IEC 61628-2:1998+AMD1:2007 CSV

Corrugated pressboard and presspaper for electrical purposes - Part 2: Methods of test

Gives test methods (type and dimension of corrugation, dimensional changes on drying, compressive strength and compression modulus) for the materials classified in IEC 61628-1. This consolidated version consists of the first edition (1998) and its amendment 1 (2007). Therefore no need to order amendment in addition to this publication.

Cartons et papiers comprimés ondulés à usages électriques - Partie 2: Méthodes d'essais

Donne des méthodes d'essais (types et dimensions de l'ondulation, variation dimensionnelle au séchage, résistance à la compression et module de compression) applicables aux matériaux définis dans la CEI 61628-1. Cette version consolidée comprend la première édition (1998) et son amendement 1 (2007). Il n'est pas nécessaire de commander l'amendement avec cette publication.

General Information

• Status: Published
• Publication Date: 29-Jul-2007
• ICS: 29.035.10 - Paper and board insulating materials
• Technical Committee: TC 15 - Solid electrical insulating materials
• Current Stage: PPUB - Publication issued
• Start Date: 30-Jul-2007
• Completion Date: 30-Jul-2007

Overview

IEC 61628-2:1998+AMD1:2007 CSV is an international standard published by the International Electrotechnical Commission (IEC) that specifies methods of test for corrugated pressboard and presspaper used for electrical purposes. This part of the IEC 61628 series focuses on test procedures to evaluate key material properties such as corrugation type and dimensions, moisture-related dimensional changes, compressive strength, and compression modulus. The document consolidates the original 1998 edition with Amendment 1 from 2007, providing a comprehensive and updated testing framework without the need to order amendments separately.

Key Topics

This standard defines precise test methods that are essential for assessing the quality and performance of corrugated pressboard and presspaper materials used in electrical applications. Key topics include:

• Type and Dimension of Corrugation

  • Measurement procedures for wavelength, amplitude, length of horizontal parts, angle of slope, and board thickness.
  • Detailed guidance on sample preparation and measurement accuracy for consistent results.

• Moisture Content and Dimensional Changes on Drying

  • Testing moisture content according to IEC 60641-2 requirements.
  • Methods to measure changes in amplitude of corrugation and dimensional variations in lengthwise and crosswise directions due to drying.
  • Test setup involving conditioning, oven drying, and precise measurement using calibrated tools.

• Compressive Strength and Compression Modulus

  • Test procedures for determining the compressive strength when force is applied perpendicularly to the plane of corrugation.
  • Calculation methods to evaluate compression modulus, crucial for understanding mechanical integrity under load.

• Conductivity of Aqueous Extract

  • Methods to assess electrical properties related to material conductivity, ensuring suitability for electrical insulation purposes.

Applications

IEC 61628-2 provides critical testing methods for manufacturers, quality control laboratories, and engineers working with corrugated pressboard and presspaper in the electrical industry. Its applications include:

• Electrical Insulation Materials Testing
  Ensuring materials meet required specifications for dielectric performance and mechanical strength in transformers, capacitors, and other electrical apparatus.

• Material Specification and Quality Assurance
  Allowing manufacturers to classify corrugated materials accurately according to IEC 61628-1, supporting standardization and reliable product performance.

• Research and Development
  Facilitating innovation by providing repeatable testing protocols that help develop improved corrugated materials with enhanced durability and electrical properties.

• Regulatory and Contractual Compliance
  Supporting compliance with international standards, helping clients and suppliers meet contractual requirements for electrical insulation components.

Related Standards

IEC 61628-2 is part of a series devoted to corrugated pressboard and presspaper for electrical purposes. Related standards include:

• IEC 61628-1:1997 - Corrugated Pressboard and Presspaper for Electrical Purposes – Definitions, Designations, and General Requirements. This document classifies materials and provides foundational terminology and standards referenced throughout IEC 61628-2.

• IEC 61628-3 (Under Development) - Specification for Individual Materials, which will extend and specify particular material properties based on the test methods established in part 2.

• IEC 60641-2:2004 - Pressboard and Presspaper for Electrical Purposes – Part 2: Methods of Test. IEC 61628-2 references this document for conditioning specimens and standardized test environments.

By adhering to IEC 61628-2, stakeholders involved in the production and usage of corrugated pressboard and presspaper for electrical purposes can ensure materials meet international quality and safety standards, improving reliability and performance in critical electrical applications.

