Electrical insulation systems (EIS) - Thermal evaluation of combined liquid and solid components - Part 1: General requirements

IEC/TS 62332-1:2011(E) is applicable to EIS containing solid and liquid components where the thermal stress is the dominant ageing factor, without restriction to voltage class. This part specifies a dual-temperature test procedure for the thermal evaluation and qualification of electrical insulation systems (EIS). The following significant technical changes with respect to the previous edition have been made - Modifications have been made based on an extensive test series conducted using this methodology given in the first edition. This included updating expected times and tempertatures to use in order to obtain useful results, as well as making the range of equipment covered broader. The method can now cover electrotechnical devices using different sealing systems, as well as devices using enamel covered wires.

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Publication Date
13-Mar-2011
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IEC/TS 62332-1
Edition 2.0 2011-03
TECHNICAL
SPECIFICATION
Electrical insulation systems (EIS) – Thermal evaluation of combined liquid and
solid components –
Part 1: General requirements
IEC/TS 62332-1:2011(E)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC/TS 62332-1
Edition 2.0 2011-03
TECHNICAL
SPECIFICATION
Electrical insulation systems (EIS) – Thermal evaluation of combined liquid and
solid components –
Part 1: General requirements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
ICS 29.080.30 ISBN 978-2-88912-404-6
® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – TS 62332-1  IEC:2011(E)
CONTENTS

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

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

1 Scope ............................................................................................................................... 7

2 Normative references ....................................................................................................... 7

3 Terms and definitions ....................................................................................................... 8

4 Thermal ageing test apparatus ....................................................................................... 10

4.1 General description ............................................................................................... 10

4.2 Construction of the test apparatus ......................................................................... 10

4.2.1 Ageing cells ............................................................................................... 10

4.2.2 Immersion heaters ..................................................................................... 11

4.2.3 Power supply ............................................................................................. 11

4.2.4 Control circuit system ................................................................................ 11

4.2.5 Gas blanketing system .............................................................................. 11

4.2.6 Safety system ............................................................................................ 12

4.3 Monitoring and data collection ............................................................................... 12

5 Construction of the test object ........................................................................................ 12

5.1 General ................................................................................................................. 12

5.2 Determination of component volumes .................................................................... 12

5.3 Test object ............................................................................................................ 12

5.3.1 General ..................................................................................................... 12

5.3.2 Conductor assembly .................................................................................. 13

5.3.3 Liquid component ...................................................................................... 13

5.3.4 Other components ..................................................................................... 14

6 Test procedures ............................................................................................................. 14

6.1 General ................................................................................................................. 14

6.2 Preparation of the test objects ............................................................................... 14

6.2.1 General ..................................................................................................... 14

6.2.2 Reference test object................................................................................. 14

6.2.3 Candidate test object ................................................................................. 15

6.3 Diagnostic tests ..................................................................................................... 15

6.3.1 General ..................................................................................................... 15

6.3.2 Solid insulation .......................................................................................... 15

6.3.3 Liquid insulation ........................................................................................ 16

6.4 Thermal ageing ..................................................................................................... 16

6.4.1 Recommended solid-component ageing temperatures ............................... 16

6.4.2 Recommended liquid ageing temperatures ................................................ 16

6.4.3 Reference EIS ageing temperatures .......................................................... 16

6.4.4 Ageing procedures of the candidate EIS .................................................... 17

6.5 End-point testing ................................................................................................... 17

7 Analysis of data .............................................................................................................. 17

7.1 End-point criteria ................................................................................................... 17

7.1.1 General ..................................................................................................... 17

7.1.2 End-of-life of the liquid component ............................................................ 17

7.1.3 End-of-life of the solid component ............................................................. 18

7.1.4 Extrapolation of data ................................................................................. 18

7.2 Report ................................................................................................................... 18

---------------------- Page: 4 ----------------------
TS 62332-1  IEC:2011(E) – 3 –

Annex A (informative) Component volume ratio spreadsheet example ................................. 19

Bibliography .......................................................................................................................... 20

Figure 1 – Ageing cell cross-section ..................................................................................... 11

Figure 2 – Example of an insulation package for a transformer winding ................................ 13

Table 1 – Recommended ageing temperatures and periods for expected thermal class ........ 16

Table A.1 – Examples of component volume ratio calculations .............................................. 19

---------------------- Page: 5 ----------------------
– 4 – TS 62332-1  IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ELECTRICAL INSULATION SYSTEMS (EIS) –
THERMAL EVALUATION OF COMBINED LIQUID
AND SOLID COMPONENTS –
Part 1: General requirements
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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indispensable for the correct application of this publication.

