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Transcript of NE Railway Training report
TABLE OF CONTENTS
Acknowledgement
Preface
Introduction To Indian Railways.
Module 1: Microwave Communication.
Module 2: Railway Signalling And Signal Workshop.
Conclusion
1
Acknowledgement
Behind the completion of any successful work there lies the contribution
of not one but many individuals who may have directly or indirectly contributed
to it.
First and foremost I am grateful to the management of NORTH
EASTERN RAILWAY,GORAKHPUR for providing me the opportunity to
undertake my “Summer Industrial Training” in the organization.I specially
convey my thanks to all the staff members for their precious guidance during
our training and in completion of this project. I feel priviledged to express my
deep regards and gratitude to all the Engineers and staffs of MICROWAVE
CENTRE,N.E RLY,GORAKHPUR and SIGNAL WORKSHOP,N.E
RLY,GORAKHPUR.
I am thankful to all my teachers who have best owed upon me their
knowledge and have been guiding light through out my course. They have cast
an indelible impression on my existence.
I am much indent to my friends whose moral support always inspired me
to come out with the best.It’s great pleasure to extend my heartfelt thanks to
everybody who helped me through the successful completion of my training.
The acknowledgement would be incomplete if I fail to express deep sense
of my obligation and reverence to my parents without whom this work would
not have seen the light of the day.
Akhilesh kumar singh
2
Preface
Engineering students gain theoretical knowledge only through books. Only
theoretical knowledge is not sufficient for absolute mastery in any field.
Theoretical knowledge in our books is not of much use without knowing its
practical implementation. It has been experienced that theoretical knowledge is
volatile in nature; however practical knowledge imparts solid foundation in our
mind.
The practical industrial training is a part of four year degree
course.Practical industrial training mainly aims at making one aware of
industrial environment which means that one gets to know the
limitations,constraints and freedom under which an engineer works.
To accomplish this aspect “Gautam Buddh Technical University (GBTU), Lucknow(U.P.)” has included 4 weeks summer training for B.Tech 3rd Year students in our curriculm.
This report is infact a summary of, what I have learnt and seen during my
training in N.E Railways. It simply summarizes the Microwave communication,
signaling and signal workshop as carried out in Indian railways.The training
mainly involves industrial and complete knowledge about designing,assembling
and manufacturing of equipments.Thus it is very necessary before becoming a
professional engineer.
INDIAN RAILWAYS
3
FOUNDED - 16TH APRIL,1853
HEADQUARTER - New Delhi,India
AREA SERVED - India
INDUSTRY - Railway and Locomotives
SERVICES - Rail Transport
REVENUE - Rs. 107.66 billion
EMPLOYEES - 1,406,430
INDIAN RAILWAYS(BHARTIYA RAIL) abbreviated as IR,is a state
owned railway company of India,which owns and operate most of the
country’s rail transport.It is overseen by Ministry of Railways and
Government of India.
Indian Railways has one of the largest and busiest rail networks in the
world,transporting over 18 million passengers and more than two million tones
of freight daily.It is the world’s largest commercial or utility employer,with
more than 1.4 million employees.The railways traverse the length and breadth
of the country,covering 6,909 stations over a total route length of more than
63,327 kms (39,350 miles).As to rolling stock,IR owns over 20,000 freight
4
wagons, 50,000 coaches and 8,000 locomotives.Railways were first introduced
to India in 1853.By 1947,the year of India’s independence,there were 42 rail
systems.In 1951,the systems were nationalized as one unit,becoming one of the
largest networks in the world.IR operates both long distance and sub-urban rail
systems on a multi-gauge network of broad,meter and narrow gauges.It also
owns locomotives and coach production facilities.
As the economy of India improved,almost all railway production units
were ‘Indigenized’(produced in India).By 1985,steam locomotives were phased
out in favour of Diesel and Electric locomotive.The entire railway reservation
system was streamlined with computerization between 1987 and 1995.
In 2003,the Indian Railways celebrated 150 years of its
existence.Various zones of the railways celebrated the event by running
Heritage trains on routes similar to the ones on which the first trains on the
zones ran.The Ministry of Railway commemorated the event by launching a
special logo celebrating the completion of 150 years of service.Also launched
was a new mascot for the 150 th year celebrations,named “Bholu,the Guard
Elephant”.
