SIST EN 60383-1:1997

SLOVENSKI STANDARD
SIST EN 60383-1:1997
01-november-1997
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Insulators for overhead lines with a nominal voltage above 1 kV -- Part 1: Ceramic or
glass insulator units for a.c. systems - Definitions, test methods and acceptance criteria
Isolatoren für Freileitungen mit einer Nennspannung über 1 kV -- Teil 1: Keramik- oder
Glas-Isolatoren für Wechselstromsysteme - Begriffe, Prüfverfahren und
Annahmekriterien
Isolateurs pour lignes aériennes de tension nominale supérieure à 1 kV -- Partie 1:
Eléments d'isolateurs en matière céramique ou en verre pour systèmes à courant
alternatif - Définitions, méthodes d'essai et critères d'acceptation
Ta slovenski standard je istoveten z: EN 60383-1:1996
ICS:
01.040.29 Elektrotehnika (Slovarji) Electrical engineering
(Vocabularies)
29.080.10 Izolatorji Insulators
29.240.20 Daljnovodi Power transmission and
distribution lines
SIST EN 60383-1:1997 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60383-1:1997SIST EN 60383-1:1997

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SIST EN 60383-1:1997SIST EN 60383-1:1997

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SIST EN 60383-1:1997SIST EN 60383-1:1997

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SIST EN 60383-1:1997SIST EN 60383-1:1997

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SIST EN 60383-1:1997SIST EN 60383-1:1997

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SIST EN 60383-1:1997SIST EN 60383-1:1997

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SIST EN 60383-1:1997SIST EN 60383-1:1997

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SIST EN 60383-1:1997SIST EN 60383-1:1997
NORME
CEI
INTERNATIONALE IEC
383-1
INTERNATIONAL
Quatrième édition
STANDARD
Fourth edition
1993-04
Isolateurs pour lignes aériennes
de tension nominale supérieure à 1 000 V
Partie 1:
Eléments d'isolateurs en matière céramique
ou en verre pour systèmes à courant alternatif -
Définitions, méthodes d'essai et
critères d'acceptation
Insulators for overhead lines
with a nominal voltage above 1 000 V
Part 1:
Ceramic or glass insulator units for a.c. systems -
Definitions, test methods
and acceptance criteria
© CEI 1993 Droits de reproduction réservés — Copyright — all rights reserved
Aucune partie de cette publication ne peut être reproduite ni of this publication may be reproduced or utilized in
No part
utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,
cédé, électronique ou mécanique, y compris la photocopie et including photocopying and microfilm, without permission
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Genève, Suisse
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé
Commission Electrotechnique Internationale CODE PRIX /rr
/^I'1
International Electrotechnical Commission PRICE CODE
MemuiyHapoptian aneKTpoTexHH4ecHaP I4OMHCCHR
IEC
Pour prix, voir catalogue en vigueur
• •
For price, see current catalogue

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 ©IEC: 1993 - 3 -
CONTENTS
Page
FOREWORD 11
INTRODUCTION 13
Clause
Section 1: General
1 Scope and object 15
2 Normative references 17
3 Definitions 19
3.1 Insulator string 19
3.2 Pin insulator 19
3.3 Line post insulator 21
3.4 Traction insulator 21
3.5 Lot 21
3.6 Flashover 21
3.7 Dry lightning impulse withstand voltage 21
3.8 50 % dry lightning impulse flashover voltage 21
3.9 Wet power-frequency withstand voltage 21
3.10 Electromechanical failing load 21
3.11 Mechanical failing load 21
3.12 Puncture voltage 23
3.13 Creepage distance 23
3.14 Displacements 23
3.15 Sho rt standard string 23
3.16 Specified characteristics 23
Section 2: Insulators
4 Classification, types of insulators and insulating materials 25
4.1 Insulator classes 25
4.2 Insulator types 25
4.3 Insulating materials 25
5 Identification of insulators 27
Section 3 - Classification of tests,
sampling rules and procedures
6 Classification of tests 27
6.1 Type tests 27
6.2 Sample tests 29
6.3 Routine tests 29
7 Quality assurance 29

