IEC 61858-2:2014

IEC 61858-2 ®
Edition 1.0 2014-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical insulation systems – Thermal evaluation of modifications to an
established electrical insulation system (EIS) –
Part 2: Form-wound EIS
Systèmes d'isolation électrique – Évaluation thermique des modifications
apportées à un système d’isolation électrique (SIE) éprouvé –
Partie 2: Système d’isolation électrique à enroulements préformés

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IEC 61858-2 ®
Edition 1.0 2014-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical insulation systems – Thermal evaluation of modifications to an

established electrical insulation system (EIS) –

Part 2: Form-wound EIS
Systèmes d'isolation électrique – Évaluation thermique des modifications

apportées à un système d’isolation électrique (SIE) éprouvé –

Partie 2: Système d’isolation électrique à enroulements préformés

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX T
ICS 29.080.30 ISBN 978-2-8322-1394-0

– 2 – 61858-2 © IEC:2014
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 General considerations . 9
5 Substitution of phase insulation and/or ground insulation . 11
5.1 Generically identical . 11
5.2 Substitution or addition of selected components and additives . 11
5.3 Reduction of thickness . 11
6 Substitution of winding wire . 12
6.1 Winding wire . 12
6.2 Substitution of conductor material . 13
6.3 Alternate winding wire . 13
7 Substitution of impregnating resin/varnish . 13
8 Evaluation of additions . 13
9 Procedure C – Single-point thermal ageing test . 13
9.1 Test objects . 13
9.2 Establishing the EIS relative thermal endurance index (EIS RTE) . 13
9.3 Interpretation of results . 14
10 Full thermal aging test (procedure D) . 14
Annex A (normative) Classes of winding wire . 15
Annex B (informative) Visual representation of form-wound coil manufacturing process . 16
Bibliography . 22

Figure 1 – Overview of evaluation methods . 10
Figure 2 – Substitution of phase and ground insulation . 11
Figure 3 – Substitution of winding wire . 12
Figure 4 – Substitution of conductor material . 12
Figure B.1 – Rectangular winding wire shaped into un-formed coil on coil forming
machine . 16
Figure B.2 – Un-formed coil being wrapped with a protective fabric . 17
Figure B.3 – Un-formed coil completely wrapped with protective fabric . 17
Figure B.4 – Coil forming machine stretches and bends oval coil to formed shape coil
in the shaping apparatus . 18
Figure B.5 – Formed coil with protective layer removed . 18
Figure B.6 – Close-up of formed coil’s knuckle insulation . 19
Figure B.7 – Formed coil with multiple layers of insulation . 19
Figure B.8 – Formed coils placed into the form-wound test specimen or Formette . 20
Figure B.9 – Insulation details . 21

Table A.1 – Winding wire type – Rectangular conductor . 15

61858-2 © IEC:2014 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATION SYSTEMS –
THERMAL EVALUATION OF MODIFICATIONS TO
AN ESTABLISHED ELECTRICAL INSULATION SYSTEM (EIS) –

Part-2: Form-wound EIS
FOREWORD
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