Keywords: IEC 61628-2, corrugated pressboard, presspaper, electrical insulation materials, methods of test, compressive strength, corrugation dimensions, moisture content, compression modulus, IEC standards, electrical applications, insulation quality, standardized testing procedures.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
CEI
61628-2
NORME
Edition 1.1
INTERNATIONALE
2007-07
Edition 1:1998 consolidated with amendment 1:2007
Edition 1:1998 consolidée par l'amendement 1:2007
Corrugated pressboard and presspaper
for electrical purposes –
Part 2:
Methods of test
Cartons et papiers comprimés ondulés
à usages électriques –
Partie 2:
Méthodes d’essais
Reference number
Numéro de référence
IEC/CEI 61628-2:1998+A1:2007
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INTERNATIONAL IEC
STANDARD
CEI
61628-2
NORME
Edition 1.1
INTERNATIONALE
2007-07
Edition 1:1998 consolidated with amendment 1:2007
Edition 1:1998 consolidée par l'amendement 1:2007
Corrugated pressboard and presspaper
for electrical purposes –
Part 2:
Methods of test
Cartons et papiers comprimés ondulés
à usages électriques –
Partie 2:
Méthodes d’essais
PRICE CODE
CD
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

– 2 – 61628-2 © IEC:1998+A1:2007
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative reference .6
3 General note on tests.6
4 Type and dimension of corrugation.6
5 Moisture content .8
6 Dimensional changes on drying.8
7 Compressive strength and compression modulus .9
8 Conductivity of aqueous extract .11

Figure 1 – Different types of corrugation.12
Figure 2 – Positioning of the test specimen.13
Figure 3 – Test specimen holder – Side view.13
Figure 4 – Curve of deflection versus force.14

61628-2 © IEC:1998+A1:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
________
CORRUGATED PRESSBOARD AND PRESSPAPER
FOR ELECTRICAL PURPOSES –
Part 2: Methods of test
FOREWORD
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International Standard IEC 61628-2 has been prepared by subcommittee 15C: Specifications,
of IEC technical committee 15: Insulating materials.
This consolidated version of IEC 61628-2 consists of the first edition (1998) [documents
15C/992/FDIS and 15C/1008/RVD] and its amendment 1 (2007) [documents 15/293/CDV and
15/340/RVC].
The technical content is therefore identical to the base edition and its amendment(s) and has
been prepared for user convenience.
It bears the edition number 1.1.
A vertical line in the margin shows where the base publication has been modified by
amendment 1.
– 4 – 61628-2 © IEC:1998+A1:2007
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result 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
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
61628-2 © IEC:1998+A1:2007 – 5 –
INTRODUCTION
This part of IEC 61628 is one of a series which deals with corrugated pressboard and
presspaper for electrical purposes.
This series consists of three parts:
– IEC 61628-1:1997, Corrugated pressboard and presspaper for electrical purposes – Part 1:
Definitions, designations and general requirements
– IEC 61628-2:1998, Corrugated pressboard and presspaper for electrical purposes – Part 2:
Methods of test
– IEC 61628-3,— Corrugated pressboard and presspaper for electrical purposes – Part 3:
Specification for individual materials (under consideration)

– 6 – 61628-2 © IEC:1998+A1:2007
CORRUGATED PRESSBOARD AND PRESSPAPER
FOR ELECTRICAL PURPOSES –
Part 2: Methods of test
1 Scope
This part of IEC 61628 gives methods of test applicable for the materials classified in
IEC 61628-1.
2 Normative reference
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 60641-2:2004, Pressboard and presspaper for electrical purposes – Part 2: Methods of
test
3 General note on tests
It is recommended to use a high-speed band saw with a cut width less than 1 mm to make the
test specimens. The burrs made by cutting should be carefully removed.
Unless otherwise specified, the test specimens after being cut, shall be conditioned according
to IEC 60641-2.
4 Type and dimension of corrugation
The shape and type of corrugation are defined by wavelength, maximum amplitude, the length
of horizontal parts, angle of slope and the board thickness out of which the corrugated material
is made (see figures 1a and 1b).
The following tests are made on the material as received.
4.1 Wavelength
4.1.1 Procedure
Cut at least three test samples, each test sample having a length greater than three complete
wavelengths.
With a pencil, mark the starting line of the first wavelength and the end line of the last
wavelength (minimum three wavelengths).
(The best starting and end line of a wavelength is the line of maximum amplitude for a sine
type corrugation and the centre of a horizontal part in an angular type corrugation.)
Lay the test sample on a flat surface with no strain applied.

