TC 10 - Fluids for electrotechnical applications

IEC 60567:2023 deals with the techniques for sampling free gases from gas-collecting relays from power transformers. Three methods of sampling free gases are described. The techniques for sampling oil from oil-filled equipment such as power and instrument transformers, reactors, bushings, oil-filled cables and oil-filled tank-type capacitors are no longer covered by this document, but are instead described in IEC 60475:2022, 4.2. Before analysing the gases dissolved in oil, they are first extracted from the oil. Three basic methods are described, one using extraction by vacuum (Toepler and partial degassing), another by displacement of the dissolved gases by bubbling the carrier gas through the oil sample (stripping) and the last one by partition of gases between the oil sample and a small volume of the carrier gas (headspace). The gases are analysed quantitatively after extraction by gas chromatography; a method of analysis is described. Free gases from gas-collecting relays are analysed without preliminary treatment.

IEC 60867:2022 covers specifications and test methods for unused synthetic aromatic hydrocarbons intended for use as insulating liquid in cables and capacitors.

IEC 60599:2022 describes how the concentrations of dissolved gases or free gases can be interpreted to diagnose the condition of oil-filled electrical equipment in service and suggest future action. This document is applicable to electrical equipment filled with mineral insulating oil and insulated with cellulosic paper or pressboard-based solid insulation. Information about specific types of equipment such as transformers (power, instrument, industrial, railways, distribution), reactors, bushings, switchgear and oil-filled cables is given only as an indication in the application notes. This document can be applied, but only with caution, to other liquid-solid insulating systems. In any case, the indications obtained are given only as guidance with resulting action undertaken only with proper engineering judgment.

IEC 60475:2022 is applicable to the sampling procedure used for insulating liquids in delivery containers and in electrical equipment such as power and instrument transformers, reactors, bushings, oil-filled cables, oil-filled tank-type capacitors, switchgear and load tap changers (LTCs). This document applies to liquids the viscosity of which at the sampling temperature is less than 1 500 mm2/s (or cSt). It applies to mineral oils and non-mineral oils (such as synthetic esters, natural esters, vegetable oils or silicones).

IEC TR 63025:2021(E) specifies two test methods for methanol and ethanol determination in insulating liquids.
Methanol (MeOH) and ethanol (EtOH) are two light alcohols generated during the degradation process of cellulosic materials. They are soluble in insulating liquids so they can be regarded as ageing tracers whose concentrations in oil reflect the degradation of insulating cellulosic materials in liquid-impregnated transformers.

IEC 62975:2021 provides procedures and guidelines that are intended for the use and maintenance of natural ester liquid in sealed transformers and other electrical equipment.
This document is applicable to natural esters, originally supplied conforming to IEC 62770 and other applicable standards (e.g. ASTM D6871) in transformers, switchgear and electrical apparatus where liquid sampling is practical and where the normal operating conditions specified in the equipment specifications apply.
At present, there is a limited amount of information available for electrical equipment other than transformers.
This document is also intended to assist the power equipment operator to evaluate the condition of the natural ester and maintain it in a serviceable condition. It also provides a common basis for the preparation of more specific and complete local codes of practice.
The document includes recommendations on tests and evaluation procedures and outlines methods for reconditioning and reclaiming the liquid, when necessary.

IEC 60296:2020 provides specifications and test methods for unused and recycled mineral insulating oils. It applies to mineral oil delivered according to the contractual agreement, intended for use in transformers, switchgear and similar electrical equipment in which oil is required for insulation and heat transfer. Both unused oil and recycled oil under the scope of this document have not been used in, nor been in contact with electrical equipment or other equipment not required for manufacture, storage or transport.
Unused oils are obtained by refining, modifying and/or blending of petroleum products and other hydrocarbons from virgin feedstock.
Recycled oils are produced from oils previously used as mineral insulating oils in electrical equipment that have been subjected to re-refining or reclaiming (regeneration) by processes employed offsite. Such oils will have originally been supplied in compliance with a recognized unused mineral insulating oil specification. This document does not differentiate between the methods used to recycle mineral insulating oil. Oils treated on-site (see IEC 60422) are not within the scope of this document.
Oils with and without additives are both within the scope of this document.
This document does not apply to mineral insulating oils used as impregnating medium in cables or capacitors.
This fifth edition cancels and replaces the fourth edition published in 2012. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
– This International Standard is applicable to specifications and test methods for unused and recycled mineral insulating oils in the delivered state.
– Within the transformer insulating oils, two groups, Type A and Type B, are defined, based on their performance.
– A new method for stray gassing under thermo-oxidative stress of mineral insulating oils, which has been tested in a joint round robin test (RRT) between CIGRE D1 and IEC technical committee 10, has been included.

