1 general introduction various configurations of aftc various types of aftc application related...
TRANSCRIPT
1
General introduction
Various configurations of AFTC
Various types of AFTC
Application related issues
Do’s and Don’ts for AFTC
Achievements & references on Indian Railways
2
Track Circuits
Track Circuit• An electrical circuit of which running rails of a railway track form a part.
Types of Track circuits
• AC Track Circuits: Used in DC Traction Area
• DC Track Circuits: Used in AC Traction Area
• Audio Frequency Track Circuits: Used in both AC and DC traction Area.
3
Advantages of Audio Frequency Track Circuits
Joint-Less - Insulation Rail Joints not required.
Immune to Traction - Can be used in AC/DC/Non RE Areas.
Double Rail - Both Rails are available for traction return.
Immune to harmonics - Not affected by harmonics generated by
Thyristor controlled locomotives.
Longer Lengths - Hence ideal for Automatic Block signaling.
Dependency on other departments are minimized as no joints are
required for separation of track circuits.
4
Operating frequencies of AFTC Type TI 21Operating frequencies of AFTC Type TI 21
For more than four tracks the above sequence is repeated.
Eight Operating Frequencies A - H
A & B - Paired Frequencies for FIRST Line BA B A A
C & D - Paired Frequencies for SECOND Line DC D C C
E & F - Paired Frequencies for THIRD Line FE F E E
G & H - Paired Frequencies for FOURTH Line HG H G G
5
Operating Frequencies - Values
Frequency Name
Frequency Value
A 1699 Hz
B 2296 Hz
C 1996 Hz
D 2593 Hz
E 1549 Hz
F 2145 Hz
G 1848 Hz
H 2445 Hz
6
System composition of AFTC
Transmitter Generates Audio Frequency Signal
Receiver Receives Audio Frequency Signal from Track and Picks up the Track Relay
Tuning Unit/Track Coupling Unit/ Interface Transmitter/Receiver with Track End Termination Unit
Track Relay Indicates Track Occupancy
Line Matching Unit Reduces Transmission Losses
Power Supply Unit Generates 24 V DC for Functioning of Tx/Rx
Lightening Arrestor Protects Tx/Rx from Lightening Surges/Spikes
7
AFTC Modules
8
Basic operating principle of AFTC
PowerSupply
Unit
TransmitterB
TrackRelay
Receiver B
PowerSupply
Unit
TU/TCUB
Track Circuit Frequency B
TU/TCUB
LA LA
Tx End Rx End
9
OSCILLATOR
MULTIVIBRATORMODULATOR
MATCHING/ISOLATING
OUTPUTFILTER
TRANSFORMER
OUTPUT
AMPLIFIER
TO TU/ETU/TCU
Transmitter (Tx)
• Generates and Transmits Audio Frequency (AF) Signal to Track
• Principle of Frequency Shift Keying is used for Modulation
4.8 Hz Square Wave
Corresponding Frequency A - H
Modulated Signal
f+17 f+17f-17 f-17
MODULATING WAVE 4.8 Hz
MODULATEDWAVE
F b F a F aF b
10
Receiver (Rx)
TRANSFORMERINPUT
Fa Fb Fa
INPUTFROM TRACK
FILTER AMPLIFIER FILTER DEMOULATOR
LOGICGATE DELAY CKT
2 SEC
DRIVER
RELAY
RELAY
TO TRACK
FILTER FILTERAMPLIFIER DEMOULATOR
Fa
Fb
After Logic Gate
O/P TO 2 SEC DELAY CKT
After
filter demodulator
After
INPUT
FROM TRACK
FaFb Fa Fb
Fb
Fa
• Receives AF Signal from Track and Picks up a Relay
11
Power Supply Unit (PSU)
24 V DC
T5
T85
T95
T115
T125
MOV
+
-
B24
N24
15000 uF+
-
EARTH
T105
T0
0-2 A
2-4.4 A
t20
t19
COM
RECTIFIER UNIT
110 V AC
• Generates 24 V DC required for Functioning of Transmitter and Receiver
12
• Tuning Unit (TU)
• Used for interfacing Rails with Transmitter/Receiver
T2
L
C1
TF
5
4
3
C21
2
T1
Earthing3-
Connected to Normal Power Tx
are connected to Rx
are connected to rail
Capacitors
Inductor
Transformer
or Low power Tx
L
4-5
1-2
T1-T2
TF
C1,C2
Track Interfacing Units
13
• End Termination Unit (ETU)
FREQUENCY B,D,F,HEND TERMINATION UNIT
T2
END TERMINATION UNITFREQUENCY A,C,E,G
L2
C1
L1
C2
R
1
23
5
4
C3
TF
L1
C1
R
T1
EarthingT2
or Low power Tx
are connected to rail
are connected to Rx
Connected toNormal PowerTx
4
5
TF
C2 1
23
T1-T2
4-5
3-
1-2
Inductor
Transformer
Capacitor
L-
TF-
C-
T1
• Used for interfacing Rails with Transmitter for Center Fed Application
14
• Track Coupling Unit (TCU)
Connected toTrackConnected to Rx5
4
2
1
Programming Link
Programming Link
C 2.2 50W
10TO TRACK
9TO TRACK
Connected toTx
9-10
4-5
1-2
CapacitorC
• Used for interfacing Rails with Transmitter/Receiver
15
Line Matching Unit (LMU)
90 V AC 10 V AC
Lo
Lo
Ho
Ho
LMU Tx SIDEHo
Ho
Lo
Lo
LMU TU SIDE
Lo - Lo - Connected to the Transmitter
Ho - Ho - Connected to the outdoor cable going to TU/ETU/TCU
Ho - Ho - Connected to Cable from Transmitter
Lo - Lo - Connected to TU/ETU/TCU
10 V AC 90 V AC
Used when Distance of Tx to TU is > 30 m.