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical

specification when

• the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts, or

• the subject is still under technical development or where, for any other reason, there is the

future but no immediate possibility of an agreement on an International Standard.

Technical specifications are subject to review within three years of publication to decide

whether they can be transformed into International Standards.

IEC/TS 62332-1, which is a technical specification, has been prepared by IEC technical

committee 112: Evaluation and qualification of electrical insulating materials and systems.

---------------------- Page: 6 ----------------------
TS 62332-1  IEC:2011(E) – 5 –

This second edition cancels and replaces the first edition, published in 2005, and constitutes

editorial and technical revisions.

The following significant technical changes with respect to the previous edition have been

made:

Modifications have been made to the technical specification based on an extensive test series

conducted using this methodology based on the first edition. This included updating expected

times and temperatures to use in order to get useful results, as well as making the range of

equipment covered more broad. The method can now cover electrotechnical devices using

different sealing systems, as well as devices using enamel covered wires
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
112/160/DTS 112/168/RVC

Full information on the voting for the approval of this technical specification can be found in

the report on voting indicated in the above table.

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

related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
---------------------- Page: 7 ----------------------
– 6 – TS 62332-1  IEC:2011(E)
INTRODUCTION

This technical specification describes a method for the thermal evaluation of electrical

insulation systems (EIS) for electrotechnical products with combined liquid and solid

components. Part 1 covers general test requirements. Subsequent parts should cover specific

product test requirements.

Prior to this technical specification, the procedure for determining the thermal endurance of

insulation systems for liquid-immersed products involved one of two processes: firstly, sealed-

tube ageing and, secondly, ageing of full-scale models.

The ageing of full-scale models is impractical, especially for larger products, such as power

transformers. Similarly, the use of sealed-tube ageing is not practical when testing

components having drastically different thermal capabilities. For example, testing of a system

with a solid material with an RTI of 200 °C with a liquid having a 130 °C thermal capability

cannot be performed efficiently. Accelerated ageing temperatures, which fairly age the liquid,

will result in extremely long ageing times for the solid. Accelerated ageing temperatures,

which fairly age the solid, will result in extreme, or even hazardous, ageing of the liquid.

This technical specification describes an accelerated thermal ageing procedure and model

that allows for the solid materials to be aged at temperatures separate from the liquid ageing

temperatures, all in the same apparatus. The model acts more in the true-life ageing mode of

insulation systems, where solid insulation near the active parts is exposed to much higher

temperatures than the major volume of liquid in the equipment. The model contains all the

primary EIS elements, and in relative component ratios which compare with actual
electrotechnical products.

The model has a dual temperature capability that allows independent control of the

temperatures of the solid and liquid components by the use of separate circuits. A detailed

bibliography is provided.

This technical specification has been prepared in conjunction with TC 14, Power transformers.

Any comments or suggestions from other technical committees to make this technical

specification more general are welcome.
---------------------- Page: 8 ----------------------
TS 62332-1  IEC:2011(E) – 7 –
ELECTRICAL INSULATION SYSTEMS (EIS) –
THERMAL EVALUATION OF COMBINED LIQUID
AND SOLID COMPONENTS –
Part 1: General requirements
1 Scope

This part of IEC/TS 62332 is applicable to EIS containing solid and liquid components where

the thermal stress is the dominant ageing factor, without restriction to voltage class.

This part specifies a dual-temperature test procedure for the thermal evaluation and

qualification of electrical insulation systems (EIS).
2 Normative references

The following referenced documents are indispensable for the application of this document.

