............................................................................ 16

7.1 General ................................................................................................................. 16

7.2 Suitability for testing and operation ....................................................................... 16

7.3 Trending of insulation condition ............................................................................ 17

7.4 Comparison between machines or between phases .............................................. 17

7.5 Effects at very high values of insulation resistance ............................................... 17

7.6 Limitations of the insulation resistance test ........................................................... 17

8 Recommended limits of insulation resistance and polarization index .............................. 18

8.1 General ................................................................................................................. 18

8.2 Insulation resistance ............................................................................................. 18

8.3 Polarization index ................................................................................................. 18

9 Test report ..................................................................................................................... 19

9.1 Operational aged windings .................................................................................... 19

9.2 New windings ........................................................................................................ 20

Annex A (informative) Components of the direct current ...................................................... 21

A.1 Total current I ..................................................................................................... 21

A.2 Capacitive current I ............................................................................................ 21

A.3 Conduction current I ........................................................................................... 22

A.4 Polarization current I .......................................................................................... 23

A.5 Surface leakage current I .................................................................................... 24

A.6 Stress control coating current I ........................................................................... 24

---------------------- Page: 8 ----------------------
SIST EN IEC 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 3 –

Annex B (informative) Graphical estimation of the slope parameter X for temperature

correction from measurement data ................................................................................ 25

Annex C (informative) Examples of test results of synthetic resin based high voltage

windings ........................................................................................................................ 27

C.1 Machine with dry and clean surface of the insulation ............................................. 27

C.2 Machine with a wet and contaminated surface ...................................................... 28

C.3 Machine with continuous stress control layers in galvanic contact with high

voltage conductors ................................................................................................ 29

C.3.1 Stress control coating current I .................................................................... 29

C.3.2 Effects on insulation resistance and polarization index .................................. 30

C.3.3 Examples of test results................................................................................. 30

Annex D (informative) Measurement of leakage current to assess interphase

insulation resistance ...................................................................................................... 32

Annex E (informative) Other DC tests .................................................................................. 34

E.1 General ................................................................................................................. 34

E.2 Dielectric absorption ratio (DAR) ........................................................................... 34

E.3 Monitoring charge and discharge currents ............................................................. 35

E.4 High voltage DC tests ........................................................................................... 37

E.4.1 General ......................................................................................................... 37

E.4.2 Uniform-time voltage step test ....................................................................... 37

E.4.3 Graded-time voltage step test ........................................................................ 37

E.4.4 Ramped-time voltage step test ...................................................................... 37

E.5 Wet insulation resistance measurement ................................................................ 38

Bibliography .......................................................................................................................... 39

Figure 1 – Equivalent circuit diagram of winding insulation in a DC voltage test ................... 10

Figure 2 – Connection for testing of the entire winding .......................................................... 14

Figure 3 – Connection for phase-to-earth measurement ........................................................ 14

Figure A.1 – Relationships between different currents and time ............................................ 21

Figure B.1 – Graphical estimation of the slope parameter X in a semi-logarithmic

diagram ................................................................................................................................ 26

Figure C.1 – Total current versus time on a clean and dry insulation. The scales are

logarithmic ............................................................................................................................ 27

Figure C.2 – Insulation resistance versus time on a clean and dry insulation ........................ 28

Figure C.3 – Total current versus time on a wet and contaminated insulation ........................ 28

Figure C.4 – Insulation resistance versus time on a wet and contaminated insulation .......... 29

Figure C.5 – Total current versus time on a dry and clean surface with a continuous

stress control coating ............................................................................................................ 30

Figure C.6 – Insulation resistance versus time on a dry and clean surface with a

stress control coating ............................................................................................................ 31

Figure D.1 – Connection for phase-to-phase measurement. The test instrument shall

be floating with respect to earth. Other phase to phase combinations are permitted ............. 32

Figure D.2 – Measurement of interphase leakage current with a measurement

instrument equipped with a guard connection........................................................................ 33

