Page 541 - IRSEM_Main Book

22.8.5 Induction in Metallic Bodies Situated Close to OHE

Induced voltage may appear in Signalling and Telecommunication Circuits when
the length of parallelism to the track is appreciable. Even if there is no induced
voltage in a circuit at the time of starting a work, precautionary measures listed
below shall be taken, as induced voltages may develop at any time on account of
an increase in current in the traction lines. It is also to be noted that in the case of
equipment or circuits, which are earthed, a contact, which may normally be without
danger, may give rise to an electric shock in the case of a break in the circuit or in
the earth connections. Consequently, when staff have to work on Signal and
Telecommunication Circuits on 25 KV AC electrified lines, they shall take the
following precautionary measures:

(a) They shall as a general rule, wear rubber gloves and use tools with insulated
handles.

(b) When the work to be done is of such a nature that rubber gloves cannot be
used conveniently, special precautions shall be taken by splitting the circuits
into sections or earthing them. In special cases, both the steps shall be taken
simultaneously. If these protective measures cannot be applied, staff must
insulate themselves from the ground by using rubber mats, etc.

(c) The cable conductors pertaining to the block instruments are likely to
develop heavy induced voltages and every time the staff handles the
terminals of Block Circuits, they must rigidly observe the provisions of
paragraphs (a) and (b) above. These cable terminals shall be printed
“RED” to remind the Maintenance staff of the danger. The Maintenance
SSE/JE (Signal) shall explain the meaning of this painting to the
maintenance staff and ensure that they correctly understand it.

22.8.6 Before any work is undertaken on Signalling/Telecommunication cables, the
staff shall take the following precautionary measures:
(a) Reduce the length of the circuit as much as possible.

(b) Use Rubber gloves as far as possible or alternatively use insulated rubber
mats.

(c) Before cutting the armour or the metal sheath of the cable or the wires in the
cables, an electrical connection of low resistance shall be established between
the two parts of the armour, the Sheathing and wires that are to be separated
by cutting.

22.8.7 Staff who have to work on electrical circuits shall be equipped with insulated
tools such as box spanners, pliers, screw-drivers, etc. They shall, in addition,
be supplied with rubber mats and rubber gloves. In regard to staff who have to
work on equipment directly connected to the rails, tools with insulated handles
may be supplied as far as possible and as far as practicable. A plastic sleeve
on the handle will be sufficient in most cases.

22.8.8 Staff shall make themselves familiar with the instructions for treatment of
persons suffering from electric shocks. Instruction Boards in English and in the
regional languages describing the methods to be adopted for treatment of
electric shock shall be clearly displayed in all SSEs/JEs (Signal) offices.

Chapter 22: Requirements Of Signalling in 25 KV AC Electrified Area Page 484 of 535