BS 7835:2007 2008
$198.66
Electric cables. Armoured cables with thermosetting insulation for rated voltages from 3.8/6.6 kV to 19/33 kV having low emission of smoke and corrosive gases when affected by fire. Requirements and test methods
| Published By | Publication Date | Number of Pages |
| BSI | 2008 | 64 |
This British Standard specifies requirements and test methods for the construction, dimensions and mechanical and electrical properties of armoured cables with thermosetting insulation for rated voltages from 3.8/6.6 (7.2) kV up to 19/33 (36) kV inclusive which, when assessed by the specified tests, produce lower levels of smoke and corrosive gases on exposure to fire compared to the cables specified in BS 6622. It covers cables designed for a maximum continuous conductor operating temperature of 90 °C and for a maximum short circuit conductor temperature of 250 °C, for use in fixed installations such as networks or industrial installations.
This British Standard specifies single-core and three-core cables for voltages in the range 3.8/6.6 (7.2) kV up to 19/33 (36) kV, with:
- a stranded copper, stranded aluminium or solid aluminium conductor or conductors;
- cross-linked polyethylene or cross-linked ethylene propylene rubber insulation;
- a metallic screening layer of copper wire or copper tape and/or a metallic armour of aluminium or galvanized steel wire;
- a thermoplastic oversheath.
NOTE Guidance on the selection of cables is given in Annex A. Information to be supplied by the purchaser, and items to be agreed between the purchaser and the manufacturer, at the time of enquiry and/or order, are given in Annex B. Recommendations for the installation of cables are given in Annex C. Guidance on the use of cables is given in Annex D.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 3 | Contents 1 Scope 1 2 Normative references 1 3 Terms and definitions 2 4 Voltage designation 4 5 Non-metallic materials 4 6 Conductors 4 7 Conductor screen 4 8 Insulation 4 9 Insulation screen 5 10 Assembly of three-core cables, including inner coverings and fillers 5 11 Metallic layer 7 12 Metallic armour 8 13 Oversheath 9 14 Marking 10 15 End sealing 11 16 Schedule of tests 12 17 Test conditions 14 18 Routine tests 14 19 Sample tests 16 20 Type tests – Materials 21 21 Type tests – Electrical 25 Annexes Annex A (informative) Recommendations for the selection of cables 29 Annex B (normative) Information to be supplied and items to be agreed 32 Annex C (informative) Recommendations for the installation of cables 33 Annex D (informative) Guide to use of cables 36 Annex E (normative) Fictitious calculation method for determination of dimensions of protective coverings 38 Annex F (normative) Rounding of numbers 43 Annex G (informative) Guidance on the scope of type tests 44 Annex H (normative) Thickness measurements 47 Annex I (normative) Test method for cold strippability of the extruded semi-conducting layer of an insulation screen 47 Annex J (normative) Method for measurement of resistivity of extruded semi-conducting conductor screen and insulation screen 48 Annex K (normative) Method for measurement of resistivity of lapped inner covering 51 Annex L (normative) Wet compatibility test for galvanized steel wires and semi-conducting tape layers 52 Annex M (normative) Abrasion test 53 Annex N (normative) Test for shrinkage of oversheath on cable 54 Annex O (normative) Insulation resistance constant test on oversheath 55 Bibliography 56 |
| 4 | List of figures Figure J.1 – Test piece and arrangement of electrodes for measurement of resistivity of the conductor screen 50 Figure J.2 – Test piece and arrangement of electrodes for measurement of resistivity of the insulation screen 51 Figure L.1 – Test cell for wet compatibility test of galvanized steel wires and semi-conducting tape layers 52 Figure M.1 – Abrasion test 54 List of tables Table 1 – Nominal thickness of insulation 5 Table 2 – Thickness of extruded inner covering 6 Table 3 – Nominal diameter of round armour wires 8 Table 4 – Schedule of tests 12 Table 5 – Tolerances on temperature values 14 Table 6 – DC resistance of copper wire screen 15 Table 7 – Voltage for partial discharge test 15 Table 8 – Voltage test on complete cable 16 Table 9 – Number of samples for the four-hour voltage test, the hot set test on the insulation and the smoke emission test 17 Table 10 – Minimum transmittance levels 20 Table 11 – Voltages for four-hour voltage test 21 Table 12 – Mass of zinc coating 22 Table 13 – Compatibility requirements 24 Table 14 – Tan d in relation to voltage 26 Table 15 – Tan d in relation to temperature 26 Table 16 – Voltage for impulse voltage test 27 Table A.1 – Selection of cables for three-phase a.c. systems 30 Table C.1 – Bending radius during installation 33 Table C.2 – Bending radius during installation for cables adjacent to joints or terminations 33 Table E.1 – Fictitious diameter of conductor 40 Table E.2 – Increase of diameter for concentric conductors and metallic screens 41 Table M.1 – Vertical force on cable during abrasion test 53 |