For dated references, only the edition cited applies. For undated references, the latest edition

of the referenced document (including any amendments) applies.
IEC 60085:2007, Electrical insulation – Thermal evaluation and designation

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

Test method

IEC 60216-2:2005, Electrical insulating materials – Thermal endurance properties – Part 2:

Determination of thermal endurance properties of electrical insulating materials – Choice of

test criteria IEC 60216-3, Electrical insulating materials – Thermal endurance properties –

Part 3: Instructions for calculating thermal endurance characteristics

IEC 60216-5, Electrical insulating materials – Thermal endurance properties – Part 5:

Determination of relative thermal endurance index (RTE) of an insulating material

IEC 60243-1, Electrical strength of insulating materials – Test methods – Part 1: Tests at

power frequencies

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

factor (tan δ) and d.c. resistivity

IEC 60250, Recommended methods for the determination of the permittivity and dielectric

dissipation factor of electrical insulating materials at power, audio and radio frequencies

including metre wavelengths

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

transformers and switchgear

IEC 60422, Mineral insulating oils in electrical equipment – Supervision and maintenance

guidance

IEC 60450, Measurement of the average viscometric degree of polymerization of new and

aged cellulosic electrically insulating materials
---------------------- Page: 9 ----------------------
– 8 – TS 62332-1  IEC:2011(E)
IEC 60505:2004, Evaluation and qualification of electrical insulation systems
IEC 60554-2, Cellulosic papers for electrical purposes – Part 2: Methods of test

IEC 60567, Oil-filled electrical equipment – Sampling of gases and of oil for analysis of free

and dissolved gases – Guidance

IEC 60599, Mineral oil-impregnated electrical equipment in service – Guide to the

interpretation of dissolved and free gases analysis
IEC 60763-2, Specification for laminated pressboard – Part 2: Methods of test

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

water by automatic coulometric Karl Fischer titration

IEC 61198, Mineral insulating oils– Methods for the determination of 2-furfural and related

compounds

IEC 61620, Insulating liquids – Determination of dielectric dissipation factor by measurement

of the conductance and capacitance – Test method

IEC 61857-1:2008, Electrical insulation systems– Procedures for thermal evaluation – Part 1:

General requirements – Low voltage

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

titration

ISO 287, Paper and board – Determination of moisture content of a lot – Oven-drying method

ISO 1924 (all parts), Paper and board – Determination of tensile properties
ISO 2049, Petroleum products – Determination of colour (ASTM scale)

ASTM D971-99a, Standard test method for interfacial tension of oil against water by the ring

method
3 Terms and definitions

For the purposes of this document, the following terms and definitions apply, some of which

are taken from IEC 60505.
3.1
electrical insulation system
EIS

insulating structure containing one or more electrical insulating materials (EIM) together with

associated conducting parts employed in an electrotechnical device
[IEC 60505:2004, definition 3.1.1]

NOTE EIMs with different temperature indices (ATE RTE according to IEC 60216-5) may be combined to form an

EIS, which has a thermal class that may be higher or lower than that of any of the individual components according

to IEC 60505.
—————————
A fourth edition of IEC 60505 is currently in preparation.
---------------------- Page: 10 ----------------------
TS 62332-1  IEC:2011(E) – 9 –
3.2
candidate EIS
EIS under evaluation to determine its service capability (thermal)
3.3
reference EIS

evaluated and established EIS with either a known service experience record or a known

comparative functional evaluation as a basis
3.4
thermal class

designation of an EIS that is equal to the numerical value of the maximum temperature in

degrees Celsius for which the EIS is appropriate according to Table 1 of IEC 60085:2007

NOTE An EIS may be subjected to operating temperatures exceeding its thermal class, which can result in

shorter expected life.
3.5
EIS assessed thermal endurance index
EIS ATE

numerical value of the temperature in degrees Celsius for the reference EIS as derived from

known service experience or a known comparative functional evaluation
3.6
EIS relative thermal endurance index
EIS RTE

numerical value of the temperature in degrees Celsius for the candidate EIS which is relative

to the known EIS ATE of a reference EIS, when both EIS are subjected to the same ageing

and diagnostic procedures in a comparative test
3.7
test object

piece of original equipment, a representation (model) of equipment, a component of or part of

equipment, including the EIS, intended for use in a functional test
3.8
thermal ageing factor
thermal stress that causes irreversible changes in the EIS
3.9
diagnostic test

periodic application of a specified level of a diagnostic factor to a test object to determine

whether the end-point criterion has been reached
3.10
end-point criterion

selected value of either a property or a change of property that defines the end of a

component’s life
[IEC 61857-1:2008, definition 3.11, modified]
3.11
end-of-life

end of a test object’s life, as determined by any selected component meeting its end-point

criterion
---------------------- Page: 11 ----------------------
– 10 – TS 62332-1  IEC:2011(E)
3.12
ageing cell

sealed container partially filled with the liquid EIM and in which are mounted the test object,

liquid immersion heaters and thermocouples for control and monitoring
4 Thermal ageing test apparatus
4.1 General description