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 ©IEC: 1993 – 5 –
Clause Page
8 Procedures for type and sample tests 31
8.1 Insulator selection for type tests 31
8.2 Sampling rules and procedures for sample tests 31
8.3 Re-test procedure for sample tests 31
Section 4: Test procedures for electrical tests
9 General requirements for high voltage tests 33
10 Standard atmospheric conditions and correction factors
for electrical tests 35
10.1 Standard reference atmosphere 35
10.2 Correction factors for atmospheric conditions 35
11 Artificial rain parameters for wet tests 35
12 Mounting arrangements for electrical tests 35
13 Lightning impulse voltage tests (type test) 35
13.1 Test procedure 37
13.2 Acceptance criteria 37
14 Wet power-frequency voltage tests (type test) 37
14.1 Test procedure 37
14.2 Acceptance criteria 39
15 Puncture withstand test (sample test, for class B insulators only) 39
15.1 Power-frequency puncture withstand test 39
15.2 Impulse overvoltage puncture withstand test 41
16 Routine electrical test (only on class B insulators of ceramic material
41
or annealed glass)
Section 5: Test procedures for
mechanical and other tests
17 Verification of the dimensions (type and sample test) 43
18 Electromechanical failing load test (type and sample test) 43
18.1 Test procedure 43
18.2 Acceptance criteria 45
19 Mechanical failing load test (type and sample test) 45
19.1 Test procedure for pin and line post insulators 45
19.2 Test procedure for string insulator units 45
19.3 Acceptance criteria for pin insulators 45
19.4 Acceptance criteria for string insulator units and line post insulators 47

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 ©I EC: 1993 – 7 —
Clause Page
20 Thermal-mechanical performance test (type test) 49
20.1 Test procedure 49
20.2 Acceptance criteria 49
21 Verification of the axial, radial and angular displacements (sample test) 51
21.1 Test procedure 51
21.2 Acceptance criteria for cap and pin insulators 51
21.3 Acceptance criteria for long rod insulators 53
22 Verification of the locking system (sample test) 53
22.1 Conformity of the locking device 53
22.2 Verification of locking 53
22.3 Position of the locking device 55
22.4 Procedure for the operation test 55
22.5 Acceptance criteria for the operation test 55
57
23 Temperature cycle test (sample test)
23.1 Test procedure for string insulator units, pin insulators and
line post insulators composed of ceramic material 57
23.2 Test procedure for string insulator units, pin insulators and
line post insulators composed of annealed glass 57
23.3 Special test procedure for insulators with thick sections or very large
insulators 59
23.4 Complementary specifications 59
59
23.5 Acceptance criteria
61
24 Thermal shock test (sample test)
24.1 61
Test procedure
61
24.2 Acceptance criteria
61
25 Porosity test (sample test)
61
25.1 Test procedure
25.2 Acceptance criteria 61
26 Galvanizing test (sample test) 61
26.1 Test procedures 63
26.1.1 Appearance 63
26.1.2 Determination of the coating mass by the magnetic
63
test method
26.2 Acceptance criteria 63
26.2.1 Acceptance criteria for the appearance test 63
26.2.2 Acceptance criteria for the value of coating mass 65
27 Routine visual inspection 65
27.1 Insulators with ceramic insulating parts 65
27.2 67 Insulators with glass insulating parts
28 Routine mechanical test 67
28.1 Routine mechanical test on line post insulators 67
28.2 Routine mechanical test on string insulator units 69