Reduces Transmission losses.
16
Lightening Arrestor (LA)
Rx/Tx Rx/Tx
TU TU
MOV 1 MOV 2
GDTUBE
TU -Tuning Unit
Tx -Transmitter
Rx -Receiver
MOV -Metal Oxide VaristorGD Tube-Gas Discharge Tube
• Protects Transmitter/Receiver from Lightening and High Voltage spikes
17
Application of AFTC Type TI 21 on Straight Line
Track Circuit B TU BTU B TU A TU ATU A Track Circuit A
TransmitterB
Receiver B
Receiver A
TransmitterA
19.5 m19.5 m
TU A
19.5 m
Tuned Zone Tuned Zone Tuned Zone
Receiver A
TransmitterA
18
Functioning of Electrically Separated Joint
19.5 m
Tuned Zone
T2
L
C1
TF
C2
T1
5
4
3
1
2
FromTx A
Zero Arm
Pole Arm
1
23
5
4
T2
TF
T1
L
C1C2
FromTx B
Zero Arm
Pole Arm
Tuning Unit A Tuning Unit B
Track Circuit BTrack Circuit A Electrically Separated Joint
19
Rail Voltages on Tuned Zone
Electrically Separated Joint
19.5 m
TxTuning Unit "A"
RxTuning Unit "B"
TUNED ZONE
6.5 V
0.65 V0.7 V
6.3 V
Frequency “B”Frequency “A”
20
Advantages of Z bond over impedance bonds:No copper hence no theftNo oil hence no maintenanceLighter in weight and hence easy to handle
TU'B '
TU'A '
Frequency'A '
`Z' B OND (M .S . S trap o f crosssection 50x6 m m )
Frequency'B'
'Z' B ond F ixing C lam p
Tuned Zone
More than
500 AFTC using Z bonds
are in operation
over Indian Railways.
Balancing of Traction Return Current - Z Bond
21
Decentralized Configuration
Track Circuit B TU BTU B TU A TU ATU A Track Circuit A
19.5 m19.5 m
TU B
19.5 m
Tuned Zone Tuned Zone Tuned Zone
Tx B
LA
PSU
Tx B
LA
Rx A
LA
PSU
RRx B
LA
Tx A
LA
PSU
R
Track-side Location Box Track-side Location Box Track-side Location Box
Rx AR
LA
22
Salient Features of Decentralized Configuration
• TX, RX, R, LA and PSU are mounted in LOCATION BOXESLOCATION BOXES near track.
• TU/ETU/TCU are mounted ADJACENT to TRACK.
• 2 x 2.5 Sq. mm Cu Cable is used for feeding Signal from Tx to TU/ETU/TCU
• 35 Sq. mm Cu or 50 Sq. mm Al Cable is used to connect TU/ETU/TCU to Rails.
• Internal wiring is done using 1.5 Sq. mm multi-strand Cu Wire.
