Bsi bs en 50483 5 2009

BS EN 50483-5:2009 BSI British Standards ak e co m Test requirements for low voltage aerial bundled cable accessoriess — w w w b ab Part 5: Electrical ageing geing test NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW raising standards worldwide™ BRITISH STANDARD BS EN 50483-5:2009 National foreword This British Standard is the UK implementation of EN 50483-5:2009 The UK participation in its preparation was entrusted by Technical Committee GEL/20, Electric cables, to Subcommittee GEL/20/11, Cable accessories A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © BSI 2009 ISBN 978 580 56181 ICS 29.240.20 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2009 Amendments issued since publication Date w w w b ab ak e co m Amd No Text affected BS EN 50483-5:2009 EUROPEAN STANDARD EN 50483-5 NORME EUROPÉENNE January 2009 EUROPÄISCHE NORM ICS 29.240.20 English version Test requirements for low voltage aerial bundled cable accessories Part 5: Electrical ageing test Prüfanforderungen für Bauteile für isolierte Niederspannungsfreileitungen Teil 5: Elektrische Alterungsprüfungen co m Prescriptions relatives aux essais des accessoires pour réseaux aériens basse tension torsadés Partie 5: Essai de vieillissement électrique ab ak e This European Standard was approved by CENELEC C on n 200 2008 2008-12-01 CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which the conditions for giving this European Standard ch h stipulate stipula stipul the status of a national standard without any alteration ration ation w b Up-to-date lists and bibliographical references such national standards may be obtained on rences concerning c application to the Central Secretariat or to CENELEC member o any CE C w w This European Standard exists in versions (English, French, German) A version in any other n three official o language made by translation under nder er the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same sam status as the official versions CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: avenue Marnix 17, B - 1000 Brussels © 2009 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members Ref No EN 50483-5:2009 E BS EN 50483-5:2009 EN 50483-5:2009 –2– Foreword This European Standard was prepared by a sub-group of WG 11 of the Technical Committee CENELEC TC 20, Electric cables The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50483-5 on 2008-12-01 The following dates were fixed: – – latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2009-12-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2011-12-01 This is Part of CENELEC standard EN 50483 “Test requirements for low voltage aerial bundled cable accessories”, which has six parts: – Part 1: Generalities; – elff supp Part 2: Tension and suspension clamps for self supporting system; – neu Part 3: Tension and suspension clamps for neutral messenger system; – Part 4: Connectors; – Part 5: Electrical ageing test; – Part 6: Environmental testing BS EN 50483-5:2009 –3– EN 50483-5:2009 Contents Scope Normative references Terms and definitions Symbols Type test 5.1 5.2 5.3 5.4 5.5 5.6 Annex A Principle Test arrangement Test specimen 11 Measurement 13 Heat cycle 15 Requirements 19 (normative) Equalizers 29 Annex B (informative) Determination of the value of the short-circuit current 31 Annex C (informative) Recommendations to improve accuracy of measurement 32 Bibliography 33 co m Figures e g paths aths 10 Figure – Lengths and configurations of conducting Figure – Location of thermocouples 14 ak ZZZE]I[ZFRP ZZ Z ab Figure – First heat cycle 17 b Figure – Use of a concentric return conductor duc uc 18 w w Figure – Test loop for branch connectors ctors tors w with main and branch conductors having equal cross-sections and d linear inear resistances 24 w Figure – Test loop for branch connect connectors nnec with main and branch conductors having unequal cross-sections and linear resistances 25 s an Figure – Test loop for through connectors with conductors having equal or unequal cross-sections and linear resistances 26 Figure – Test loop for pre-insulated lugs 28 Figure A.1 – Equalizers 30 Figure B.1 – Diagram of short-circuit current 31 Tables Table – Conducting path lengths 11 Table – Testing cross-sections of main and branch conductors 12 Table – Minimum elevated current heating time 16 Table – Test requirements 23 Table A.1 – Dimensions of equalizers 29 BS EN 50483-5:2009 EN 50483-5:2009 –4– Scope EN 50483 