Concepts of Automatic Block Signalling.ppt

TheAutomaticBlockSystem

For safe running of trains, different methods are
adopted to control the train movement between
two given points, say between two stations,
mainly to ensure that not more than one train is
permitted in to the block section at a time.
SYSTEM OF WORKING
“means the system adopted for the time being
for the working of trains on any portion of a
railway”.

. In Indian Railways, six systems of train
working are adopted and they are:
(a) The Absolute Block System
(b) The Automatic Block System
(c) The Following Trains System
(d) The Pilot Guard System
(e) The Train Staff and Ticket System
(f) The One Train Only System

4In Automatic Block Working system train movements are controlled by
the automatic stop signals.

These signals are operated automatically by the passage of trains into and
out of the automatic signalling sections.

Essentials of Automatic Block System : Where trains are worked
on Automatic Block System: -

(a) the line is track circuited throughout its length and divided into a
series of automatic signalling sections each of which is governed by an
Automatic Stop Signal.

(b) the movement of trains is controlled by stop signals which are
operated automatically by the passage of trains past the signals.

(c) No Automatic Signal assumes 'OFF' unless the line is clear not only
upto the stop signal ahead, but an adequate distance beyond it. Introduction :

S.No. AbsoluteBlock System Automatic Block System
1 Blockstations are classified as ‘A’,’B’,
‘C’, and Special class stations
Stations are not classified
2 Signals may be Semaphore or CLS Signalsare CLS only
3 Only manual signals are providedSignals may be automatic, semi-
automatic and manual
4 Provision of continuous TC’s/ Axle
counters on line is not required
except IBS
Line shall be provided with
continuous TC’s/ Axle counters
5 Normal aspect of signal is ‘STOP’
(RED)
Normal aspect of signal is
‘PROCEED’ (GREEN)
6 Authority is required to pass signal at
‘ON’
No Authority is required to pass
signal at ‘ON’
DIFFERENCE BETWEEN ABSOLUTE AND AUTOMATIC BLOCK SYSTEM

S.No.AbsoluteBlock System Automatic Block System
7 To start a train line clear shall be
obtained
Line clear not require to start a
train on D/L. Buton S/L Line clear
required to establish direction of
traffic.
8 Signalsmay be Two aspect or
Multiple aspects, permissive signals
may be provided
Signals shall be multiple aspects
only. Permissive signals are
provided.
9 ‘G’ Marker provided on Gate stop
signal
Besides ‘G’ Marker an illuminated
‘A’ Marker is available when gate is
closed.
10 Normally Block section between two
stations will not be divided.
Block section between two stations
are divided into no.of Automatic
block signalling sections.
DIFFERENCE BETWEEN ABSOLUTE AND AUTOMATIC BLOCK SYSTEM

What is Automatic Block?
What is the difference between automatic and absolute
system?
Where it is required ?
Why it is required?
What are the requirements ?
What are the essentials?
How it is operated?
What is the role of signaling department ?

What is Automatic Block?
Space intervals are secured automatically by the use
of Track Circuits or Axle Counters

What is the difference between automatic and absolute
system?
1)The main difference between absolute block and
automatic block is that in the latter, space intervals
are secured automatically by the use of Track
Circuits or Axle Counters while in the former by
human agencies in the form of 2 Station Masters
located at the ends of a block section.

Absolute
Automatic
2) Normal aspect on signal post

Absolute
Automatic
3) ‘A’ marker board is provided on
signal post
A

A
4) Semi auto signal post now working as
automatic signal

4) Semi auto signal post now working as
manual signal

Where it is required ?
Section where train frequencies are more.
Examples
1) Mumbai suburban ( from Mumbai CST to Kalyan)
2) Chennai suburban
3) Calcutta

Why it is required?
To improve the integrity of safe traffic without time delay.

What are the requirements ?
1) Continuous track circuit or axle counter
( means to prove the presence of train on track)
2) Three aspect signaling or four aspect signaling.

The essentials of automatic block system are–
1)The line shall be provided with Continuous Track Circuits or
Axle Counters.
Up
Down
A station B station

18The automatic Signalling Section is defined as the portion of the
running road between any two consecutive automatic stop signals and
each of these sections is protected by an automatic stop signal.