| 5 | Foreword |
| 7 | 1 Scope 2 Normative references |
| 8 | 3 Terms and definitions 3.1 rated voltage 3.2 rated voltage U0 3.3 rated voltage U |
| 9 | 3.4 maximum voltage Um 3.5 cross-linked polyethylene (XLPE) 3.6 ethylene propylene rubber compound (EPR) 3.7 nominal value 3.8 approximate value 3.9 fictitious value 3.10 routine tests 3.11 sample tests 3.12 type tests |
| 10 | 4 Voltage designation 5 Non-metallic materials 6 Conductors 7 Conductor screen 8 Insulation |
| 11 | Table 1 Nominal thickness of insulation 9 Insulation screen 9.1 General 9.2 Extruded semi-conducting layer 10 Assembly of three-core cables, including inner coverings and fillers 10.1 General 10.2 Inner coverings and fillers |
| 12 | Table 2 Thickness of extruded inner covering 10.3 Cables with a collective metallic layer 10.4 Cables with a metallic layer over each individual core |
| 13 | 11 Metallic layer 11.1 General 11.2 Metallic screen on each core 11.3 Collective metallic screen |
| 14 | 12 Metallic armour 12.1 Construction 12.1.1 General Table 3 Nominal diameter of round armour wires 12.1.2 Material 12.1.3 Application of armour 12.1.3.1 Single-core cables 12.1.3.2 Three-core cables |
| 15 | 12.2 Separation sheath 13 Oversheath 13.1 General 13.2 Thickness of oversheath |
| 16 | 13.3 Semi-conducting layer 14 Marking 14.1 External marking |
| 17 | 14.2 Identification of year of manufacture 14.3 The mark of an approval organization 14.4 Additional marking 15 End sealing |
| 18 | 16 Schedule of tests Table 4 Schedule of tests |
| 19 | Table 4 Schedule of tests (continued) |
| 20 | 17 Test conditions 17.1 Ambient temperature 17.2 Tolerances on temperature values Table 5 Tolerances on temperature values 17.3 Frequency and waveform of power-frequency test voltages 18 Routine tests 18.1 General 18.2 Spark test on oversheath 18.3 Conductor resistance |
| 21 | 18.4 Copper wire screen resistance 18.4.1 Method 18.4.2 Requirement Table 6 DC resistance of copper wire screen 18.5 Partial discharge test Table 7 Voltage for partial discharge test 18.6 Voltage test on complete cable |
| 22 | Table 8 Voltage test on complete cable 18.7 Cable markings 18.8 D.C. voltage test on oversheath 18.8.1 General 18.8.2 Method 18.8.3 Requirement 19 Sample tests 19.1 General 19.2 Sampling frequency |
| 23 | Table 9 Number of samples for the four-hour voltage test, the hot set test on the insulation and the smoke emission test 19.3 Repetition of sample tests 19.4 Conductor material and construction 19.5 Conductor screen 19.6 Hot set test on insulation |
| 24 | 19.7 Dimensions 19.7.1 Thickness of insulation 19.7.2 Concentricity of insulation 19.8 Circularity of cores 19.8.1 Method 19.8.2 Requirement 19.9 Insulation screen 19.9.1 Application |
| 25 | 19.9.2 Cold strippability 19.10 Metallic screen (wires only) 19.11 Assembly of three-core cables 19.12 Separation sheath 19.13 Semi-conducting lapped inner covering 19.14 Measurement of armour wires |
| 26 | 19.15 Oversheath thickness 19.16 Flame propagation on single cable 19.17 Smoke emission test Table 10 Minimum transmittance levels |
| 27 | 19.18 Four-hour voltage test 19.18.1 Method 19.18.2 Requirement Table 11 Voltages for four-hour voltage test 20 Type tests – Materials 20.1 General 20.2 Corrosive and acid gas 20.3 Conductor screen resistivity 20.4 Insulation material |
| 28 | 20.5 Insulation screen resistivity 20.6 Insulation screen cold strippability 20.7 Semi-conducting lapped inner covering resistivity 20.8 Separation sheath material 20.9 Mass of zinc coating of galvanized steel wires 20.9.1 Method 20.9.2 Requirement Table 12 Mass of zinc coating |
| 29 | 20.10 Wrapping test for galvanized steel wires 20.10.1 Method 20.10.2 Requirement 20.11 Wet compatibility test for galvanized steel wires and semi-conducting tape layers 20.11.1 Method 20.11.2 Requirements 20.12 Tensile test for aluminium wires 20.12.1 Method 20.12.2 Requirement 20.13 Oversheath material |