series applies to overhead line fittings for tensioning, supporting and connecting aerial bundled cables (ABC) of rated voltage U /U (U m ): 0,6/1 (1,2) kV This Part applies to the connections described in EN 50483-4, including branch connectors, Insulation Piercing Connectors (IPC), pre-insulated lugs (terminals) and through pre-insulated connectors (sleeves) The objective is to provide a method of testing the suitability of connectors when used under normal operating conditions with low voltage aerial bundled cables complying with HD 626 Two classes of connectors are covered by this standard: Class A: These are connectors intended for electricity distribution or industrial networks in which they can be subjected to short-circuits of relatively high intensity and duration As a consequence, Class A connectors will be suitable for the majority of applications Class B: These are connectors for networks in which overloads or short-circuits are rapidly cleared by the operation of protection devices co m ected ted to heat cycles and short-circuit Depending on their application, the connectors are subjected current tests e les es and short-circuit current tests Class A: the connectors are subjected to heat cycles ak ZZZE]I[ZFRP ZZ ab Class B: the connectors are subjected to heat cycles only w w w b e heati The object of this Part is to define the heating cycles test methods and requirements which ctors, tors, insulation in i apply to compression through connectors, piercing connectors and all other type of ndled cables connections for low voltage aerial bundled NOTE This European Standard does not invalidate existing approvals of products achieved on the basis of national standards and specifications and/or the demonstration of satisfactory service performance However, products approved according to such national standards or specifications cannot directly claim approval to this European Standard It may be possible, subject to agreement between supplier and purchaser, and/or the relevant conformity assessment body, to demonstrate that conformity to the earlier standard can be used to claim conformity to this standard, provided an assessment is made of any additional type testing that may need to be carried out Any such additional testing that is part of a sequence of testing cannot be done separately Normative references 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 EN 50483 series, Test requirements for low voltage aerial bundled cable accessories EN 61238-1:2003, Compression and mechanical connectors for power cables for rated voltages up to 36 kV (Um = 42 kV) – Part 1: Test methods and requirements (IEC 61238-1:2003, mod.) IEC 60050-461, International Electrotechnical Vocabulary (IEV) – Part 461: Electric cables BS EN 50483-5:2009 –5– EN 50483-5:2009 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60050-461 and the following apply 3.1 adiabatic occurring with no addition or loss of heat from the system under consideration 3.2 aerial bundled cable (ABC) aerial cable consisting of a group of insulated conductors which are twisted together including, or not, a non insulated conductor [IEV 461-08-02, modified] NOTE The terms bundled conductors, bundled cables, bundled cores, conductor bundles and bundle could be used as equivalent to the term aerial bundled cable (ABC) m 3.3 aerial-insulated-cable insulated cable designed to be suspended overhead and outdoors [IEV 461-08-01] e co 3.4 branch connector ctorr to a main conductor at an intermediate metallic device for connecting a branch conductor point on the latter [IEV 461-17-05] ab ak ZZZE]I[ZFRP ZZ w w w b 3.5 branch conductor onduc conductor connected to the main conduct conductor by a connector 3.6 conductor insulation insulation applied on a conductor [IEV 461-02-02, modified] 3.7 conductor (of a cable) part of a cable which has the specific function of carrying current [IEV 461-01-01] 3.8 connector metallic device to connect cable conductors together [IEV 461-17-03] 3.9 core assembly comprising conductor and its own insulation [IEV 461-04-04, modified] 3.10 equalizer arrangement used in the test loop to ensure a point of equipotential in a stranded conductor [EN 61238-1:2003, 3.8] BS EN 50483-5:2009 EN 50483-5:2009 –6– 3.11 insulation (of a cable) insulating materials incorporated in a cable with the specific function of withstanding voltage [IEV 461-02-01] 3.12 insulation piercing connector (IPC) connector in which electrical