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 ©
IEC: 1993 – 9 –
Clause Page
Section 6: Pin insulators
29 Mounting arrangements for tests on pin insulators 71
29.1 Standard mounting arrangement for electrical tests 71
29.2 Mounting arrangements for electrical tests reproducing
service conditions 73
29.3 Mounting arrangement for the mechanical failing load test 73
Section 7: Line post insulators
30 Coefficients for statistical analysis of the test results on
line post insulators 75
30.1 Coefficient for type tests 75
30.2 Coefficients for sample tests 75
31 Mounting arrangements for tests on line post insulators 77
31.1 Standard mounting arrangement for electrical tests 77
31.2 Mounting arrangements for electrical tests reproducing
service conditions 79
31.3 Mounting arrangement for the mechanical failing load test 79
Section 8: String insulator units
32 Prescriptions concerning type tests on string insulators 81
32.1 Electrical type tests on string insulators 81
32.2 Mechanical type tests 83
33 Coefficients for statistical analysis of the test results on string insulators 83
33.1 Coefficient for type tests 83
33.2 Coefficients for sample tests 83
34 Mounting arrangements for electrical tests on string insulator units 87
Section 9: Insulators for overhead electric traction lines
35 Mounting arrangements for electrical tests on insulators for
overhead electric traction lines 89
35.1 Standard mounting arrangement 89
35.2 Mounting arrangement representing service conditions 89
Figures 91
Annexes
A Method of comparison of the results of electromechanical or mechanical type
and sample tests 93
B Illustration of the mechanical and electromechanical test acceptance procedure
for string insulator units and line post insulators 97
C List of normative documents given for information 109

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 © IEC: 1993 -11 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
INSULATORS FOR OVERHEAD LINES
WITH A NOMINAL VOLTAGE ABOVE 1 000 V
Part 1: Ceramic or glass insulator units
for a.c. systems -
Definitions, test methods and acceptance criteria
FOREWORD
1)
The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
Their preparation is entrusted to technical committees; any IEC National Committee interested in
the subject dealt with may participate in this preparatory work. International, governmental and
non-governmental organizations liaising with the IEC also participate in this preparation. The IEC
collaborates closely 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 the IEC on technical matters, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
3) They have the form of recommendations for international use published in the form of standards, technical
reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
International Standard IEC 383-1 has been prepared by sub-committee 36B: Insulators for
overhead lines, of IEC technical committee 36: Insulators.
Part 1, together with Part 2, replaces the third edition of IEC 393 (1983) and constitutes a
technical revision.
The text of this standard is based on the following documents:
Six Months' Rule Report on Voting Two Months' Procedure Repo rt on Voting
36B(CO)87-I and ll 36B(CO)91
36B(CO)95 36B(CO)97 and 97A
36B(CO)89 36B(CO)93
Full information on the voting for the approval of this standard can be found in the reports
on voting indicated in the above table.
IEC 383 consists of the following parts, under the general title: Insulators for overhead
lines with a nominal voltage above 1 000 V.
-
Part 1: Ceramic or glass insulator units for a.c. systems - Definitions, test methods
and acceptance criteria
- Part 2: Insulator strings and insulator sets for a.c. systems - Definitions, test
methods and acceptance criteria
Annexes A, B and C are for information only.

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 © IEC: 1993 –13 –
INTRODUCTION
This part of IEC 383 is divided into nine sections.
The first five sections cover general clauses, including general requirements and relevant
test procedures.
Sections six to nine deal with four different types of insulators:
Section 6: Pin insulators
Section 7: Line post insulators
Section 8: String insulator units
Section 9: Insulators for overhead electric traction lines.
Sections 6, 7 and 8 begin with a cross-reference table giving the tests applicable to the
insulators and the quantity of insulators to be tested.
Section 9, dealing with traction insulators, does not have a cross-reference table as
traction insulators can be referenced to one of the three other types of insulator dealt with
by this part of IEC 383.
The user of this part need only refer to the section dealing with the type of insulator to be
tested and to the general requirements and relevant test procedures contained in sections
one to five.

