BS英国标准BS EN 503562002 Method for spark testing of cables.doc

BRITISH STANDARD BS EN50356:2002Method for spark testing of cablesThe European Standard EN 50356:2002 has the status of aBritish StandardICS 29.060.20 BS 50356:2002National forewordThis British Standard is the official English language version ofEN 50356:2002. It partially supersedes BS 5099:1992.The UK participation in its preparation was entrusted by Technical Committee GEL/20, Electric cables, to Subcommittee GEL/20/17, Low voltage cables, which has the responsibility to:aid enquirers to understand the text;present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed;monitor related international and European developments and promulgate them in the UK.A list of organizations represented on this subcommittee can be obtained on request to its secretary.Cross-referencesThe British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard does not of itself confer immunity from legal obligations.This British Standard, having been prepared under the direction of the Electrotechnical Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on23 July 2002© BSI 23 July 2002ISBN 0 580 40133 2Summary of pagesThis document comprises a front cover, an inside front cover, the EN title page,pages 2 to 18, an inside back cover and a back cover.The BSI copyright date displayed in this document indicates when the document was last issued.Amd. No.DateCommentsAmendments issued since publicationEUROPEAN STANDARDEN 50356NORME EUROPÉENNEEUROPÄISCHE NORMApril 2002ICS 29.060.20English versionMethod for spark testing of cablesEssai diélectrique au défilement à sec des câbles électriquesDurchlaufspannungsprüfung an elektrischen Kabeln und LeitungenThis European Standard was approved by CENELEC on 2002-03-01. 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, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.CENELECEuropean Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische NormungCentral Secretariat: rue de Stassart 35, B - 1050 Brussels© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.Ref. No. EN 50356:2002 E- 5 -EN 50356:2002ForewordThis European Standard was prepared by the Technical Committee CENELEC TC 20, Electric cables.The text of the draft was submitted to the Unique Acceptance Procedure and was approved by CENELEC as EN 50356 on 2002-03-01.The following dates were fixed:-latest date by which the EN has to be implemented at national level by publication of an identicalnational standard or by endorsement(dop) 2003-03-01-latest date by which the national standards conflictingwith the EN have to be withdrawn(dow) 2005-03-01_ContentsIntroduction.41 Scope.52 Types of voltage waveform . 53 Procedure.54 Equipment .55 Test voltages.86 Sensitivity.87 Calibration .9Annex A (informative) Recommended minimum voltage levels. 14Annex B (informative) Example of an artificial fault device. 16Annex C (informative) Notes on the use of spark testing machines . 17Bibliography. 18Figure 1 Requirements for pulsed waveforms Rise time . 11Figure 2 Requirements for pulsed waveforms Fluctuation of peak value and pulse repetition rate . 12Figure 3 Requirements for pulsed waveforms Pulse duration . 13Figure B.1 Needle for use in the artificial fault device . 16IntroductionThe practice of using spark-testers to detect defects in the insulation or sheathing layers of electric cables has been developed over many years of practical experience.The operation of the equipment using the verification method described in this document has proved to be satisfactory. This method employs an artificial fault simulator and its performance has been shown to be comparable to that using operational efficacy tests involving the detection of artificially prepared defects (i.e. faults in the insulation/sheathing material) in lengths of cable.1ScopeThe spark-test method specified in this standard is intended for the detection of defects in the insulation or sheathing layers of electric cables. For single core cables with no outer metallic layer, the general process is accepted as being equivalent to subjecting samples of those cables to a voltage test in water.This standard specifies the operational requirements for the spark-test equipment, as well as the principal characteristics, functional parameters and calibration procedures for each type of test equipment.2Types of voltage waveformFor the purposes of this standard, the types of voltage waveform used for spark-testing are divided into the following groups:a.c.an alternating current (a.c.) voltage of approximately sine-wave form, at the industrial frequency of 40 Hz to 62 Hz;d.c. a direct current (d.c.) voltage;h.f. an alternating current (a.c.) voltage of approximately sine-wave form, at frequencies between500 Hz and 1 MHz;pulsed a voltage waveform comprising a fast rise time and highly damped wave-tail, as defined in 4.2.NOTE Provided the manufacturer can demonstrate equivalent effectiveness, h.f. voltages at frequencies below 500 Hz may be used.3ProcedureThe insulated conductor or sheathed cable shall be passed through an electrode energised at the test voltage. The method detailed in this standard provides for the application of a.c., d.c., h.f. and pulsed voltages.The requirements for voltage waveform, frequency and test voltage are given in 4.2 and clause 5. The maximum speed at which the cable shall pass through the electrode is determined by the minimum residence time specified