contact with the conductor is made by metallic protrusions which pierce the insulation of the ABC core [IEV 461-11-08, modified] 3.13 median connector connector which during the first heat cycle records the third highest temperature of the six connectors in the test loop [EN 61238-1:2003, 3.11] 3.14 pre-insulated (terminal) lug insulated metallic device for connecting an insulated cable conductor to other electrical equipment e co m 3.15 pre-insulated through connector (sleeve) utive ve le insulated metallic device for connecting two consecutive lengths of insulated conductors ZZZE]I[ZFRP ZZ Z w b ab ak 3.16 reference conductor length of conductor(s) without any joints, wh which is included in the test loop and which enables ce e resis the reference temperature and reference resistance(s) to be determined w w 3.17 reusable connector connector for connecting ABC to stripped cable or bare conductor where only the branch connection can be reused 3.18 sheath uniform and continuous tubular covering of metallic or non metallic material, generally extruded [IEV 461-05-03] 3.19 shear head head of a bolt, or a device fitted over the head of a bolt or a nut, which is designed to break at a specified torque 3.20 type test test required to be made before supplying a type of material covered by this standard on a general commercial basis, in order to demonstrate satisfactory performance characteristics to meet the intended application NOTE These tests are of such a nature that, after they have been made, they need not be repeated unless changes are made to the accessory materials, design or type of manufacturing process which might change the performance characteristics BS EN 50483-5:2009 –7– EN 50483-5:2009 Symbols A, A1, A2 electrical cross-sectional area of the conductors D conductor diameter D Eq equalizer diameter d conductor length between connectors I direct current flowing through a connection during resistance measurement I rms equivalent r.m.s short-circuit current IN alternating current necessary to maintain the reference conductor at its equilibrium temperature la, l b, lj lengths of the conductor assembly associated with the measurement points after jointing le length of equalizer l r, l , l rb length of the reference conductor between ween en m measurement points R1, R linear resistance of conductors of respectively cross-section A and A ZZZE]I[ZFRP ZZ Z R 20 , R , R rb the calculated resistance between etwee two equalizers and corrected to 20 °C TC thermocouple t1 heating period within nh heat cycle t2 cooling period within heat cycle t 1-a time period to reach the required temperature on the reference cable t 1-b time period of stable temperature on the median connector U AB potential difference between measurement points of reference conductor of cross-section A U CD potential difference between measurement points of the connector U EF potential difference between measurement points of reference conductor of cross-section A α temperature coefficient of resistance at 20 °C β mean scatter of the connector resistance factors Δθ j temperature difference between reference cable and connector δ initial scatter of the connector resistance factors BS EN 50483-5:2009 EN 50483-5:2009 –8– λ resistance factor ratio; change in the resistance of the connector relative to its initial resistance θ temperature of a connector while measuring resistances θ max maximum temperature recorded on a connector over the total period of test θN highest rated temperature of insulating compound in normal operation θR temperature of the reference conductor determined in the first heat cycle θr temperature of the reference conductor while measuring resistances θ ref temperature of the reference conductor at the moment of measuring θ max Type test 5.1 Principle ke c om Connectors shall be subjected to 000 cycles of heating a and cooling The cold resistance of eter the connectors shall be measured at specific steps to deter determine their suitability when used with conductors carrying a load Heat cycle and, short-circuit tests shall be made with al alternating current ZZZE]I[ZFRP Z ZZ Direct current may be used for heat cycle only y when agreed between customer and manufacturer 5.2 Test arrangement b w w Installation w 5.2.1 ab NOTE n in F The test circuit shall be as shown Figure 5, 6, or Figures 5, 6, and represent the test circuits respectively for main and branch connectors having equal cross-sections and linear