Page 370 - IRSEM_Main Book

(k) While laying the cables in accordance with the above instructions, the
following instructions should be adhered-

(i) Outside the station section, the cables should generally be laid at not
less than 5.5 meters from the centre of the nearest track.

(ii) Within the station section, the trenches shall preferably be dug at a
distance of not less than 3 meters from the centre of the track, width of
the trench being outside the 3 meters distance.

(iii) At each end of the main cable an extra loop length of 6 to 8 meters should
be kept.

(l) After laying the cables, back filling of the trenches should be done properly.
The soil excavated shall be put back on the trench, rammed and
consolidated.

(m) Cable joints of approved type shall be used.

(n) Cable markers of approved type shall be provided which should be placed
at suitable interval and at diversion points to mark the route.

(o) Where the cables are entering the Cable room/Relay room/apparatus case etc.,
the cables shall be firmly held with suitable clamping arrangement, so as to
avoid downward displacement. Suitable ducts, ladder supports, cable guides
etc., shall be provided for the cables inside the Cable room/Relay room. Sharp
cable bends shall be avoided.

15.2.4 Cable Crossing

(a) When a cable has to cross the track, is should be ensured that-

(i) The cable crosses the track at right angles.
(ii) The cable does not cross the track under points and crossings.
(iii) The cable is laid in concrete/GI/DWC-HDPE pipes of approved type,
suitable ducts or in any other approved manner while crossing the track.
(iv) Wherever feasible horizontal directional drilling method may be used.

(b) Wherever practical, the cable may be taken underground across the drain
bed at a suitable depth for crossing small culverts with low flood level,
horizontal directional drilling method may be used where ever feasible.

(c) When the cables have to cross any roads, high banks etc. where
necessary, horizontal directional drilling method may be used.

(d) When cables have to cross a metallic bridge, they should be placed inside
a metallic trough/GI pipe which may be filled, as an anti-theft measure, with
sealing compound or any other suitable means. The cable should be
supported across the bridge in a manner which would involve minimum
vibrations to the cable and which will facilitate maintenance work. Adequate
cable length to the extent of 2 to 3 meters shall be made available at the
approaches of bridge.

(e) It is desirable that the excavation of the trenches is not done in long lengths
and does not remain uncovered for long period. It is preferable that cables
are laid and refilling done on the same day.

Chapter 15: Cables Page 318 of 535