Snapshots :-
It encompasses 6,909 stations over a total route length of
more than
63,028 kilometres of route length and a track length of 111,600 km .
It is one of the world's largest commercial or utility employers,
with more than 1.6 million employees.
5
It grossed a revenue of ` 88,355 cr and bagging a net income
of ` 951 cr in
the financial year 2009-10 .
It moves 2 million tons of freight & 20 million people daily
across the
county with the help of 200,000 (freight) wagons.
7,000 passenger trains across the country services 20 million
people to
their destinations .
Vivek Sahai is the current Chairman of Railway Board .
Organizational Structure-:
Indian Railways is a department owned and controlled by the Government of
India, the Ministry of Railways . IR is administered by the Railway Board,
which has a financial commissioner, five members and a chairman.
Railway zones :-
IR is divided into zones, which are further sub-divided into divisions. The
number
of zones in Indian Railways increased from six to eight in 1951, nine in 1952,
and finally 16 in 2003. Each zonal railway is made up of a certain number of
divisions, each having a divisional headquarters. There are a total of 67
divisions under 16 zones , presently operating in the country .
6
Each of the 16 zones, is headed by a General Manager (GM) who reports
directly to the Railway Board. The zones are further divided into divisions
under the control of Divisional Railway Managers (DRM). The divisional
officers of engineering, mechanical, electrical, signal and telecommunication,
accounts, personnel, operating, commercial and safety branches report to
the respective Divisional Manager and are in charge of operation and
maintenance of assets.
7
Further down the hierarchy tree are the Station Masters who control individual
stations and the train movement through the track territory under their stations'
administration.
Practical Training under NER :-
We've received the scheduled Summer Practical Training, as a part of our
curriculum, from June 22, 2010 – July 12, 2010 under Divisional Railway
Manager,NER,Gorakhpur.
.
We've studied about the following operational technologies in the IR -
1. Microwave Communication & Links.
2. Railway Signalling.
3. Signal Workshop(Automatic track changer,Electronic point machines and
relays)
8
MODULE I
MICROWAVE COMMUNICATION
Microwaves are electromagnetic waves whose frequencies range from 1 GHz
to 1000 GHz. Microwaves are so called since they are defined in terms of their
wave -length.There are large number of bands in microwave region.
Microwaves are used for controlling of trains.It is necessary to give correct
running and stopping of the trains and there should be a single train on a single
track.
Microwaves help the railway staff to communicate for this purpose.Stations on
average of 40km can communicate with each other by microwave.there are
large number of bands in microwave region. Before the advent of fiber optics,
these microwaves formed the heart of the long distance telephone transmission
system.
➔ In its simplest form the microwave link can be one hop, consisting
of one pair of antennas spaced as little as one or two kilometers
apart, or can be a backbone, including multiple hops, spanning
several thousand kilometers.
➔ A single hop is typically 30 to 60 km in relatively flat regions for
frequencies in the 2 to 8 GHz bands. When antennas are placed
between mountain peaks, a very long hop length can be achieved.
Hop distances in excess of 200 km are in
existence.
➔ The "line-of-sight" nature of microwaves has some very attractive
advantages over cable systems. Line of sight is a term which is only
partially correct when describing microwave paths.
9
Microwave Transmitter and Receiver-:
Below figure shows block diagram of microwave link transmitter and receiver
section --
➔ The voice, video, or data channels are combined by a technique known as
multiplexing to produce a BB signal. This signal is frequency modulated to an
IF
and then up converted (heterodyned) to the RF for transmission through the
atmosphere.
➔ The reverse process occurs at the receiver. The microwave transmission
frequencies are within the approximate range 2 to 24 GHz.
➔ The frequency bands used for digital microwave radio are recommended by
the
CCIR. Each recommendation clearly defines the frequency range, the number
of
channels that can be used within that range, the channel spacing the bit rate and
the polarization possibilities.
10
Microwave Transmitter and Receiver.
Application Of Microwave In Indian Railways -:
Microwaves are used for controlling of trains.