IEC 63012:2019 defines requirements for the characterization of unused modified esters or blends of unused esters used as insulating liquids for electrotechnical applications. It does not cover liquids that contain any proportion of used liquids. The liquids covered by this document are intended mainly for transformer applications.
Unused modified/synthetized esters are derived from a natural or synthetic base, or are blends of both. This document covers a variety of ester liquids not covered by other standards specific to natural esters (IEC 62770) or synthetic esters (IEC 61099). As it addresses various categories of liquids, this document also covers a wide range of values for certain performance characteristics. An important property is viscosity, which can affect the design and cooling performance of electrical equipment. A categorization is defined based on the kinematic viscosity of the different liquids. The category of low viscosity ester liquids is established.

IEC 60480:2019 provides criteria for the re-use of sulphur hexafluoride (SF6) and its mixtures after recovery and reclaiming from electrical equipment (e.g. for maintenance, at the end-of-life).
Sulphur hexafluoride (SF6), nitrogen (N2) and carbon tetrafluoride (CF4), are gases commonly used for electrical equipment. Taking into account environmental concerns, particular attention is paid to re-use criteria for SF6 and its mixtures with N2 and CF4 for its use in electrical equipment. Procedures for recovering and reclaiming used SF6 and its mixtures are outside the scope of this document and are described in IEC 62271-4.
This document provides several annexes on the description of the different methods of analysis, on by-products, on the procedure for evaluating the potential health effects from by-products, on cryogenic reclaiming of SF6, and on reclaiming recommendations.
Storage, transportation and disposal of SF6 and its mixtures are outside the scope of this document and are covered by IEC 62271-4. Procedures to determine SF6 leakages are described in IEC 60068-2-17.
For the purposes of this document, the complementary gases used in SF6 mixtures will be limited to N2 or CF4.
This third edition cancels and replaces the second edition, published in 2004. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
• specifications for the re-use of SF6 have been confirmed;
• specifications for the re-use of SF6 mixtures, namely SF6/N2 and SF6/CF4 mixtures are included;
• as a result of a new repartition of annexes in IEC 60376, IEC 60480 and IEC 62271-4, this new edition now contains the following five annexes:
– Annex A: Description of methods of analysis (on-site and laboratory);
– Annex B: By–products of SF6 and its mixtures;
– Annex C: Procedure for evaluating the potential effects on health from by products of SF6 and its mixtures;
– Annex D: Reclaiming recommendations.
– Annex E: Cryogenic reclaiming of SF6;

IEC 62961:2018 establishes the measurement of the interfacial tension between insulating liquid and water by means of the Du Noüy ring method close to equilibrium conditions. In order to obtain a value that provides a realistic expression of the real interfacial tension, a measurement after a surface age of approximately 180 s is recorded.

IEC 60156:2018 is now available as IEC 60156:2018 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60156:2018 specifies the method for determining the dielectric breakdown voltage of insulating liquids at power frequency. The test procedure is performed in a specified apparatus, where the oil sample is subjected to an increasing AC electrical field until breakdown occurs. The method applies to all types of insulating liquids of nominal viscosity up to 350 mm2/s at 40 °C. It is appropriate both for acceptance testing on unused liquids at the time of their delivery and for establishing the condition of samples taken in monitoring and maintenance of equipment. This third edition cancels and replaces the second edition published in 1995. This edition constitutes a technical revision and, mainly, confirms the content of the previous edition even if some advances are included. The test method has not been changed for practical reason due to the very large number of instrumentation disseminated around the world, even if the use of stirring is now recommended.

