IEC 60422 Edition 4.0 2013-01 INTERNATIONAL STANDARD NORME INTERNATIONALE Mineral insulating oils in electrical equipment – Supervision and maintenance guidance Huiles minérales isolantes dans les matériels électriques – Lignes directrices pour la maintenance et la surveillance IEC 60422:2013 ---------------------- Page: 1 ---------------------- THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright © 2013 IEC, Geneva, Switzerland

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FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

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

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

3 Terms and definitions ....................................................................................................... 9

4 Properties and deterioration/degradation of oil ............................................................... 10

5 Oil tests and their significance ........................................................................................ 11

5.1 General ................................................................................................................. 11

5.2 Colour and appearance ......................................................................................... 12

5.3 Breakdown voltage ................................................................................................ 12

5.4 Water content ........................................................................................................ 12

5.4.1 General ..................................................................................................... 12

5.4.2 Water in oil ................................................................................................ 12

5.4.3 Water content in the oil/paper-system ........................................................ 14

5.4.4 Interpretation of results.............................................................................. 15

5.5 Acidity ................................................................................................................... 15

5.6 Dielectric dissipation factor (DDF) and resistivity ................................................... 15

5.7 Inhibitor content and oxidation stability .................................................................. 18

5.7.1 Oxidation stability ...................................................................................... 18

5.7.2 Monitoring of uninhibited oils ..................................................................... 18

5.7.3 Monitoring of inhibited oils ......................................................................... 18

5.8 Sediment and sludge ............................................................................................. 18

5.9 Interfacial tension (IFT) ......................................................................................... 19

5.10 Particle count ........................................................................................................ 19

5.11 Flash point ............................................................................................................ 19

5.12 Compatibility of insulating oils ............................................................................... 20

5.13 Pour point ............................................................................................................. 20

5.14 Density .................................................................................................................. 20

5.15 Viscosity................................................................................................................ 20

5.16 Polychlorinated biphenyls (PCBs) .......................................................................... 21

5.17 Corrosive sulphur .................................................................................................. 21

5.18 Dibenzyl disulphide (DBDS) .................................................................................. 22

5.19 Passivator ............................................................................................................. 22

6 Sampling of oil from equipment ...................................................................................... 22

7 Categories of equipment ................................................................................................. 23

8 Evaluation of mineral insulating oil in new equipment ..................................................... 23

9 Evaluation of oil in service .............................................................................................. 24

9.1 General ................................................................................................................. 24

9.2 Frequency of examination of oils in service ........................................................... 25

9.3 Testing procedures ................................................................................................ 26

9.3.1 General ..................................................................................................... 26

9.3.2 Field tests.................................................................................................. 26

9.3.3 Laboratory tests ........................................................................................ 27

9.4 Classification of the condition of oils in service ...................................................... 27

9.5 Corrective action ................................................................................................... 27

10 Handling and storage ..................................................................................................... 32

11 Treatment ....................................................................................................................... 33

11.1 WARNING ............................................................................................................. 33

11.2 Reconditioning ...................................................................................................... 34

11.2.1 General ..................................................................................................... 34

11.2.2 Reconditioning equipment ......................................................................... 35

11.2.3 Application to electrical equipment ............................................................ 36

11.3 Reclaiming ............................................................................................................ 37

11.3.1 General ..................................................................................................... 37

11.3.2 Reclaiming by percolation .......................................................................... 37

11.3.3 Reclaiming by contact ............................................................................... 38

11.3.4 Renewal of additives ................................................................................. 38

11.4 Decontamination of oils containing PCBs .............................................................. 38

11.4.1 General ..................................................................................................... 38

11.4.2 Dehalogenation processes using sodium and lithium derivatives ............... 38

hydroxide (KPEG) ...................................................................................... 39

11.4.4 Dehalogenation in continuous mode by closed circuit process ................... 39

12 Replacement of oil in electrical equipment ...................................................................... 39

and associated equipment ..................................................................................... 39

12.2 Replacement of oil in transformers rated 72,5 kV and above ................................. 39

12.3 Replacement of oil in electrical equipment contaminated with PCB ........................ 40

13 Passivation ..................................................................................................................... 40

Annex A (informative) Evaluating water in oil and insulation................................................. 41

Annex B (informative) Particles ............................................................................................ 43

Annex C (informative) Test method for determination of sediment and sludge ...................... 44

Bibliography .......................................................................................................................... 45

Figure 1 – Example of variation in saturation water content with oil temperature and

acidity for insulating oil originally conforming to IEC 60296 ................................................... 14

Figure 2 – Example of variation of resistivity with temperature for insulating oils ................... 17

Figure A.1 – Typical correction factors .................................................................................. 41

Table 1 – Tests for in-service mineral insulating oils ............................................................. 11

Table 2 – Categories of equipment ....................................................................................... 23

Table 3 – Recommended limits for mineral insulating oils after filling in new electrical

equipment prior to energization ............................................................................................. 24

Table 4 – Recommended frequency of testing .................................................................... 26

Table 5 – Application and interpretation of tests (1 of 4) ....................................................... 28

Table 6 – Summary of typical actions .................................................................................... 32

Table 7 – Conditions for processing inhibited and/ or passivator containing mineral

insulating oils ........................................................................................................................ 35

Table A.1 – Guidelines for interpreting data expressed in per cent saturation ....................... 42

Table B.1 – Typical contamination levels (particles) encountered on power transformer

insulating oil as measured using IEC 60970 .......................................................................... 43

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International Standard IEC 60422 has been prepared by IEC technical committee 10: Fluids

This fourth edition cancels and replaces the third edition, published in 2005, and constitutes a

This new edition represents a major revision of the third edition, in order to bring in line this

standard with latest development of oil condition monitoring, containing new limits for oil

The action limits for all oil tests have been revised and changes made where necessary to

enable users to use current methodology and comply with requirements and regulations

In addition, this standard incorporates changes introduced in associated standards since the

Full information on the voting for the approval of this standard can be found in the report on

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

The contents of the corrigendum of December 2013 have been included in this copy.