resistance(s); for main and branch connectors having unequal cross-sections and linear resistance(s); for through connectors having equal or unequal cross-sections and linear resistance(s); for terminal lugs 5.2.1.1 Optional immersion test EN 50483-6, 8.4.3.1 provides an optional immersion test for samples which are intended for use in saline polluted areas When the inclusion of this test has been agreed between the manufacturer and the customer this heat cycle test shall be modified to accommodate immersion of the test samples during each cycle 5.2.2 Disconnection devices The test circuit may include sectioning joints so that it can be dismantled and short-circuit tests can be made easily In Figure 6, the disconnection devices (X) are • closed when the circuit is carrying heating current, and • opened when resistance measurements and short-circuit applications are being made BS EN 50483-5:2009 EN 50483-5:2009 – 20 – Actual connector resistance is calculated as follows: êĐ Rra Ã Đ Rrb à ì l a áá + ăă ì l b ááằ R j = R 20 ôăă â la + lb ạẳ ơâ l a + l b Connector resistance: Đ R ì l + Rrb ì l b à áá R j = R 20 ăă a + l l a b â where is the voltage drop between measurement points of the connector; U AB is the voltage drop between measurement points of reference conductor of cross-section A ; U EF is the voltage drop between measurement points of reference conductor of cross-section A 2; θ is the connector temperature while measuring resistances; sur θr is the reference conductor temperature while measuring resistances; ure e whi whil R 20 is the calculated resistance between een en two tw equalizers and corrected to 20 °C; la is the distance from connector to equ equalizer on cross-section A conductor; lb ec is the distance from connector to equalizer on cross-section A conductor; R is the resistance of cross-section oss-sec ss-sec A reference conductor and corrected to 20 °C; R rb is the resistance e of cross-section cr cro A reference conductor and corrected to 20 °C; α is the coefficient of variation in resistivity with temperature -3 -1 -3 -1 for Al and Cu = 4,0 x 10 K , Al alloy = 3,6 x 10 K e co m U CD w w w b ab ak ZZZE]I[ZFRP ZZ Z 5.6.2.1 Initial scatter The scatter between the six values of R j (one value for each connector) at cycle zero shall be calculated as follows: Calculate the mean value: R0 = ¦Rj j =1 then the standard deviation: s0 = ( ¦ R j − R0 j =1 ) BS EN 50483-5:2009 – 21 – EN 50483-5:2009 and finally the initial scatter: δ= s0 × × ts R0 where ts is the Student coefficient; ts = 4,032 for 99 % two-sided confidence level and five degrees of freedom Hence, the initial scatter is: δ = 1,65 s0 R0 Mean scatter β 5.6.2.2 For each connector, its mean value over the interval x = -5 to +5 shall be calculated: +5 ¦R j 11 −5 e co m Rj = valu Hence six values are obtained The mean of these six va values shall be calculated: ak ZZZE]I[ZFRP ZZ ab ¦R j w b R = s= ( ¦ Rj −R ) w w The standard deviation: and the scatter: β= s × × tS R where ts = 4,032 as before Hence, the mean scatter is: β = 1,65× s R BS EN 50483-5:2009 EN 50483-5:2009 5.6.2.3 – 22 – Assessment of resistance stability for each connector For each connector, its mean value over the interval x = -5 to +5 shall be calculated Rj = +5 ¦R j 11 −5 and ΔR j = R j max − R j the resistance stability is given by the ratio ΔR j Rj 5.6.2.4 Resistance factor ratio λ= Rj Rj0 where Rj0 is the connector resistance of the he sam same connector measured at cycle zero e co m is the connector resistance for each conne connector found at any stage of the measurement series; ak ZZZE]I[ZFRP ZZ the w For each connector, 11 measurements .b Temperature stability temperature peratur eratu w 5.6.3.1 ab Temperatures stability shall be estimated over the last w 5.6.3 Rj 11 Δθ j = ¦ Δθ j j =1 11 where Δθ j 5.6.3.2 = temperature difference between reference cable and connector Maximum temperature of each connector Each connector temperature , θ j shall be lower than or equal to the warmest reference conductor: θj ≤ θR BS EN 50483-5:2009 – 23 – 5.6.4 EN 50483-5:2009 Test requirements Table – Test requirements Parameter Maximum value Initial scatter į 0,3 Mean scatter ß 0,3 Assessment of resistance stability 15 % Resistance factor ratio λ 2,0 Temperature stability Δ θ j Δθ j − 10 ≤ Δθ j ≤ Δθ j + 10 Maximum temperature θ j of each connector θR NOTE An explanation of the terms used in the preceding statistical analysis and background papers may be founded in EN 