It is necessary to give correct running and stopping of the trains and there
should be a single train on a single track.
Microwave communication help the railway staff to communicate for this
purpose.
Stations on average of 40 km can communicate with each other by
microwave.
11
Frequency Range In Microwave Region-:
BANDS FREQUENCY(GHZ)
L 1.1-1.7
LS 1.7-2.6
S 2.6-3.9
C 3.9-8.0
X 8.0-12.5
Ku 12.5-18.0
K 18.0-26.0
Ka 26.0-40.0
How Terrestrial Microwave Transfer And Receive Data :
Terrestrial microwaves communication employs earth based transmitters
and receivers to transfer and receive data.
The frequencies used are in the low giga-hertz range,which limits all
communication to line of sight.
Examples of terrestrial microwave equipment-Telephone relay
towers,which are placed every few miles to relay telephone signals across
country.
12
Antennas Are Used To Transfer Data -:
Microwave transmissions typically use a parabolic antenna that
produces a narrow,highly directional signals.
A similar antenna at the receiving site is sensitive to signals only within a
narrow focus.
Because the transmitter and receiver are highly focused,they must be
adjusted carefully so that the transmitted signal is aligned with the
receiver.
Role Of Microwaves In Passenger Reservation System -:
In PRS,the Gorakhpur Zone is connected to the main server through
communication lines and there is the need of non stop working of PRS in
Indian Railways otherwise there will be big loss to Indian
Railways.
So to increase the reliability of PRS,the main server is also connected to
the zones through microwave links.In case if there is a failure in the
physical mediathen the PRS can be operated by microwave.
Microwave Systems -:
There are two types of Microwave Systems.In first schematic processing is in
analog form and in second schematic processing is in digital form.
According to this there are two types of microwave systems as follows-:
13
1. Analog system.
2. Digital system.
The analog system is old system and digital system is new one.
Analog Systems -:
The analog system is simple and this system consists of Transmitter,Receiver
and communication media which is Microwave here.
Transmitter:
The role of Transmitter is to send the signals and it consists of following parts:-
Multiplexer(MUX):-
This is used to transmit various signals simultaneously.Here there is
many Input and there is only one output.The output of the multiplexer is
given to the Radio Equipment.
Radio Equipment:-
It receives the output of the multiplexer and then processes the
signals.This is the most important part of the transmitter and the antenna
is connected to the radio equipment directly.
Transmitting Antenna:-
This is a metallic object and this is used to transmit the signals in free
space.The antenna transmit the signals at 7 GHz in the space.Here the
antenna consists of a parabolic reflector and a Horn antenna.The antenna
is directional and directive.
Tower:-
The tower is a metallic and this is used only to give height to the antenna.
14
Receiver:-
The role of receiver is to receive the signals.The receiver consists of
following parts:
Receiving Antenna:
The receiving antenna receives the incoming signal and then it gives the
signals to the mixer.
Mixer:
Here in the mixer the frequency mixing takes place and now the output
frequency is different.And the output of the mixer is given to the
Discriminator.
Discriminator:
The Discriminator seperates the signals and the demodulation process is
done here.This means that the carrier signal is removed and only the
Message signals are taken.
Demultiplexer:
The demultiplexer has only one input and here the separation process is
done and the sent signals are recovered back.
Digital Systems :
This system has a large number of advantages over analog system.This
system is a new system and uses digital technology.Digital system is
more reliable and efficient.
Digital system consists of following parts:
Transmitter-:
The transmitter of digital system is different from analog system.In this
transmitter two types of multiplexers are used which are as follows:
Primary multiplexer:
15
This is the first multiplexer at the transmitter side.It multiplexes 30 voice
signals and in the digital system sixteen multiplexers are used of this
type.The output of every primary multiplexer is 2.04 Mbps.
Higher order multiplexers:
This multiplexer is big and multiplexes the signal coming from the
primary multiplexers.The output of this multiplexer is 34.368 Mbps.
Radio Equipment:-
The output of the higher order multiplexer is given to the radio
equipment.Radio equipment process these signals and make them able to
be transmitted by antenna.