IEC 60376:2018 defines the quality for technical grade sulphur hexafluoride (SF6) and complementary gases such as nitrogen (N2) and carbon tetra-fluoride (CF4), for use in electrical equipment. Detection techniques, covering both laboratory and in-situ portable instrumentation, applicable to the analysis of SF6, N2 and CF4 gases prior to the introduction of these gases into the electrical equipment are also described in this document.
This document provides some information on sulphur hexafluoride in Annex A and on the environmental effects of SF6 in Annex B.
Information about SF6 by-products and the procedure for evaluating the potential effects of SF6 by-products on human health are covered by IEC 60480, their handling and disposal being carried out according to international and local regulations with regard to the impact on the environment. Handling of SF6 and its mixtures is covered by IEC 62271-4.
Procedures to determine SF6 leakages are described in IEC 60068-2-17.
For the purposes of this document, the complementary gases used in SF6 mixtures will be limited to N2 or CF4.
This third edition cancels and replaces the second edition published in 2005. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) the requirements for the use of SF6 in electrical equipment have been confirmed;
b) a specification for complementary gases to be used in SF6 mixtures with N2 and CF4 has been included;
c) the introduction and scope have been merged;
d) a new repartition of the annexes of IEC 60376, IEC 60480 and IEC 62271-4 has been included.

IEC TR 62697-3:2018(E) specifies a test method for the quantitative determination of elemental sulfur in used and unused insulating liquids over a 2 mg kg–1 to 400 mg kg–1 concentration range.

IEC TR 62697-2:2018(E) specifies a test method for the quantitative determination of total corrosive sulfur (TCS) in unused and used insulating liquids and solid matrices through the conversion of corrosive sulfur species to metal (copper, silver etc.) sulfides. The sulfides formed are quantitatively converted to sulfates; sulfates are determined through turbidity measurement or with ion chromatography.
The method is applicable with the following matrices:
a) Unused and used insulating liquids, for example mineral insulating oils and natural esters, which allow the determination of corrosive sulfur compounds over concentrations ranging between 2,5 mg kg-1 to 80 mg kg-1 TCS.
b) Solid matrices that come in contact with the insulating liquid, for example insulating papers in electrical equipment. The quantification limits for these matrices depend on the amount of matrix used during the determination. The method can be used for the quantitative or semi-quantitative determination of copper sulfide on paper after the test according to IEC 62535. The method can provide unambiguous quantitative assessment of copper sulfide present on paper rather than qualitative results obtained with the SEM-EDX examination stipulated in case of doubts in the interpretation of results obtained from the inspection of paper according to IEC 62535:2008, 6.3.
c) Paper and other solid insulating material/s obtained from failed transformers, reactors and other electrical equipment to assist in failure diagnostics.
d) Metal deactivator or passivators additives present in insulating liquids (qualitative assessment).
However, the method is not applicable for assessing corrosion phenomena for example the dissolution of copper in insulating liquids and deposition on solid matrices, which do not lead to sulfide formation.

IEC 61125:2018 describes a test method for evaluating the oxidation stability of insulating liquids in the delivered state under accelerated conditions regardless of whether or not antioxidant additives are present. The duration of the test can be different depending on the insulating liquid type and is defined in the corresponding standards (e.g. in IEC 60296, IEC 61099, IEC 62770). The method can be used for measuring the induction period, the test being continued until the volatile acidity significantly exceeds 0,10 mg KOH/g in the case of mineral oils. This value can be significantly higher in the case of ester liquids.
Additional test methods such as those described in IEC TR 62036 based on differential scanning calorimetry can also be used as screening tests, but are out of the scope of this document.
This second edition cancels and replaces the first edition published in 1992 and Amendment 1: 2004. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) the title has been modified to include insulating liquids different from mineral insulating oils (hydrocarbon);
b) the method applies for insulating liquids in the delivered state;
c) former Method C is now the main normative method;
d) precision data of the main normative method has been updated concerning the dissipation factor;
e) former Method A has been deleted;
f) former Method B has been transferred to Annex B;
g) a new method evaluating the thermo-oxidative behaviour of esters is included in Annex C.

