BS-EN-60243-3-1994 IEC-60243-3-1993.pdf

BRITISH STANDARD BS EN 60243-3:1994 IEC 243-3: 1993 Methods of test for Electric strength of solid insulating materials Part 3: Additional requirements for impulse tests The European Standard EN 60243-3:1994 has the status of a British Standard UDC 621.315.61:620.1:621.317.333.8 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 60243-3:1994 This British Standard, having been prepared under the direction of the Cables and Insulation Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 May 1994 © BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference CIL/15 Special announcement in BSI News March 1994 ISBN 0 580 23316 2 Cooperating organizations The European Committee for Electrotechnical Standardization (CENELEC), under whose supervision this European Standard was prepared, comprises the national committees of the following countries: AustriaItaly BelgiumLuxembourg DenmarkNetherlands FinlandNorway FrancePortugal GermanySpain GreeceSweden IcelandSwitzerland IrelandUnited Kingdom Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 60243-3:1994 © BSI 01-2000i Contents Page Cooperating organizationsInside front cover National forewordii Foreword2 Text of EN 60243-33 National annex NA (informative) Committees responsibleInside back cover National annex NB (informative) Cross-referenceInside back cover Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 60243-3:1994 ii © BSI 01-2000 National foreword This British Standard has been prepared under the direction of the Cables and Insulation Standards Policy Committee and is the English language version of EN 60243-3:1994 Methods of test for electric strength of solid insulating materials Part 3: Additional requirements for impulse tests, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC 243-3:1993 published by the International Electrotechnical Commission (IEC). A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 60243-3 January 1994 UDC 621.315.61:620.1:621.317.333.8 Descriptors: Solid electrical insulating materials, tests, determination, electric strength, impulse voltage strength English version Methods of test for electric strength of solid insulating materials Part 3: Additional requirements for impulse tests (IEC 243-3:1993) Méthodes dessai pour la détermination de la rigidité diélectrique des matériaux isolants solides Partie 3: Prescriptions complémentaires pour les essais de choc (CEI 243-3:1993) Prüfverfahren zur Bestimmung der elektrischen Durchschlagfestigkeit von festen, isolierenden Werkstoffen Teil 3: Zusätzliche Festlegungen für Stoßspannungsprüfungen (IEC 243-3:1993) This European Standard was approved by CENELEC on 1993-12-08. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels © 1994 Copyright reserved to CENELEC members Ref. No. EN 60243-3:1994 E Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60243-3:1994 © BSI 01-2000 2 Foreword The text of document 15A(CO)65, as prepared by Sub-Committee 15A: Short-time tests, of IEC Technical Committee 15: Insulating materials, was submitted to the IEC-CENELEC parallel vote in March 1993. The reference document was approved by CENELEC as EN 60243-3 on 8 December 1993. The following dates were fixed: Annexes designated “normative” are part of the body of the standard. In this standard, Annex ZA is normative. Contents Page Foreword2 Introduction3 1Scope3 2Normative reference3 3Definitions3 4Significance of the tests3 5Electrodes and specimens4 6Conditioning before tests4 7Surrounding medium4 8Electrical apparatus4 9Procedure4 10Application of voltage4 11Criterion of breakdown5 12Number of tests5 13Report5 Annex ZA (normative) Other international publications quoted in this standard with the references of the relevant European publications7 Figure 1 Full impulse-voltage wave6 Figure 2 Electrode arrangement for tests on shaped insulating parts6 latest date of publication of an identical national standard(dop) 1994-12-01 latest date of withdrawal of conflicting national standards(dow) 1994-12-01 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60243-3:1994 © BSI 01-20003 Introduction This part of IEC 243 is one of a series which deals with tests for electric strength of solid insulating materials. The series will consist of four parts: Part 1: Tests at power frequencies; (IEC 243-1) Part 2: Additional requirements for tests using direct voltage; (IEC 243-2) Part 3: Additional requirements for impulse tests; (IEC 243-3) Part 4: Statistical treatment and interpretation. (IEC 243-4) (under consideration) 1 Scope This part of IEC 243 gives requirements, additional to those in IEC 243-1, for the determination of the electric strength of solid insulating materials under impulse voltage stress. NOTEThis part is based upon ASTM Method D3426, to which it is intended to be technically identical. 2 Normative reference The following normative document contains provisions which, through reference in this text, constitute provisions of this part of IEC 243. At the time of publication, the edition indicated was valid. All normative documents are subject to revision, and parties to agreements based on this part of IEC 243 are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 243-1:1988, Methods of tests for electric strength of solid insulating materials Part 1: Tests at power frequencies. 3 Definitions For the purpose of this part of IEC 243, the following definitions, together with those given in clause 2 of IEC 243-1, apply. 