Antenna-:
The antenna is same as we are using in analog system.Here also we use
horn antenna and parabolc reflector.Horn antenna is at the focus and it
send the signals to the parabolic reflector surface.After striking from the
surface,the signals are parallel and it is transmitted in such form.
Tower-:
Here also the role of tower is to give height to antenna.In Microwave
station (Gorakhpur) of Indian railways,there are two towers ,one is for
analog and the other one is for digital communication.
Receiving Antenna-:
The receiving antenna is at the receiving side,receives the signals and
sends it to radio equipment.There is line of sight communication of
microwave in between transmitting and receiving antenna.
Radio Equipment-:
16
The radio receiver receives the signal coming from the antenna.Here the
signals are processed and then these signals are sent to higher order
demultiplexers.
Higher Order Demultiplexers-:
In this demultiplexer the signals are separated.And the output of this
multiplexer is given to the low level multiplexer.There is sixteen outputs
and every output has a bit rate of 2.048 Mbps.
Low level multiplexer-:
This multiplexer receives the output from the higher order multiplexer.It
has one input and thirty outputs.The output frequency rate is 0-4
KHZ.This is the frequency range of human voice.Here the original voice
signals are obtained.
Power Reqirement -:
Both systems require power for their operation.A dc current is
required for both systems.This dc current is provided by a set of
batteries.An extra set of battery is also kept for emergency.
Analog System-:Analog system requires a dc voltage of -24v for its
operation.
Digital communication-:Digital system requires a voltage of 48 v for its
operation.
Essential Environment For Analog And Digital Systems-:
There are some requirements for these systems for there proper
functioning.Following are some of the requirements:-
1. Air Conditioning.
17
2.Dust Free Environment.
3.Uninterrupted Power supply.
4.Proper trained staff.
Use Of Repeaters -:
After travelling some distance the microvave gets distorted.
The Repeater is a device which is used to obtain distortion free
microwave and this clean and distortion free microwave is transmitted
again in forward direction.
Repeaters are used at the average distance of 40 km.
Fault Control Procedure -:
In a typical Railway Telecom network Scenario,following types of
Telecom Network coexists:
Transmission-:
1.Microwave/UHF Network.
2.Optical Fibre Cable Network.
3.RE Telecom Cable Control Network.
4.Railway’s Overhead Wire Control Network.
5.DOT owned Overhead wire control Network.
Switching-:
1.Electronic Telephone Exchanges.
2.Electromechanical Telephone Exchanges.
18
Others-:
1.Single Channel Duplex UHF/VHF Radio Systems.
2.Multiple Access Radio Relay.
3.Pair Gain System.
4.VHF/UHF Simplex Trans-receivers.
5.Talk Back systems for Major yards.
It is indeed very necessary to established well defined Fault Control
procedures for satisfactory maintenance of such diverse Railway
Telecommunication Networks so as to meet the demanding requirements of
Indian Railways in 21st century.
Typical Telecom Fault Control Setup -:
Typical telecom fault control setupon railway shall consist of
following-:
1. Zonal Telecom Fault Control Setup.
2. Divisional Telecom Fault Control Setup.
The Zonal Telecom Fault Control Setup shall be one for entire zonal railway.
The Divisional Telecom Fault control setup shall be established in each
Division of the zonal railway.
1.Zonal Telecom Fault control setup-:
It shall be manned by Section Engineer(Telecom) in a general shift.Three
section engineers(Telecom) shall be earmarked and should man the zonal fault
control setup round the clock in case of emergencies.Following Telecom
Network shall be monitored by zonal Telecom fault control Room.
19
Microwave/UHF Network on the entire zonal Railway -:
The Zonal Telecom Fault Control room shall also function as an
emergency telecom control room in case of emergencies requiring
immediate telecom facilities/restoration.The emergencies may consist of
the following-:
Major rail accidents.
Cyclones.
Breaches.
When the Zonal Telecom Fault control room function as the Emergency
Telecom Control room,the divisional Telecom fault control rooms of the
affected Division(s)shall report their positions to the Zonal Telecom Fault
control room which in turn shall advice the Telecom officials at HQs of the
latest developments.
The zonal Telecom Fault Control Room shall function under the direct control
of Dy. Chief Signal & Telecom Engineer(Microwave) or any other officer
designated by communication engineer of railway.