in 4.6.When used as an alternative to a voltage test in water, it is recommended that the test be restricted to layer thicknesses not greater than 2,0 mm and to a.c. and d.c. test voltages.The requirements are not applicable to cable insulation having a rated voltage (U0) greater than 3 kV. Annex A provides recommended voltages for each voltage waveform, to be used in the absence ofany alternative voltages in the relevant cable standard.4Equipment4.1SafetyTo limit the effect of electrical shock to personnel, for all types of voltage source, the equipment shall be constructed such that the short-circuit current is limited to less than 10 mA r.m.s. or equivalent.This requirement is additional to, or may be superseded by, any national regulation that prevails at the time.NOTE Guidance on the limiting of shock currents can be found in IEC 60479-1 and IEC 60479-2.- 7 -EN 50356:2002Further aspects of operational safety are given in Annex C.4.2High voltage sourceThe high voltage electrode shall be supplied in one of the following forms, as defined in clause 2: a.c., d.c., h.f. or pulsed.For a d.c. test, connection to the test electrode shall be by means of a low capacitance unscreened lead. For d.c. and pulsed voltage testing, the test electrode may be either positive or negative polarity, the other pole being earthed.The requirements for pulsed waveforms are presented in Figures 1, 2 and 3.For pulsed waveforms, the rise time of the wave front shall reach 90 % of the specified peak value in less than 75 s see Figure 1. Fluctuations of the actual peak value, due to variations of input power into the generator, shall not exceed ± 2 % of the specified peak value see Figure 2. The peak value shall not show more than 5 % reduction in the event of an increase of capacitive load of 50 pF, during the operation, from an initial load of 25 pF between electrode and instrument ground. The time that each pulse remains at a voltage greater than 80 % of the specified peak voltage shall be between20 s and 100 s see Figure 3. The pulse repetition frequency shall be greater than 170 per second and less than 500 per second. This corresponds to pulse separations between 2 000 s and 5 880 s. Visible or audible corona shall be evident in the electrode structure when operating at the specified voltage.4.3Voltage monitoring equipmentFor a.c., d.c. and h.f. sources, the voltage between electrode and earth shall be displayed on a meter either by connection directly to the output terminal of the high voltage source or by any suitable equivalent arrangement. The measurement system shall have an accuracy of ± 5 % of the indicated value.For a pulse source there shall be a peak reading instrument voltmeter connected directly to the electrode, continually indicating the voltage at the electrode, with or without a grounded test wire in the test chamber. The peak reading voltmeter shall indicate full deflection at a peak value not exceeding25 kV and with a precision level of ± 5 % of the indicated value.NOTE If the spark-tester is to be controlled remotely, it should be noted that the current drawn by the cable under test can cause variation of the test voltage. In this situation, the regulation of the voltage source needs to be sufficient to maintain the voltage within the 5 % accuracy limit.4.4Fault indicatorThere shall be a detection circuit to provide a visible and/or audible indication of failure of the insulation or sheath to maintain the specified voltage. The fault detector shall be arranged to operate a digital display counter such that one count per discrete fault is registered. It shall also be of a totalizer type and cumulative to the end of the cable run. The counter shall maintain the indication until either the next succeeding fault is registered or until the indication is manually cancelled.4.5ElectrodesAn appropriate choice of electrode shall be made in order to obtain the maximum effective rate of detection.Types of cable to be tested (construction, materials, etc.) and the test conditions (linear speed, voltage source mode, etc.) form some of the parameters to be considered.Examples of electrode types are- contact types:bead chain, spring loaded hyperbola, brushes (rotating or fixed),- non-contact types:metallic tube, rings.4.6Design of electrodes4.6.1Contact typeThe electrode shall be of metallic construction and its length shall be such that every point of the insulated conductor or non-metallic sheath under test is in electrical contact with the electrode for times not less than the following:a) for a.c. supply to the electrode: 0,05 sNOTE 1 This time represents a maximum linear throughput speed of 1,2 m/min per millimetre of electrode. The minimum length of the electrode (mm) is therefore given by 0,833 v, where v is the linear throughput speed in m/min.b) for d.c. supply to the electrode : 0,001 sNOTE 2 This time represents a maximum linear throughput speed of 60 m/min per millimetre of electrode. The minimum length of the electrode (mm) is therefore given by 0,017 v, where v is the linear throughput speed in m/min.c) for h.f. supply to the electrode:0,002 5 sfwhere f is the supply frequency in kHz.NOTE 3 This time represents a maximum linear throughput speed of 24 f m/min per millimetre of electrode. The minimum length of the electrode (mm) is therefore given by 0,042 v/f, where v is the linear throughput speed in m/min.d) for pulse supply to the electrode:2,5 s