Dielectric and resistive properties of solid insulating materials - Part 3-1: Determination of resistive properties (DC methods) - Volume resistance and volume resistivity - General method

IEC 62631-3-1:2016 covers a method of test for the determination of volume resistance and volume resistivity of electrical insulation materials by applying a DC voltage. This edition includes the following significant technical changes with respect to the second edition of IEC 60093:
a) IEC 60093 has been completely revised, both editorially and technically, and incorporated into the new IEC 62631 series;
b) test methods have been updated to current day state of the art;
c) volume and surface resistance and resistivity are now separated to appear in this part of IEC 62631 and in IEC 62631-3-2, respectively.

Propriétés diélectriques et résistives des matériaux isolants solides - Partie 3-1: Détermination des propriétés résistives (méthodes en courant continu) - Résistance transversale et résistivité transversale - Méthode générale

L'IEC 62631-3-1:2016 couvre une méthode d'essai pour déterminer la résistance transversale et la résistivité transversale de matériaux isolants électriques en appliquant une tension continue. Cette édition inclut les modifications techniques majeures suivantes par rapport à a deuxième édition de l'IEC 60093:
a) l'IEC 60093 a été entièrement révisée, au niveau éditorial et technique, et insérée dans la nouvelle série IEC 62631;
b) les méthodes d'essai ont été mises à jour à l'état actuel de la technique;
c) les résistances et les résistivités transversales et superficielles sont maintenant séparées pour figurer dans la présente partie de l'IEC 62631 et dans l'IEC 62631-3-2, respectivement.

General Information

Status
Published
Publication Date
22-Mar-2016
Current Stage
PPUB - Publication issued
Start Date
23-Mar-2016
Completion Date
23-Mar-2016
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IEC 62631-3-1
Edition 1.0 2016-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Dielectric and resistive properties of solid insulating materials –
Part 3-1: Determination of resistive properties (DC methods) – Volume
resistance and volume resistivity – General method
Propriétés diélectriques et résistives des matériaux isolants solides –
Partie 3-1: Détermination des propriétés résistives (méthodes en courant

continu) – Résistance transversale et résistivité transversale – Méthode générale

IEC 62631-3-1:2016-03(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 62631-3-1
Edition 1.0 2016-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Dielectric and resistive properties of solid insulating materials –
Part 3-1: Determination of resistive properties (DC methods) – Volume
resistance and volume resistivity – General method
Propriétés diélectriques et résistives des matériaux isolants solides –
Partie 3-1: Détermination des propriétés résistives (méthodes en courant

continu) – Résistance transversale et résistivité transversale – Méthode générale

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.99; 29.035.01 ISBN 978-2-8322-3254-5

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 62631-3-1:2016  IEC 2016
CONTENTS

FOREWORD ......................................................................................................................... 3

1 Scope ............................................................................................................................ 5

2 Normative references..................................................................................................... 5

3 Terms and definitions .................................................................................................... 5

4 Significance ................................................................................................................... 6

5 Method of test ............................................................................................................... 6

5.1 General ................................................................................................................. 6

5.2 Power supply, voltage ........................................................................................... 6

5.3 Equipment ............................................................................................................ 7

5.3.1 Accuracy ........................................................................................................ 7

5.3.2 Guarding ........................................................................................................ 7

5.3.3 Electrodes ..................................................................................................... 8

5.4 Calibration .......................................................................................................... 10

5.5 Test specimen ..................................................................................................... 10

5.5.1 General ....................................................................................................... 10

5.5.2 Recommended dimensions of test specimens and electrode

arrangements ............................................................................................... 10

5.5.3 Manufacturing of test specimens .................................................................. 11

5.5.4 Number of test specimen .............................................................................. 11

5.5.5 Conditioning and pre-treatment of test specimen .......................................... 11

5.6 Procedures for specific materials ......................................................................... 11

6 Test procedure ............................................................................................................ 11

6.1 General ............................................................................................................... 11

6.2 Measurement of volume resistance ...................................................................... 11

6.3 Calculation of volume resistivity ........................................................................... 12

7 Test report................................................................................................................... 12

8 Repeatability and reproducibility .................................................................................. 12