• Signaling Cable from/to Tx/Rx is terminated inside location box on M-6 terminals
23
Centralized Configuration
LMU TUSide
LMU TUSide
Track Circuit B TU BTU B TU A TU ATU A Track Circuit A
19.5 m19.5 m
TU B
19.5 m
Tuned Zone Tuned Zone Tuned Zone
Tx B
LA
Rx A
PSU
R Tx BRx A
PSU
RRx B Tx A
PSU
R
LMU TxSide
LA LA LA
LMU TxSide
LA LA
LMU TxSide
LMU TUSide
Cable Termination Rack
Centralized Equipment Room
0.9 mm Dia Quad Cable
24
Salient Features of Centralized Configuration
• TX, RX, R, LA, LMU-Tx Side and PSU are located in a Centralized Equipment Room.
• TU/ETU/TCU and LMU TU-Side are located Adjacent to Track.
• Line Matching Unit is used to reduce Transmission Losses.
• 0.9 mm dia 4 Quad Cable is used for feeding from Tx to TU/ETU/TCU and fromTU/ETU/TCU to Rx.
• 35 Sq. mm Cu or 50 Sq. mm Al Cable is used to connect TU to Rails.
• Quad Cable from Outdoor is terminated on CT Rack in equipment Room
• Internal wiring is done using 1.5 Sq mm Multi-strand Cu cable.
• Easy maintenance and fault-findingEasy maintenance and fault-finding since all equipment are located at the same place.
25
End Fed Track Circuit
110 V AC
LA
PowerSupply
Unit
TransmitterB
TrackRelay
Receiver B
PowerSupply
Unit
TU/TCUB
Track Circuit Frequency B
TU/TCUB
LA
110 V AC
AFTC Signal is fed from one end and received at the other end.
As per Railway Board Guide Lines maximum length of End Fed AFTC should be
450 m for better maintenance.
Tx End Rx End
26
Center Fed Track Circuit Track Circuit Frequency B
PowerSupply
Unit
TransmitterB
ETU B
LA
110 V AC 110 V AC
LA
TrackRelay-2
Receiver-2 B
PowerSupply
Unit
TU/TCUB
110 V AC
LA
TrackRelay-1
Receiver-1 B
PowerSupply
Unit
TU/TCUB
AFTC Signal is fed from CENTER and received at both the ends. As per Railway Board Guide Lines Center Fed AFTC should be
used for track circuits of length 450-700 m for better maintenance.
Relays of Rx-1 and Rx-2 are connected in series to feed TPR. End Termination Unit is used at Tx end for center feeding.
Rx-1 End Rx-2 End Tx End
27
PowerSupply
Unit
Receiver-2B
LA
110 V AC
110 V AC
LA
Transmitter B
PowerSupply
Unit
TU/TCUB
PowerSupply
Unit
35 mm sq Cu cableor MS Strap
AFTC JUMPER
110 V AC
LA
TrackRelay-1
Receiver-1 B
TU/TCUB
TrackRelay-2
Track Relays of Rx-1 and Rx-2 are proved in series
Point Zone Track Circuit With One Turn Out
28
Point Zone Track Circuit with Two Turn Outs
Transmitter B
PowerSupply
Unit110 V AC
LA
Receiver-1 B
TU/TCUB
TCU B
PowerSupply
Unit
Receiver-2B
LA
110 V AC
TCU B
110 V AC
LA
TrackRelay-2
PowerSupply
Unit
TU/TCUB
AFTC JUMPER35 mm sq Cu cable or MS Strap
PowerSupply
Unit
Receiver-3B
LA
110 V AC
TrackRelay-1
Track Relay-3
Track Relays of Rx-1, Rx-2 and Rx-3 are proved in series
29
Interfacing with other track circuits
Track Circuit B DC Track CircuitTCU BTU/TCU
B
Traction RailMS Strap
Interfacing with Non Track Circuited area
Track Circuit BNon track
Circuited AreaTU BTU/TCU
B
17.8 m MS StrapOR
35 Sq. mmCu Cable
30
Track Circuit B TCU BTU/TCU
B
MS Strap
TCU DTU/TCU
DTrack Circuit D
Traction Rail
Traction Rail
Interfacing with AFTC other than PAIRED frequency
31
Tuned Zone RatiosPole
(TU of TrackCircuit under
Test)
Zero(Adjacent TU)
Ratiogreater
than
Tx ACEG Rx BDFH 10:1
Tx BDFH Rx ACEG 15:1
Rx ACEG Rx BDFH 10:1
Rx BDFH Rx ACEG 15:1
Tx ACEG Tx BDFH 6:1
Tx BDFH Tx ACEG 9:1
Rx ACEG Tx BDFH 6:1
Rx BDFH Tx ACEG 9:1
• Measure the Voltage on TU of Track circuit to be tested. This is the POLE Voltage.