Figure D.3 – Measurement of interphase leakage current with a measurement

instrument not equipped with a guard connection .................................................................. 33

Figure E.1 – Measurement of current and insulation resistance that results in a DAR

of 1,09 .................................................................................................................................. 35

---------------------- Page: 9 ----------------------
SIST EN IEC 60034-27-4:2018
– 4 – IEC 60034-27-4:2018 © IEC 2018

Figure E.2 – Charge and discharge currents after a step voltage of 2,5 kV for the

three-phase windings of a 50 MVA hydro-generator: ............................................................. 36

Table 1 – Values of the parameter X for the temperature correction ...................................... 12

Table 2 – Guidelines for DC voltage magnitudes to be applied during the insulation

resistance measurement ....................................................................................................... 15

Table 3 – Recommended minimum insulation resistance values at a base temperature

of 40 °C ................................................................................................................................ 18

Table 4 – Recommended minimum values of polarization index for high voltage

insulation systems ................................................................................................................ 19

Table B.1 – Example data from insulation resistance measurements at different

winding temperatures ............................................................................................................ 25

---------------------- Page: 10 ----------------------
SIST EN IEC 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –
Part 27-4: Measurement of insulation resistance and polarization
index of winding insulation of rotating electrical machines
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

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

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

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

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.

International Standard IEC 60034-27-4 has been prepared by IEC technical committee 2:

Rotating machinery.
The text of this International Standard is based on the following documents:
FDIS Report on voting
2/1880/FDIS 2/1890/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 11 ----------------------
SIST EN IEC 60034-27-4:2018
– 6 – IEC 60034-27-4:2018 © IEC 2018

A list of all parts in the IEC 60034 series, published under the general title Rotating electrical

machines, can be found on the IEC website.

NOTE A table of cross-references of all IEC TC 2 publications can be found in the IEC TC 2 dashboard on the

IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 12 ----------------------
SIST EN IEC 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 7 –
INTRODUCTION

This document provides guidelines for measurement of the insulation resistance and the

polarization index on stator and rotor winding insulation of rotating electrical machines. The

document also describes typical insulation resistance characteristics, the effect of influential

factors which impact or change these characteristics, and how these characteristics indicate

winding condition. It recommends minimum acceptable values of insulation resistance for AC

and DC rotating machine windings. Interpretation will depend on the nature of the insulation

materials – specifically if the insulation is of the thermoset or thermoplastic type.

Insulation resistance measurement has been recommended and used for over 50 years to

evaluate the condition of electrical insulation. It is recommended to track periodic

measurements, accumulated over months and years of service or in connection with servicing

and overhaul of rotating machines.

Empirical limits verified in practice can be used as a basis for evaluating the quality of stator

winding insulation systems in manufacturing. Furthermore, trend evaluation, e.g. diagnostic

tests as part of the functional evaluation of insulation systems or in connection with servicing

and overhaul of rotating machines, can also provide information on ageing processes,

possible repair options and the recommended time interval between tests. These

measurements give no indication of local weak points in the insulation system and the trend

evaluations cannot be used to predict the time to failure of the winding insulation.

---------------------- Page: 13 ----------------------
SIST EN IEC 60034-27-4:2018
– 8 – IEC 60034-27-4:2018 © IEC 2018
ROTATING ELECTRICAL MACHINES –
Part 27-4: Measurement of insulation resistance and polarization
index of winding insulation of rotating electrical machines
1 Scope
This part of IEC 60034 provides recommended for the measurement of
test procedures

insulation resistance and polarization index of stator and rotor winding insulation of

rotating electrical machines.
This document recommends minimum acceptable values of insulation resistance and

polarization index of winding insulation valid for fully processed low and high voltage AC and

DC rotating electrical machines with a rated power of 750 W or higher.
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 60050-411, International Electrotechnical Vocabulary – Chapter 411: Rotating machinery