IEC 60599:2015 is available as IEC 60599:2015 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60599:2015 describes how the concentrations of dissolved gases or free gases may be interpreted to diagnose the condition of oil-filled electrical equipment in service and suggest future action. This standard is applicable to electrical equipment filled with mineral insulating oil and insulated with cellulosic paper or pressboard-based solid insulation. Information about specific types of equipment such as transformers (power, instrument, industrial, railways, distribution), reactors, bushings, switchgear and oil-filled cables is given only as an indication in the application notes. This standard may be applied, but only with caution, to other liquid-solid insulating systems. This third edition cancels and replaces the second edition published in 1999 and Amendment 1:2007. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) revision of 5.5, 6.1, 7, 8, 9, 10, A.2.6, A.3, A.7;
b) addition of new sub-clause 4.3;
c) expansion of the Bibliography;
d) revision of Figure 1;
e) addition of Figure B.4.

IEC 60836:2015 covers specifications and test methods for unused silicone liquids intended for use in transformers and other electrotechnical equipment. Besides the standard transformer applications there are other applications of silicone liquids, such like cable accessories, capacitors, electrical magnets etc. This edition includes the following major technical changes with regard to the second edition:
a) classification of liquids according to IEC 61039 have been adapted with respect to the latest edition of IEC 61039:2008;
b) classification of liquids according to IEC 61100:1992 have been removed as IEC 61100 has been withdrawn;
c) minimum requirements for other silicone liquids for electrotechnical purposes have been added.

IEC TR 62874:2015 is a Technical Report which provides guidance for the estimation of consumed thermal life of transformers' cellulosic insulators, through the analysis of some compound dissolved in the insulating mineral oil. A comparison between analytical results of 2-furfural (2-FAL) and carbon oxides and their correspondent typical values estimated for different families of equipment gives information on the estimated thermal degradation of papers.

IEC 62021-3:2014 describes two procedures for the determination of the acidity of unused and used electrical non-mineral insulating oils. Method A is potentiometric titration and Method B is colourimetric titration. The method may be used to indicate relative changes that occur in non-mineral insulating oil during use under oxidizing conditions regardless of the colour or other properties of the resulting non-mineral oil. The acidity can be used in the quality control of unused non-mineral insulating oil. As a variety of oxidation products present in used non-mineral insulating oil contribute to acidity and these products vary widely in their corrosion properties, the test cannot be used to predict corrosiveness of non-mineral insulating oil under service conditions.

IEC 62770:2013 describes specifications and test methods for unused natural esters in transformers and similar oil-impregnated electrical equipment in which a liquid is required as an insulating and heat transfer medium. Natural esters with additives are within the scope of this standard. Because of their different chemical composition, natural esters differ from insulating mineral oils and other insulating fluids that have high fire points, such as synthetic esters or silicone fluids. Natural, ester-derived insulating fluids with low viscosity have been introduced but are not covered by this standard. Pertinent properties of such fluids are given in Annex B. This standard is applicable only to unused natural esters. Reclaimed natural esters and natural esters blended with non-natural esters fluids are beyond the scope of this standard.

IEC 60422:2013 gives guidance on the supervision and maintenance of the quality of the insulating oil in electrical equipment. This International 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 specifications apply. This International 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 for the preparation of more specific and complete local codes of practice. The standard includes recommendations on tests and evaluation procedures and outlines methods for reconditioning and reclaiming oil and the decontamination of oil contaminated with PCBs. This fourth edition cancels and replaces the third edition, published in 2005, and constitutes a technical revision. The main changes with respect to the previous edition are as follows:
- 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 parameters, suggested corrective actions in the tables and new test methods.
- 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 affecting safety and environmental aspects.
- In addition, this standard incorporates changes introduced in associated standards since the third edition was published. The contents of the corrigendum of December 2013 have been included in this copy.

IEC 62697-1:2012 specifies a test method for the quantitative determination of corrosive sulfur compounds-dibenzyl disulfide (DBDS) in used and unused insulating liquids over a 5 to 600 mg kg-1 concentration range.