• Measure the voltage on the ADJACENT TU. This is the ZERO Voltage.
• Calculate Pole Voltage/Zero Voltage.
•This value should be GREATER THAN value specified in the above
table.
32
Gain = 390 where V= The voltage across the V1 resistor at gain setting 13 in mV.
Current flowing up = 1 + 9 = 10Current flowing down = 3Thus gain = 10 – 3 = 7
Note: Negative gain cannot exist.
For gain of 13 the track circuit will operate for current above approx. 15 mA
Gain setting for TI 21 receiver
From TU/ETU/TCU
1H
1L
9H
3H
9L
3L
9
3
1
1 ohm resistor
GAIN determines the sensitivity of Receiver for a particular Input signal level
33
Train Shunt Resistance
It is the Maximum value of resistance when connected to the rails at the Receiving End of the track will cause the relay to drop.
TSR is Minimum at Receiving End and Maximum at Transmitting End.
As TSR INCREASES, Reliability DECREASES while Safety INCREASES.
As TSR DECREASES, Safety DECREASES while Reliability INCREASES.
Track circuit should never be left with TSR < 0.5 Ohm at Receiving End.
Value of TSR in Tuned Zone is 0.15 Ohm
As Gain INCREASES, TSR DECREASES and as Gain DECREASES, TSR INCREASES.
34
Criteria for Feeding using 4 Quad Cable
The distance of nearest location box (where quad cable is terminated)
from TU/TCU/TCU should not be greater than 100 m.
4 Quad cable of 0.9 mm dia is be used
Separate Quad Cables are used for Tx and Rx
For Transmitter:
• Single Pair is used for feeding distances up to 1 Km.
• Pairs are doubled for feeding distance greater that 1 Km.
For Receiver:
• Single Pair is used for feeding distances up to 2 Km.
• Pairs are doubled for feeding distance greater that 2 Km.
For Feeding distances < 300 m 2x2.5 Sq. mm Signaling cable can be used
instead of quad cable.
35
Criteria for Distribution of Frequencies in Quad Cable
1
12
2 3
34
4
5
56
6 7
78
8
Quad 1 Quad 2
Quad 3Quad 4
1a
1a1b
1b 2a
2a2b
2b
3a
3a3b
3b 4a
4a4b
4b
Quad 1 Quad 2
Quad 3Quad 4
• Individual Circuits should use Opposite conductors.
• 1&1 form One circuit while 2&2 form another circuit.
•Equipment of same frequency should be allocated in Opposite quads (eg. Quad 1 & Quad 3)
While using Single Pair
While using Double Pair
• Individual circuits use all 4 conductors, using opposite conductors in
parallel. I.e. 1a & 1a form one side of one circuit,
1b & 1b form the return side of the same circuit.
• Equipment of same frequency should be allocated in Opposite quads (eg. Quad 1 & Quad 3)
36
Collection of Traction Return Current at Sub Station
Rx-TUTx-TU
Sub Station Earth
Impedance Bond
Rail Earthing - No Part of Rail should be directly connected to earth. Rail can be earthed through center tap of Impedance Bond
Rx-TUTx-TU
Impedance Bond
37
Connection of OHE Mast to Outer Rail
As per current practice OHE Mast is connected to outer rail to earth the OHE mast.
It does not have any effect on performance on AFTC but may adversely affect Broken Rail protection of outer rail.
More than 600 AFTC Type TI 21 working satisfactorily in various sections of Indian Railways where OHE Mast is connected to outer rail.
38
Dos and Don’ts of AFTC Type TI 21
Location BoxLocation Box
Track Circuit B TU B
Rx BR
TU B
Tx B
<=30 m<=350 m
2x2.5 Sq. mmCu Cable
For decentralized version (when LMU is not used) ensure that the maximum distance
from Tx to TU/ETU/TCU is not greater than 30 m and for Rx to TU/ETU/TCU the maximum
distance is not greater than 350 m.
39
Dos and Don’ts of AFTC Type TI 21
BA B A A
BA B A A
DC D C C
Between track-circuits of same frequency pair on different Lines, there should be a minimum separation of two lines.
FE F E E
BA B A A
BA B A A
DC D C C Separation of Two Tracks}
40
Do’s and Don’ts for AFTC Type TI 21
Tx A
Axle CounterHead
TU/TCUA
TU/TCU/
ETU
A
Track Circuit A
200 m 200 m
Tx E/G
Axle CounterHead
TU/TCUE/G
TU/TCU/
ETU
E/GTrack Circuit E/G
100 m 100 m
5 kHz axle counter detector head shall not be installed
(a) Within 200 m of ‘A’ frequency Transmitter (Tx)
(b)within 100 m of ‘E’ and ‘G’ frequency
Transmitter (Tx).
