Implementing Locomotive Cab Signal Aids to Assure Train Safety for Meiso – Dewanle Railway Line
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Date
2015-06
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Addis Ababa University
Abstract
Railway signaling is the baseline safety system controlling the movements of trains. It is the safety critical part of the train control function of the railway. Railway line safety methods are going to be implemented for Meiso-Dewanle new project as it’s specified in the preliminary design document. The safety methods of the project contain of Track-circuit block system, computer interlocking system and lightning protection system. This all methods concentrate on controlling Wayside signals, Switches and power line protection system for safe train transport by controlling and signaling equipments situated at fields. For safe transit at the end of each blocks the deriver expected to see the color of Wayside signals from some KM distance before the signal .But Field signals have limitations for sight hindering natural or artificial circumstances. Cab signal system provides block occupancy necessary information immediately for the driver and guides him to function the train with a full knowhow of the dynamic line situations ahead of him. Speed controlling is the very mechanism of avoiding danger and by giving line status data’s timely, Cab signal helps the train operator to derive safely.
This thesis done on cab signaling partly due to: to exploit the wide application of cab signaling for its safety protection mechanism for Semi-Automatic block system. And, in addition, its physical location closeness to the train operator is also the other reason. Design of Cab signaling for Meiso-Dewanle have implemented using Ac 25 Hz coded track circuit communication system. Wayside signal at stations are grouped into 8 groups and encoded using Extended hamming codes for error detection, modulated with Bpsk modulation for good error probability, Transmitted through the rails to the cab for decoding and demodulation for better signal detection.
Mat lab simulation for the encoding, decoding, modulation/demodulation, transmission, and band filter have included in this thesis. Transmission parameter design analysis on amplitude and phase of the signal also carried out in the simulation part.
The transmission of the signal is affected by rail resistance, rail inductance and most importantly by ballast resistance. Distributed rail model for the rail and Lumped model for the train length with rail and ballast impedance have used in the thesis to calculate the accurate values of the current in the leading wheels of the train. The worst ballast resistance also used to caluculate the maximum safe working length of the track circuit which is 1.2KM.
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Keywords
Locomotive Cab Signal Aids, Train Safety, Meiso – Dewanle Railway Line