| 30 | 20.14 Compatibility test Table 13 Compatibility requirements 20.15 Flame propagation on multiple cables 20.16 Smoke emission test 20.17 Abrasion test |
| 31 | 20.18 Test for shrinkage of oversheath on cable 21 Type tests – Electrical 21.1 General 21.2 Partial discharge test 21.3 Bending test 21.3.1 Method 21.3.2 Requirements |
| 32 | 21.4 Tan d in relation to voltage Table 14 Tan d in relation to voltage 21.5 Tan d in relation to temperature 21.5.1 Method 21.5.2 Requirements Table 15 Tan d in relation to temperature 21.6 Heating cycle test 21.6.1 Method |
| 33 | 21.6.2 Requirement 21.7 Impulse voltage test Table 16 Voltage for impulse voltage test 21.8 Four-hour voltage test 21.9 Adherence of screens at short circuit temperature 21.9.1 Method |
| 34 | 21.9.2 Requirement 21.10 Insulation resistance constant of oversheath |
| 35 | Annex A (informative) Recommendations for the selection of cables A.1 General A.2 Voltage ratings a) Category A. This category comprises those systems in which any phase conductor that comes in contact with earth or an earth conductor is disconnected from the system within 1 min. b) Category B. This category comprises those systems which, under fault conditions, are operated for a short time with one phase… c) Category C. This category comprises all systems which do not fall into categories A or B. |
| 36 | Table A.1 Selection of cables for three-phase a.c. systems A.3 Metallic coverings A.4 Selection of metallic coverings in relation to earth fault capacity |
| 37 | A.5 Semi-conducting layer on the oversheath a) when the oversheath is required to perform an insulating function during the operation of the cable. This applies when the me… b) when damage to the oversheath is likely to lead to corrosion of an essential metallic layer which it protects, due to an environment aggressive to the particular metal. A.6 Current carrying capacity |
| 38 | Annex B (normative) Information to be supplied and items to be agreed B.1 Information to be supplied by the purchaser at the time of enquiry and/or order a) length of cable required, and individual drum lengths, if particular drum lengths are required; b) voltage designation (see Clause 4); c) number of cores; d) size of phase conductor; e) conductor material (i.e. copper or aluminium) (see Clause 6); f) type of conductor (i.e. stranded or solid) (see Clause 6); g) type of insulation (i.e. XLPE or EPR) and limiting dimensions (if any) of the cores; h) whether the insulation screen is required to be cold strippable (see 9.2); i) type of metallic insulation screen (see Clause 11); j) cross-sectional area of metallic insulation screen; k) if an armour layer with a special construction is required which requires the armour to be made of magnetic material (see 12.1.2); l) if a steel armour layer with a specific minimum conductance is required (see 12.1.2 Note). m) nominal thickness of oversheath if a thickness other than that specified in 13.2 is required; n) if a d.c. voltage test on the oversheath is required (see 13.3 and 18.8). B.2 Items to be agreed between the purchaser and the manufacturer a) colour of the oversheath if a colour other than black is required (see 13.1 Note); b) sampling frequency for sample tests if different from that specified in 19.2. |
| 39 | Annex C (informative) Recommendations for the installation of cables C.1 Minimum temperature during installation C.2 Minimum installation radius Table C.1 Bending radius during installation Table C.2 Bending radius during installation for cables adjacent to joints or terminations C.3 Prevention of moisture ingress |
| 40 | C.4 Joints and terminations a) moulded components; b) various tapes; c) heat shrinkable tubes. C.5 Compound filling |
| 41 | C.6 Earthing of armour and screen(s) C.7 Tests after installation C.7.1 Tests on insulation a) The cable should be tested for 5 min with the phase-to-phase voltage of the system applied between the conductor and the metallic screen or sheath. b) The cable should be tested for 24 h with the normal operating voltage. |
| 42 | C.7.2 D.C. voltage test on oversheath Annex D (informative) Guide to use of cables D.1 General D.2 Cable selection in relation to installation design a) In a solidly or directly earthed system, in general the earth fault current is at least equal to the three-phase or phase-to-phase fault current. b) When an earth fault current is specified for a system, it is necessary to ensure that the phase conductor of the cable selected has a corresponding earth fault capacity. c) Some work on spiking of cables has been undertaken by the British cable industry and it has shown that, in general, the spiking capability of the screen(s) is less than their through fault capacity. |
