IEC 62631-2-1:2018

IEC 62631-2-1 ®
Edition 1.0 2018-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Dielectric and resistive properties of solid insulating materials –
Part 2-1: Relative permittivity and dissipation factor – Technical frequencies
(0,1 Hz to 10 MHz) – AC methods

Propriétés diélectriques et résistives des matériaux isolants solides –
Partie 2-1: Permittivité relative et facteur de dissipation – Fréquences techniques
(0,1 Hz à 10 MHz) – Méthodes en courant alternatif

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IEC 62631-2-1 ®
Edition 1.0 2018-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Dielectric and resistive properties of solid insulating materials –

Part 2-1: Relative permittivity and dissipation factor – Technical frequencies

(0,1 Hz to 10 MHz) – AC methods

Propriétés diélectriques et résistives des matériaux isolants solides –

Partie 2-1: Permittivité relative et facteur de dissipation – Fréquences techniques

(0,1 Hz à 10 MHz) – Méthodes en courant alternatif

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.99; 29.035.01 ISBN 978-2-8322-5414-1

– 2 – IEC 62631-2-1:2018 © IEC 2018
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Method of test . 7
4.1 General theory . 7
4.2 Power supply (voltage) . 10
4.3 Equipment . 10
4.3.1 Accuracy . 10
4.3.2 Choice of measuring methods . 10
4.3.3 Measurement setup with applied electrodes to the material . 11
4.4 Calibration . 14
4.5 Test specimen . 14
4.5.1 General . 14
4.5.2 Recommended dimensions of test specimen and electrode
arrangements . 15
4.5.3 Manufacturing of test specimen . 15
4.5.4 Number of test specimen . 15
4.5.5 Conditioning and pre-treatment of test specimen . 16
4.6 Procedures for specific materials . 16
5 Test procedure . 16
5.1 General . 16
5.2 Calculation of permittivity and relative permittivity . 16
5.2.1 Relative permittivity . 16
5.2.2 The dielectric dissipation factor tan δ . 16
6 Report . 16
7 Repeatability and reproducibility . 17
Annex A (informative) Basic fundamentals . 18
A.1 Error for the effective area in guard ring electrodes – Examples with d =
25 mm, 50 mm or 100 mm and w = 1 mm . 18
A.2 Computation of edge correction of effective area . 19
A.3 Determining H and calculating B . 20
Bibliography . 21

Figure 1 – Dielectric dissipation factor . 8
Figure 2 – Equivalent circuit diagrams . 9
Figure 3 – Cylindrical electrode with guard ring for plate designed specimen . 12
Figure 4 – Specimen with liquid electrodes . 13
Figure A.1 – Area error of h in e with Ɛ = 1 . 18
% r
Figure A.2 – Area error of h in e with Ɛ = ∞ . 18
% r
Figure A.3 – Error calculation for different Ɛ and d . 18
r 1
Figure A.4 – Flow chart for the computation of edge correction of effective area . 19
Figure A.5 – Factor H versus gap and height . 20

Table 1 – Test specimen . 15

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –

Part 2-1: Relative permittivity and dissipation factor –
Technical frequencies (0,1 Hz to 10 MHz) – AC methods

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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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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interested IEC National Committees.
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6) All users should ensure that they have the latest edition of this publication.
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Publications.
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 62631-2-1 has been prepared by IEC technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.
This first edition cancels and replaces the first edition IEC 60250, published in 1969. This
edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) technical frequencies confined to AC methods;
b) update on measurements on solid dielectric materials.

