CABLE TERMINATION AND JOINTING
Unless otherwise permitted, all cable termination and jointing works shall only be carried out in the presence of the S.O.’s Representative. A plastic laminated plate engraved with details such as size of cable, number of core, date of commissioning, date of jointing, length of cable, distance of cable joint etc. shall be securely fixed near the termination. All cable terminations and jointing shall be undertaken by competent persons as prescribed in Electricity Regulations 1994.
9.1 TERMINATION OF PVC INSULATED ARMOURED CABLE
PVC/SWA/PVC, XLPE/SWA/PVC, XLPE/AWA/PVC, and XLPE/PVC cable shall be provided with compression cable gland for termination. The cable gland shall be of gunmetal or brass type and shall grip both the inner and outer PVC sheath of the cable and so designed that any strain on the cable is taken by the steel wire armouring which shall be effectively sealed between the gland itself and the outer cable sheath. If so directed by the S.O.’s Representative, termination by heat shrinkable method shall be used as described in 9.2 hereafter.
9.2 TERMINATION OF PAPER INSULATED CABLE
Paper insulated cables, unless otherwise specified, shall be terminated by the heat shrinkable method. The cables shall be tested for moisture before termination is commenced. Samples of paper both from the layer nearest to and furthest from the conductor shall be immersed in transformer oil or paraffin wax, heated to a temperature of approximately 115 0C.
If any residual moisture is present this will be immediately detected by bubbling. Samples of paper should be tested singly and should not be touched by hand but gripped in a pair of tweezers. Phasing and insulation resistance tests shall be taken on each length of cable laid before termination is commenced.
The heat shrinkable termination materials used shall be supplied in a complete kit to suit various sizes of cable and to provide stress control, non-tracking and environmentally sealed termination. It shall consist of high permittivity, high resistivity, heat shrinkable, stress control, UV stable, non-tracking polymeric materials and heat activated sealant to prevent ingress of moisture and contamination. The termination shall meet the performance test of IEC 60112, and identification of conductors by colour shall comply with IEC 60446. It shall also have the following performance characteristics: –
(a) Voltage withstand for 15 minutes, 50 Hz : 4 KV phase to earth.
(b) Voltage withstand for 4 hours, 50 Hz : 3 KV phase to earth.
(c) Impulse voltage withstand positive and 10 negative, micro seconds : 8 KV peak phase to earth.
(d) Continuous a.c.voltage : 1.5 KV phase to earth.
(e) Insulation resistance between phase conductor and ground : 1000 Megaohms or greater.
9.3 CABLE JOINTING
The type of cable boxes, compound and jointing materials used shall be factory manufactured. Unless otherwise specified cast iron joint boxes shall be used, and all jointing kits shall be approved by the S.O.’s Representative before joints being carried out. Every cable joint shall be started and finished on the same day.
Whenever cables are to be jointed in the open during wet weather conditions, the Electrical Contractor shall take all necessary precautions to prevent moisture getting into the cables. When cable sheaths is used as earth continuity conductor, the glands must
have necessary contact surfaces to provide a low resistance path under fault conditions. Phasing and insulation resistance tests shall be taken before jointing is commenced.
Core numbers printed on the papers shall be observed when jointing and whenever possible such numbers shall be maintained throughout the system. Core number ‘O’, ‘1’, ‘2’ and ‘3’ shall denote as neutral, red, yellow and blue phases respectively. In the case of two core cable, number ‘1’ shall denote the phase conductor and ‘0’ the neutral. Crossing of core in the boxes shall be avoided wherever possible but connections shall be consistent with the foregoing requirements. The jointing of cables shall be undertaken only by competent cable jointer as prescribed in Electricity Regulations 1994