Page 547 - IRSEM_Main Book

(c) Structure Bonds: All structures supporting overhead equipment either in AC or D.C.
track circuited areas are connected to the running rails for ensuring good earthing.
Failure of insulator or leakage of current switches off the supply from the sub station
so that men coming in contact with supporting structure etc., do not get electric
shock. Removal or tampering of such bonds can, therefore, result in unsafe
conditions. Since the structure are grouted in concrete, they are likely to become
charged in case such bonds are kept disconnected. Similarly, other steel structures
such as foot-over bridges, sheds, etc., in the vicinity of O.H.E lines are also connected
to rails through similar structure bonds.

283 Special Instructions to Staff working in Traction area:

1) Need for Precautions: Precautions are required to be taken on account of following:

(a) Proximity of a Live Conductor: The risk of direct contact with live O.H.E is ever
present while working in electrified sections such as for painting of steel work of
through spans of bridges and platform cover.

(b) Build up of Potential due to Return Current in Rails: The return current in the rails
may cause a potential difference:

(i) Between rail and the surrounding mass of earth;

(ii) Between two ends of a fractured rail;

(iii) Between the two rails at an insulated joint; &

(iv) Between earth and any other metallic mass.

2) The following precautions should, therefore, be taken while working in traction areas: -

(a) No work shall be done within a distance of two meters from the live parts of the
O.H.E without a 'permit-to-work'.

(b) For work adjacent to overhead equipment the Engineering Inspect or shall apply to
the proper authority sufficiently in advance for sanctioning the traffic and power
block required. The Traction Power Controller through Traction Foreman will arrange
to isolate and earth the section concerned on the date and at the time specified in
consultation with the Traffic Controller. He shall then issue 'Permit-to-work' to the
Engineering Inspector. On completion of the work the' Perm it-to-work' should be
cancelled and Traction Power Controller advised, who will then arrange to remove
the Earth and restore Power supply.

(c) No part of a tree shall be nearer than 4 meters from the nearest live conductor. Any
tree or branches likely to fall on live conductors should be cut or trimmed periodically
to maintain this clearance. Authorized O.H.E staff should do cutting or trimming.

(d) No fallen wire or wires should be touched unless power is switched off and the wire
or wires suitably earthed. In case the wires drop at a level crossing, the Gatekeeper
shall immediately make arrangements to stop all road traffic.

(e) Work on Station Roofs and Signal Gantries: Staff working on station roofs and signal
gantries and similar structures adjacent to live Overhead Equipment shall not use any
measuring tapes, tools and materials when there is a possibility of their being
dropped or carried by wind on to the live overhead equipment.

Chapter 22: Requirements Of Signalling In 25 KV AC Electrified Area Page 490 of 535