The adequate distance also be termed as 'overlap' and not less than
120 M unless otherwise directed by approved special instructions.
AUTOMATIC
SIGNALLING SECTION
OVER LAP
TRACK
120 Mts
204 206
BERTHING
TRACK
208
OVER LAP
TRACK
BERTHING
TRACK
AUTOMATIC
SIGNALLING SECTION

19Automatic Stop Signal General Description and numbering: Automatic Stop Signals are Multiple aspect colour light signals and are
either 3 aspect or 4 aspect.

These signals are numbered serially, ODD numbers in one direction and
even numbers in the other direction, for UP and DOWN lines or vice versa.

There is an attempt at numbering these signals according to their location
with respect to the kilometrage. This requires a code consisting of a group
of digits in which the last two digits indicate the telegraph or traction pole
and the first group of digits indicating the kilometres at which the signal is
located.

For example 2611 means the automatic signal located at 11th telegraph or
traction pole between 26th and 27th kilometre. For distinguishing UP and
DN signals the last digit can be made ODD in one direction and EVEN in the
other approximate to the nearest telegraph or traction poles.

Up
Down
A station
B station
2) The line between two stations may where
required be divided into a series of section known
as "Automatic Block Signalling Section".
Automatic Block
Signalling Section

Up
Down
A station B station
3) Entry into each block signalling section is protected by a
colour light Multiple Aspect Stop Signal.
Automatic Block
Signalling Section

4)Track Circuits or Axle Counters should controls the
aspects of the Signal such that:
i)It cannot display the `OFF' aspect unless the line is
clear not only up to the next stop signal but also for an
adequate distance beyond it.
{ ‘OFF' aspect can be yellow, double yellowor green. }
ii) The Signal is automatically replaced to `ON' soon after
it is passed by a Train.

a)Yellowwith the minimum clearance of oneBlock
plus Overlap.
b) Double yellowwith minimum clearance of two
Block stations plus Overlap
c) Greenwith minimum clearance of threeBlock
stations plus Overlap

Up
Down
A station B station

117Aspect Control Circuits for Signal No.1. Sometimes 3HR front contact is used in 1DR circuit as a direct
proof that 3 TR and A3TR are in pick up condition in addition to the
3 HECR and 3DECR contacts

3
HHECR
HECR
3 TPR 3 RECR
3
GECR
3
N24B24
GECPR
3
1
HYR
N24B24
3
GECR
GECR
3
GECPR
3
N24
B24
S-3S-1
1T 1 AT 3T
3
DECR
TPR
1
HYR
11A
1
HR
TPR
N24B24

1
1 1 1 1 1
AHEAD SIGNAL
IS 'YY' OR 'G'
& SECTION IS CLEAR
SECTION IS CLEAR
IS 'Y' &
AHEAD SIGNAL
AHEAD SIGNAL
NOT BLANK
SIGNAL-3
ECPR1HECRHHECRDECR TPR
1
HYR
1 1A
1
HR
ECPR2
HR
TPR
N24 B24
3
ECPR2
ECPR2
3
ECPR1
3
3
ECPR1
HR
3
3
HR
3
GECPR
GECPR
3
1
DR
1
HHR
HR
1
HHR
1
HYR
1
N24
B24
SIGNAL-1
HR
1
1
HHR

120 The aspect control and lamp control circuits for all signals are
same as for signal No.1 Sometimes, it is
customary to eliminate
the control relay HR
making use of the track
relays directly in the
lamp control circuit

121CASCADING( Cutting in) Arrangements.
Whenever the lamp fuses with the signal displaying a particular aspect,
then it is likely that the signal becomes blank and there is a chance that
the driver may miss the signal and overshoot.
Even if the driver observes the signal, the signal with no light has to be
treated as a defective signal and GR 278, 279 will have to be observed.
This will have a deleterious effect on capacity, so if a lamp of clear aspect
fuses the signal should display a more restrictive aspect than no light
which is equivalent to 'Red'.
To avoid this conditions, an arrangement in the lamp control circuit can be
adopted in such a way that if a lamp fuses the signal can be restored to a
more restrictive aspect.
This arrangement is called the "cascading (cutting-in) arrangement".