IEC 61181:2007+A1:2012 Specifies oil-sampling procedures, analysis requirements and procedures, and recommends sensitivity, repeatability and accuracy criteria for the application of dissolved gas analysis (DGA) to factory testing of new power transformers, reactors and instrument transformers filled with mineral insulating oil when DGA testing has been specified. The most effective and useful application of DGA techniques to factory testing is during the performance of long-term tests, typically temperature-rise (heat run) and overloading tests on power transformers and reactors, also impulse tests on instrument transformers. DGA may also be valuable for over-excitation tests run over an extended period of time. Experience with DGA results, before and after short-time dielectric tests, indicates that DGA is normally less sensitive than electrical and acoustic methods for detecting partial discharges. However, DGA will indicate when these partial discharges become harmful to the insulation and may be detected by inspection [2]. This edition includes the following significant technical changes with respect to the previous edition:
a) the specific procedures used during factory tests (sampling location, sampling frequency, gas extraction and chromatographic analysis in the laboratory) are described in more detail;
b) information is provided in Annex A concerning the residual gas contents recommended before thermal tests on power transformers, typical gas values observed during the tests and cases where gas formation during the tests was followed by problems in the transformers;
c) typical values observed during chopped lightning-impulse tests on instrument transformers are indicated in Annex B. This consolidated version consists of the second edition (2007) and its amendment 1 (2012). Therefore, no need to order amendment in addition to this publication.

Applies to capacitors according to IEC 60831-1 and gives the requirements for ageing test, self-healing test and destruction test for these capacitors.

IEC 60296:2012 is now available as IEC Standards+ 60296:2012 which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60296:2012 is applicable to specifications and test methods for unused mineral insulating oils. It applies to oil intended for use in transformers, switchgear and similar electrical equipment in which oil is required for insulation and heat transfer. This edition includes the following significant technical changes with respect to the previous edition:
- specifications for corrosive sulphur compounds that can lead to copper sulphide deposition in transformers (in non-passivated and passivated oils);
- definitions of additives in oil; and
- re-insertion of a missing note on oxidation.

IEC 60475:2011 is applicable to the procedure to be used for insulating liquids in delivery containers and in electrical equipment such as power and instrument transformers, reactors, bushings, oil-filled cables, oil-filled tank-type capacitors, switchgear and load tap changers. The main changes with respect to the previous edition are as follows:
- withdrawal of askarels;
- addition of recommendations concerning general health, safety and environmental protection;
- additional details regarding the sampling of oil from electrical equipment, using various types of sampling devices appropriate for the different types of oil tests to be performed in the laboratory.

IEC 60567:2011 deals with the techniques for sampling free gases from gas-collecting relays from power transformers. Three methods of sampling free gases are described. The techniques described take account, on the one hand, of the problems peculiar to analyses associated with acceptance testing in the factory, where gas contents of oil are generally very low and, on the other hand, of the problems imposed by monitoring equipment in the field, where transport of samples may be by un-pressurized air freight and where considerable differences in ambient temperature may exist between the plant and the examining laboratory. Since the publication of the previous edition, CIGRE TF.D1.01.15 has made progress in several areas of dissolved gas analysis (DGA). These advances are included in this fourth edition.

IEC 61099:2010 covers the specification and test methods for unused synthetic organic esters. It applies to synthetic organic esters, delivered to the agreed point and time of delivery intended, for use in transformers, switchgear and similar related equipment in which synthetic organic esters are required as an insulant and for heat transfer. The main changes of this new edition with respect to the previous one relate to the aim of giving a more updated specification of synthetic organic esters when used as insulating liquids.

IEC 60666:2010 provides methods concerning the detection and determination of specified additives in unused and used mineral insulating oils. The detection methods may be applied to assess whether or not a mineral insulating oil contains an additive as specified by the supplier. The determination methods are used for the quantitative determination of additives known to be present or previously detected by the appropriate detection method. The main changes with respect to the previous edition are listed below:
- a change in the title from "Detection and determination of specified anti-oxidant additives in insulating oils";
- new Annexes B and C which provide methods for the determination of two additives different from the anti-oxidants.

IEC 62535:2008 specifies a test method for detection of potentially corrosive sulphur in used and unused mineral insulating oil. Most recent failures due to corrosive sulphur are related to the formation of copper sulphide deposits in and on the surface of winding cellulosic paper. The test method uses a copper conductor, wrapped with one layer of paper, immersed in the oil and heated to evaluate the capability of the oil to yield copper sulphide and transfer it to paper layers. The growth of copper sulphide on bare copper may cause the presence of conductive particulates in the oil, which can act as nuclei for electrical discharge and may lead to a fault. Other test methods exist using a bare copper strip immersed in oil and heated to detect the corrosive behaviour of oil against copper. ASTM D1275 Method B is also used for this test and a modified procedure using low oil volumes is included in Annex A. Tests with and without paper are considered as complementary and may lead to different results.