2.Divisional Telecom Fault Control Setup-:
The Divisional Telecom Fault Control setup shall have two components:
For monitoring all telecom networks other than Microwave/UHF called
Divisional Telecom Fault Control Room.
20
For monitoring Microwave/UHF networks called Divisional Microwave
Fault Control Room.
Each of these Contol rooms shall be headed by a Senior Section
Engineer(Telecom) in a general shift.Three section engineers
(Telecom)/Jr. Engineer(Telecom)shall man the fault control room round
the clock.
Following Telecom Networks shall be monitored by the Divisional
Fault control Room-:
Optical fibre Cable Network.
RE Telecom Cable Control Network.
Railway’s Overhead wire control network.
DOT owned Overhead Wire Control Network.
Electronic Telephone Exchanges.
Electro-mechanical Telephone Exchanges.
Single channel Duplex UHF/VHF
MODULE II
21
Railway Signalling & Signal Workshop
Introduction-:
Signaling is one of the most important aspects of Railway
communication. In the very early days of the railways there was no fixed
signaling to inform the driver of the state of the line ahead. Trains were driven
“on sight”. But several unpleasant incidents accentuated the need for an
efficient signaling system. Earliest system involved the Time Interval
technique. Here time intervals were imposed between trains mostly around 10
mins. But due to the frequent breakdown of trains in those days this technique
resulted in rear-end collisions. This gave rise to the fixed signaling system
wherein the track was divided into fixed sections and each section was
protected by a fixed signaling. This system is still being continued although
changes have been brought about in the basic signaling methods. Earlier
mechanical signals were used but today block signaling is through electric
instruments.
When trains run on railway tracks they follow rules of operations in
which safety plays a very important role.The most important rule in respect of
safety is to ensure that two trains do not occupy the sameposition on the track
at the same time. To make this rule work operation of trains uses signaling
to controlmovement of trains on tracks and divides tracks into several
sections which are protected by the signals.
22
Fig shows a representation of a railway signaling arrangement. The horizontal
liner represents the railway track, the signals are depicted by the symbol of the
circle with a horizontal and vertical line to this circle and the red rectangles are
the trains. This representation is however to explain how trains are run safely.
Locking-:
There are three types of locking
a) Direct
b) Approach
c) Route
Direct locking is available as long as a signal is clear or track is occupied or a
point is set. This is the most fundamental level of locking.
23
When signal S1 is cleared the cleared condition of the signal locks other signals
which can cause trains to run on any part of the route over which S1 allows a
train to run. Thus with S1 cleared allowing trains to move to track T1 signal S4
cannot be cleared and willbe locked as the latter also allows trains to occupy
track T1. Other form of direct locking is the locking of the point in the route for
which signal S1 is cleared. If S1 is cleared to the straight route T0 – T1 – T2
then the point P1 will be set and locked to allow a train to move on the straight
route over Point P1.Attempts to move point P1 from this position will not be
allowed and hence will be locked. Conversly if the point P1 is not set for
straight the signal S1 will be locked. The occupation of a track also locks
signals if T1 is occupied then signal S1 cannot be cleared. Signal S1 is therefore
directly locked to the cleared status of the track. Points are directly locked to
track circuits over the point zones. If the track circuit over a point zone is
occupied the it is locked so that it cannot move. This is the direct locking of the
point.
24
Approach Locking -:
While ensuring safety for train running it is not only necessary to ensure that
safety is ensured over all portions of track for which signals have been given
but also over portions over track which can get occupied due to trains
approaching a signal which protects these portions of track failing to stop at this
signal. Such protection is required under the condition when the signal
protecting had not been cleared.
Flank protection and isolation -:
When a train is allowed to move by a signal it is also necessary to ensure that
no part of the train will be Involved in a side collision.
