prEN IEC 62631-2-1:2026

• Status: Not Published
• Publication Date: 12-Dec-2027
• ICS: 17.220.99 - Other standards related to electricity and magnetism
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: CLC/SR 112 - Evaluation and qualification of electrical insulating materials and systems (to be defined)
• Drafting Committee: IEC/TC 112 - IEC_TC_112
• Current Stage: 4060 - Enquiry results established and sent to TC, SR, BTTF - Enquiry
• Start Date: 14-Aug-2026
• Completion Date: 14-Aug-2026
• Ref Project: oSIST prEN IEC 62631-2-1:2026 - Dielectric and resistive properties of solid insulating materials - Part 2-1: Relative permittivity and dissipation factor - Technical frequencies (0,1 Hz - 10 MHz) - AC Methods

• Referred By: EN IEC 60684-2:2025 - Flexible insulating sleeving - Part 2: Methods of test
• Effective Date: 26-May-2026
• Revises: EN IEC 62631-2-1:2018 - 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
• Effective Date: 30-Nov-2021

Overview

prEN IEC 62631-2-1:2026 specifies standardized test methods for evaluating the dielectric and resistive properties of solid insulating materials using AC methods at technical frequencies ranging from 0.1 Hz to 10 MHz. It focuses on determining two key properties: relative permittivity (dielectric constant) and dissipation factor (tan δ or loss tangent). Governed by the International Electrotechnical Commission (IEC), this standard is essential for quality control, performance assessment, and material selection within the electrical and electronics industries.

Proper measurement of dielectric properties ensures the reliability, safety, and efficiency of electrical insulating materials used in various applications such as electrical equipment, components, power systems, and cables.

Key Topics

• Scope and Purpose:
  The standard outlines AC testing methods specifically suited to technical frequencies for determining relative permittivity and dissipation factor in solid insulating materials.

• Measurement Methods:
  Three main methods are highlighted:

  • Null method (e.g., Schering bridge)
  • Impedance analyser/LCR meter method
  • Digital phase shift method

• Test Setup and Equipment:

  • Use of guard-electrodes to ensure measurement accuracy
  • Detailed recommendations for electrode materials and arrangements (e.g., silver paint, evaporated metals, foils)
  • Calibration procedures and documentation of measurement uncertainty

• Specimen Preparation:

  • Guidance on thickness, dimensions, and uniformity for reproducible results
  • Special considerations for sheet, film, tube, and rod specimens

• Parameter Definitions:

  • Relative permittivity: the ability of a material to store electrical energy
  • Dissipation factor: indicates the dielectric losses within the material when subjected to alternating current

• Test Conditions:

  • Stable voltage supply and sinusoidal waveform requirements
  • Environmental and specimen conditioning to minimize measurement errors

Applications

The test methods described in prEN IEC 62631-2-1:2026 offer significant practical value in fields such as:

• Quality Assurance in Manufacturing:
  Manufacturers of insulating components can verify that materials meet specified dielectric properties for operational reliability.

• Material Selection and R&D:
  Research and development teams rely on these standardized methods to compare and optimize new insulating materials based on permittivity and loss characteristics.

• Compliance Testing for Electrical Equipment:
  Ensures that insulators used in transformers, capacitors, cables, and switchgear comply with safety standards and technical specifications.

• Predictive Maintenance and Aging Studies:
  Tracking changes in permittivity and dissipation factor over time helps assess the aging of insulating materials and schedule timely maintenance or replacement.

• Academic and Standardization Work:
  Facilitates reproducible, internationally-accepted test results for scientific publication and regulatory compliance.

Related Standards

For comprehensive evaluation and contextual understanding, the following standards are relevant to prEN IEC 62631-2-1:2026:

• 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
• IEC 62631 Series - Covers broader aspects of dielectric and resistive properties for various forms of insulating materials
• IEC 60247 - Insulating liquids - Measurement of relative permittivity and dissipation factor by AC bridge methods
• IEC 60455, IEC 60464, IEC 61212, IEC 60674 - Standards for specific insulating material product types and their test samples

This standard is part of a harmonized framework that supports international consistency in testing and the global trade of electrical insulating materials. Proper application of prEN IEC 62631-2-1:2026 enhances safety, efficiency, and innovation in modern electrical systems.

SLOVENSKI STANDARD
01-julij-2026
Dielektrične in uporovne lastnosti trdnih izolacijskih materialov - 2-1. del:
Relativna permitivnost in faktor dielektričnih izgub - Tehnične frekvence (0,1 Hz -
10 MHz) - Metode AC
Dielectric and resistive properties of solid insulating materials - Part 2-1: Relative
permittivity and dissipation factor - Technical frequencies (0,1 Hz - 10 MHz) - AC
Methods
Dielektrične in uporovne lastnosti trdnih izolacijskih materialov - 2-1. del: Relativna
permitivnost in faktor izgube - Tehnične frekvence (0,1 Hz – 10 MHz), metode AC (IEC
62631-2-1:2018)
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
Ta slovenski standard je istoveten z: prEN IEC 62631-2-1:2026
ICS:
17.220.99 Drugi standardi v zvezi z Other standards related to
elektriko in magnetizmom electricity and magnetism
29.035.01 Izolacijski materiali na Insulating materials in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