61628-2 © IEC:1998+A1:2007 – 7 –
Measure with a ruler (precise to 0,5 mm) the distance between the pencil lines.
Divide the measured value by the number of wavelengths between the lines.
4.1.2 Results
Report the mean, minimum and maximum values of the measurements.
4.2 Amplitude
4.2.1 Procedure
Cut at least nine specimens, each being (100 ± 10) mm wide, and one-and-a-half to two
wavelengths in length, so that two full bottom peaks are included.
Lay the test specimens on a flat surface with no strain applied.
With a gauge (precise to 0,1 mm), measure the distance between the highest point and the
lowest point.
4.2.2 Results
Report the mean, minimum and maximum values of the measurements.
4.3 Length of horizontal parts of corrugation
4.3.1 Procedure
On at least three different corrugations, mark with a pencil the vertical projections of the
theoretical points where the oblique parts of the corrugation meet the horizontal part. The
pencil marks shall be positioned on a line in the direction of the corrugation wavelength.
Measure the distance between the pencil marks with a calliper precise to 0,1 mm (distance E in
figure 1b).
Repeat the measurements at the opposite side of the sheet to measure the distance D in
figure 1b.
Because D and E may be intentionally different, both measurements shall be reported.
4.3.2 Results
Report for D and E the mean, minimum and maximum values of the measurements.
4.4 Angle of slope
4.4.1 Procedure
Cut at least three specimens, each being (100 ± 10) mm wide, and one-and-a-half to two
wavelengths in length, so that two full bottom peaks are included.
Lay the test sample on a flat surface with no strain applied.
α of the central
With an adequate protractor (precise to 0,5°), measure the two angles
corrugation.
– 8 – 61628-2 © IEC:1998+A1:2007
4.4.2 Results
Report the mean, minimum and maximum values of the measurements.
4.5 Thickness of board
4.5.1 Procedure
With an external screw type micrometer as described in IEC 60641-2, make at least nine
different measurements of the board thickness with an accuracy of ± 0,01 mm at points where
the corrugation curve is flat, or in the area of the inflection point for a sine type corrugation.
NOTE Measures on the horizontal flat part should be avoided as the board thickness may have been affected by
the direct action of the forming press when mechanical pressure has been used to manufacture the corrugated
material.
4.5.2 Results
Report the mean, minimum and maximum values of the measurements.
5 Moisture content
Moisture content shall be determined according to IEC 60641-2.
6 Dimensional changes on drying
6.1 Change of amplitude
6.1.1 Procedure (see figure 2)
Cut three specimens (50 ± 5) mm wide and five wavelengths long and condition them
according to IEC 60641-2.
Place the specimens on a flat steel plate the dimensions of which shall exceed the dimensions
of the specimen by at least 50 mm. Place a second flat rigid plate of calibrated thickness T,
50 mm wide and of sufficient length to cover all the corrugations, on top of the specimen. The
weight of this plate shall guarantee that all the corrugations are in flat contact with both top and
bottom plate and shall be defined in the specification sheets of IEC 61628-3.
NOTE The weight of the plate can be adjusted by additional weights added on top of it.
If all the corrugations of any specimen are not in contact with top and bottom plate under this
pre-load, the specimen shall be discarded.
The amplitude of the corrugation of the specimen is measured by means of a gauge precise to
0,1 mm with a semi-spherical sensor in the following way:
– lower the sensor of the gauge on to the bottom steel plate and adjust the pointer to zero;
– set the sensor on the top plate and read the measured values at three different points near
the centre of the plate and form the mean of these three measures.
Record this value as value B for each specimen.
Remove and dry the test specimens in a ventilated oven at 105 °C ± 5 K for (48 ± 1) h. After
cooling at room temperature in a desiccator, repeat the measurements as above.
Record for each specimen the new value as C.