3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-411 and the

following 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
3.1
rated voltage

rated line-to-line voltage for a three-phase AC machine, line-to-

earth voltage for a single phase machine and rated direct voltage for DC machines or field

windings
3.2
insulation resistance

capability of the electrical insulation of a winding to resist direct

current and is determined by the quotient of the applied direct voltage divided by the total

current across the machine insulation, taken at a specified time t from start of voltage

application

Note 1 to entry: The voltage application time is usually 1 min (R ) and 10 min (R ); however other values can be

i1 i10

used. Unit conventions: subscript values of 1 through 10 are assumed to be in minutes, subscript values of 15 and

greater are assumed to be in seconds.
Note 2 to entry: Insulation resistance is sometimes abbreviated as IR.
---------------------- Page: 14 ----------------------
SIST EN IEC 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 9 –
3.3
polarization index

quotient of the insulation resistance measured at two different times, usually t = 1 min and

t , = 10 min after application of the direct voltage, that is an indicator of the condition of the

insulation
Note 1 to entry: Other times are discussed in Clause E.2.
3.4
polarization current

current resulting from polarization processes, which decays with time of DC voltage

application at a decreasing rate from an initial value to essentially zero
Note 1 to entry: The polarization current is also called absorption current.
3.5
conduction current

ohmic current that is constant with time and passes through the

bulk of the main insulation
3.6
surface leakage current

ohmic current that is constant with time and passes over the surface of the end windings of

the stator winding or between exposed conductors and the rotor body in insulated rotor

windings if there are depositions of conductive materials, e.g., moisture or contamination

3.7
capacitive current

current of comparatively high magnitude and short duration

(typically < 1 s), which decays exponentially with time of DC voltage application

3.8
stress control coating current

ohmic current that is constant with time, flowing in parallel to the surface leakage current

through a continuous stress control coating on the surface of the end winding insulation

between conductor and earth
3.9
total current

time dependent current, which is usually measured during insulation resistance measurement

and is the sum of all current components
Note 1 to entry: The total current is the basis for the determin
...

SLOVENSKI STANDARD
SIST EN 60034-27-4:2018
01-oktober-2018

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Rotating electrical machines - Part 27-4: Measurement of insulation resistance and

polarization index of winding insulation of rotating electrical machines (IEC 60034-27-

4:2018)

Drehende elektrische Maschinen - Teil 27-4: Messung des Isolationswiderstands und

des Polarisationsindexes der Wicklungsisolierung drehender elektrischer Maschinen

(IEC 60034-27-4:2018)

Machines électriques tournantes - Partie 27-4: Mesure de la résistance d'isolement et de

l'index de polarisation sur le système d'isolation des enroulements des machines
électriques tournantes (IEC 60034-27-4:2018)
Ta slovenski standard je istoveten z: EN IEC 60034-27-4:2018
ICS:
29.160.01 Rotacijski stroji na splošno Rotating machinery in
general
SIST EN 60034-27-4:2018 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 60034-27-4:2018
---------------------- Page: 2 ----------------------
SIST EN 60034-27-4:2018
EUROPEAN STANDARD EN IEC 60034-27-4
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2018
ICS 29.160.01
English Version
Rotating electrical machines - Part 27-4: Measurement of
insulation resistance and polarization index on winding insulation
of rotating electrical machines
(IEC 60034-27-4:2018)

Machines électriques tournantes - Partie 27-4: Mesure de la Drehende elektrische Maschinen - Teil 27-4: Messung des

résistance d'isolement et de l'index de polarisation sur le
Isolationswiderstands und des Polarisationsindexes der

système d'isolation des enroulements des machines Wicklungsisolierung drehender elektrischer Maschinen

électriques tournantes (IEC 60034-27-4:2018)
(IEC 60034-27-4:2018)

This European Standard was approved by CENELEC on 2018-02-28. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,

Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 60034-27-4:2018 E
---------------------- Page: 3 ----------------------
SIST EN 60034-27-4:2018
EN IEC 60034-27-4:2018
European foreword