Insulating mineral oils are used in electrical equipment employed in the generation,

transmission, distribution and use of electrical energy, so that the amount of oil in service,

Monitoring and maintaining oil quality is essential to ensure the reliable operation of oil-filled

electrical equipment. Codes of practice for this purpose have been established by electrical

A review of current experience reveals a wide variation of procedures and criteria. It is

possible, however, to compare the value and significance of standardized oil tests and to

If a certain amount of oil deterioration (by degradation or contamination) is exceeded, there is

inevitably some erosion of safety margins and the question of the risk of premature failure

should be considered. While the quantification of the risk can be very difficult, a first step

involves the identification of potential effects of increased deterioration. The philosophy

underlying this standard is to furnish users with as broad a base of understanding of oil

quality deterioration as is available, so that they can make informed decisions on inspection

Unused mineral oils are limited resources and should be handled with this in mind. Used

mineral oils are, by most regulations, deemed to be controlled waste. If spills occur this may

have a negative environmental impact especially if the oil is contaminated by persistent

This International Standard, whilst technically sound, is mainly intended to serve as a

common basis for the preparation of more specific and complete codes of practice by users in

the light of local circumstances. Sound engineering judgement will have to be exerted in

This International Standard does not purport to address all the safety problems associated

with its use. It is the responsibility of the user of this standard to establish appropriate health

and safety practices and determine the applicability of regulatory limitations prior to use.

The mineral oils and oil additives which are the subject of this standard should be handled

with due regard to personal hygiene. Direct contact with the eyes may cause slight irritation.

In the case of eye contact, irrigation with copious quantities of clean running water should be

carried out and medical advice sought. For more information, refer to the safety data sheet

provided by the manufacturer. Some of the tests specified in this standard involve the use of

processes that could lead to a hazardous situation. Attention is drawn to the relevant standard

This standard is applicable to mineral oils, chemicals and used sample containers.

Attention is drawn to the fact that, at the time of writing this standard, some mineral oils in

Because of this, safety countermeasures should be taken to avoid risks to workers, the public

and the environment during the life of the equipment, by strictly controlling spills and

emissions. Disposal or decontamination of these oils should be carried out strictly according

to local regulations. Every precaution should be taken to prevent release of mineral oil into

This International Standard gives guidance on the supervision and maintenance of the quality

This standard is applicable to mineral insulating oils, originally supplied conforming to

IEC 60296, in transformers, switchgear and other electrical apparatus where oil sampling is

reasonably practicable and where the normal operating conditions specified in the equipment

This standard is also intended to assist the power equipment operator to evaluate the

condition of the oil and maintain it in a serviceable condition. It also provides a common basis

The standard includes recommendations on tests and evaluation procedures and outlines

methods for reconditioning and reclaiming oil and the decontamination of oil contaminated

NOTE The condition monitoring of electrical equipment, for example by analysis of dissolved gases, furanic

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

IEC 60156, Insulating liquids – Determination of the breakdown voltage at power frequency –

IEC 60247, Insulating liquids – Measurement of relative permittivity, dielectric dissipation

IEC 60296:2012, Fluids for electrotechnical applications – Unused mineral insulating oils for

IEC 60666:2010, Detection and determination of specified additives in mineral insulating oils

IEC 60814, Insulating liquids – Oil-impregnated paper and pressboard – Determination of

IEC 61125:1992, Unused hydrocarbon based insulating liquids – Test methods for evaluating

IEC 61619, Insulating liquids – Contamination by polychlorinated biphenyls (PCBs) – Method

IEC 62021-1, Insulating liquids – Determination of acidity – Part 1: Automatic potentiometric

IEC 62021-2, Insulating liquids – Determination of acidity – Part 2: Colourimetric titration

IEC 62535:2008, Insulating liquids – Test method for detection of potentially corrosive sulphur

IEC 62697-1:2012, Test methods for quantitative determination of corrosive sulfur compounds

in unused and used insulating liquids - Part 1: Test method for quantitative determination of

ISO 3104, Petroleum products – Transparent and opaque liquids – Determination of kinematic

ISO 3675, Crude petroleum and liquid petroleum products – Laboratory determination of

ISO 4406:1999, Hydraulic fluid power – Fluids – Method for coding the level of contamination

EN 14210, Surface active agents – Determination of interfacial tension of solutions of surface

ASTM D971, Standard Test Method for Interfacial Tension of Oil Against Water by the Ring

ASTM D1275:2006, Standard Test Method for Corrosive Sulfur in Electrical Insulating Oils

DIN 51353: Testing of insulating oils; Detection of corrosive sulphur; Silver strip test

Note 1 to entry: Such regulations may be defined by local, regional or national legislation or even the owner or

operator of the equipment itself. They are always to be considered as the most stringent of any combina