61238-1:2003 ZZZE]I[ZFRP ZZ BS EN 50483-5:2009 – 24 – e co m EN 50483-5:2009 w w w b ab ak ZZZE]I[ZFRP Key l a = l b = l and = l r = l d conductor length between two connectors d  80 A or 500 mm minimum reference conductor insulated between equalisers A conductor cross-section (mm ) connectors p.p potential point TC thermocouple Figure – Test loop for branch connectors with main and branch conductors having equal cross-sections and linear resistances BS EN 50483-5:2009 EN 50483-5:2009 e co m – 25 – w w w b a ba k ZZZE]I[ZFRP Key reference conductor A R insulated between equalisers NOTE For branch cable having a cross-section below 16 mm , the impedance adapter may not be necessary if agreed between manufacturer and customer In this case only the branch conductor shall be maintained within the temperature limit reference conductor A R insulated between equalisers d conductor length between two connectors d  80 A or 500 mm minimum connectors A conductor cross-section (mm ) conductor A R insulated between equalisers p.p potential point conductor A R insulated between equalisers TC thermocouple impedance adapter disconnection device If the difference between the main and branch electrical cross-sections is greater than half a step as defined below, this test loop shall be used Where the change is lower than or equal to half a step, Figure shall be used Cross-sections steps (mm ): 1,5, 2,5, 4, 6, 10, 25, 35, 50, 70, 95, 120, 150, 185, 240 Figure – Test loop for branch connectors with main and branch conductors having unequal cross-sections and linear resistances BS EN 50483-5:2009 – 26 – ak e c om EN 50483-5:2009 w w w b ab ZZZE]I[ZFRP Key When the connectors have equal cross-section, then l a = l b and l = l rb conductor A R insulated between equalisers d conductor length between two connectors d  80 A or 500 mm minimum conductor A R insulated between equalisers A conductor cross-section (mm ) A = A or A - The largest conductor cross-section shall be used reference conductor A R insulated between equalisers p.p potential point connectors TC thermocouple reference conductor A R insulated between equalisers thermocouple middle of the conductor Figure – Test loop for through connectors with conductors having equal or unequal cross-sections and linear resistances BS EN 50483-5:2009 EN 50483-5:2009 e co m – 27 – w w w b ab ak ZZZE]I[ZFRP Key l a = l b = l and = l r = l reference conductor insulated between equalisers d conductor length between two connectors d  80 A or 500 mm minimum thermocouple middle of the conductor A conductor cross-section (mm ) p.p potential point TC thermocouple a) Test loop for pre-insulated lugs BS EN 50483-5:2009 EN 50483-5:2009 – 28 – Key intermediate part of material and cross-section identical to those of the connections palms: 14 mm thickness TC thermocouple nut and bolt p.p potential point b) Test loop for pre-insulated lugs – Lug connection detail e co m ula Figure – Test loop for pre-insulated lugs w w w b ab ak ZZZE]I[ZFRP ZZ BS EN 50483-5:2009 – 29 – EN 50483-5:2009 Annex A (normative) Equalizers For stranded conductors, potential between the strands at measuring points may cause errors in measuring electrical resistance Welded or soldered equalizers may be used to overcome this problem, and to ensure uniform current distribution in the reference conductor Welded or soldered equalizers are the recommended methods to ensure reliable measurements Other methods may be used provided they give comparable results and not affect the temperature of the connectors or the reference conductor A.1 Copper conductors Special equipment: silver solder; - support; - cooling plates; - heating equipment e co m - Stranded aluminium conductors nducto ducto (Figure A.1) w w A.2 w b ab ak Cut the conductors square and clean the ends s Place the ends in contact in a support Solder the ends with a silver solder, ensuring that hat at the conductor remote from the ends is kept sufficiently cool not to be affected Special equipment: - apparatus for TIG (Tungsten Inert Gas) or MIG (Metal Inert Gas) welding; - welding support; - welding rod A5 (1 100), welding rod A5 (1 050) or equivalent Cut the conductors square, clean the ends, and melt them with the welding torch (For cable cross-sectional areas greater than 95 mm , melt the periphery first and then add weld metal to the centre to complete the chamfer.) The length of the chamfer "a" and the separation between the conductors for final