IEC 61039:2008 establishes the detailed classification of the N family (insulating liquids) that belongs to class L (lubricants, industrial oils and related products) in accordance with ISO 8681 and ISO 6743-99, affecting product categories that include products derived from petroleum processing, synthetic chemical products and synthetic and natural esters. The main change with regard to the previous edition concerns the updating of the classification of insulating liquids, taking into account the largest number possible of substances that have, or may have, possible application in electrical components.

Describes the sampling procedures and methods for the determination of particle concentration and size distribution. Three methods are specified. One uses an automatic particle size analyser, working on the light interruption principle. The other two use an optical microscope, in either the transmitted light or incident light mode, to count particles collected on the surface of a membrane filter. The optical microscope methods are described in ISO 4407. All three methods are applicable to both used and unused insulating liquids. Annex A contains an alternative sampling procedure using a syringe and Annex B reports a reference for the calibration of automatic particle counters. The significant technical changes with respect to the previous edition are as follows: - new calibration procedures for automated laser particle; - three figures contamination code; - new procedure of sample pre-treatment when automated laser counter method are used.

Describes a procedure for determination of the acidity of unused and used electrical mineral insulating oils. The method may be used to indicate relative changes that occur in a mineral insulating oil during use under oxidizing conditions that may or may not be shown by other properties of the resulting mineral oil. The acidity can be used in the quality control of unused mineral oil. As a variety of oxidation products present in used mineral oil contribute to acidity and these products vary widely in their corrosion properties, the test cannot be used to predict corrosiveness of a mineral oil under service conditions.

Describes how the concentrations of dissolved gases or free gases may be interpreted to diagnose the condition of oil-filled electrical equipment in service and suggests future action. Applicable to electrical equipment filled with mineral insulating oil and insulated with cellulosic paper or pressboard-based solid insulation. Information about specific types of equipment such as transformers (power, instrument, industrial, railways, distribution), reactors, bushings, switchgear and oil-filled cables is given only as an indication in the application notes. May be applied only with caution to other liquid-solid insulating systems. In any case, the indications obtained should be viewed only as guidance and any resulting action should be undertaken only with proper engineering judgement.

To develop a rapid oxidation stability test method based on differential scanning calorimetry (DSC) to assess the oxidation stability of mineral insulating oils

Describes a test method for the classification of mineral insulating oils as either paraffinic or naphthenic, by means of low-temperature differential scanning calorimetry (DSC). For the purpose of this technical report, the typical operating temperature range extends from -100 °C to +100 °C. The temperature range can be extended, depending upon the instrumentation used. The method is applicable to mineral insulating oils obtained from petroleum crudes. It may be also applied to mineral oils containing pour point depressants, as these additives do not prevent the formation of paraffin crystals but only the growing of such micro-crystals.

Specifies oil-sampling procedures, analysis requirements and procedures, and recommends sensitivity, repeatability and accuracy criteria for the application of dissolved gas analysis (DGA) to factory testing of new power transformers, reactors and instrument transformers filled with mineral insulating oil when DGA testing has been specified. The most effective and useful application of DGA techniques to factory testing is during the performance of long-term tests, typically temperature-rise (heat run) and overloading tests on power transformers and reactors, also impulse tests on instrument transformers. DGA may also be valuable for over-excitation tests run over an extended period of time. Experience with DGA results, before and after short-time dielectric tests, indicates that DGA is normally less sensitive than electrical and acoustic methods for detecting partial discharges. However, DGA will indicate when these partial discharges become harmful to the insulation and may be detected by inspection [2]. This edition includes the following significant technical changes with respect to the previous edition: a) the specific procedures used during factory tests (sampling location, sampling frequency, gas extraction and chromatographic analysis in the laboratory) are described in more detail; b) information is provided in Annex A concerning the residual gas contents recommended before thermal tests on power transformers, typical gas values observed during the tests and cases where gas formation during the tests was followed by problems in the transformers; c) typical values observed during chopped lightning-impulse tests on instrument transformers are indicated in Annex B.