41
Do’s and Don’ts for AFTC Type TI 21
Track Circuit B TU B TU A Track Circuit A
19.5 m
Tuned Zone
Axle CounterHead
5 m 5 m
(c) within 5 m of any Tuned Zone
Tx/Rx
Axle CounterHeadTU/TCU TCU/ETUTrack Circuit
15 m 15 m
(d) within 15 m of ETU/TCU
42
Do’s and Don’ts for AFTC Type TI 21
Track Circuit B TU B TU A Track Circuit A
19.5 m
Tuned Zone
AWSMagnet
AWS track magnet should not placed in the tuned zone.
(d) It is preferable to install a Receiver rather than Transmitter adjacent to Axle counter section.
43
Do’s and Don’ts for AFTC Type TI 21
Track Circuit B Track Circuit ATU B TU A
19.5 m
Tuned Zone
Tuned zone should not be located in a level crossing /bridge/check rails. Tuning Unit (TU) can however be located
on either side of the level crossing, but with the tuned zone reading away from the crossing
Track Circuit B Track Circuit ATU B TU A
19.5 mTuned Zone
It is recommended that track circuits containing level crossings are in normal power mode with the
Receiver located near to the level crossing.
44
Do’s and Don’ts for AFTC (General)
Maximum TWO Transmitters or EIGHT Receivers of different frequencies can be connected to the
same power supply unit.
PSURx-A
Rx-B
Rx-C
Rx-D
Rx-E Rx-F
Rx-G Rx-H
PSU Tx-BTx-A
All the Receivers of the same track circuit (Point Zone and Center Fed), can be connected to the same power supply unit.
Current Rating of 1 PSU 4.4 A
Current drawn by 1 Tx 2.2 A (Max)
Current drawn by 1 Rx 0.5 A (Max)
Tx and Rx of the same frequency should never be connected to the same PSU.
Fuse for Tx 3.0 A r.m.s
Fuse for Rx 0.6 A
Fuse for PSU 1.6 A
45
Do’s and Don’ts for AFTC (General)
• Track circuits Less than 200 m should be connected in Low power mode and track circuits more than 200 m
should be connected in Normal power mode.
•Point Zone Track circuits, Track circuits having Z Bonds and Track circuits using TCU in Transmitter
are always connected in Normal Power Mode.
• Normal Power Track circuit feeds about 40 W Power in the track while a Low Power Track circuit
feeds about 3 W Power in the track.
• For Normal Power Track circuits Cable from Transmitter is connected to 4&5 terminals of
TU/ETU/TCU.
• For Low Power Track circuits Cable from Transmitter is connected to 1&2 terminals of
TU/ETU.
• For both Normal Power and Low Power Track circuits Cable from to Receiver is connected
to 1 & 2 terminals of TU/ETU/TCU.
46
Do’s and Don’ts for AFTC (General)
Rx ATx ARx B
300 M (NP)
Tx BRx A
Tuned Zone
19.5 m
120 M (LP)
140 M
Tuned Zone
19.5 m
No Receiver (Rx) should be positioned less than 200m from a normal power Transmitter (Tx) of the same frequency or
50m from a low power Transmitter (Tx) of the same frequency.
This is not applicable if Insulation joints or Z Bond are present between these track circuits.
47
Tx ARx ATx BRx BRx A
Tx CRx CTx DRx DTx C
TrackCircuit B
TrackCircuit A
Tx ATrack
Circuit A
Rx CTrack
Circuit CTrack
Circuit CTrack
Circuit D
Traction Bondings
Tuned Zone19.5 m
Tuned Zone19.5 m
Tuned Zone19.5 m
Tuned Zone19.5 m
Do’s and Don’ts for AFTC (General)
For double rail track circuit there should be no traction bonding between adjacent rails
48
Tx ARx ATx BRx BTx A
Tx CRx CTx DRx DTx C
TrackCircuit B
TrackCircuit A
Rx ATrack
Circuit A
Rx CTrack
Circuit CTrack
Circuit CTrack
Circuit D
Tuned Zone19.5 m
Tuned Zone19.5 m
Tuned Zone19.5 m
Tuned Zone19.5 m
Cross Bonding between parallel tracks can be done by connecting center tap of Impedance Bonds
Do’s and Don’ts for AFTC (General)