welding "b" are: Table A.1 – Dimensions of equalizers Cross-sectional area A mm A ≤ 95 95 < A ≤ 240 A > 240 a (mm) to 5 to 10 to 12 b (mm) to 2 to to With the conductors supported and spaced by dimensions "b", build weld metal up at the centre, and turn the conductors so as to obtain a uniform circular weld profile Ensure that the conductor remote from the ends is kept sufficiently cool in order not to change the mechanical properties of the conductor in the region where the contact will be made BS EN 50483-5:2009 EN 50483-5:2009 A.3 – 30 – Dimensions The dimensions of the equalizer shall be as indicated in Table A.1 .b ab ak e co m a) Ends prepared w w w b) Welding/soldering support g/solde sold Key D ≤ D Eq ≤ 1,2 D l e = 10 mm to 15 mm for cross-sectional area A ≤ 95 mm l e = 15 mm to 25 mm for cross-sectional area 95 mm < A ≤ 240 mm l e = 25 mm to 35 mm for cross-sectional area A > 240 mm c) Welded/soldered equalizer Figure A.1 – Equalizers marking for potential point BS EN 50483-5:2009 – 31 – EN 50483-5:2009 Annex B (informative) Determination of the value of the short-circuit current I max0 I max1 co m Key ak e Figure B.1 – Diagram of short-circuit hort-ci ort-c current w b ab nction o On the diagram giving the current as a function of time, the total time BT is divided into ting ng cu 10 equal parts and the value of the alternating current component is measured at the verticals at points 0, 1, 2, 10 w w These values are designated by I max0 ax0 , I ma max1 , I max2 , I max10 Then effective values Ii = I max where I max is the maximum value of the alternating component of the current at each point The equivalent r.m.s current during this time BT is given by: I rms = [ ( ) ( ) 2 2 2 2 2 I + I1 + I + I + I + I + I + I + I + I + I10 30 NOTE The direct current component (CC ’ ) is neglected NOTE This annex is consistent with EN 61238-1:2003 ] BS EN 50483-5:2009 EN 50483-5:2009 – 32 – Annex C (informative) Recommendations to improve accuracy of measurement C.1 Handling the test loop Bending or vibrations during transport and handling may give rise to mechanical forces, which affect the contact resistance of the test objects and should be avoided The same measuring points should be used throughout the test, since calculation always refers to the initial situation Verification of measuring points, especially after short-circuit test is advised C.2 Measurements, instruments and readings In the case of stranded conductors the distances between any equalizer in the test set up where no connectors are installed may be used for verification of resistance measurements co m e a All recorded values should show that the equalizers have acceptable stability throughout the test ak e Check the validity of calibration or make a calibration each instrument prior to the test tion on of e ab If possible, calibrate the whole measuring chain hain ain w w b hecked ecked at a temperature of 100 °C in boiling water and Temperature readings may easily be checked at °C in ice water w ibrate brate shunt may be introduced into the test loop For measuring the current, a calibrated If possible, use the same instrument for voltage ( Δ U d.c.), current ( Δ U d.c of a shunt) and temperature ( Δ U d.c of thermocouple-voltage output) measurement A calibrated resistance with a value in the same order as the readings may be used for the calibration of the voltage measurement or a direct measurement of the resistance A check should be made before, during and after the test It is recommended • to use the same instruments during the whole test, • to avoid whenever possible the replacement of any instrument or the change in the systematic uncertainty may influence the assessment of the measuring results, • to use automatic storage of the measured values to avoid copy errors, • to use a validated computer program for the calculation to avoid errors by accident Every effort should be made to avoid spurious readings Data of instrument performance should be given in the test report BS EN 50483-5:2009 – 33 – EN 50483-5:2009 Bibliography HD 626, Overhead distribution cables of rated voltage Uo/U(Um): 0,6/1 (1,2) kV w w w b ab ak e co m IEC 60949:1988, Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects British Standards Institution (BSI) BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Information on standards British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would 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