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 ©IEC: 1993 - 15 -
INSULATORS FOR OVERHEAD LINES
WITH A NOMINAL VOLTAGE ABOVE 1 000 V
Part 1: Ceramic or glass insulator units
for a.c. systems -
Definitions, test methods and acceptance criteria
Section 1: General
1 Scope and object
This pa rt of IEC 383 applies to insulators of ceramic material or glass for use on a.c.
overhead power lines and overhead traction lines with a nominal voltage greater than
1 000 V and a frequency not greater than 100 Hz.
It also applies to insulators for use on d.c. overhead electric traction lines.
This part applies to string insulator units, rigid overhead line insulators and to insulators of
similar design when used in substations.
It does not apply to insulators forming pa rts of electrical apparatus or to pa rts used in their
construction or to post insulators which are covered by IEC 168: Tests on indoor and
outdoor post insulators of ceramic material or glass for systems with nominal voltages
greater than 1 000 V.
It may be regarded as a provisional standard for insulators for use on d.c. overhead power
lines. IEC 438: Tests and dimensions for high-voltage d.c. insulators, gives general
guidance for those insulators.
NOTE - An international standard dealing with tests on insulators for d.c. overhead lines is in preparation
and is intended to replace the relevant clauses of IEC 438.
Tests on insulator strings and insulator sets (for example, wet switching impulse voltage)
are dealt with in pa rt 2 of IEC 383.
NOTES
1 This part does not include artificial pollution tests, radio-interference tests or residual strength tests.
These subjects and relevant test methods are dealt with in the following IEC repo rts:
IEC 437: Radio interference test on high-voltage insulators
IEC 507: Artificial pollution tests on high-voltage insulators to be used on a.c. systems
IEC 797: Residual strength of string insulator units of glass or ceramic material for overhead lines after
mechanical damage of the dielectric.
2 The term "ceramic material" is used in this part to refer to porcelain materials and, contrary to North
American practice, does not include glasses.

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 © IEC: 1993 -17 -
The object of this part is:
- to define the terms used;
- to define insulator characteristics and to prescribe the conditions under which the
specified values of these characteristics shall be verified;
- to prescribe test methods;
- to prescribe acceptance criteria.
This part does not include requirements dealing with the choice of insulators for specific
operating conditions.
NOTE - A guide for the choice of insulators under polluted conditions has been published, see IEC 815.
Numerical values for insulator characteristics are specified in IEC 305, IEC 433 and
IEC 720.
2 Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this part of IEC 383. At the time of publication, the editions
indicated were valid. All normative documents are subject to revision, and pa rties to
agreements based on this part of IEC 383 are encouraged to investigate the possibility of
applying the most recent edition of the normative documents indicated below. Members of
IEC and ISO maintain registers of currently valid International Standards.
IEC 50(471): 1984, International Electrotechnical Vocabulary (IEV) - Chapter 471:
Insulators
IEC 60-1: 1989, High-voltage test techniques - Pa rt 1: General definitions and test
requirements
IEC 120: 1984, Dimensions of ball and socket couplings of string insulator units
IEC 305: 1978,
Characteristics of string insulator units of the cap and pin type
IEC 372: 1984, Locking devices for ball and socket couplings of string insulation units:
Dimensions and tests
IEC 433: 1980, Characteristics of string insulator units of the long rod type
IEC 471: 1977, Dimensions of clevis and tongue couplings of string insulator units
IEC 720: 1981, Characteristics of line post insulators
IEC XXX: 19XX,
Puncture testing of insulators of glass or ceramic material for overhead
lines with a nominal voltage greater than 1 000 V (under consideration)