– 4 – IEC 62631-2-1:2018 © IEC 2018
The text of this standard is based on the following documents:
FDIS Report on voting
112/412/FDIS 112/417/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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
Tan δ, also called loss tangent, or dissipation factor is a basic parameter for the quality of
insulating materials. The measurement of capacitance and loss angle is a classical method
well established in the industry over 100 years.
The dissipation factor (tan δ) is dependent on several parameters, such as electrode design,
material characteristics, environmental issues, moisture, temperature, voltage applied, and
highly dependent on frequencies, the accuracy of measuring apparatus and other parameters
applied to the measured specimen.
The frequency range is limited, depending on the test cell and electrode design, the
dimension of the samples and connection leads. In this standard the parameters for the
frequencies applied are therefore limited in the range of very low frequency (VLF) from less
than 1 Hz and up to 10 MHz. However, measuring instruments can provide a broader
frequency range, whereby the usable and suitable frequency range is limited by the whole test
setup.
– 6 – IEC 62631-2-1:2018 © IEC 2018
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –

Part 2-1: Relative permittivity and dissipation factor –
Technical frequencies (0,1 Hz to 10 MHz) – AC methods

1 Scope
This part of IEC 62631 describes test methods for the determination of permittivity and
dissipation factor properties of solid insulating materials (AC methods from 0,1 Hz up to
10 MHz).
NOTE This part of the standard mainly considers measuring setups with guard-electrodes.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 60212, Standard conditions for use prior to and during the testing of solid electrical
insulating materials
ISO 4593, Plastics – Film and sheeting – Determination of thickness by mechanical scanning
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
electrical insulating material
solid with negligibly low electric conductivity, used to separate conducting parts at different
electrical potentials
Note 1 to entry: The term "electrical insulating material" is sometimes used in a broader sense to designate also
insulating liquids and gases. Insulating liquids are covered by IEC 60247.
3.2
dielectric properties
comprehensive behaviour of an insulating material measured with AC comprising the
capacitance, absolute permittivity, relative permittivity, relative complex permittivity, dielectric
dissipation factor
3.3
absolute permittivity
electric flux density divided by the electric field strength

3.4
relative permittivity
ratio of the absolute permittivity to the permittivity of a vacuum ε
3.5
relative complex permittivity
permittivity in a complex number representation, under steady sinusoidal field conditions
3.6
dielectric dissipation factor tan δ (loss tangent)
numerical value of the ratio of the imaginary to the real part of the complex permittivity
3.7
capacitance C
property of an arrangement of conductors and dielectrics which permits the storage of
electrical charge when a potential difference exists between the conductors
3.8
voltage application
application of a voltage between electrodes
Note 1 to entry: Voltage application is sometimes referred to as electrification.
3.9
measuring electrodes
conductors applied to, or embedded in, a material to make contact with it to measure its
dielectric or resistive properties
Note 1 to entry: The design of the measuring electrodes depends on the specimen and the purpose of the test.
4 Method of test
4.1 General theory
The measured permittivity (formerly known as dielectric constant) ε of an insulating material is

