Back Ground: TPWS (Train Protection and Warning System), term used by Indian Railways, It applies to the ETCS Level 1 concepts and the UIC/UNISIG specifications. It does not, in Indian terms, apply to the UK implementation that is based on different technology.
The TPWS project on Southern Railway installed in the Chennai Central/ Chennai Beach – Gummidipundi section of Chennai division was commissioned on 2nd May 2008 on 4 EMU rakes to begin with. The works on the balance 37 rakes were progressively completed in the next few months. Presently all the 41 rakes proposed to be provided with TPWS on-board equipments are functional. The TPWS track side equipments in the section were fully provided, commissioned and made functional right from the date of commissioning.
The TPWS project on Southern Railway installed in the Chennai Central/ Chennai Beach – Gummidipundi section of Chennai division was commissioned on 2nd May 2008 on 4 EMU rakes to begin with. The works on the balance 37 rakes were progressively completed in the next few months. Presently all the 41 rakes proposed to be provided with TPWS on-board equipments are functional. The TPWS track side equipments in the section were fully provided, commissioned and made functional right from the date of commissioning.
Problems: This TPWS project based on the European Train Control System (ETCS) Level-I system faced many hurdles during the initial installation, proto-type testing, obtaining the required clearances from RDSO and CRS. The major problems noticed during initial revenue service included
1. On-Board system not booting.
2. On-Board system going into System failure (SF) during booting.
3. SDMI ( Simplified Driver Machine Interface) going blank.
4. Speed display bouncing on the SDMI leading to braking.
5. Brake application in the rear non-driving motor coach on run.
Corrective Actions Taken by Railways:
1. Intermittent BTM failure: - Analysis revealed that there was antenna impedance mismatch. The standing wave ratio (SWR) was found more than the tolerance limit of 1.2 to 1.4. Interference from EMI was also suspected. There was problem in communication between the onboard computer (OBC) and BTM. The corrective actions for these problems included modifying the existing antenna protection cover and providing copper braided shields for the Tx-Rx cable between antenna and BTM and for the COTDL and PROFIBUS cable between OBC and BTM. The BTM configuration files were also modified
based on some internal parameters.
2. Error in Train Interface Unit: - Analysis revealed that there was problem in communication between some modules of the OBC and now screened twisted pair cables have been introduced to protect the signals from external noise and EMI.
3. Error in Speed Sensor: - To improve the performance of the Odometric system, the signal cables between OBC and speed sensors have been provided with copper braided shield firmly connected to the coach body. To suppress the noise in the 110V DC voltage derived from the motor coach battery, a filter has been provided at the input point of the OBC. The traction control relay has been shifted outside the OBC cubicle to reduce EMI. To improve earthing of the motor coach body, a 50 sq mm copper cable is to be connected between the EMU body and its bogie.
4. Back EMF from the EB & EP relay coils: - To cover come this problem, the relay coils and EB valve solenoid coils to be terminated with 180/200V MOVRs and the body of EB & SB relays to be firmly connected to the coach body.
5. EB application in rear coach:- To overcome the problem of application of EB in the rear coach while running, the brake interface circuit has been modified to bypass the EB when the TPWS system in the sleeping mode (SM) i.e., when the cab is not the driving one.
6. SDMI Blanking:- To overcome the problem of SDMI blanking, its software has been upgraded. Apart from this, the OBC-SDMI communication cable connector cover which was earlier plastic has been changed to metallic. The OBC-SDMI communication cable and the SDMI power supply cable have been shielded with copper braids firmly connected to the coach body. A filter has been provided at the 110 VDC input point of the SDMI to suppress the ripples in the power supply.
(Source: IRSTE)