The text of document 2/1880/FDIS, future edition 1 of IEC 60034-27-4:2018, prepared by IEC/TC 2

"Rotating machinery" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC

as EN IEC 60034-27-4:2018.
The following dates are fixed:
(dop) 2018-12-29
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2021-06-29
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice

The text of the International Standard IEC 60034-27-4:2018 was approved by CENELEC as a

European Standard without any modification.
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SIST EN 60034-27-4:2018
EN IEC 60034-27-4:2018
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60050-411 - International Electrotechnical Vocabulary - -
(IEV) - Chapter 411: Rotating machinery
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SIST EN 60034-27-4:2018
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SIST EN 60034-27-4:2018
IEC 60034-27-4
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Rotating electrical machines –
Part 27-4: Measurement of insulation resistance and polarization index of
winding insulation of rotating electrical machines
Machines électriques tournantes –

Partie 27-4: Mesure de la résistance d’isolement et de l’index de polarisation sur

le système d’isolation des enroulements des machines électriques tournantes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.160.01 ISBN 978-2-8322-5252-9

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SIST EN 60034-27-4:2018
– 2 – IEC 60034-27-4:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 8

4 Insulation resistance – components and influence factors .............................................. 10

5 Polarization index .......................................................................................................... 10

6 Measurement ................................................................................................................. 11

6.1 Influences on the measurement of the insulation resistance .................................. 11

6.1.1 General ......................................................................................................... 11

6.1.2 Winding temperature correction ..................................................................... 11

6.2 Measuring equipment ............................................................................................ 12

6.3 Test object and measuring circuit .......................................................................... 13

6.3.1 General ......................................................................................................... 13

6.3.2 Three-phase stator windings .......................................................................... 13

6.3.3 Other windings .............................................................................................. 14

6.4 Measuring voltage................................................................................................. 15

6.4.1 Type and magnitude ...................................................................................... 15

6.4.2 Polarity .......................................................................................................... 15

6.5 Measuring time ..................................................................................................... 15

6.6 Safety ................................................................................................................... 15

6.7 Measurement procedures ...................................................................................... 15

6.7.1 Standard procedure ....................................................................................... 15

6.7.2 Special procedures ........................................................................................ 16

7 Interpretation of measurement results ............................................................................ 16

7.1 General ................................................................................................................. 16

7.2 Suitability for testing and operation ....................................................................... 16

7.3 Trending of insulation condition ............................................................................ 17

7.4 Comparison between machines or between phases .............................................. 17

7.5 Effects at very high values of insulation resistance ............................................... 17

7.6 Limitations of the insulation resistance test ........................................................... 17

8 Recommended limits of insulation resistance and polarization index .............................. 18

8.1 General ................................................................................................................. 18

8.2 Insulation resistance ............................................................................................. 18

8.3 Polarization index ................................................................................................. 18

9 Test report ..................................................................................................................... 19

9.1 Operational aged windings .................................................................................... 19

9.2 New windings ........................................................................................................ 20

Annex A (informative) Components of the direct current ...................................................... 21

A.1 Total current I ..................................................................................................... 21

A.2 Capacitive current I ............................................................................................ 21

A.3 Conduction current I ........................................................................................... 22

A.4 Polarization current I .......................................................................................... 23

A.5 Surface leakage current I .................................................................................... 24

A.6 Stress control coating current I ........................................................................... 24

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SIST EN 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 3 –

Annex B (informative) Graphical estimation of the slope parameter X for temperature

correction from measurement data ................................................................................ 25

Annex C (informative) Examples of test results of synthetic resin based high voltage

windings ........................................................................................................................ 27

C.1 Machine with dry and clean surface of the insulation ............................................. 27

C.2 Machine with a wet and contaminated surface ...................................................... 28

C.3 Machine with continuous stress control layers in galvanic contact with high

voltage conductors ................................................................................................ 29

C.3.1 Stress control coating current I .................................................................... 29

C.3.2 Effects on insulation resistance and polarization index .................................. 30

