|Electrical Installation - Basic Vocational Knowledge|
|3. Laying of underground cables|
Prior to making conductive connections at the cable, the individual insulation layers will have to be removed.
Processing plastic insulated cable is quite simple. For a cable according to fig. 3.2. the following working steps will be taken:
1. Removal of plastic sheath
Take measurements; by dismantling device make longitudinal incision in plastic sheath; make the circular cut; pull off sheath.
2. Bringing out the concentric conductor
Deflect the individual armouring wires and bunch the wires
3. Cutting of sheet
Nick the sheet by triangular file just above the deflected armouring and tear off
4. Removal of the common conductor cover
Make longitudinal incision by dismantling device; make circular cut; fan out conductor; tear off common conductor cover; clean conductors plastic insulation from adhering residues of plastic material.
1 plastic sheath, 2 cable fixing clamp, 3 concentric conductor, 4 common conductor cover, 5 plastic insulation, 6 conductor, 7 clip 10 x 1 mm in a distance of approx. 120 mm, 8 cable terminal
For removal of the insulation layers from paper-insulated compound-impregnated lead-sheathed cable the following working steps are to be taken: (see fig. 3.13.)
1. Make tie and remove the external jute cover.
2. Fit collar out of a piece of armouring sheet, cut the armouring by filing and remove same.
3. Remove cushioning layer.
4. Clean lead sheathing by a non-inflammable dissolvent.
5. Solder on copper strand to lead sheath.
6. Make circular incision on lead sheath; make parallel incision in lead sheath; roll-back the loose strip by flat pliers; tear off lead sheath along circular cut; slightly widen the upper edge of the remaining lead sheath.
7. Tie off the belt insulation; unwind and tear off belt insulation.
8. Spread conductors and cutt off fillers.
9. Tie off conductor insulation; remove conductor insulation; clean conductors; finally deflect conductors.
Special care has to be taken in soldering on the earthing strand. For this purpose propane gas soldering devices or a blow lamp for soldering are being employed. The lead sheath and the copper strand to be soldered on are to be cleaned from all oxides. The lead sheath may be cleaned by scraping with a stripper. The copper strand is to be tautly placed around the lead sheath and the soldering surface to be wetted by soldering flux. Solder tin stick is to be laid on in pieces and to be shaped like a bulb by means of a dampened rag after thoroughly warming the soldering surface.
Caution! In case of too much warming of the lead sheath at one point, perforations of the lead sheath may result!
1 lead sheath, 2 copper strand, 3 soldering surface