Bibliography ....................................................................................................................... 13

Figure 1 – Basic connection for guarded electrodes ............................................................... 8

Figure 2 – Specimen with liquid electrodes ............................................................................ 9

Table 1 – Test specimen ..................................................................................................... 10

---------------------- Page: 4 ----------------------
IEC 62631-3-1:2016  IEC 2016 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –
Part 3-1: Determination of resistive properties (DC methods) –
Volume resistance and volume resistivity – General method
FOREWORD

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

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

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with the International Organization for Standardization (ISO) in accordance with conditions determined by

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

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

International Standard IEC 62631-3-1 has been prepared by IEC technical committee TC 112:

Evaluation and qualification of electrical insulating materials and systems.

This first edition of IEC 62631-3-1 cancels and replaces the second edition of IEC 60093,

published in 1980. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the second

edition of IEC 60093:

a) IEC 60093 has been completely revised, both editorially and technically, and incorporated

into the new IEC 62631 series;
b) test methods have been updated to current day state of the art;

c) volume and surface resistance and resistivity are now separated to appear in this part of

IEC 62631 and in IEC 62631-3-2, respectively.
---------------------- Page: 5 ----------------------
– 4 – IEC 62631-3-1:2016  IEC 2016
The text of this standard is based on the following documents:
FDIS Report on voting
112/339/FDIS 112/350/RVD

Full information on the voting for the approval of this standard 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.

A list of all parts in the IEC 62631 series, published under the general title Dielectric and

resistive properties of solid insulating materials, can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 62631-3-1:2016  IEC 2016 – 5 –
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –
Part 3-1: Determination of resistive properties (DC methods) –
Volume resistance and volume resistivity – General method
1 Scope

This part of IEC 62631 covers a method of test for the determination of volume resistance and

volume resistivity of electrical insulation materials by applying a DC voltage.
2 Normative references

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

undated references, the latest edition of the referenced document (including any
amendments) applies.

IEC 60212, Standard conditions for use prior to and during the testing of solid electrical

insulating materials

IEC 60455 (all parts), Resin based reactive compounds used for electrical insulation

IEC 60464 (all parts), Varnishes used for electrical insulation

IEC 61212 (all parts), Industrial materials – Industrial rigid round laminated tubes and rods

based on thermosetting resins for electrical purposes

ISO 868, Plastics and ebonite – Determination of indentation hardness by means of a

durometer (Shore hardness)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
volume resistance
part of the insulation resistance which is due to conduction through the volume
Note 1 to entry: Volume resistance is expressed in the unit of Ω.
3.2
volume resistivity
volume resistance of a material related to its volume
Note 1 to entry: Volume resistivity is expressed in the unit of Ωm.

Note 2 to entry: For insulating materials, the volume resistivity is usually determined by means of measuring

electrodes arranged on a sheet of the material.

Note 3 to entry: According to IEC 60050-121: Electromagnetism, “conductivity” is defined as “scalar or tensor

quantity, the product of which by the electric field strength in a medium is equal to the electric current density” and

“resistivity” as “the inverse of the conductivity when this inverse exists”. Measured in this way, the volume

---------------------- Page: 7 ----------------------
– 6 – IEC 62631-3-1:2016  IEC 2016

resistivity is an average of the resistivity over possible heterogeneities in the volume incorporated in the

measurement; it includes the effect of possible polarization phenomena at the electrodes.

3.3
stray current

leakage current in the earth or in metallic structures buried in the ground and resulting from

their intended or unintended earthing
4 Significance

Insulating materials are used in general to electrically isolate components of an electrical

system from each other and from earth. Solid insulating material may also provide mechanical

support. For these purposes it is generally desirable to have the insulation resistance as high

as possible, consistent with acceptable mechanical, chemical and heat resistance properties.

Volume resistance is a part of the insulating resistance.

Volume resistivity can be used as an aid in the choice of an insulating material for a specific

application. The change in resistivity with temperature and humidity may be great and has to

be known when designing for operation conditions.

When a direct voltage is applied between electrodes in contact with a specimen, the current

through it decreases asymptotically towards a steady-state value. The decrease of current

with time may be due to dielectric polarization and the sweep of mobile ions to the electrodes.

