IEC 60076-2:2011

Power transformers - Part 2: Temperature rise for liquid-immersed transformers

IEC 60076-2:2011 applies to liquid-immersed transformers, identifies power transformers according to their cooling methods, defines temperature rise limits and gives the methods for temperature rise tests. This new edition includes the following significant technical changes with respect to the previous edition:
- the winding hot-spot temperature rise limit was introduced among the prescriptions;
- the procedures for the temperature rise test were improved in relation to the new thermal requirements;
- five informative annexes were added in order to facilitate the implementation of this standard.

Transformateurs de puissance - Partie 2: Echauffement des transformateurs immergés dans le liquide

La CEI 60076-2:2011 s'applique aux transformateurs immergés dans un liquide, identifie les transformateurs de puissance selon leurs méthodes de refroidissement, définit les limites d'échauffement et présente les méthodes d'essais d'échauffement. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- les modalités de réalisation des essais d'échauffement ont été améliorées de façon à tenir compte des nouvelles exigences de performances thermiques;
- cinq nouvelles annexes informatives ont été introduites pour faciliter l'application de cette norme.

General Information

• Status: Published
• Publication Date: 22-Feb-2011
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: TC 14 - Power transformers
• Drafting Committee: MT 6 - TC 14/MT 6
• Current Stage: PPUB - Publication issued
• Start Date: 15-Feb-2011
• Completion Date: 23-Feb-2011

Relations

• Revises: IEC 60076-2:1993 - Power transformers - Part 2: Temperature rise
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60076-2 ®
Edition 3.0 2011-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power transformers –
Part 2: Temperature rise for liquid-immersed transformers

Transformateurs de puissance –
Partie 2: Echauffement des transformateurs immergés dans le liquide

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IEC 60076-2 ®
Edition 3.0 2011-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power transformers –
Part 2: Temperature rise for liquid-immersed transformers

Transformateurs de puissance –
Partie 2: Echauffement des transformateurs immergés dans le liquide

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX X
ICS 29.180 ISBN 978-2-88912-346-9

– 2 – 60076-2  IEC:2011
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Cooling methods . 8
4.1 Identification symbols . 8
4.2 Transformers with alternative cooling methods . 9
5 Normal cooling conditions. 9
5.1 Air-cooled transformers . 9
5.2 Water-cooled transformers . 10
6 Temperature rise limits . 10
6.1 General . 10
6.2 Temperature rise limits at rated power . 10
6.3 Modified requirements for special cooling conditions . 12
6.3.1 General . 12
6.3.2 Air-cooled transformers . 12
6.3.3 Water-cooled transformers . 13
6.4 Temperature rise during a specified load cycle . 13
7 Temperature rise tests . 13
7.1 General . 13
7.2 Temperature of the cooling media . 13
7.2.1 Ambient temperature . 13
7.2.2 Water temperature . 14
7.3 Test methods for temperature rise determination . 14
7.3.1 General . 14
7.3.2 Test by short-circuit method for two winding transformers. 14
7.3.3 Test modification for particular transformers . 15
7.4 Determination of liquid temperatures . 16
7.4.1 Top-liquid temperature . 16
7.4.2 Bottom and average liquid temperatures . 17
7.5 Determination of top, average and bottom liquid temperature rises . 18
7.6 Determination of average winding temperature . 18
7.7 Determination of winding resistance at the instant of shutdown . 19
7.8 Determination of average winding temperature rise at the instant of
shutdown . 19
7.9 Determination of the average winding to liquid temperature gradient . 19
7.10 Determination of the hot-spot winding temperature rise . 20
7.10.1 General . 20
7.10.2 Determination by calculation . 20
7.10.3 Direct measurement during the temperature rise test . 20
7.11 Uncertainties affecting the results of the temperature rise test. 21
7.12 Dissolved gas-in-oil analysis . 21
7.13 Corrections. 21
Annex A (informative) Hot-spot winding temperature rise determination for OFAF and
OFWF cooled transformers based on the top-liquid temperature in tank . 23
Annex B (informative) Methods to estimate the hot-spot winding temperature rises. 25

60076-2  IEC:2011 – 3 –
Annex C (informative) Techniques used in temperature rise testing of liquid-immersed
transformers . 30
Annex D (informative) Dissolved gases analysis for the detection of local overheating . 39
Annex E (informative) Application of optical fibre sensors for winding hot-spot
measurements . 43
Bibliography . 47

Figure B.1 – Temperature rise distribution model for ON cooling methods . 26
Figure B.2 – Value of factor Q as a function of rated power and strand height (W) . 27
Figure B.3 – Typical liquid flow paths in a disk winding with diverting washers . 28
Figure C.1 – Recommended circuit for transformers with a low resistance winding
using two separate direct current sources, one for each winding . 32
Figure C.2 – Alternative recommended circuit using only one direct current source for
both windings. 32
Figure C.3 – Average winding temperature variation after shutdown . 33
Figure C.4 – Extrapolation of the cooling down curve, using the fitting curve
−t/T
w
θ (t ) = A − kt+ Be . 38
w 0
Figure E.1 – Optical fibre sensor application for a disk winding of core type transformer . 45
Figure E.2 – Optical fibre sensor application for a transposed cable of core type
transformer . 45
Figure E.3 – Modality of optical fibre sensor application in the winding spacer of core
type transformer . 46
Figure E.4 – Optical fibre sensor application for high voltage winding of shell type
transformer . 46

Table 1 – Temperature rise limits . 11
Table 2 – Recommended values of temperature rise corrections in case of special
service conditions . 12
Table 3 – Exponents for the corrections of temperature rise test results . 22
Table A.1 – Hot-spot winding temperature rises for some specific transformers
determined from conventional heat run test data combined with calculated hot-spot
winding temperature rise, and from direct fibre-optic measurements . 24
Table C.1 – Example of cooling down curve calculation spreadsheet . 37
Table D.1 – Minimum detectable value S of gases in oil . 40
D
Table D.2 – Admissible limits for gas rate increases . 41
Table E.1 – Minimum recommended number of sensors for three-phase transformers . 43
Table E.2 – Minimum recommended number of sensors for single-phase transformers . 43

– 4 – 60076-2  IEC:2011
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 2: Temperature rise for liquid-immersed transformers

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide or
...