BS 4553:1988 download.British Standard Specification for 600/1000 V PVC-insulated single—phase split concentric cables with copper conductors for electricity supply.
1 Scope
BS 4553 specifies requirements and dimensions for PVC-Insulated single-phase split concentric cables for operation on an earthed neutral system at nominal voltages up to and including 1000 V between phases and 600 V to earth. The cables have a central phase conductor insulated with red PVC and a concentric layer comprising bare copper wires (earth continuity conductor) and copper wires covered with black PVC (neutral conductor).
The cables are suitable for underground or general use in situations where the combination of ambient temperature and temperature rise due to loading current results In a conductor temperature not exceeding 70 °C.
NOTE. The titles of the publications referred to In BS 4553 are listed on the Inside back cover.
2 Definitions
For the purposes of BS 4553 the definitions given In BS 4727 : Part 2 : Group 08 apply, together with the following.
2.1 rated voltage U0. The nominal power-frequency voltage between phase conductor and earth, for which the cable Is suitable.
2.2 rated voltage U. The nominal power-frequency voltage between phase conductors for which the cable Is suitable.
2.3 maximum voltage Urn. The maximum sustained power- frequency voltage between phase conductors for which the cable Is suitable.
2.4 nominal value. The value by which a quantity Is designated and which is often used in tables.
2.5 approxImate value. A value which is only indicative.
NOTE. In BS 4553, values described as approximate’ do not constitute requirements to be checked by measurements.
3 Voltage designation
The cables shall be designated by the rated voltages U0 and U, expressed In the form 1J01U.
For the purposes of BS 4553 the voltage designation is 600/1000 V.
For the purposes of BS 4553 the maximum designated voltage, Urn, is 1100 V.
NOTE. Guidance on the selection and operation of cables Is given In appendix A.
4 Phase conductor
The phase conductor shall be circular stranded or compacted stranded plain annealed copper (class 2), and, as given In table 1, shall comply with BS 6360.
5 Insulation
s The Insulation of the central phase conductor shall be red
PVC compound complying with type Til of BS 6746.
It shall be applied by an extrusion process and shall form a compact homogeneous layer.
The core shall be spark tested In accordance with 15.1.
6 Thickness of insulation
The thickness of insulation, determined by taking the average of a number of measurements as described in 16.1, shall be not less than the value given In table 2, and the smallest of the measured values shall not fall below the value given In the table by more than (10 % + 0.1 mm).
7 Concentric layer
7.1 Neutral conductor
The neutral conductor shall be manufactured from plain annealed copper wires. When measured in accordance with 15.5, the number of wires and the resistance of the neutral conductor shall comply with the values given in table 2.
To distinguish the neutral from the earth continuity conductor, each wire shall be covered by extrusion with black PVC compound complying with type Til or type 2 of BS 6746 at the manufacturer’s discretion, to a diameter approximately the same as that of the individual wires In the earth continuity conductor.
NOTE. The covering should not be regarded as Insulation.
7.2 Earth continuity conductor
The earth continuity conductor shall be manufactured from bare plain annealed copper wires. When measured in accordance with 15.5, the number of wires and the resistance of the earth continuity conductor shall comply with the values in table 2.
7.3 PVC string separators
PVC string separators shall be approximately the same diameter as the individual bare wires forming the earth continuity conductor.
7.4 Application of concentric layer
The concentric layer shall be applied with a right hand direction of lay. The wires forming the neutral conductor and earth continuity conductor shall be applied in individual groups over the Insulation with PVC string separators.
Either one or two PVC string separator(s) shall be located on either side of the group of bare copper wires to separate it from the group of covered wires.
The length of lay and the number of strings shall be such that a coverage of approximately 90 % is achieved. For the 16 mm2, 25 mm2 and 35 mm2 sizes, the length of lay shall be not less than the value given in table 2.
8 Binders
One or more overlapped synthetic binder tape(s) shall be applied immediately over the concentric layer.
9 Oversheath
The oversheath shall be an extruded layer of black PVC compound complying with type TMI of BS 6746. The oversheath shall be spark tested In accordance with 15.2.
10 Thickness of oversheath
When measured In accordance with 16.1, the minimum thickness of the oversheath shall not fall below the value given In table 2 by an amount more than (15 % + 0.1 mm).
11 Cable marking
11.1 Embossing of oversheath
The external surface of the PVC oversheath shall be embossed with the following legend:
ELECTRIC CABLE 600/1000 V
The legend shall be along two or more lines approximately equally spaced around the circumference on cables having a tabulated overall diameter above 15 mm and along one or more lines for smaller cables.
The letters and figures shall be raised and shall consist of upright block characters. The minimum size of characters shall be 15 % of the tabulated diameter of the cable, or 3 mm, whichever is the greater. The gap between the end of one legend and the beginning of the next shall be not greater than 150 mm.
11.2 IdentificatIon of manufacturer
A means of identifying the manufacturer shall be provided throughout the length of the cable, If this is by means of embossing, this shall not affect the spacing between repetitions of legends as specified in 11.1.
12 End sealing
Both ends of every length of cable shall be sealed in such a manner that the sealing encloses the oversheath.
NOTE. One example of end sealing is the use of close fitting pastlcs caps.
13 Schedule of tests
Table 1 lIsts the complete range of tests applicable to the cables covered by this standard and refers to the relevant clauses of the standard specifying the requirements and test methods. The final column indicates, by means of the symbols R, RS and T, the category of each test.
The categories and corresponding symbols are as follows.
(a) Routine tests (RI: tests made at the manufacturer’s works on all cables in the finished state or, as appropriate (e.g. spark test), during manufacture.
(b) Regular sample tests (RS): tests made at the manufacturer’s works on representative samples selected regularly by the manufacturer, or as specified by the purchaser at the time of ordering.
(c) Type tests (TI: tests made on specimens of cables as produced by a specific manufacturer to demonstrate the manufacturer’s ability to produce satisfactorily a range of cables designed to comply with this standard. These tests, after they have been successfully completed, need not be repeated unless changes are made which might affect compliance with the test requirements.
14 Test conditions
14.1 Ambient temperature
Tests shall be made at ambient temperature of 20 ± 15 DC unless otherwise specified In the details for the particular test.
14.2 Frequency and waveform of power frequency tst voltages
Unless otherwise specified in the relevant test method, the frequency of the alternating voltages shall be in the range of 49 Hz to 61 Hz. The waveform shall be substantially sinusoidal.
15 Routine tests at works
15.1 Spark test on phase core
A spark test shall be applied to the phase core at the insulation stage of manufacture In accordance with BS 5099 and the test voltage given In table 3.