| 43 | d) This standard specifies different forms of metallic screen having different earth fault capacities. In general, copper tape s… e) It is essential that connections at joints between, and terminations onto, metallic elements carrying fault currents to earth have an earth fault capacity at least equal to that of the metallic elements. D.3 Environmental factors a) for use as self supporting aerial cables; b) for use as submarine cable or for laying in water-logged conditions; c) for use in situations where subsidence is likely, unless special precautions are taken to minimize damage if subsidence should occur; d) for use in situations where they could be exposed to excessive heat. D.4 Installation |
| 44 | D.5 Storage and handling of drums D.6 Incineration of scrap cable Annex E (normative) Fictitious calculation method for determination of dimensions of protective coverings |
| 45 | E.1 General |
| 46 | E.2 Method E.2.1 Conductors Table E.1 – Fictitious diameter of conductor E.2.2 Cores E.2.3 Diameter over laid-up cores |
| 47 | E.2.4 Inner coverings a) three-core cables: b) single-core cables: E.2.5 Concentric conductors and metallic screens Table E.2 – Increase of diameter for concentric conductors and metallic screens a) tape screen |
| 48 | b) wire screen (with a counter helix, if any) E.2.6 Separation sheath E.2.7 Armour |
| 49 | Annex F (normative) Rounding of numbers F.1 Rounding of numbers for the purpose of the fictitious calculation method a) When the figure in the second decimal place, before rounding, is 0, 1, 2, 3 or 4, then the figure retained in the first decimal place shall remain unchanged (i.e. the value shall be rounded down). b) When the figure in the second decimal place, before rounding, is 5, 6, 7, 8 or 9, then the figure in the first decimal place shall be increased by one (i.e. the value shall be rounded up). F.2 Rounding of numbers for other purposes a) If the last figure to be retained is followed, before rounding, by 0, 1, 2, 3 or 4, it shall remain unchanged (i.e. the value shall be rounded down). b) If the last figure to be retained is followed, before rounding, by 5, 6, 7, 8 or 9, it shall be increased by one (i.e. the value shall be rounded up). |
| 50 | Annex G (informative) Guidance on the scope of type tests G.1 General G.2 Invoking of type tests G.3 Sequential electrical type tests |
| 51 | G.4 Compatibility test (see 20.14) G.5 Type tests on components |
| 52 | G.6 Flame propagation (see 20.15) G.7 Smoke emission (see 20.16) G.8 Abrasion test (see 20.17) G.9 Corrosive and acid gas (see 20.2) G.10 Change of material G.11 Evidence of type testing |
| 53 | Annex H (normative) Thickness measurements H.1 Sampling H.2 Procedure a) for the insulation: the minimum thickness and the maximum thickness; b) for the separation sheath: the minimum thickness; c) for the oversheath: the minimum thickness. Annex I (normative) Test method for cold strippability of the extruded semi-conducting layer of an insulation screen |
| 54 | Annex J (normative) Method for measurement of resistivity of extruded semi-conducting conductor screen and insulation screen J.1 Preparation of test pieces J.2 Procedure |
| 55 | J.3 Calculations J.3.1 Conductor screen J.3.2 Insulation screen |
| 56 | Figure J.1 Test piece and arrangement of electrodes for measurement of resistivity of the conductor screen |
| 57 | Figure J.2 Test piece and arrangement of electrodes for measurement of resistivity of the insulation screen Annex K (normative) Method for measurement of resistivity of lapped inner covering |
| 58 | Annex L (normative) Wet compatibility test for galvanized steel wires and semi-conducting tape layers Figure L.1 Test cell for wet compatibility test of galvanized steel wires and semi-conducting tape layers |
| 59 | Annex M (normative) Abrasion test Table M.1 Vertical force on cable during abrasion test |
| 60 | Figure M.1 Abrasion test Annex N (normative) Test for shrinkage of oversheath on cable N.1 General N.2 Selection of samples N.3 Preparation of test piece |
| 61 | N.4 Procedure N.5 Evaluation of results Annex O (normative) Insulation resistance constant test on oversheath O.1 Procedure O.2 Calculation of results |
| 62 | Bibliography [1] Conférence Internationale des Grands Réseaux Electriques. Report 1968-21-01. [2] Institute of Electrical and Electronics Engineers. Paper No. 69, CP88-PWR. |