122 The cutting in arrangements
can also be provided by by-
passing the control relay
contacts by the lamp checking
relay contacts. This looks
simple, but requires more
number of ECR contacts.

DR
1
1
HECR
1
HHECR DECR
1
1
DECRHHECR
1
HECR
1
11
11
11
1
1
1
RG
RECR
1
NX110
1
HR
BX110 HR
1
DR
HG
DR DECR
DECRDR
DR
HECR
1
1
DR
DG
DECR
1
1
HHR
1
HR
1
HHECR
DR
DR DECR
11
DECRDR
NX110
HRBX110 HHR
HHG
DR
R
C
R
C
R
C
R
C

124Protection for Red Lamp Failure.
When red lamp in the automatic signal fails, the cutting in
arrangement cannot restore the signal to a more restrictive aspect.
Hence, the signal goes blank aspects not in a position to protect the
automatic signal section specially when a train occupies this section.
Under these conditions, the usual practice is to force the rear signal
to danger so that it assumes the protection of not only its section,
but also the section in advance and as a result the rear signal will
remain at red till the train clears two sections ahead.
The circuit arrangements required for this can be provided in three
different methods.

125First Method

In this method, the red lamp checking relay 3 RECR front contact
is included in series with the 3TR front contact in the 'cut
section' arrangement between 3TR and A1TR
whenevertheaspectchanges,itbecomesblankduringwhichallECRsmaydrop
causingthedisconnectionoffeedtotherearberthtrackthusreplacingtherear
signaltodangerautomatically.ThisundesirableeffectcanbeeliminatedifECRs
aremadeslowtorelease.

126
theoverlaptrackrelayisshuntedwiththebackcontactsofRECR&A3TRsothat
whenredlampfails3TRisshuntedandhence,itdrops.
ThiscausesdisconnectionoffeedtotherearberthtrackcausingA1TRtodrop
whichwillrestoresignalNo.1toredtillthetrainclearsadvancesection.
Thedisconnectionofthis
shortcircuitingloopacross
3TReliminatesthered
lampprotectionwithout
anyindication.
Second Method

127
Third Method
Inthisthefrontcontactof3RECRinserieswiththecutsectionarrangementasin
thefirstmethodbut
A3TRfrontcontactisprovidedtobypassthe3RECRfrontcontacttomaintainthe
supplytothereartrackwhentheadvancesectionisclearsothatthesignalinrear
canchangeitsaspecttooff.
This method
eliminatesthe
undesirable
featuresoffirst
and second
methods.

128
Four-Aspect Automatic Signalling
Generallywhentheautomaticsignalsareprovidedwithdistancebetweenthe
signalsnotlessthanBDthen3-aspectsignalswillservethepurpose.
ButifthedistancebetweentwoconsecutivesignalsislessthanBDonaccountof
stationsbeingverycloseortoimprovethesectioncapacitybyreducingthe
headwaybetweentrainsandreducingtheautomaticsignallingsections,thenthe
automaticsignalshavetobeprovidedwith4aspects.
Inthiscase,thesequenceofaspects,whenatrainpassesasignalisRed,Yellow
doubleYellowandGreenasthetrainoccupiesthesectionafterpassingasignal
andclearingonesection,twosectionsand3sectionsaheadofthesignal
respectively.
-

129
Inthis,itiscustomarytoensurethatthedistancebetweenthesignaldisplaying
redandasignaldisplayingdoubleyellowisatleastequaltoB.D.
Ifthisdistanceisnotavailablethen,thedoubleyellowaspectsarerepeatedtill
thelastsignaldisplayingdoubleyellowisatabreakingdistanceinrearofthe
signaldisplayingRed.

130
Aspect control of Four -aspect automatic signals
Whenasignalis
displayingGreen,all
thecontrolrelaysare
keptenergised.
First Method

131

132
Second Method
Any one yellow up

Thank you
P. SRINIVASA RAO M.Sc.,
INSTRUCTOR / ODS LAB /IRISET/ SC

Concepts of Automatic Block Signalling.ppt

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