Protection in the overlap -:
When a train is approaching a signal a possibility exists that the train may fail to
stop at the signal where it is intended to stop due to mechanical failure or due to
25
human failure. While there is no absolute arrangement to control against this
eventuality a partial safety is ensured by providing a small part of the track
beyond the signal at which the train is to stop free of any conflict or obstruction
to the train if it fails to stop at the foot of the signal. Typically when train TR1
is approaching S1 it will normally be ensured that the track section onto T2 is
free of any obstruction. This includes possibility of any train from the opposite
direction reaching T2. Hence if TR1 is allowed to approach S1 it will be
ensured that the train TR2 does not at the same time approach signal S2. Any
point in this portion of the track also needs to be set and locked in the position
allowing safe movement through it. If TR1 is approaching signal S1 it will
mean point P2A must be set and locked for the straight route. The point P2A
and track T2 is referred to be in the overlap for signal S1 and locks the signal
allowing approach of a train to signal S1 if not found free. Conversely if signal
S1 is cleared any condition which can lead to the overlap from failing to remain
in the condition to maintain safety for train TR1 approaching S1 will be locked.
Release of locking -:
Signals indicate when a route which it checks is safe for a train to travel. The
safety is checked from different angles as explained above. After a signal has
been cleared for a train it is required to be put back to danger as the train moves
past it. There are two reasons for doing this-:
a) To ensure the safety of the train which has moved past.
b) To allow clearance of other signals which has been locked by it.
The release of locking is done automatically as a train moves along the route a
signal had cleared for it. The locking is released in stages-:
a) As the train moves past the signal the approach locking is brought back to
normal.
26
b) As the train clears the first track after the signal the direct locking gets
released.
c) As the train moves the route locking , flank or isolation protection for the
portions of the route cleared by the train is removed.
d) After the train has come to a stop at the next signal for sufficient time to
prove that it is not moving the overlap is released. This is the normal release
with the passage of train. There can however be occasions when it is required to
cancel a signal which has been cleared and yet to be passed by the train. When
this is required the signal is canceled. When the signal is canceled it is
necessary to ensure that the locking it had enabled also get canceled. Here again
the cancellation starts from release of the approach locking followed by release
of the route locking, locking of flank and isolation and finally the overlap. The
release is done only after it is established that a train which had been
approaching the train has come to a stopped at the signal before the locking to
other signals are released.
Detection of trains -:
Signals control movement of trains. For it to effectively control movement of
signals there is a need to know the location of trains on the track. The railway
tracks are divided into short sections normally referred to as track sections. At
any time only one train can occupy one such a section. Track circuits or axle
counters are used for the detection of trains in these sections. Only one train can
occupy a
track section at any time. Normally the detector is fed with the signal from the
source through the rails and as long the detector receives a signal it concludes
that the track section is not occupied. If a train occupies the track section being
monitored it short circuits the track cutting off the signal from the source to the
detector. When the detector fins loss of signal from the source it concludes that
27
the section is occupied by a train. Principles of fail safety is also very well
demonstrated in this arrangement. In case of a failure like a broken wire, rail
fracture, power supply failure, failure of the source the detector will lose the
signal and conclude the section is occupied by a train. This will allow the
detection to maintain safety even under failure condition and satisfy
requirments of fail safety.
Control and drive to points -:
Points are driven by electrical motors. The motors are known as point motors
and moves point using a mechanism which including the motor is referred to as
point machine. A point machine mechanism moves switches of a point through
a mechanical arrangement of rods and gears.
Signal s-:
Signals indicate to the train drivers whether the route till the next signals is
reached is safe or not. Before a signal is cleared the signal control logic verifies
that everything is safe for a train which follows it. This will mean-:
a) All track sections over which the train will be routed is unoccupied. This is
checked by checking the status of the track circuit relays. Track proving relays
of all track sections which are clear will be picked up. By checking the status of
these relays which are referred as track relays the signaling control logic can
determine
that the route is clear.
b) Routes of any signals which conflict with the signal is not cleared and that
none of the signals have been approach locked.
28
c) There is not route set over a track section conflicting with the route of the
desired signal. This is proved by checking that all track circuits over which the
signal reads is clear of route locking.
Implementation of Signaling Systems –
Train running and signaling the drivers of the trains depends to a significant
extent on mechanized equipment. The technologies used for this application
ranges from very rudimentary systems to highly sophisticated equipment. The
technologies are based to a great degree on mechanical arrangement at large
number of installations. Advanced technologies are in use on sections where
train densities are high and
specially where Railway Electrification has already been done. Technologies
used for this application are for two reasons :-
1) To ensure safety of train running.
