IEC 61251:2015
(Main)Electrical insulating materials and systems - AC voltage endurance evaluation
Electrical insulating materials and systems - AC voltage endurance evaluation
IEC 61251:2015 describes many of the factors involved in voltage endurance tests on electrical insulating materials and systems. It describes the voltage endurance graph, lists test methods illustrating their limitations and gives guidance for evaluating the sinusoidal a.c. voltage endurance of insulating materials and systems from the results of the tests. This International Standard is applicable over the voltage frequency range 20 Hz to 1 000 Hz. The general principles can also be applicable to other voltage shapes, including impulse voltages. The terminology to be used in voltage endurance is defined and explained. This first edition of IEC 61251 cancels and replaces the second edition of IEC TS 61251, published in 2008. This edition constitutes a technical revision and includes the following significant technical changes with respect to the second edition of IEC TS 61251:
a) upgrade from Technical Specification to an International Standard;
b) clarification of issues raised since publication of IEC TS 61251.
Systèmes et matériaux isolants électriques - Évaluation de l'endurance a la tension alternative
L'IEC 61251:2015 décrit plusieurs des facteurs intervenant dans les essais d'endurance à la tension de systèmes et de matériaux isolants électriques. Elle décrit le graphe d'endurance à la tension, donne une liste des méthodes d'essai en indiquant leurs limites et donne des lignes directrices pour évaluer l'endurance à la tension alternative de systèmes et de matériaux isolants à partir des résultats des essais. La présente Norme internationale est applicable sur la plage de fréquences de la tension allant de 20 Hz à 1 000 Hz. Les principes généraux peuvent également être applicables à d'autres formes de tension, y compris les tensions de chocs. La terminologie à utiliser dans le cadre de l'endurance à la tension est définie et expliquée. Cette première édition de l'IEC 61251 annule et remplace la deuxième édition de l'IEC TS 61251 parue en 2008. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à la deuxième édition de l'IEC TS 61251:
a) transformation d'une Spécification technique en Norme internationale;
b) clarification des questions soulevées depuis la publication de l'IEC TS 61251.
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IEC 61251 ®
Edition 1.0 2015-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulating materials and systems – AC voltage endurance evaluation
Systèmes et matériaux isolants électriques – Évaluation de l'endurance à la
tension alternative
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IEC 61251 ®
Edition 1.0 2015-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulating materials and systems – AC voltage endurance evaluation
Systèmes et matériaux isolants électriques – Évaluation de l'endurance à la
tension alternative
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.99; 29.035.01 ISBN 978-2-8322-2990-3
– 2 – IEC 61251:2015 © IEC 2015
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols. 6
3.1 Terms and definitions . 6
3.2 Symbols . 7
4 Voltage endurance . 7
4.1 Voltage endurance testing . 7
4.2 Electrical stress . 7
4.3 Voltage endurance (VE) graph . 8
4.4 Short-time electric strength . 8
4.5 Voltage endurance coefficient (VEC) . 9
4.6 Differential VEC (n ) . 9
d
4.7 Electrical threshold stress (E ) . 9
t
4.8 Voltage endurance relationship . 10
5 Test methods . 11
5.1 Introductory remarks . 11
5.2 Tests at constant stress . 11
5.2.1 Conventional VE test . 11
5.2.2 Diagnostic measurements . 12
5.2.3 Detection of an electrical threshold . 12
5.3 Tests at higher frequency. 12
5.4 Progressive stress tests . 13
5.5 Preliminary tests to determine the initial part of the VE line . 15
5.6 Recommended test procedure . 15
6 Evaluation of voltage endurance . 15
6.1 Significance of the VEC . 15
6.2 Significance of the electrical threshold stress . 16
6.3 Dispersion of data and precision requirements . 16
6.4 Presentation of the results . 16
Annex A (informative) The Weibull distribution . 18
A.1 Weibull distribution times to dielectric breakdown . 18
A.2 Weibull distribution dielectric breakdown stresses . 18
A.3 Generalized Weibull distribution of the dielectric breakdown stresses . 18
A.4 Inverse power model for the time to dielectric breakdown . 19
Bibliography . 20
Figure 1 – General voltage endurance line . 8
Figure 2 – Determination of the differential VEC n at a generic point P of the VE line . 9
d
Figure 3 – Plotting the VE line in a progressive stress test using different rates of
stress rise . 14
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATING MATERIALS AND SYSTEMS –
AC VOLTAGE ENDURANCE EVALUATION
FOREWORD
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