The thermal ageing test apparatus shall be designed to allow the separate ageing of solid and

liquid components. The reference and candidate EIS shall be exposed to test periods at

selected elevated temperatures. These test periods consist of a specific time exposure at the

selected temperature followed by diagnostic tests.
The test system consists of the following elements:
• ageing cells;
• power supply;
• control system;
• safety system;
• sampling system;
• monitoring/data collection system.
4.2 Construction of the test apparatus
4.2.1 Ageing cells

Each ageing cell is a container constructed of stainless steel, the size to be determined by the

size of the test object. The cell volume shall consider the space required for thermal

expansion of the liquid at ageing temperatures. The two ends of the cell shall be fitted with

removable, sealable bolt-on covers. The test object is mounted within the ageing cell.

Ports shall be provided for
• sampling of the liquid,
• pass-through of electrical circuits for heating of the active parts,
• monitoring and control elements,
• immersion heaters,
• gas blanketing and associated pressure relief system.

The design of the ageing cell shall be configured to maintain the thermocouples controlling

the liquid and the solid component of the test objects immersed in the liquid under all ageing

temperatures. See also 5.3.3.
For specific details, see Figure 1.
---------------------- Page: 12 ----------------------
TS 62332-1  IEC:2011(E) – 11 –
Oil Flow
Bulk press
board
Level at Test Temperature
Wood strips
20 °C – Fill
Hot press
board
Oil flow
Test Piece
Assembly
Conductor
assembly
Conductor loop
Core steel
IEC 1523/05
Figure 1 – Ageing cell cross-section
4.2.2 Immersion heaters

Immersion heaters shall have thermal capability to maintain the temperature of the test liquid

within the temperature range defined by the test procedure.
4.2.3 Power supply
Separate power supplies shall be provided to independently establish the defined
temperatures in the liquid and the test object:

• current through the test object shall establish the required temperature defined by the test

procedure;
• the power capacity shall comply with 4.2.2.
For safety reasons, ageing cells shall be connected to earth.
4.2.4 Control circuit system

Automatic monitoring with thermal sensors controls the temperatures of the test object and

liquid. A control feedback circuit shall be used to maintain each temperature within ± 2 K.

4.2.5 Gas blanketing system

A gas blanketing system shall be provided which simulates the insulation system used in the

electrotechnical product being evaluated. This can be a sealed nitrogen system, which

maintains a gas blanket over the liquid in the cell for the purpose of eliminating the possibility

of oxidation of the liquid, or it could be a system simulating a desiccated air system. In each

case, the gas blanket in each cell shall be regulated to maintain a positive pressure.

---------------------- Page: 13 ----------------------
– 12 – TS 62332-1  IEC:2011(E)
4.2.6 Safety system

A pressure relief valve shall be installed on each cell to prevent the internal cell pressure to

raise above equipment capability.

NOTE For low thickness walls (e.g.1,2 mm), valves controlling a pressure of 35 kPa would be sufficient and for

higher wall thicknesses (e.g. 8 mm) valves controlling a pressure of 85 kPa could be suitable. In any case the

pressure should be calculated.

An over-temperature protection device shall be provided, responding to the temperature

sensors in both the liquid and the test object in each cell. The sensors for the over-

temperature protection shall be independent of the sensors for temperature control.

4.3 Monitoring and data collection

The output of all temperature sensing devices shall be monitored. Any deviations from the

set-point range for more than 1 h shall be recorded hourly until corrected.
5 Construction of the test object
5.1 General

The test object is designed to model the EIS portion of the electrotechnical products under

evaluation and usually consists of
• a current-carrying conductor,
• a conductor insulation,
• insulation spacers/barriers,
• a liquid.
Other components may be used as appropriate.
5.2 Determination of component volumes

It is important that the ratios of volumes of components used to construct the test object shall

be representative of the electrotechnical product being modelled. Therefore the total volume

of the individual components in the products shall be evaluated. Determine the percentage of

each individual component as a part of the total volume. The percentages shall be used to

determine the volume of those individual components to be used in the construction of the

test object. In a family of products with the same specific EIS, the ratio of volume of the

individual components to the total volume should be similar.
NOTE 1 The liquid volume is determined at 20 °C.

An example is included in Annex A for calculating the volumes and dimensions of the

components.
NOTE 2 Additional components may be inserted into the ageing ce
...

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