LV and MIV polymeric insulated cables for use by distribution and generation utilities

BS 7870-7.2:2003 pdf free.LV and MIV polymeric insulated cables for use by distribution and generation utilities一 Part 7: Specification for power cables having rated voltages of 3.8/6.6 kV and 6.35/11 kV with special fire performance for use in power stations – Section 7.2: Single core and 3 core cables with halogen-free materials and with aluminium or steel wire armouring.
The marking of elements a) to d) shall be by embossing, by indenting on the oversheath, or by other durable means agreed with the purchaser.
Elements a), b) and c) shall appear, in any sequence that is deemed neither to confuse nor to conflict, on two or more primary lines along the axis of the cable, approximately equally spaced around the circumference of the cable.
Elements d) and e) shall appear on at least one line.
NOTE Elements d) and e) may be on one of the primary lines or a secondary line or Lines and need not be on the same line. The letters and figures shall consist of upright block characters. The characters shall have a minimum height of 3 mm.
The distance between the end of one element of marking and the beginning of the next identical element of marking shall be not greater than 550 mm for elements a), b) and c), and not greater than 1 100 mm for elements d) and e).
Conformity shall be checked by visual examination and measurement.
4.5.2 Identification of year of manufacture
A means of identifying the year of manufacture of the cable shall be provided throughout the length of the cable, either internally or by use of an identification thread or externally by marking on the surface of the cable.
If the identification is internal, the distance between the end of one mark and the beginning of the next mark shall be not greater than 550 mm.
If the identification is by marking on the external surface, the distance between the end of one element of marking and the beginning of the next identical element. shall be not greater than 1100 mm.
Conformity shall be checked by visual examination and measurement.
4.5.3 Mark of an approval organization
If the mark of an approval organization is used it shall be provided throughout the length of the cable, either as an identification thread or by marking on the external surface of the cable, as specified by the approval organization.
Tithe mark is on the external surface of the cable, it shall be in the form of the symbol(s) specified by the approval organization, and the distance between the end of one element of marking and the beginning of the next identical element shall be not greater than 1100 mm.Conformity shall be checked by visual examination and measurement.
4.5.4 Additional marking
Where additional marking is made it shall be throughout the length of the cable, and on the external surface of the cable, or by means of a tape or thread within the cable, or by a combination of these methods. If the additional marking is applied to the surface of the cable it shall not render illegible the marking specified in 4.5.1. 4.5.2 and 4.5.3.
The additional marking, however made, shall he repeated at intervals not exceeding 1 100 mm.
Conformity shall be checked by visual examination and measurement.
4.6 Routine tests
4.6.1 Voltage test (Type I and Type 2)
The cable shall be tested in accordance with BS 7870.2:1999, 3.2.1. using a voltage of 4U0, gradually
imposed and held for a period of 15 mm. No breakdown shall occur.
4.6.2 D.C. test on otersheath of single core cables (Type I and Type 2)
When tested in accordance with 118 7870.2:1999, 3.2.3.1. the oversheath shall not break down during the
application of 8 kV/mm of specified thickness of oversheath, subject to a maximum of 25 kV.
4.6.3 Partial discharge test (Type 1 and Type 2)
The cable shall he subjected to a partial discharge test in accordance with BS 7870.2:1999, 3.10.3. The test voltage shall be raised to 2.25U0, held for not more than 1 mm, and reduced to 2U0, at which voltage the discharge magnitude (q) shall not exceed 10 pC.
4.7 Sample tests
4.7.1 Thickness measurement (Type I and Type 2)
A sample shall be taken from one end of each drum length of cable selected for the test, and any portion of the cable that may have suffered damage shall be discarded. The thickness of insulation, extruded bedding and oversheath shall be measured in accordance with the tests specified in Table 5.
If any of the thicknesses measured does not conform to 6.3.2. 6.3.5 and 6.3.7. two further samples shall be checked for the non.conforming factors. If both the further samples meet the specified requirements, the cable shall be deemed to conform, but if either sample does not meet the specified requirements, the cable shall be deemed not to conform.
4.7.2 Strippability of extruded semi-conducting insulation screen (Type I and Type 2) The screen shall be capable of removal without impairing the performance of the insulation. When tested in accordance with BS 7870-2:1999. 2.2.8.6. the force required to remove the screen shall he not less than 18 N and not more than 80 N.
4.8 Type tests
4.8.1 General
Satisfactory completion of all type tests on the following sizes shall he deemed to be sufficient to cover the full range of cables listed in Table 1, Table 2, Table 3 and Table 4. for the particular insulating material (XLPK or EPR) and the particular type of cable (Type I or Type 2):
a) for 3-core cables: 70 mm2 or 95 mm2 6.35/11 kV cable; b) for single core cables: 500 mm2 or 630 mm2 6.35/I I kV cable.
NO’rE Tht’ cables tested may have enher copper or aluminium conductors. and either accl or a’uminium wire armouring.
To cover the full range of 3.8/6.6 kV cables only, the same two sizes as above, but of 3.8/6.6 kV rating, shall
be tested.
4.8.2 Measurement of extruded semi-conducting screen resistivity (Type I and Type 2) When measured in accordance with 138 7870.2:1999, 3.9.3, the resistivity shall not exceed 500 Qm at 90 °C.
4.8.3 Compatibility test (Type 1 and Type 2.)
When tested in accordance with 85 7870.2:1999, 2.4.12.2. the sample being aged for 7 days at (100 * 2) °C, the performance shall conform to the values specified in Table 6.
4.8.4.1 Type I
When a sample of completed cable is tested in accordance with BS 7870-2:1999. 2.4.5. the oversheath shall be deemed to conform provided that, following the test, examination of the sample without magnification reveals no cracks or splits in the internal or external surfaces.
4.8.4.2 Type 2
%rhen a sample of completed cable is tested in accordance with BS 7870-2:1999. 2.4.5. the oversheath shall be deemed to conform provided that, following the test, examination of the sample without magnification reveals no cracks or splits in the internal or external surfaces and that, when the sample is subsequently tested in accordance with 4.6.2. the oversheath does not break down.
4.8.5 Bedding and mersheath resistance test (Type I and Type 2)
This shall be measured on a single core cable between the insulation metal screen and the armour, and between the armour and the water as described in BS 7870-2:1999. 3.3.4, except that the nominal voltage shall be not less than 500 V d.c.
The insulation resistance shall be not less than 1 M[1km when corrected to 20 °C.BS 7870-7.2 pdf download.LV and MIV polymeric insulated cables for use by distribution and generation utilities