C.3.3 Examples of test results................................................................................. 30

Annex D (informative) Measurement of leakage current to assess interphase

insulation resistance ...................................................................................................... 32

Annex E (informative) Other DC tests .................................................................................. 34

E.1 General ................................................................................................................. 34

E.2 Dielectric absorption ratio (DAR) ........................................................................... 34

E.3 Monitoring charge and discharge currents ............................................................. 35

E.4 High voltage DC tests ........................................................................................... 37

E.4.1 General ......................................................................................................... 37

E.4.2 Uniform-time voltage step test ....................................................................... 37

E.4.3 Graded-time voltage step test ........................................................................ 37

E.4.4 Ramped-time voltage step test ...................................................................... 37

E.5 Wet insulation resistance measurement ................................................................ 38

Bibliography .......................................................................................................................... 39

Figure 1 – Equivalent circuit diagram of winding insulation in a DC voltage test ................... 10

Figure 2 – Connection for testing of the entire winding .......................................................... 14

Figure 3 – Connection for phase-to-earth measurement ........................................................ 14

Figure A.1 – Relationships between different currents and time ............................................ 21

Figure B.1 – Graphical estimation of the slope parameter X in a semi-logarithmic

diagram ................................................................................................................................ 26

Figure C.1 – Total current versus time on a clean and dry insulation. The scales are

logarithmic ............................................................................................................................ 27

Figure C.2 – Insulation resistance versus time on a clean and dry insulation ........................ 28

Figure C.3 – Total current versus time on a wet and contaminated insulation ........................ 28

Figure C.4 – Insulation resistance versus time on a wet and contaminated insulation .......... 29

Figure C.5 – Total current versus time on a dry and clean surface with a continuous

stress control coating ............................................................................................................ 30

Figure C.6 – Insulation resistance versus time on a dry and clean surface with a

stress control coating ............................................................................................................ 31

Figure D.1 – Connection for phase-to-phase measurement. The test instrument shall

be floating with respect to earth. Other phase to phase combinations are permitted ............. 32

Figure D.2 – Measurement of interphase leakage current with a measurement

instrument equipped with a guard connection........................................................................ 33

Figure D.3 – Measurement of interphase leakage current with a measurement

instrument not equipped with a guard connection .................................................................. 33

Figure E.1 – Measurement of current and insulation resistance that results in a DAR

of 1,09 .................................................................................................................................. 35

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SIST EN 60034-27-4:2018
– 4 – IEC 60034-27-4:2018 © IEC 2018

Figure E.2 – Charge and discharge currents after a step voltage of 2,5 kV for the

three-phase windings of a 50 MVA hydro-generator: ............................................................. 36

Table 1 – Values of the parameter X for the temperature correction ...................................... 12

Table 2 – Guidelines for DC voltage magnitudes to be applied during the insulation

resistance measurement ....................................................................................................... 15

Table 3 – Recommended minimum insulation resistance values at a base temperature

of 40 °C ................................................................................................................................ 18

Table 4 – Recommended minimum values of polarization index for high voltage

insulation systems ................................................................................................................ 19

Table B.1 – Example data from insulation resistance measurements at different

winding temperatures ............................................................................................................ 25

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SIST EN 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –
Part 27-4: Measurement of insulation resistance and polarization
index of winding insulation of rotating electrical machines
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

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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

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

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.

International Standard IEC 60034-27-4 has been prepared by IEC technical committee 2:

Rotating machinery.
The text of this International Standard is based on the following documents:
FDIS Report on voting
2/1880/FDIS 2/1890/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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SIST EN 60034-27-4:2018
– 6 – IEC 60034-27-4:2018 © IEC 2018

A list of all parts in the IEC 60034 series, published under the general title Rotating electrical

machines, can be found on the IEC website.