the product of its relative permittivity ε and the permittivity of a vacuum ε :
r 0
ε=ε ⋅ε (1)
0 r
The permittivity is expressed in farad per meter (F/m); the permittivity of vacuum ε has the
following value:
F
−12
ε = 8,854187817⋅10 (2)
m
Relative permittivity is the ratio of the absolute permittivity to the permittivity of a vacuum ε .
In the case of constant fields and alternating fields of sufficiently low frequency the relative
permittivity of an isotropic or quasi-isotropic dielectric is equal to the ratio of the capacitance
of a capacitor, in which the space between and around the electrodes is entirely and
exclusively filled with the dielectric, to the capacitance of the same configuration of electrodes
in vacuum.
– 8 – IEC 62631-2-1:2018 © IEC 2018
In practical engineering it is usual to employ the term permittivity when referring to relative
permittivity. The relative permittivity ε of an insulating material is the quotient of capacitance
r
C of a capacitive test specimen (capacitor), in which the space between the two electrodes is
x
entirely and exclusively filled with the insulating material in question, and the capacitance C
of the same configuration of electrodes in vacuum:
C
x
ε = (3)
r
C
The relative permittivity ε of dry air free from carbon dioxide, at normal atmospheric pressure
r
in Pa, equals 100053 Pa, so that in practice, the capacitances C of the configuration of
a
electrodes in air can normally be used instead of C to determine the relative permittivity ε
0 r
with sufficient accuracy.
Relative complex permittivity is permittivity in a complex number representation under steady
sinusoidal field conditions expressed as
' " − jδ
ε =ε − jε =⋅ε ⋅ e (4)
r r r
r
where ε' and ε'' have positive values.
r r
ε
NOTE 1 The complex permittivity is customarily quoted either in terms of ε' and ε'' , or in terms of ε
r r r
r
and tan δ. If ε' > ε'' then ε ≈ ε' which are both called relative permittivity.
r r r r
NOTE 2 ε'' is termed loss index.
r
I
I
δ
U
I
ϕ
I U
w
IEC
Figure 1 – Dielectric dissipation factor
The dielectric dissipation factor tan δ (loss tangent) is the numerical value of the ratio of the
imaginary to the real part of the complex permittivity.
"
ε
r
tanδ= (5)
'
ε
r
R C
s s
R
p
C
p
IEC
Figure 2 – Equivalent circuit diagrams
Thus, the dielectric dissipation factor tan δ of an insulating material is the tangent of the
angle δ by which the phase difference ϕ between the applied voltage and the resulting current
deviates from π/2 rad when the solid insulating material is exclusively used as dielectric in a
capacitive test specimen (capacitor) (compare with Figure 1). The dielectric dissipation factor
can also be expressed by an equivalent circuit diagram using an ideal capacitor with a
resistor in series or parallel connection (see Figure 2).

(6)
tanδ=ωC ⋅ R =
s s
ωC ⋅ R
p p
with
C
p 1
= (7)
C
s 1+ tan δ
and
R
p 1
= 1+ (8)
R
tan δ
s
NOTE 3 R and R respectively are not directly related to but affected by the volume and the surface resistance of
S P
an insulating material. Therefore the dielectric dissipation factor may also be affected by these resistive materials
properties.