Gives guidance on the supervision and maintenance of the quality of the insulating oil in electrical equipment. This standard is applicable to mineral insulating oils, originally supplied conforming to IEC 60296, and used in transformers, switchgear and other electrical apparatus where oil sampling is reasonably practicable and where the normal operating conditions specified in the equipment specifications apply. This standard assists the power equipment operator to evaluate the condition of the oil and maintain it in a serviceable condition. It also provides a common basis for the preparation of more specific and complete local codes of practice. This standard includes recommendations on tests and evaluation procedures and outlines methods for reconditioning and reclaiming oil and the decontamination of oil contaminated with PCB. NOTE The condition monitoring of electrical equipment, for example by analysis of dissolved gases, furanic compounds or other means is outside the scope of this standard. The main changes with regard to the previous edition are as follows: This standard has been revised to take into account changes in oil and equipment technology and to have due regard for the best practices currently in use world-wide. 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 affecting safety and environmental aspects. This guidance incorporates changes introduced in associated standards since the publication of the second edition.

Specifies the particular safety requirements, including essential performance, for electrocardiographic (ECG) monitoring equipment. This standard is applicable to equipment used in a hospital environment. If the equipment is used outside the hospital environment, such as in ambulances and air transport, the equipment shall comply with this standard.

Deals with the techniques for sampling free gases from gas-collecting relays and for sampling oil from oil-filled equipment such as power and instrument transformers, reactors, bushings, oil-filled cables and oil-filled tank-type capacitors. Three methods of sampling free gases and three methods of sampling oil are described; the choice between the methods often depends on the apparatus available and on the quantity of oil needed for analysis. Before analysing the gases dissolved in oil, they must first be extracted from the oil. Three basic methods are described, one using extraction by vacuum (Toepler and partial degassing), another by displacement of the dissolved gases by bubbling the carrier gas through the oil sample (stripping), and the last one by partition of gases between the oil sample and a small volume of the carrier gas (head space). The gases are analysed quantitatively after extraction by gas chromatography; a method of analysis is described. Free gases from gas-collecting relays are analysed without preliminary treatment. The preferred method for assuring the performance of the gas extraction and analysis equipment, considered together as a single system, is to degas samples of oil prepared in the laboratory and containing known concentrations of gases ("gas-in-oil standards") and quantitatively analyse the gases extracted. Two methods of preparing gas-in-oil standards are described. For daily calibration checks of the chromatograph, it is convenient to use a standard gas mixture containing a suitable known amount of each of the gas components to be in a similar ratio to the commons ratios of the gases extracted from transformer oils. The techniques described take account, on the one hand, of the problems peculiar to analyses associated with acceptance testing in the factory, where gas contents of oil are generally very low and, on the other hand, of the problems imposed by monitoring equipment in the field, where transport of samples may be by un-pressurized air freight and where considerable differences in ambient temperature may exist between the plant and the examining laboratory. The main changes with respect to the previous edition are listed below. Since the publication of the second edition of this standard, a number of new gas extraction methods have been developed and are commercially available, such as mercury-free versions of the standard Toepler and partial degassing methods, which are referenced to in Annex C of the present edition. The head space method, based on a new concept for the extraction of gases from oil is introduced as a full method in this third edition, and reference is made to a simplified version of it also in Annex C (shake test method). More sensitive chromatographic techniques have also been developed since the last edition, and are presented in this third edition.

This International Standard defines the quality requirements and properties for technical grade sulfur hexafluoride (SF6) for use in electrical equipment. It covers the properties and methods of test applicable to SF6 when this substance is supplied for use in connection with any electrical equipment. This second edition differs widely from the first one. The focus is now on the specification of the gas needed for electrical applications. As a consequence, the term employed to name this gas is "technical grade" in place of "new". Based on experience, the acceptable impurity levels have been increased. However, the gas as defined in this new second edition has the same performance in electrical equipment as the gas previously defined in the first edition. The analytical methods for the SF6 analysis have been removed as it has been found confusing to prescribe methods that can become obsolete very rapidly.

