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In PCC type TF, busbars are located at the top and cable entry is possible from the bottom. To facilitate punching cutouts for glands, bottom plates are provided in two segments.
When top cable entry is desired, there are two alternatives:
Retaining busbars at top: Add-On-Chambers (AOCs) are provided to accommodate cables.
Or
Busbars are shifted to the bottom and cables are taken through top plates, without adding AOC.
Cabling guidelines
While routing the cables in the cable alley, adequate bending radii (R >=12 x overall diameter of cables) should be considered. This will prevent cables from exerting pressure on the termination.
Ensure proper clamping of cables on the glands and cable clamps to avoid weight of cables acting directly on the termination.
Block all unused holes.
Replace all shrouds, if they are removed for cable termination.
Take following steps for cable termination:
i) Remove insulation from cable end without damaging conductor strands. Cut the ends clean and square.
ii) Clean the conductor and coat immediately with inhibiting compound.
iii) In case sector shape conductors are used, from the conductor using a circular forming die. Forming should be done prior to cleaning and applying inhibiting compound.
iv) Use lugs with serrated barrels for crimping aluminium conductors. Serration increases the pull strength after crimping. It also cuts through the oxide film, if any, formed on the conductor.
v) Coat the lug barrel with inhibiting compound from inside.
vi) Use proper crimping dies, as recommended by the lug manufacturer. For aluminium conductors, use ring or hexagonal dies. Ensure that the die surfaces meet during crimping. Incomplete crimping will result in higher temperature rise at the joint.
vii) In case of long barrel lugs, increase number of crimps i.e. crimp the lug at 2 to 2 places.
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