112/721/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 62631-2-1 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-05-22 2026-08-14
SUPERSEDES DOCUMENTS:
112/710/CD, 112/719/CC
IEC TC 112 : EVALUATION AND QUALIFICATION OF ELECTRICAL INSULATING MATERIALS AND SYSTEMS
SECRETARIAT: SECRETARY:
Germany Mr Bernd Komanschek
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
TC 10, TC 15
ASPECTS CONCERNED:
Electricity transmission and distribution
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
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The attention of IEC National Committees, members of CENELEC,
is drawn to the fact that this Committee Draft for Vote (CDV) is
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The CENELEC members are invited to vote through the CENELEC
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AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Dielectric and resistive properties of solid insulating materials – Part 2-1: Relative permittivity and dissipation
factor – Technical Frequencies (0,1 Hz - 10 MHz) – AC Methods

PROPOSED STABILITY DATE: 2031
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IEC CDV 62631-2-1 © IEC 2026
CONTENTS
FOREWORD . 2
INTRODUCTION . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Method of test . 6
4.1 General theory . 6
4.2 Power supply (voltage) . 8
4.3 Equipment . 9
4.3.1 Accuracy . 9
4.3.2 Choice of measuring methods . 9
4.3.3 Measurement setup with applied electrodes to the material . 10
4.4 Calibration . 12
4.5 Test specimen . 12
4.5.1 General . 12
4.5.2 Recommended dimensions of test specimen and electrode
arrangements . 13
4.5.3 Manufacturing of test specimen . 13
4.5.4 Number of test specimen . 14
4.5.5 Conditioning and pre-treatment of test specimen . 14
4.6 Procedures for specific materials . 14
5 Test procedure . 14
5.1 General . 14
5.2 Calculation of permittivity and relative permittivity . 14
5.2.1 Relative permittivity . 14
5.2.2 The dielectric dissipation factor tan δ . 15
6 Report . 15
7 Repeatability and reproducibility . 15
Annex A (informative) Basic fundamentals . 16
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 . 16
A.2 Computation of edge correction of effective area . 16
A.3 Determining H and calculating B . 17
Bibliography . 19

Figure 1 – Dielectric dissipation factor . 7
Figure 2 – Equivalent circuit diagrams . 7
Figure 3 – Cylindrical electrode with guard ring for plate designed specimen . 11
Figure A.1 – Area error of ℎin 𝑒% with 𝜀𝑟 = 1 . 16
Figure A.2 – Area error of ℎ in 𝑒% with 𝜀𝑟 = ∞ . 16
Figure A.3 – Error calculation for different Ɛ and d . 16
r 1
Figure A.4 – Flow chart for the computation of edge correction of effective area . 17
Figure A.5 – Factor H versus gap and height . 17

Table 1 – Test specimen . 13

IEC CDV 62631-2-1 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Dielectric and resistive properties of solid insulating materials –
Part 2-1: Relative permittivity and dissipation factor –
Technical Frequencies (0,1 Hz - 10 MHz) – AC Methods

FOREWORD
a) 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 this end and
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liaising with the IEC also participate in this preparation. IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
b) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
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h) 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.
i) 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 second edition cancels and replaces the first edition published in 2017. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– Removal of liquid electrode
– Editoral updates
IEC CDV 62631-2-1 © IEC 2026
The text of this standard is based on the following documents:
Draft Report on voting
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.
IEC CDV 62631-2-1 © IEC 2026
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 an d 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.
IEC CDV 62631-2-1 © IEC 2026
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.
ISO 4593, Plastics – Film and sheeting – Determination of thickness by mechanical scanning
IEC 60212, Standard conditions for use prior to and during the testing of solid electrical
insulating materials
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:
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
3.1
solid insulating material
Solid insulating material: Solid material of low electric conductivity, used to separate conducting
parts at different electric potentials or to isolate such parts from the surroundings
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.
Note 2 to entry: Modified defintion by using insulating material [IEV 212-11-01]
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
IEC CDV 62631-2-1 © IEC 2026
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 Farads per meter (F/m); the permittivity of vacuum ε has the
following value:
1 𝐹
−12
𝜀 = ≈ 8,85418781728 · 10
0 (2)
𝑚
√𝜇 · 𝑐
0 0
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.
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:
IEC CDV 62631-2-1 © IEC 2026
𝐶
𝑥
𝜀 = (3)
𝑟
𝐶
The relative permittivity ε of dry air free from carbon dioxide, at normal atmospheric pressure
r
equals to 1,00059 [1] . In practice, the capacitances C of the configuration of electrodes in air
a
can normally be used instead of C to determine the relative permittivity ε with sufficient
0 r
accuracy.
Relative complex permittivity is permittivity in a complex number representation under steady
sinusoidal field conditions expressed as
′ " −𝑗𝛿
𝜀 = 𝜀 − 𝑗𝜀 =· 𝜀 · 𝑒
𝑟 𝑟 𝑟 𝑟 (4)
−
where ε' and ε'' have positive values.
r r
NOTE 1 The complex permittivity ε is customarily quoted either in terms of ε' and ε'' , or in terms of ε and tan δ.
r r r r
′ ′′
If 𝜀 ≫ 𝜀 then ε ≈ ε' which are both called relative permittivity.
𝑟 𝑟
r r
NOTE 2 ε'' is termed loss index.
r
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
(5)
tan𝛿 =
′
𝜀
𝑟
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).
tan𝛿 = 𝜔𝐶 · 𝑅 =
(6)
𝑠 𝑠
𝜔𝐶 · 𝑅
𝑝 𝑝
IEC CDV 62631-2-1 © IEC 2026
with
𝐶 1
𝑝
= (7)
𝐶 1 + tan 𝛿
𝑠
and
𝑅 1
𝑝
= 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 the absolute value of quantity q of charge of one of the electrode to the absolute
value of the potential difference U between the electrodes.
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
...