Capacitance C is the property of an arrangement of conductors and dielectrics which permits
the storage of electrical charge when a potential difference exists between the conductors.
C is the ratio of a quantity q of charge to a potential difference U. A capacitance value is
always positive. The unit is farad when the charge is expressed in coulomb and the potential
in volts.
q
C= (9)
U
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 permittivity and dielectric dissipation factor is to be done carefully and
under consideration of the electric properties of the measuring circuit as well as the specific
electric properties of the material.

– 10 – IEC 62631-2-1:2018 © IEC 2018
NOTE 4 To carry out the test, in most cases the use of high voltage is necessary. Care shall be taken to prevent
from electric shock.
The basic principles of apparatus and methods are not described here. Some references to
the literature is given in the bibliography.
4.2 Power supply (voltage)
The power source shall provide a stable sinusoidal voltage. For the measuring duration the
measured value of the supplied voltage shall be maintained within ± 5 %.
The voltage wave shape shall approximate to a sinusoid with the difference of the magnitudes
of the positive and negative peak values being less than 2 %.
The deviation of the sinusoidal shape (the ratio of peak to r.m.s. values equals 2 ) shall be

within ± 5 %.
Preferred voltages are 0,1 V; 0,5 V; 10 V; 100 V; 500 V; 1 000 V; 2 000 V.
Higher voltages may be applicable in order to perform tests at operating field strength. Other
voltage levels shall be documented in the report.
NOTE Partial discharge can lead to erroneous measurements when a specific inception voltage is exceeded. In
air, below 340 V no partial discharges will occur.
4.3 Equipment
4.3.1 Accuracy
The measuring device should be capable of determining the unknown permittivity and
dielectric dissipation factor in accordance with the expected material properties. The accuracy
of the measuring system must be documented in the report.
NOTE The user can choose the measuring system accuracy according to the requirements of the measuring
results.
4.3.2 Choice of measuring methods
4.3.2.1 General
Methods for measuring the permittivity and dissipation factor can be divided into three groups:
• null method
• impedance analyser method
• digital phase shift method
4.3.2.2 Null method
For measurements of permittivity and dissipation factor, substitution techniques can be used
that is, the bridge is balanced by adjustment mainly in one arm of the network, with and
without the specimen connected. The networks normally used are the Schering bridge, the
transformer bridge (i.e. a bridge with ratio arms coupled by mutual inductance) and the
parallel-T. The transformer bridge has the advantage of allowing the use of a guard electrode
without any additional components or operations; it has no disadvantages in comparison with
the other networks.
4.3.2.3 Impedance analyser method
There exist a lot of commercially available instruments (impedance analyzers or LCR meters).
These instruments determine the impedance of the specimen as the ratio of the measured