2) To improve operational efficiency.
Basic Principles :
Safety of train running in practice means ensuring that two trains do not occupy
the same location at the same time. Since trains are bound onto Railway tracks
it means ensuring two trains do not occupy same location of the track at the
same time. This is ensured in two stages-:
1) By dividing the Railway track into sections.
2) Entry into each of these sections are controlled by suitable signaling system
which ensures through various means that when a train is signaled to Basics of
Railway Signaling.
29
3) The drivers controlling the train are signaled sufficiently in advance so that
they can stop the train before signals which are not cleared. Since trains
typically move at a speed of around 100 Km./Hr. it requires a braking distance
of 1 Km before a signal at which it is required to stop. Hence signaling system
ensures that signals are conveyed to the Drivers sufficiently in advance to bring
the train to stop safely.
4)It should not be possible to move a point when a train is over the point or is
very near to the point having picked up signal allowing the train to move over
the point likely to be moved. In addition to above various other rules are applied
to
make a signaling system safe. These rules are results of experiences gained after
accidents. Thus one rule msays that if a passenger train has to run through a line
then this run through line should be isolated from other connected lines in the
station by suitable means. This rule has been introduced to ensure that if there
is a train standing on a connected line and it starts rolling it cannot result in a
devastating collision as it is kept isolated from run through line on which high
speed train has been signaled to go through.
Basic Rules -:
The basic rules of safety in connection with train running is implemented
through various methods. The Railway Engineering is very old and, therefore,
implementation methods also are old. Availability of modern electrical &
electronic technology is gradually changing the implementation of Railway
signaling systems. The technologies used in Railway signaling system depended
on human element initially. Gradually mechanical systems were introduced
followed by electrical/electromechanical and now
electronics/electrical/electromechanical systems. The human element in
30
Railway signaling is getting reduced wore & more for improving safety and
efficiency of train operations.
The Human element :
Signaling Systems exist where setting of the point and locking of the same is
entirely manual. The locking of the point is achieved through key and lock
system.
The signals are all hand Signals. A more mechanized arrangement is where
switches turning points are connected to levers and signals are given by
mechanical arms known as semaphore signals. In both the systems the human
element ensure that the routes a train will take is not obstructed. The set person
who is clearing the signals for passage of the trains achieves this entirely
visually. The oldest signaling Systems are entirely manual where even the
checking that a route has been properly is manual.
The 50 Hz & 83&113 Hz signal source is used in a manner similar to D.C.
voltage and requires no special mention as the detector is simply a relay. In case
of 83&1/3 Hz system normally 3 phase system is used and two phases are used
on any section. The feed end gives one phase and a second phase is always fed
to the detecting relay. When the track circuited section is free the two phases
create a rotary force as in a AC electric motor. Absence of one of the phase via
the rails due to presence of a train removes the rotating force dropping the relay.
The 83&1/3 Hz track circuits is a popular track circuiting arrangement.
Electronics in Railway Signaling for improved
Safety-:
The audio frequency track circuit is the latest entrant in the field. This
arrangement feeds an Audio frequency signal which causes pick up of Relay via
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the detector. A simple Audio frequency generator is used and at the detecting
end a L.C. resonant circuit is used for picking up the desired Audio frequency
signal & rejecting others. Due to the use of high frequency it is possible to use
the Railway track as a
transmission line and use of physical insulating pieces electrically isolating one
section as "R' from 'A-B" is not required. By using resonant L.C. circuits at
suitable points the AF signal can be made to stop beyond any particular point
without the need of any insulating joint. This feature is a big advantage for this
type of track circuit as there is no need to cut Rails & insert insulating pieces.
Indian Railways but considerable difficulties, faced on account of loss of track
side equipment due to theft has rendered the system ineffective. As a corollary
to this simple arrangement, systems of continuous automatic control of trains
are also available. Such systems continuously control speed of trains through
transfer of signals from the track side to the engine. The system is quite
elaborate consisting of a receiver located in the engine and suitable transmitter
coils located on the sleepers between the track. A computer computes the
required speed of trains running on the track for ensuring safety as well as for
ensuring that trains run on time speeding as necessary or slowing when needed.