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 © IEC: 1993 -19 -
ISO 1459: 1973,
Metallic coatings - Protection against corrosion by hot dip galvanizing -
Guiding principles
ISO 1460: 1973, Metallic coatings - Hot dip galvanized coatings on ferrous metals -
Determination of the mass per unit area - Gravimetric method
ISO 1461: 1973, Metallic coatings - Hot dip galvanized coatings on fabricated ferrous
products - Requirements
ISO 1463: 1982, Metal and oxide coatings - Measurement of coating thickness -
Microscopical method
ISO 2064: 1980,
Metallic and other non-organic coatings - Definitions and conventions
concerning the measurement of thickness
ISO 2178: 1982, Non-magnetic coatings on magnetic substrates - Measurement of
coating thickness - Magnetic method
3 Definitions
For the purposes of this part of 'EC 383, the following definitions apply.
The term "insulator" is used in this pa rt to refer to the object being tested.
The definitions given below are those which either do not appear in 1EC 50(471) or differ
from those given in IEC 50(471).
3.1 Insulator string
One or more connected string insulator units intended to give flexible suppo rt to overhead
line conductors and stressed mainly in tension.
3.2 Pin insulator
A rigid insulator consisting of an insulating component intended to be mounted rigidly on a
supporting structure by means of a pin passing up inside the insulator. The insulating
component may consist of one or more pieces of insulating material permanently
connected together. The fixing of the insulating component to the pin can either be
separable or permanent (pin insulator with integral pin).
Unless otherwise stated, the term "pin insulator" does not include the pin if separable.
NOTE - The pin can have two basic shapes. With one shape, the insulating component is fixed to the end
of the pin and does not allow contact of the insulating component with the supporting structure. With the
other shape, the insulating component is fixed by means of the pin in contact with the supporting structure
either directly or with a plate in between, the plate being either a separate washer or part of the pin
(sometimes referred to as a pin post insulator).

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 ©IEC: 1993 – 21 –
3.3 Line post insulator
A rigid insulator consisting of one or more pieces of insulating material permanently
assembled with a metal base and sometimes a cap intended to be mounted rigidly on a
supporting structure with the metal base attached by means of a stud or one or several
bolts.
3.4 Traction insulator
An insulator or insulator set intended to give flexible or rigid support for overhead electric
traction lines. All types of overhead line insulators may be used for this purpose.
3.5 Lot
A group of insulators offered for acceptance from the same manufacturer, of the same
design and manufactured under presumed similar conditions of production. One or more
lots may be offered together for acceptance; the lot(s) offered may consist of the whole, or
part, of the quantity ordered.
3.6 Flashover
A disruptive discharge external to the insulator, connecting those parts which normally
have the operating voltage between them.
NOTE - The term "flashover" used in this part includes a flashover across the insulator surface as well as
disruptive discharges by sparkover through air adjacent to the insulator.
3.7 Dry lightning impulse withstand voltage
The lightning impulse voltage which the insulator withstands dry, under the prescribed
conditions of test.
3.8 50 % dry lightning impulse flashover voltage
The value of the lightning impulse voltage which, under the prescribed conditions of test,
has a 50 % probability of producing flashover on the insulator, dry. Represented by
U50.
3.9 Wet power-frequency withstand voltage
The power-frequency voltage which the insulator withstands wet, under the prescribed
conditions of test.
3.10 Electromechanical failing load
The maximum load reached when a string insulator unit is tested under the prescribed
conditions of test.
3.11 Mechanical failing load
The maximum load reached when a string insulator unit or a rigid insulator is tested under
the prescribed conditions of test.

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 © I EC: 1993 — 23 —
3.12
Puncture voltage
The voltage which causes puncture of a string insulator unit or a rigid insulator under the
prescribed conditions of test.
3.13 Creepage distance
The shortest distance or the sum of the shortest distances along the ceramic or glass
insulating parts of the insulator between those parts which normally have the operating
voltage between them.
NOTE - The surface of cement or other non-insulating jointing material is not considered as forming part
of the creepage distance. If high resistance coating is applied to parts of the insulating pa rt of an insulator
such pa rts are considered to be effective insulating surfaces and the distance over them is included in the
creepage distance.
3.14
Displacements
Axial or radial displacement
The maximum positional variation of a definite point of the considered insulator during one
complete revolution around the insulator axis.
Angular displacement
The angular deviation around the insulator axis between corresponding planes of the two
coupling pieces.
3.15
Short standard string
A short standard string is used to verify characteristics of a unit which are significant only
for an insulator string. It consists of:
For cap and pin units:
An insulator string of a least 5 insulator units and not more than 1,5 m in length.
For long rod insulator units:
An insulator string between 1 m and 2 m in length for long rod insulator units intended to
be assembled in a string. For long rod insulator units less than 1 m long intended to be
used singly as a string, the unit itself is considered as a short standard string.
3.16 Specified characteristics
A specified characteristic is:
— either the numeric value of a voltage or of a mechanical load or any other
characteristic specified in an !EC international standard;
— or the numeric value of any such characteristic agreed between the purchaser and
the manufacturer.
Specified withstand and flashover voltages are referred to standard atmospheric
conditions (see clause 10).

