RAILWAY TRAIN DETECTION |SYSTEM SAFETY|PERFORMACE REQUIREMENTS|OCCUPATIONAL SAFETY|MAINTAINABILITY|RELIABILITY|OCCUPATIONAL SAFETY|ENVIRONMENT|DISCRETE SYSTEM|CONTINUOUS SYSTEM|MOVING BLOCK SYSTEM|BLOCK SYSTEMS|LEVEL CROSSING| BONDING
Railway Train detection
PERFORMACE REQUIREMENTS
- SYSTEM SAFETY
- OCCUPATIONAL SAFETY
- RELIABILITY
- MAINTAINABILITY
- ENVIRONMENT
SYSTEM SAFETY -GENERAL
SYSTEM SAFETY
- SAFETY INTEGRITY LEVEL
- SAFETY PERFORMANCE BENCH MARK
- SERIES TRACK CIRCUIT BONDING
- OVERCURRENT PROTECTION
- INSULATION AND ISOLATION
- SURGE ARRESTERS
- POSITION OF TRAIN DETECTION EQUIPMENT
OCCUPATIONAL SAFETY
- HIGH VOLTAGE
- TRACK CIRCUIT FUSING
- INSULATION OF TERMINALS
- SAFETY LABELLING
- SAFETY EARTHING
- CONDUCTOR RAIL PROTECTION BOARDING
- NEWLY SPECIFIED SYSTEMS
RELIABILITY
- DUPLICATE TRACK CIRCUIT RAIL CONNECTIONS
- PARALLEL(YELLOW) BONDING
MAINTAINABILITY
- COMMUNICATIONS
- CUT SECTION MONITORING
- PROVISION OF DISCONNECTION BOXES
- PROVISION OF CONDITION MONITORING
ENVIRONMENT
- TRACK CIRCUIT SYSTEM
- AC ELECTRIFIED
- DC ELECTRIFIED
- DUAL ELECTRIFIED
- NON ELECRIFIED
CONTINUOUS SYSTEM
To detect presence or absence of vehicles with in the limit of track section E.g.Track circuits, Axle counter
DISCRETE SYSTEM
To detect that a train has reached ,is passing or passed a specific position . Discrete systems are generally provided in addition to continuous system E.g.. Treadles
MOVING BLOCK SYSTEM
To detect absence of vehicles with in an envelope ahead of a train that progress with the passage of the train.
BALLAST RESISTANCE AND TRACK CIRCUIT LENGTH
- BALLAST RESISTANCE TYPICAL VALUES 2 TO 10
- RAIL RESISTANCE 0.25 OHM/KM AND RAIL IMPEDENCE DEPENDS ON FREQUENCY
50 HZ – 0.3 OHM/KM
400 HZ – 2.5 OHM/KM
2000HZ – 10 OHM/KM
THESE IMPEDENCE VALUES MAY BE INCREASED FURTHER BY LARGE TRACTION CURRENT ,DUE TO RAIL BEING DRIVEN TOWARD SATURATION.
Train Detection Overview
Block Systems
- Block Systems require the absence of a train to be proved either by
- Continuous train detection or
- Entry and/or exit train detection by discrete track circuit or other devices.
Level Crossing
- For automatic level crossing operation required to prove :
- The absence of an approaching train to allow the crossing to be opened to road traffic, and
- The presence of the train on the exit side before the crossing can be normalised after operation.
Other Functions
- Indicating on the signaller’s display system
- Approach releasing a signal
- Allowing a permissive route to be set
- Allowing a ground frame to be released
- Train approaching indication / warning
- Train detection device may also be used to calculate the speed or acceleration of a train
- The length of a train may need to be measured.
Different types of train detection systems
- Track circuits
- Axle counters
- Other type of wheel detector, e.g, treadle, electromagnetic proximity device(used for HABD)
- Supplementary systems, e.g, track circuit assistor interference detector(TCAID), track circuit interrupter.
TCAID is a train detection equipment mounted on the track which detect the presence of a working of TCA. TCA is a another train mounted device which provide to improve the operation of track circuit.
Key attributes and limitation of each type of track circuit
Type | Suitable for Lightly Used Lines | IRJs Required | Immunity From 50Hz a.c. d.c. |
Suitable for S&C | |
DC medium voltage (AC immune) #1 | Yes | Yes | Yes | No | Yes |
DC Diode #1 | Yes | Yes | No | No | No |
T1.21 #1 | No | No | Yes #4 | Yes | No |
HVI #1 | Yes | Yes | Yes | Yes | Yes |
DC Low voltage plain | No | Yes | No | No | Yes |
DC Low voltage(AC immune) | No | Yes | Yes | No | Yes |
DC medium volt plain | Yes | Yes | No | No | Yes |
DC medium voltage AC immune/DC tolerant | Yes | Yes | Yes | Yes #2 | Yes |
AC 831/3 Hz Vane | No | Yes | Yes | Yes | Yes #3 |
BONDING
- SERIES AND PARELLEL BONDING
- DETECTION OF RAIL BREAKS
- BONDING TYPES
BONDING
YELLOW BONDING
PERMISSIBLE SPURS AND SPUR BONDING
CLEARANCES AND PHYSICAL STAGGERING