For materials having volume resistivity less than about 10 Ωm the steady state is generally

reached within 1 min and the resistance is determined after this time of electrification. For

materials with higher volume resistivity the current may continue decreasing for several

minutes, hours, days or even weeks. For such materials, therefore, longer electrification times

may be necessary.
NOTE For very high electric field strengths different behaviour can occur.
5 Method of test
5.1 General

This general method describes common values for general measurements. If a method for a

specific type of material is described in this standard, the specific method shall be used.

The measurement of volume resistance (and volume resistivity respectively) shall be carried

out carefully and taking into account the electric properties of the measuring circuit as well as

the specific electric properties of the material.

To carry out the test, in most cases the use of high voltages is necessary. Care shall be taken

to prevent electric shock.

Polarization effects can influence the measurement. Therefore it is not acceptable to achieve

the measured resistance twice in two consecutive experiments without a sufficient space of

time in-between.

NOTE For materials with volume resistance of not more than 10 Ω a period of 1 h after voltage application might

be sufficient.
5.2 Power supply, voltage

A source of very steady direct voltage is required. This may be provided either by batteries or

by rectified and stabilized power supply. The degree of stability required is such that the

change in current due to any change in voltage is negligible compared with the current to be

measured.
---------------------- Page: 8 ----------------------
IEC 62631-3-1:2016  IEC 2016 – 7 –

NOTE 1 The ripple of the voltage source is important. A typical value for 100 V is <5 × 10 peak to peak.

Commonly specified test voltages to be applied to the complete specimen are 10 V, 100 V,

500 V, 1 000 V, and 10 000 V.
If not otherwise stipulated, a voltage of 100 V is to be used.

NOTE 2 In air, below 340 V no partial discharges will occur. Partial discharge can lead to erroneous

measurements of the resistance when a specific inception voltage is exceeded.
5.3 Equipment
5.3.1 Accuracy
Any suitable equipment may be used. The measuring device should be capable of
determining the unknown resistance with an overall accuracy of at least
• ±10 % for resistances below 10 Ω,
10 14
• ±20 % for resistances between 10 Ω and 10 Ω,
• ±50 % for values higher than 10 Ω.
5.3.2 Guarding

The insulation of the measuring circuit is composed of materials which, at best, have

properties comparable with those of the material under test. Errors in the measurement of the

specimen may arise from:

• stray current from spurious external voltages which are usually unknown in magnitude and

often sporadic in character;

• inadequate shunting of the specimen resistance, reference resistors or the current

measuring device by insulation, having resistance of unknown, and possibly variable

magnitude;
• the surface resistance may be lower than the volume resistance by one order of
magnitude.

An approximate correction of these difficulties may be obtained by making the insulation

resistance of all parts of the circuit as high as possible under the conditions of use. This may

lead to unwieldy apparatus which is still inadequate for measurement of insulation resistances

higher than the magnitude of some hundred MΩ. A more satisfactory correction is obtained by

using the technique of guarding.

Guarding depends on interposing, in all critical insulated parts, guard conductors which

intercept all stray currents that might otherwise cause errors. The guard conductors are

connected together, constituting the guard system and forming with the measuring terminals a

three terminal network. When suitable connections are made, stray currents from spurious

external voltages are shunted away from the measuring circuit by the guard system, the

insulation resistance from either measuring terminal to the guard system shunts a circuit

element which should be of very much lower resistance, and the specimen resistance

constitutes the only direct path between the measuring terminals. By this technique the

probability of error is considerably reduced. The basic connections for guarded electrodes

used for volume resistance is shown in Figure 1.
---------------------- Page: 9 ----------------------
– 8 – IEC 62631-3-1:2016  IEC 2016
IEC
Figure 1 – Basic connection for guarded electrodes
NOTE Dimensions of specimen are given in 5.5

Voltages (e.g. electrochemically or thermally induced) between guard and guarded terminals

can be compensated if they are small. Care shall be taken so that such voltages do not

introduce significant errors in the measurements.