vector of voltage and current. The vector is the value of the magnitude and a phase. Typically,
the impedance is determined at one or more fixed frequencies or as a sweep over a frequency
range.
Most instruments allow to express the impedance as a loss capacitance (C, tan δ or D) using
either a serial or a parallel equivalent circuit for a given frequency. For the purposes of this
International Standard the parallel equivalent circuit is to be used.
Care should be taken that the influence of cables is to be compensated in a correct manner.
For this reason typically an OPEN and SHORT compensation of the measuring circuit is to be
done and in some cases also LOAD compensation. Irregular compensation will lead to
erroneous measurements.
Precision of impedance analysers depends on the instruments quality itself but may also
strongly depend on the magnitude of the measured impedance (capacity) and on frequency.
Any instrument can be used. However, the precision of the instrument shall be appropriate for
the material under test and is to be stated in the test report.
4.3.2.4 Digital phase shift method
The measuring principle is based on precise recording of the currents through the standard
capacitor (reference) and the test object path, with the voltage as a reference phase shift
marker. The dielectric dissipation factor is calculated by measurement of the phase shift
between these currents.
The measurement of sinusoidal-wave current and voltage in both voltage paths with amplitude
and time precision is provided by high precision analogue to digital conversion
simultaneously. Harmonics and external noise at current and voltage sinusoidal-wave may be
suppressed with digital filtering, for example Fast Fourier Transformation (FFT) in the time or
frequency domain. The dissipation factor tan δ and capacitance C are calculated based on
x
phase shift and amplitude information extracted from the digital current measurement.
-4
To reach a required precision tan δ ≤1,10 of the test results, the A/D converter should have
a resolution of ≥16 bit.
Due to safety reasons it is recommended to decouple the measuring devices, which are
placed in the voltage area, from the control unit for the operator, for example fibre optics.
4.3.3 Measurement setup with applied electrodes to the material
4.3.3.1 General
The electrodes for insulating materials should be of a material that is readily applied, that
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 given form and dimensions. It may be advantageous to use two
different electrode materials or two methods of application to see if significant error is
introduced.
The measurement of the dimensions of the electrode shall be according to ISO 4593.
NOTE The accuracy of the measurement of the dimensions of the electrode is directly related to the accuracy of
the expected test result.
The mechanical force, which is applied by the fixture electrode to the specimen, should be
approximately 1 Pa for pressure sensitive test specimen. Other electrode forces are possible
and shall be documented in the test report. The mechanical electrode force should not
overstress the test specimen.
– 12 – IEC 62631-2-1:2018 © IEC 2018
4.3.3.2 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:
• edge effects of the electrical field which influence the measured capacity
• the surface resistance which may influence the dielectric dissipation factor, especially at
low frequencies
A satisfactory correction is obtained by using the technique of guarding.
The guard conductors are connected together, constituting the guard system and forming with
the measuring terminals a three-terminal network. The basic connections for guarded
electrodes used for measurement of permittivity and dielectric dissipation factor are shown in
Figure 3.
Measuring electrode
Guard
electrode
d g
Specimen h
HV
electrode
IEC
Figure 3 – Cylindrical electrode with guard ring for plate designed specimen
The surface area A (in mm ) defined in Equation (10), is π/4 multiplied by square of the sum
of electrode diameter d and gap space g.
π
A= (d + B⋅ g)
(10)
A − A
B=1 B≠1
e = ⋅100%
%
(11)
A
B≠1
The factor B is a function of the ratio of the gap and thickness of the specimen and of the
dielectric constant. Equation (10) assumes a relative permittivity of ε →∞ . Equation (11)
r
represents the possible error of the effective area, neglecting the factor B.
The specimen with its own electrodes shall then be mounted between metal backing
electrodes, these being slightly smaller than the specimen electrodes. The equations for
computing the capacitance of different arrangements of disk-shaped or cylindrical electrodes
as weIl as empirical equations for computing the edge capacitance correction for this
condition are given in Annex A.
4.3.3.3 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 specimen 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.
4.3.3.4 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.
4.3.3.5 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 4,
shows the electrode arrangement. Alloys containing for example gallium, indium and tin,
which are liquid at room temperature, have been proved as suitable. Mercury is not
recommended.
IEC
Legend:
1 Test voltage electrode
2 Specimen
3 Guard electrode
4 Measurement electrode
Figure 4 – Specimen with liquid electrodes
4.3.3.6 Metal foil
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.
All adhesive materials may be of influence on the measurement results and should be
minimized.
NOTE Silicon grease with a sufficient low dielectric loss has been found suitable.
4.3.3.7 Tube specimen
The most appropriate electrode system for a tube specimen will depend on its permittivity,
wall thickness, diameter, and the accuracy of measurement required. In general, the electrode
system shall consist of an inner electrode and a somewhat narrower outer electrode, with a
guard electrode at each end. The gap between the outer and guard electrodes shall be small
compared with the thickness of the tube wall. For tube specimen of small and medium
diameters, three bands of foil or deposited metal can be applied to the outside of the tube, the
centre band serving as the working outer electrode with the two bands of foil or deposited
metal, one on each side, serving as guard electrodes. Inner electrodes of liquid metal,
deposited metal film or a tightly fitting mandrel may be used.