Such a system is being implemented on Metro Railway Calcutta in India for the
first time. Such systems are important for Metro Railway services where time
between two successive trains is are required to be kept very small to as much
as one min or less. Even with such small interval between trains complete safety
& punctuality can be attained using the continuous automatic train control and
protection system. Use of Electrical/Electronic Gadgets for ease of operation
Over and above allowing higher levels of safety by using sophisticated controls
the use of electrical/electronic gadgets for Railway Signaling is also made for
ease of train operations and higher efficiencies. Systems known as Panel
Interlocking and its sophisticated variety known a Route Relay Interlocking are
for control of signals and points with higher efficiencies.
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Design of Signaling Circuits -:
The design of signaling circuits is based on simple principles. Railway
Signaling being one of the oldest control engineering is based on very simple
methods
and principles. One of the main reasons of its simplicity lies in the fact that
technological aids for design were not very high till late 21st century and
complicated design principles and methods could not be supported. as a result
of this the circuits are drawn using very simple symbols and names are kept
short. If looked in the context of the fact that the circuits had to be hand drawn
in times where duplicating facilities were very primitive the reason why they
are so simple
can easily be understood. Signaling circuits are based on defining relays of the
following types-:
a) Those signifying states in progress of a command
b) Those indicating steady state of the signaling functions.
c) The last operation has been completed properly .All circuits of Railway
Signaling has to ensure safety. Hence both the type of relays defined above also
always ensure safety. This fundamentally means that in absence of any voltage
to the circuit the relays shall assume safe state which is the drop state for all
neutral relays and can be dropped or one of the latched state for relays which
are latched electrically or mechanically.
Signal Workshop -:
In the signal workshop of Indian railways,following machine are
manufactured which are used as a part of signaling system-:
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1. Electric point machine.
2. Relays.
Points are provided to divert the running trains from one track to another. The
points have movable switches which can be operated electrically by a point
machine. A point can be single-ended point or double-ended point depending on
whether the movable switches are provided at one end or two ends of the point,
The two switch rails of the point are rigidly connected together by a cross bar so
that they can be moved from one position to the other position together by the
point machine. If the position of the switches is such that the train is moved on
to the main line as shown above, then the point is said to be in its normal (N)
position. If the switch rails are moved to the other position as shown below so
that the train is diverted to the loop line, then the point is said to be in its
REVERSE (R) position.
Solid State Interlocking -:
Solid State Interlocking is a data-driven signal control system designed for use
throughout the British railway system. SSI is a replacement for
electromechanical interlockings---which are based on highly reliable relay
technology---and has been designed with a view to modularity, improved
flexibility in serving the needs of a diversity of rail traffic, and greater
economy. The hugely complex relay circuitry found in many modern signalling
installations is expensive to install, difficult to modify, and requires extensive
housing---but the same functionality can be achieved with a relatively small
number of interconnected solid state elements as long as they are individually
sufficiently reliable. SSI has been designed to be compatible with current
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signalling practice and principles of interlocking design, and to maintain the
operator's perception of the behavior and appe arance of the control system.
A schematic view of SSI processor.
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Conclusion
This report takes a pedagogical stance in demonstrating how results from
theoretical electronics may be applied to yield significant insight into the
behavior of the devices .Electronics & communication engineering practice
seeks to put in place, and that this is immediately attainable with the present
state of the art. The focus for this detailed study is provided by the type of solid
state signaling and various communication systems currently being deployed
throughout mainline railways. Safety and system reliability concerns dominate
in this domain. With such motivation, two issues are tackled: the special
problem of software quality assurance in these data-driven control systems, and
the broader problem of design dependability. In the former case, the analysis is
directed towards proving safety properties of the geographic data which encode
the control logic for the railway interlocking; the latter examines the fidelity of
the communication protocols upon which the distributed control system
depends.
We have covered in this report the history ,latest developments in Railway
systems as well as related fields. We have studied the various uses of
electronics and communications in railways like microwave
communication,signaling,electronic point machines etc..
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