Page 398 - IRSEM_Main Book

17.5.6 Track Bonding in RE Area

(a) The Objectives of Track Bonding are:

(i) To provide a path for traction return current, which ensures that no
component of the track/traction return network rises above 25 V to
remote earth, under normal traction load conditions and 430 V under
traction short circuit conditions.

(ii) To ensure that protective equipment operates satisfactorily.

(iii) To minimize damage to installations due to traction short circuit.

(iv) To maintain correct operation of track circuits.

(b) Planning for Track Bonding

(i) When planning electrification schemes, base plans will be provided. The
plans will be issued to the signal department showing the track layout
and proposed position of all electrification and associated structures.

(ii) The signal department will then indicate on these plans the proposed
position of insulated joints, impedance bonds, signal structures and
track circuit bonding and in single rail track circuited areas, will identify
the track circuit rail by marking with a thickened line. In double rail
track circuited areas S&T department shall specifically indicate the
provision of earth wire for structure earthing.

(iii) The plans must then be returned to electrical department who will
indicate the position of continuity bonds, cross bonds, structure bonds
and all earth connections to the traction system. The plans will then be
returned to the signal department for final approval and issue to
concerned parties.

(c) Bonding of Single Rail Track Circuits in RE Area

(i) The track circuit rail must be series bonded in order to ensure that
defective bonding cannot cause a wrong side failure of the track circuit.
Accordingly, the bonding arrangement of the track circuit rail must
ensure that the conductive path between the track circuit feed
connection and the relay or receiver end connection is interrupted in
the event of a disconnection.

(ii) Because of traction return considerations, it is not possible for the
traction return rail to be series bonded. It is therefore essential to avoid
bonding disconnection to minimize the risk of loss of train shunt.

(iii) In single rail track circuits, in the event of a break in the uninsulated
rail, very heavy current will flow through the track relay as well as the
equipment at the feed point. To avoid this, the uninsulated rails of the
adjacent tracks shall be cross bonded at intervals of not more than 100
meters. In case the track circuit is less than 100 meters, the cross
bonding shall be provided on the uninsulated rail at either end of the
track circuit. (Ref: Drg no. 17-D3)

Chapter 17: Train Detection Track Circuits & Axle Counters Page 346 of 535