– 14 – IEC 62631-2-1:2018 © IEC 2018
For tube specimen of high permittivity, the inner and outer electrodes may extend the
complete length of the tube and the guard electrodes may be dispensed with.
For tubes or cylinders of large diameter, the electrode system can be either a circular or
rectangular patch, a portion only of the tube periphery being tested. Such specimen can be
treated as sheet specimen. Inner electrodes of metal foil, deposited metal film, or a tightly
fitting mandrel are employed with outer and guard electrodes of metal foil or deposited metal.
A flexible, expanding clamp may be necessary inside the tube to ensure satisfactory contact
between the inner electrode and the specimen if a foil electrode is used.
For tube specimen having relative permittivity ε up to about 10, the most convenient
r
electrodes are foils or liquid metal. For tube specimen having relative permittivity above about
10, deposited metal electrodes shall be employed; fired-on electrodes shall be used for
ceramic tubes. The electrodes may be applied to the complete circumference of the tube as
bands or to only a portion of the circumference.
4.3.3.8 Micrometre controlled parallel electrodes, in air
The capacitance can be adjusted to the same value with and without the specimen inserted,
and the permittivity determined without reference to the electrical calibration of the measuring
system.
4.3.3.9 Fluid displacement method
In a liquid, whose permittivity is nearly equal to that of the specimen and whose dissipation
factor is negligible, the measurement depends less critically than usual on exact knowledge of
the thickness of the specimen. By using two fluids in turn, the thickness of the specimen and
the dimensions of the electrode system can be eliminated from the equations.
The test specimen shall be a disk having the same diameter as the ceIl electrodes, or, for
micrometre electrodes, the specimen may be sufficiently small to make edge effects
negligible.
To make the edge effects negligible in the micrometre electrodes, the specimen diameter
shall be smaller than that of the micrometre electrodes by at least twice the thickness of the
specimen.
4.4 Calibration
The equipment shall be calibrated in the dielectric dissipation factor measured.
4.5 Test specimen
4.5.1 General
For determining the permittivity and dissipation factor of a material, sheet specimen are
preferable; but material may be available only in tubular form. The specimen under test shall
have a thickness close to its application.
When high accuracy is needed in measuring permittivity, the source of the greatest
uncertainty is the dimensions of the specimen, and particularly its thickness, which shall
therefore be large enough to allow its measurement with the required accuracy. The choice of
thickness depends on the method of producing the specimen and the likely variation in
thickness from point to point. The thickness shall be determined by measurements distributed
systematically over the area of the specimen, which is used in the electrical measurement,
and shall be uniform to within ± 1 % of the average thickness. The area chosen for the
specimen shall be such as to provide a specimen capacitance, which can be measured to the
desired accuracy.
NOTE 1 Experience shows that the capacitances of typical test specimen are approximately between 10 pF and
100 pF.
When small values of the dissipation factor are being measured, it is essential that the loss
introduced by the series resistance of the leads be as small as possible or it needs to be
corrected, that is, the product of the resistance and the capacitance being measured shall be
as small as possible. Also, the ratio of the measured capacitance to the total capacitance
shall be as large as possible.
NOTE 2 The first point indicates a need for keeping the lead resistances as low as possible and the desirability of
having a small specimen capacitance. The second point indicates the need for low total capacitance in the arm of
the bridge to which the specimen is connected and the desirability of having a large specimen capacitance.
Frequently the best compromise is a specimen having a capacitance of about 20 pF, used with a measuring circuit
which does not connect more than about 5 pF in parallel with the specimen.
NOTE 3 If not otherwise specified, a plate ≥ 100 mm × ≥ 100 mm × (1 mm ± 0,5 mm) can be used.
4.5.2 Recommended dimensions of test specimen and electrode arrangements
If not otherwise stipulated in the relevant product standard the following dimensions (see
Table 1) for test specimen are recommended:
Table 1 – Test specimen
Type of product Recommended dimensions Remarks
of test specimen
Thermoplastic moulding compounds ISO 294-1 and ISO 294-3
60 mm × 60 mm × 1 mm
Thermosetting moulding compounds ISO 295
Long fibre reinforced polyester and vinyl
100 mm × 100 mm × 3 mm
ester moulding compounds (SMB BMC)
Epoxy based sheets and laminates
Impregnating resins and varnishes Materials described in the
IEC 60455 and IEC 60464 series
Casting resins Materials described in the
IEC 60455 series
Pipes bars rods Materials described in
IEC 61212
Elastomeric material
100 mm × 100 mm × 3 mm
The dimensions of test specimen shall be greater than the dimensions of the measuring
electrode including the guard ring.
4.5.3 Manufacturing of test specimen
The production and shape of the test specimen shall be determined by the relevant standards
for the material. During removal and production of the specimen the condition of the material
shall not be changed and the specimen shall not be damaged.
If the surface of the test specimen is machined at the contact areas of the electrodes, the type
of machining shall be specified in the test report. The test specimen shall have a
geometrically simple shape (plate with parallel measuring areas, cylinder, etc.).
Specimens from products shall be prepared with the product thickness, if possible.
4.5.4 Number of test specimen
The number of specimen to be tested shall be determined by the relevant product standards.
If no such data is available, at least three specimens shall be tested.

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4.5.5 Conditioning and pre-treatment of test specimen
Conditioning and any other pre-treatment of the test specimen shall be done according to the
relevant product standard. If no product standard exists, conditioning shall be done for at
least 4 days at 23 °C and 50 % RH according to IEC 60212 (standard climate B).
4.6 Procedures for specific materials
Procedures for specific materials are described in material specifications. If a specific
procedure for a specified material exists this specification shall be used. The measuring
procedure including preparation of test specimen shall be described in the report.
5 Test procedure
5.1 General
A number of specimens as described in the relevant specification are to be prepared. If not
otherwise specified, 3 specimens shall be tested. Thickness of the sample should be
measured at 5 points at least be
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