61628-2 © IEC:1998+A1:2007 – 9 –
6.1.2 Calculation
The change of amplitude is calculated as a percentage of the original amplitude and is given by
the formula:
CB−
change of amplitude = × 100
BT−
There is normally an increase of amplitude after drying.
6.1.3 Results
Report the mean value obtained. Minimum and maximum values should also be reported.
6.2 Lengthwise and crosswise dimensional changes
6.2.1 Procedure
Cut three specimens (250 ± 0,5) mm × (250 ± 0,5) mm and condition them according to
IEC 60641-2. Place the specimen on a flat steel plate of at least 300 mm × 300 mm. A second
flat rigid plate of the same dimension is placed on top of the specimen. Its mass, which will be
defined in the specification sheets of IEC 61628-3, shall guarantee that all corrugations are in
contact with both top and bottom plates.
Measure the lengthwise and crosswise dimensions with a calliper precise to 0,1 mm (or
equivalent) at two different positions.
Record the mean value of the two measurements as the initial dimensions of the specimen.
Remove and dry the test specimens in a ventilated oven at 105 °C ± 5 K for (48 ± 1) h. After
cooling at room temperature in a desiccator, repeat the measurements as above.
6.2.2 Results
The dimensional changes lengthwise and crosswise are calculated for each specimen as the
per cent change in dimensions from those of the original conditioned specimen. Report all
calculated values and the means of the lengthwise and crosswise values.
7 Compressive strength and compression modulus
7.1 Purpose and principle of the test
The purpose of the test is to calculate the compressive strength and the compression modulus
of the material when the corrugation is submitted to a force applied on the corrugation and
perpendicular to the original plane of the corrugated material.
The perpendicular force is applied with the ends of the test specimens subjected to total
restraint (see figure 3).
– 10 – 61628-2 © IEC:1998+A1:2007
7.2 Test specimens
Cut five test specimens (50 ± 0,5) mm wide and five full wavelengths long unless the
wavelength is <10 mm, in which case a number of wavelengths to give a total length ≥50 mm
shall be used. If the wavelength is >60 mm, it is permitted to use three full wavelengths instead
of five. The ends of the test specimens are cut within 1 mm of the crest of a corrugation, or in
case of a angular type corrugation, within 1 mm of the centre line of a flat horizontal part.
The two end cuts shall be parallel to the corrugation and to each other within 0,1 mm.
Condition the test specimens in accordance with IEC 60641-2.
7.3 Test apparatus
The test apparatus shall consist of:
– a compression tester which will measure and record graphically the applied force with an
accuracy of ±1 % and the crosshead movement with a magnification of at least 10 times.
The crosshead speed shall be such that the end point of the test is reached within 10 s
to 30 s;
– a test specimen holder, (an example is shown in figure 3);
– a pressure plate whose dimensions cover completely all the crests of the specimen's
corrugations.
7.4 Procedure
– Place the test specimen in the test holder.
– Adjust the mobile end of the holder so that both ends touch evenly the ends of the test
specimen without exerting any lateral force.
– Place the pressure plate on the test specimen.
– With a calliper precise to 0,1 mm, measure the distance L between the pressure plate and
the bottom end part of the holder. Six measurements shall be made: three on each side of
the test specimen, one at each end and one at the centre of each side. L shall be recorded
as the mean value of these six measurements.
NOTE The pressure plate should be centred approximately on the test specimen and the pressure foot applied
centrally to the pressure plate. The offset of the axis of the load application from the centre of the test specimen
should be less than 5 mm.
– Record the force and the crosshead movement up to the point when the force increases
sharply after collapse (see figure 4).
7.5 Calculation
The force of failure is the value of the force at the first turning point (maximum or point of
inflection) at each force/movement graph.
The compressive strength of the test specimen is the force at failure divided by the projected
area of the test specimen and is usually expressed in megapascals (MPa).
The compression modulus is calculated as follows:
On the graph (see figure 4) mark the points A and B where the force reaches 25 % and 50 % of
the force at failure. Draw a straight line through A and B. This line crosses the deflection axis
at point C, at a distance λ from the origin.

61628-2 © IEC:1998+A1:2007 – 11 –
This value λ represents the settling of the test specimen when applying the force and is due to
the unevenness of the corrugation.
Δl is the difference between the deflection of the test specimen at point B and the deflection at
point A.
ΔF is the variation of the force between point B and point A.
The compression modulus is given by the formula:
Δ F
compression modulus =
Δ I
× S
L − λ
The value is expressed in megapascals (MPa).
In this formula:
ΔF is the force at point B minus force at point A expressed in newtons (N);
Δl is the deflection at point B minus deflection at point A expressed in millimetres (mm);
λ is the deflection at point C expressed in millimetres (mm);
L is the mean corrugation height measured as stated above, expressed in millimetres (mm);
S is the projected area of the test piece, expressed in square millimetres (mm ).
7.6 Results
7.6.1 Compressive strength
Report the mean value as the result; the highest and lowest values are reported.
7.6.2 Compression modulus
Report the mean value as the result; the highest and lowest values are reported.
8 Conductivity of aqueous extract
The conductivity of aqueous extract shall be measured according to IEC 60641-2.
...