prEN IEC 61203:2023

SLOVENSKI STANDARD
01-november-2023
Sintetični estri - Smernice za vzdrževanje in uporabo v električni opremi
Synthetic esters - Guidelines for maintenance and use in electrical equipment
Synthetische organische Ester für elektrotechnische Zwecke - Leitlinie zur Wartung von
Transformator-Estern in Betriebsmitteln
Esters organiques de synthèse à usages
électriques - Guide de maintenance des esters pour transformateurs dans
les matériels
Ta slovenski standard je istoveten z: prEN IEC 61203:2023
ICS:
29.035.20 Plastični in gumeni izolacijski Plastics and rubber insulating
materiali materials
29.180 Transformatorji. Dušilke Transformers. Reactors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

10/1203/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61203 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2023-09-08 2023-12-01
SUPERSEDES DOCUMENTS:
10/1177/CD, 10/1198/CC
IEC TC 10 : FLUIDS FOR ELECTROTECHNICAL APPLICATIONS
SECRETARIAT: SECRETARY:
Italy Mr Massimo Pompili
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:

TC 14, SC 17A, TC 20, SC 36A, TC 38, TC 99, TC 112
Other TC/SCs are requested to indicate their interest, if any, in
this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for Vote
(CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some Countries” clauses to be
included should this proposal proceed. Recipients are reminded that the CDV stage is the final stage for submitting ISC clauses.
(See AC/22/2007 or NEW GUIDANCE DOC).

TITLE:
Synthetic esters – Guidelines for maintenance and use in electrical equipment

PROPOSED STABILITY DATE: 2028
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

– 2 – IEC CDV 61203 © IEC 2023
CONTENTS
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 8
4 Categories of equipment . 8
5 In-service synthetic ester diagnostic tests. 9
6 Evaluation of synthetic esters in new equipment . 10
7 Evaluation of synthetic ester in equipment in service . 11
7.1 General . 11
Application of synthetic esters in transformers is recommended for both sealed and free breathing
equipment. . 11
7.2 Frequency of examination . 11
7.3 Testing procedures . 12
7.3.1 Field tests . 12
7.3.2 Laboratory tests . 12
8 General requirements for corrective actions . 17
9 Interpretation of results . 17
9.2 Colour and appearance . 17
9.3 Breakdown voltage . 17
9.5 Acidity . 18
9.6 Dielectric Dissipation Factor (DDF) and Resistivity . 18
9.7   Fire points . 19
9.8 Interfacial tension (IFT) . 19
9.9 Density . 19
9.10 Pour point. 19
9.11 Additives . 20
9.12  Particle (identification, counting and sizing) . 20
9.13 Compatibility and Miscibility of Synthetic Esters,. 20
9.14 Oxidation stability . 21
9.15 Refractive Index . 21
Refractive index shall be determined by DIN 51423-1 or ISO 5661 (ref method). 21
10 Sampling of synthetic esters from equipment . 22
Annex A - Water and Synthetic Esters (informative) . 23
A.1 General . 23
A.2.1 General . 23
A.2.2 Water in synthetic esters . 23
Annex B - Replacement and treatments of Synthetic Esters in Transformers (informative) . 26
B.1 Transformer retrofilling with synthetic esters . 26
B.2 Reconditioning and reclaiming . 27
General . 27
B.2.1 Reconditioning . 27
B.2.2 Reclaiming . 27
(informative). 30

IEC CDV 61203 © IEC 2023 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SYNTHETIC ESTERS –
GUIDELINES FOR MAINTENANCE AND USE IN ELECTRICAL EQUIPMENT

FOREWORD
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International Standard IEC 61203 has been prepared by IEC technical committee 10: Liquids for
electrotechnical applications. The text of this standard is based on the following documents:
FDIS Report on voting
XX/XX/FDIS XX/XX/RVD
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until the stability
date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific
publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 4 – IEC CDV 61203 © IEC 2023

Full information on the voting for the approval of this standard can be found in the report on voting
indicated in the above table.
The National Committees are requested to note that for this publication the stability date is 20XX.
THIS TEXT IS INCLUDED FOR THE INFORMATION OF THE NATIONAL COMMITTEES AND WILL BE DELETED AT
THE PUBLICATION STAGE.
IEC CDV 61203 © IEC 2023 – 5 – 10/1203/CDV
1 INTRODUCTION
2 Synthetic esters are increasingly being used in transformers and electrical equipment employed in
3 electrical power generation, transmission, distribution and industrial applications.
4 Synthetic esters are used in transformers over a wide range of voltage classes. These may be sealed or
5 free breathing. Synthetic esters should only be used in transformers where the internal insulation system
6 has been designed to run with these liquids, given the different electrical performance of synthetic ester
7 as compared to mineral oil. Retrofilling mixtures are not covered in the Normative part of this standard.
8 See Annexe B for more information. When in doubt, contact the transformer or liquid manufacturer for
9 more information.
10 Monitoring and maintaining liquid quality is essential to ensure the reliable operation of synthetic ester
11 filled electrical equipment. Codes of practice for this purpose have been established by electrical power
12 authorities, power companies and industries in many countrie
...