Errors in the measurement of current may result from the fact that the current-measuring

device is shunted by the resistance between the guarded terminal and the guard system. To

ensure satisfactory operation of the equipment, a measurement should be made with the lead

from the voltage source to the specimen disconnected. Under this condition, the equipment

should indicate infinite resistance within its sensitivity. If suitable standards of known values

are available, they may be used to test the operation of the equipment.
5.3.3 Electrodes
5.3.3.1 General

The electrodes for insulating materials should be of a material that is readily applied, allows

intimate contact with the specimen surface and introduces no appreciable error because of

electrode resistance or contamination of the specimen. The electrode material should be

corrosion resistant under the conditions of the test. The electrodes shall be used with suitable

backing plates of the given form and dimensions. It may be advantageous to use two different

electrode materials or two methods of application to see if any significant error is introduced.

The following are typical electrode materials that may be used.
5.3.3.2 Conductive silver paint

Certain types of commercially available, high-conductivity silver paints, either air-drying or

low-temperature-baking varieties are sufficiently porous to permit diffusion of moisture

through them and thereby allow the test specimens to be conditioned after application of the

electrodes. This is a particularly useful feature in studying resistance-humidity effects as well

as changes with temperature. However, before conductive paint is used as an electrode

material, it should be established that the solvent in the paint does not affect the electrical

properties of the specimen. Reasonably smooth edges of guard electrodes may be obtained

with a fine-bristle brush. However, for circular electrodes, sharper edges may be obtained by

the use of a compass for drawing the outline circles of the electrodes and filling in the

enclosed areas by brush. Clamp-on masks may be used if the electrode paint is sprayed on.

5.3.3.3 Evaporated or sputtered metal

Evaporated or sputtered metal can be used where it can be shown that the material is not

affected by ion bombardment, temperature stress or vacuum treatment.
---------------------- Page: 10 ----------------------
IEC 62631-3-1:2016  IEC 2016 – 9 –
5.3.3.4 Liquid electrodes

Liquid electrodes can be used and give satisfactory results. The liquid forming the upper

electrode should be confined, for example, by stainless steel rings, each of which should have

its lower rim reduced to a sharp edge by bevelling on the side away from the liquid. Figure 2,

shows the electrode arrangement. Alloys e.g. containing gallium, indium and tin which are

liquid at room temperature had been proved as suitable. Mercury is not recommended.

IEC
Key
1 Measurement electrode
2 Specimen
3 Guard electrode
4 Liquid metal electrode
Figure 2 – Specimen with liquid electrodes
5.3.3.5 Colloidal graphite

Colloidal graphite dispersed in water or other suitable medium, may be used under the same

conditions as given for conductive silver paint.
5.3.3.6 Conducting rubber

Conducting rubber may be used as an electrode material. It has the advantage that it can be

applied and removed from the specimen quickly and easily. As the electrodes are applied only

during the time of measurement they do not interfere with the conditioning of the specimen.

The resistance of the rubber electrode shall be less than 1 000 Ω.

The conducting rubber material shall be soft enough to ensure that effective contact to the

specimen is obtained when a reasonable pressure, for example 2 kPa (0,2 N/cm ), is applied.

Shore A hardness according to ISO 868 in the range of 65 to 85 has been found suitable.

NOTE Results of resistivity measurements obtained with the application of electrodes made of conducting rubber

are always higher (few tens to few hundreds %) in comparison to that obtained for metallic electrodes.

5.3.3.7 Metal foil

Metal foil can be applied to specimen surfaces as electrodes for volume resistance

measurement, but it is not suitable for surface resistance measurement. Aluminum and tin foil

are in common use. They are usually attached to the specimen by a minimum quantity of

petrolatum, silicone grease, oil or other suitable material, as an adhesive.
---------------------- Page: 11 ----------------------
– 10 – IEC 62631-3-1:2016  IEC 2016

All adhesive materials may be of influence to the measurement results and should be

minimized.

NOTE A pharmaceutically obtainable jelly of the following composition is suitable as a conductive adhesive:

– anhydrous polyethylene glycol of molecular mass 600 to 800 parts by mass;
– water: 200 parts by mass;
– soft soap (pharmaceutical quality): 1 part by mass;
– potassium chloride: 10 parts by mass;
Soft soap is a non-corrosive, neutral so
...

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