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 © IEC: 1993 – 25 –
Section 2: Insulators
4 Classification, types of insulators and insulating materials
4.1
Insulator classes
Overhead line string insulators are divided into two classes according to their design:
Class A: an insulator or insulator unit in which the length of the shortest puncture path
through solid insulating material is at least equal to half the arcing distance. An example
of a class A insulator is a long rod insulator with external fittings.
Class B:
an insulator or insulator unit in which the length of the shortest puncture path
through solid insulating material is less than half the arcing distance. An example of a
class B insulator is a cap and pin insulator.
4.2
Insulator types
For the purposes of this part of IEC 383, overhead line insulators are divided into the four
following types:
– pin insulators
- line post insulators
- string insulator units, divided into two sub-types:
• cap and pin insulators
• long rod insulators
insulators for overhead electric traction lines
NOTE - Insulators for overhead traction lines are normally insulators of one of the first three types above,
with or without special adaptations of the metal fittings, designed for use on overhead electric traction
lines.
4.3 Insulating materials
The insulating materials of overhead line insulators covered by this pa rt
are:
– ceramic material, porcelain;
– annealed glass, being glass in which the mechanical stresses have been relaxed by
thermal treatment;
– toughened glass, being glass in which controlled mechanical stresses have been
induced by thermal treatment.
NOTES
1 Further information on the definition and classification of ceramic and glass insulating materials can be
found in IEC 672-1 and IEC 672-3.
rth
2 The term "ceramic material" is used in this part to refer to porcelain materials and, contrary to No
American practice, does not include glass.

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 ©IEC:1993 – 27 –
5 Identification of insulators
Each insulator shall be marked, either on the insulating component or on a metal pa rt, with
the name or trade mark of the manufacturer and the year of manufacture. In addition, each
string insulator unit shall be marked with the specified electromechanical or mechanical
failing load whichever is applicable. These markings shall be legible and indelible.
The designations included in IEC 305, IEC 433 and IEC 720 may be used.
Section 3: Classification of tests,
sampling rules and procedures
6 Classification of tests
The tests are divided into three groups as follows:
6.1 Type tests
Type tests are intended to verify the main characteristics of an insulator which depend
mainly on its design. They are usually carried out on a small number of insulators and only
once for a new design or manufacturing process of insulator and then subsequently
repeated only when the design or manufacturing process is changed. When the change
affects only certain characteristics, only the test(s) relevant to these characteristics need
to be repeated. Moreover, it is not necessary to perform the electrical, mechanical and
thermal-mechanical type tests on a new design of insulator if a valid test certificate is
available on an insulator of equivalent design and same manufacturing process. The
meaning of equivalent design is given in the relevant clauses when applicable. The results
of type tests are certified either by test certificates accepted by the purchaser or by test
certificates confirmed by a qualified organization.
For mechanical tests, the certificate shall be valid for ten years from the date of issue.
There is no time limit for the validity of certificates for electrical type tests.
Within the above limits, the type test certificates remain valid while there is no significant
disparity between the results of the type tests and subsequent corresponding sample
tests. A method for comparing type and sample test results is given in annex A.
Type tests shall be carried out only on insulators from a lot which meets the requirements
of all the relevant sample and routine tests not included in the type tests.

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SIST EN 60383-1:1997SIST EN 60383-1:1997
383-1 © l EC: 1993 – 29 –
6.2 Sample tests
Sample tests are carried out to verify the characteristics of an insulator which can vary
with the manufacturing process and the quality of the component materials of the
insulator. Sample tests are used as acceptance tests on a sample of insulators taken at
random from a lot which has met the requirements of the relevant routine tests.
NOTE - The acceptance coefficients and sample sizes used in this part of IEC 383 for the statistical
evaluation of results by variables have been chosen to reproduce as closely as possible the operating
characteristic
...