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

BS 7870 4.10:1999 pdf free.LV and MV polymeric insulated cables for use by distribution and generation utilities一 Part 4: Specification for distribution cables with extruded insul ation for rated voltages of 11 kV and 33 kV一 Section 4.10: Single-core 11 kV and 33 kV cables (Implementation of HD 620).
The insulation shall be XLPE or EPH conforming to the requirements of this section of BS 7870.
The insulal ion shall be applied by extrusion and cross-linked to form a compact and homogeneous layer. The colour of the insulation shall be such that it is easily (listinguishable front the screening materials.
The thickness of the insulation shall conform to the sjwcifications in Tables 1 to 3.
4.2.4 Insulation screen
The insulation screen shall consist of an extnided layer of cross-linked semi-conducting compound. The screen shall be either bonded or cold strippable, by agreement between the manufacturer and the purchaser. It shall he continuous and cover the surface of the insulation completely and shall not separate from the insulation due to the effects of bending, load cycling and shoil-circuit.
4.3 MetallIc screen
A layer of copper wires shall be applied over the semi-conducting insulation screen in a single helical layer. The number. approximate (halneter of the wires and earth fault capability, based upon a 35 mm2 screen, shall conform to the specifications in Tables 1 to 3. The wires shall be spaced with art average gap not greater than 4 nun and no gap shall exceed 8 mm.
NOTE 1 When an alternative earth f1LLIt capacity is required, this !ihOIII(l 1w %pecifivd by the I)Itr(ha%(r.
NOTE 2 Al the option of 11w manufacturer a semi-conducting bedding tape may be applied under and/or a binder tape may be applied over the metallic scrpen
NOTE 3 Lngnndinl water blocking may 1w prrnided by agreement between the manufacturer and the purchaser.
4A Oversheath
The oversheath shall comprise of an extruded layer of nwdium density polyethylene (MDPE) conforming to the requirements of this section of uS 7870. The oversheath colour shall be red for 11 kV cables and black for 3.3 kV cables.
The thickness of the oversheath shall conform to the specifications in Tables 1 to 3.
4.5.1 Marking of oversheath
The external surface of all cables conforming to this section of BS 7870 shall be legibly marked with the following elements of marking.
The marking of elements a) to d) shall Lw by enhl)ossing or indenting on the oversheath. The marking of element e) may, as an alternative to embossing or indenting, be by printing on the oversheath.
Elements a), b) and c) shall appear 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 he on one of the primary tines or a secondary hoe or lines and need no he on the sanw 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 the one element of marking and the beginning of the next identical element of marking shall be not greater than 554) mm. for elements a), b) and c), and not greater than 1 1(X) mm for elements d) and e).
4.5.2 Identification of year of manttfacture A meamis of identifying the year of manufacture of the cable shall be provided throughout the length of the cable, either internally or 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 he not greater than 550 mm.
As an alternative to internal marking, an identification thread may be used.
If the identification is by marking on the surface it shall be embossed or indented and conform to 4.5.1 in respect of minimum height of 3 nun and the maximum distance of 1 100 mm between marks.
4.5.3 The mark of an approval organisation If the mark of an approval organisation is used it shall be provided throughout the length of the cable.
4.5.4 Metre marking
If metre marking is used it shall be legible throughout the length of the cable.
4.6 Sealing and drumming
Before despatch, the manufacturer shall cap the ends of all cable in order to form a seal to prevent the ingress of water during lransportaton and storage. Cable dninis shall be lagged in order to protect the cable from damage, and the end of the cable proje(iing from the drorn shall also he protected from damage.
Each drum shall bear a distinguishing number on the outside of the flange and particulars of the cable, ie. voltage, length, conductor size and cable type.
The gross mass shall be shown and the direction for rolling shall be indicated by an arrow.
4.7 Dimensions The dimensions of the component layers shall conform to the specifications in Tables 1 to 3.
6 Routine tests
6.1 Spark test
The oversheath of the cable shall be subjected to a spark t(-’St ifl a(cor(laflCe with uS 7870-2:1999, 3.6.1. No failure shall occur.
6.2 Conductor resistance
The d.c. resistance of each eon(luctor shall be measured in accordance with BS 7870-2:1999. 3.1.1 and shall 1w as given in 115 6360, Tables I and 2.
6.3 Copper wire screen resistance
The d.c. resistance of the copper wire screen shall be measured in accordance with
BS 7870-2:1999, 3.1.1 and shall not exceed Ihe values given in Table 5.
6.4 Insulation screen cutting test S’here the insulation screen is cold strippable from the underlying insulation, the cable shall be subjected to an insulation screen cutting test in accordance with BS 7870-2:1999, 2.2.11. No ciii in the insulat ion shall occur.
6.5 Voltage test
The cable shall be subjected to a voltage test of 4 U, gr.idually imposed and held for a period of 15 nunutes in accordance with BS 7870-2:1999, 3.2.1. No breakdown shall occur.
6.6 Partial discharge test
The cable shall be subjected to a partial discharge test in accordance with BS 7870-2:1999,3.10.3. The test voltage shall be raised to 2.25 U0, held for not more than 1 mm, and reduced to 2 U0 a, which voltage the discharge magnitude (q) shall not exceed 10 pC.
6.7 (‘able markings
The cable markings shall be checked by visual exanunat ion and nicasurenient, and shall conform to the requirenwnts of 4.5.
6.8 D.C. voltage test on oversheath
When requested in the order the following test shall be carried out.BS 7870 4.10 pdf free download.LV and MV polymeric insulated cables for use by distribution and generation utilities