NOTE A table of cross-references of all IEC TC 2 publications can be found in the IEC TC 2 dashboard on the

IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
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SIST EN 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 7 –
INTRODUCTION

This document provides guidelines for measurement of the insulation resistance and the

polarization index on stator and rotor winding insulation of rotating electrical machines. The

document also describes typical insulation resistance characteristics, the effect of influential

factors which impact or change these characteristics, and how these characteristics indicate

winding condition. It recommends minimum acceptable values of insulation resistance for AC

and DC rotating machine windings. Interpretation will depend on the nature of the insulation

materials – specifically if the insulation is of the thermoset or thermoplastic type.

Insulation resistance measurement has been recommended and used for over 50 years to

evaluate the condition of electrical insulation. It is recommended to track periodic

measurements, accumulated over months and years of service or in connection with servicing

and overhaul of rotating machines.

Empirical limits verified in practice can be used as a basis for evaluating the quality of stator

winding insulation systems in manufacturing. Furthermore, trend evaluation, e.g. diagnostic

tests as part of the functional evaluation of insulation systems or in connection with servicing

and overhaul of rotating machines, can also provide information on ageing processes,

possible repair options and the recommended time interval between tests. These

measurements give no indication of local weak points in the insulation system and the trend

evaluations cannot be used to predict the time to failure of the winding insulation.

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SIST EN 60034-27-4:2018
– 8 – IEC 60034-27-4:2018 © IEC 2018
ROTATING ELECTRICAL MACHINES –
Part 27-4: Measurement of insulation resistance and polarization
index of winding insulation of rotating electrical machines
1 Scope
This part of IEC 60034 provides recommended for the measurement of
test procedures

insulation resistance and polarization index of stator and rotor winding insulation of

rotating electrical machines.
This document recommends minimum acceptable values of insulation resistance and

polarization index of winding insulation valid for fully processed low and high voltage AC and

DC rotating electrical machines with a rated power of 750 W or higher.
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 60050-411, International Electrotechnical Vocabulary – Chapter 411: Rotating machinery

3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-411 and the

following 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
3.1
rated voltage

rated line-to-line voltage for a three-phase AC machine, line-to-

earth voltage for a single phase machine and rated direct voltage for DC machines or field

windings
3.2
insulation resistance

capability of the electrical insulation of a winding to resist direct

current and is determined by the quotient of the applied direct voltage divided by the total

current across the machine insulation, taken at a specified time t from start of voltage

application

Note 1 to entry: The voltage application time is usually 1 min (R ) and 10 min (R ); however other values can be

i1 i10

used. Unit conventions: subscript values of 1 through 10 are assumed to be in minutes, subscript values of 15 and

greater are assumed to be in seconds.
Note 2 to entry: Insulation resistance is sometimes abbreviated as IR.
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SIST EN 60034-27-4:2018
IEC 60034-27-4:2018 © IEC 2018 – 9 –
3.3
polarization index

quotient of the insulation resistance measured at two different times, usually t = 1 min and

t , = 10 min after application of the direct voltage, that is an indicator of the condition of the

insulation
Note 1 to entry: Other times are discussed in Clause E.2.
3.4
polarization current

current resulting from polarization processes, which decays with time of DC voltage

application at a decreasing rate from an initial value to essentially zero
Note 1 to entry: The polarization current is also called absorption current.
3.5
conduction current

ohmic current that is constant with time and passes through the

bulk of the main insulation
3.6
surface leakage current

ohmic current that is constant with time and passes over the surface of the end windings of

the stator winding or between exposed conductors and the rotor body in insulated rotor

windings if there are depositions of conductive materials, e.g., moisture or contamination

3.7
capacitive current

current of comparatively high magnitude and short duration

(typically < 1 s), which decays exponentially with time of DC voltage application

3.8
stress control coating current

ohmic current that is constant with time, flowing in parallel to the surface leakage current

through a continuous stress control coating on the surface of the end winding insulation

between conductor and earth
3.9
total current

time dependent current, which is usually measured during insulation resistance measurement

and is the sum of all current components

Note 1 to entry: The total current is the basis for the determination of the insulation resistance R a

...

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