Covers specifications and test methods for unused silicone liquid intended for use in transformers and other electrotechnical equipment. The specified characteristics of silicone transformer liquid Type 1 are described in Table 1. Other specifications will be added when required. NOTE Maintenance of used silicone liquid in electrotechnical equipment is covered in a separate publication IEC 60944. This edition includes the following major technical changes with regard to the first edition: a) the title has been modified; b) the scope has been adapted to meet the changes in the title; c) health, safety and environmental requirements have been revised in order to follow the environmental practice carried out for other insulating liquids. Isopropyl alcohol now replaces chlorinated dissolvents for cleaning test equipment; d) Clause 8 replaces Section 2 of the first edition. In line with other TC10 documents, ISO 2592 is now the only method specified for measuring fire point and IEC 60814 for water content. Breakdown voltage measurement has now been transferred to IEC 60156; e) Table 1 replaces Sheet 1 of the first edition. Two technical changes have been made: - the minimum fire point is increased from 330 °C to 340 °C (in conformity with ASTM D4652) and recognizes also that the test values registered for production are even higher. - neutralization values have been reduced from 0,02 to 0,01 mg KOH/g, in line with production test data. f) Annex A has been deleted.

Concerns the re-use of sulfur hexafluoride (SF6) after removal from electrical equipment (for maintenance, or at the end of life). This standard recommends procedures for reclaiming used SF6 and for restoring its quality to an acceptable level, which would allow the filling of new or existing electrical equipment. This standard provides guidance to operational and maintenance personnel for the testing and safe handling of used SF6 . The main changes with respect to the previous edition are listed below:
- updating of standard as it relates to environmental issues, storage and analytical methods;
- addition of specification for the re-use of gas;
- inclusion of a regeneration process for sulfur hexafluoride taken from electrical equipment.

Describes methods for the determination of the dielectric dissipation factor, relative permittivity and d.c. resistivity of any insulating liquid material at the test temperature. The methods are primarily intended for making reference tests on unused liquids. They can also be applied to liquids in service in transformers, cables and other electrical apparatus. However the method is applicable to a single phase liquid only. When it is desired to make routine determinations, simplified procedures, as described in Annex C, may be adopted. With insulating liquids other than hydrocarbons, alternative cleaning procedures may be required. The main changes from the previous edition deal with the preferred measurement method.

Contains specific requirements for the construction and testing of electrical apparatus with the type of protection flameproof enclosure "d", intended for use in explosive gas atmospheres. The contents of the corrigendum of February 2007 have been included in this copy.

Covers specifications and test methods for unused mineral insulating oils. It applies to oil delivered to the agreed point and time of delivery, intended for use in transformers, switchgear and similar electrical equipment in which oil is required as an insulant and for heat transfer. These oils are obtained by distillation and refining of crude petroleum. Oils with and without additives are both within the scope of this standard. This standard is applicable only to unused mineral insulating oils. Reclaimed oils are beyond the scope of this standard. This standard does not apply to mineral oils used as impregnants in cables or capacitors. NOTE Mineral insulating oils complying with the requirements of this standard, of the same class and containing no additives (see 3.4), are considered to be compatible with one another and can be mixed in any proportion. This does not apply to oils containing additives. Where the user wishes to mix such oils, a check is recommended to be made to ensure that the mixture meets the requirements of this standard. Main changes with regard to previous edition include: the three classes of previous edition have been replaced by only two: transformer oil and low temperature switchgear oil, but a new concept, the lowest cold start energizing temperature, has been included; new properties have been added (i.e. charging tendency); values for properties have been revised.

Describes the procedure for the determination of the acidity of unused and used electrical mineral insulating oils. The method may be used to indicate relative changes that occur in a mineral insulating oil during use under oxidizing conditions regardless of the colour or other properties of the resulting mineral oil. The acidity can be used in the quality control of unused mineral oil. As a variety of oxidation products present in used mineral oil contribute to acidity and these products vary widely in their corrosion properties, the test cannot be used to predict corrosiveness of a mineral oil under service conditions. The acidity results obtained by this test method may or may not be numerically the same as those obtained by colorimetric methods, but they are generally of the same magnitude.