3.1 full-impulse-voltage wave an aperiodic transient voltage that rises rapidly to a maximum value, then falls less rapidly to zero 3.2 peak value (of an impulse-voltage wave), Up the maximum value of voltage 3.3 virtual peak value (of an impulse-voltage wave), U a value derived from a recording of an impulse-voltage wave on which high-frequency oscillations, or overshoot of a limited magnitude, may be present 3.4 virtual origin (of an impulse-voltage wave) the point of intersection O1 with the line of zero voltage of a line drawn through the points of 0,3 and 0,9 times the virtual peak value on the front of an impulse-voltage wave (see Figure 1) 3.5 virtual front time (of an impulse-voltage wave) equal to 1,67 times the interval tf between the instants when the voltage is 0,3 and 0,9 times the peak value (t1, Figure 1) 3.6 virtual time to half-value the time interval t2 between the virtual origin 01 and the instant on the tail when the voltage has decreased to half the peak value 4 Significance of the tests In addition to the information of clause 3 of IEC 243-1 which is applicable, the following points shall be considered when using impulse-voltage tests: 4.1 Insulating materials used in high-voltage equipment may be subjected to transient voltage stresses resulting from such causes as nearby lightning strokes. This is particularly true of apparatus such as transformers and switchgears used in electrical power transmission and distribution systems. The ability of insulating materials to withstand these transient voltages is important in establishing the reliability of apparatus insulated with these materials. 4.2 Transient voltages caused by lightning may be of either positive or negative polarity. In a symmetrical field between identical electrodes, the polarity has no effect on the electric strength. However, with dissimilar electrodes, there may be a pronounced polarity effect. It is common practice, when using dissimilar electrodes, to make negative that electrode at which the higher gradient will appear. When assymetrical electrodes are used for testing materials with which the tester has no previous experience or knowledge, it is recommended that comparative tests be made with both directions of polarity. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60243-3:1994 4 © BSI 01-2000 4.3 The standard wave shape is a 1,2/50 4s wave, reaching peak voltage in approximately 1,2 4s, and decaying to 50 % of peak value in approximately 50 4s after the beginning of the wave. This wave is intended to simulate a lightning stroke that may strike a system without causing failure on the system. NOTEIf the object being tested has appreciable inductive characteristics, it may be difficult or impossible to attain the specified wave shape with less than 5 % oscillations, as given in 8.2.2. However, the procedures given in this publication are expected ordinarily to be applied to configurations of specimens and electrodes which are primarily capacitive. Testing of more complex configurations, such as between coils of completed apparatus or models of such apparatus, should be performed in accordance with the specifications for that apparatus. 4.4 Because of the short time involved, dielectric heating, other thermal effects and the influence of injected space-charges may be reduced during impulse testing of most materials. Thus, impulse tests usually give higher values than the voltage peak of short-term a.c. tests. From comparisons of the impulse electric strength with the values drawn from longer time tests, inferences may be drawn as to the modes of failure under the various tests for a given material. 5 Electrodes and specimens 5.1 Clause 4 of IEC 243-1 is applicable. 5.2 Tests on shaped insulating pieces which cannot be placed between electrodes with flat faces should be made using opposing identical spherical electrodes. Commonly used electrodes for tests of this nature have diameters of 12,5 mm or 20 mm (see Figure 2). 6 Conditioning before tests Clause 5 of IEC 243-1 is applicable. 7 Surrounding medium Clause 6 of IEC 243-1 is applicable. 8 Electrical apparatus 8.1 Voltage source The test voltage applied to the electrode shall be provided by an impulse generator having the following characteristics. 8.1.1 A choice of either positive or negative polarity shall be provided, one of the connections to the electrodes being earthed. 8.1.2 Controls within the generator shall be capable of adjusting the shape of the wave applied to the specimen under test to have a virtual front time of 1,2 4s ± 0,36 4s, and virtual time to half-value of 50 4s ± 10 4s (see Figure 1). 8.1.3 The voltage capability and energy-storage capacity of the generator shall be sufficient to apply impulse waves of the proper shape to any specimens to be tested, up to the breakdown voltage or specified proof voltage of the material. 8.1.4 The peak value of the voltage is taken as the virtual peak value, provided that the conditions of 8.2.2 are satisfied. 8.2 Voltage measurement 8.2.1 Provision shall be made for recording the voltage wave as applied to the test specimen, and for measuring the virtual peak voltage, the virtual front time and the virtual time to half-value within ± 5 % of the true value. 8.2.2 If the voltage wave has oscillations with a magnitude of no more that 5 % of the peak value, and a frequency of at least 0,5 MHz, a mean curve may be drawn, the maximum amplitude of which is the virtual peak value. If the oscillations are of greater magnitude, or of lower frequency, the voltage wave is not acceptable for a standard test. 9 Procedure Clause 8 of IEC 243-1 is applicable. 10 Application of voltage 10.1 The voltage impulses shall be applied in an increasing series of sets of three waves. The peak voltage of the initial set should be approximately 70 % of the expected breakdown voltage. 10.2 Increase the peak voltage of each set by 5 % to 10 % of the peak value of the first set. Table I of IEC 243-1 is applicable. 10.3 Allow sufficient time between successive impulses for the generator to become completely charged. Normally a time of three times the charging time constant for the generator is sufficient. 10.4 Sufficient time shall also be allowed between successive impulses to allow dissipation of any injected space-charge. For many materials, the charging time of the generator will cover this eventuality. For materials having a longer space-charge retention period, this should be specified in the material specification sheet. If this information is not known, but a long space-charge retention period is suspected, then additional tests should be run with longer intervals between impulses, to determine if a significant difference in breakdown values is obtained. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 60243-3:1994 © BSI 01-20005 10.5 A valid test on a specimen is one in which impulse waves are applied at at least two voltage levels without failure, before failure occurs at the th