Railways still existed for a long time when electric traction appeared. Beginning from steam locomotive, and later diesel locomotive which offered an alternative, finally the electric locomotive offered an improvement. Compared to the prime mover trains later developed the multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver.
Multiple units are classified by their power source and are of two main types: electric multiple unit (EMU) or diesel multiple unit (DMU). Diesel-powered units may be further classified by their transmission type: diesel-electric (DEMU), diesel-mechanical (DMMU) or diesel-hydraulic (DHMU).
A railway electrification system supplies electrical energy to railway locomotives and multiple units so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world. Railway electrification has many advantages but requires significant capital expenditure for installation. Electrification of the railway allows for faster, greener, more reliable train journeys, improves passenger services and supports economic growth.
In this series, we will look at the Electrification of railways in detail.
Why Electrify the Railways?
Electrification of the railway allows for faster, greener, more reliable train journeys, improves passenger services and supports economic growth.
The benefits of Electric trains over Diesel /Steam trains can be many as discussed below,
- The main advantage of electric traction is a higher power-to-weight ratio than forms of traction such as diesel or steam that generate power on board. Electricity enables faster acceleration and higher tractive effort on steep gradients.
- More capacity for passengers: more seats than diesel trains of the same length.
- Faster than diesel trains: superior braking and acceleration make journey times shorter.
- Quieter than diesel trains: good news for people living near the railway – our lineside neighbours.
- Better for the environment: their carbon emissions are 20 to 35 per cent lower than those from diesel trains, and there are no emissions at the point of use, improving air quality in pollution hot spots, such as city centres.
- Lighter weight means less maintenance is needed because electric trains cause less wear to the track, so the railway is more reliable for passengers.
- Good for the economy: faster trains with more seats and better connections with previously hard-to-reach areas improve access to jobs and services, and open up new business opportunities.
- Lower running cost of locomotives and multiple units lower maintenance cost of locomotives and multiple units higher power-to-weight ratio, resulting in fewer locomotives and faster acceleration.
- Higher practical limit of power means higher limit of speed with less noise pollution (quieter operation)
However, there are few disadvantages of electric train to be noted,
- The upgrading brings significant capital cost, especially where tunnels and bridges and other obstructions have to be altered for Electrical clearances and Speed Clearances.
- Also, the alterations or upgrades will be needed on the railway signalling to take advantage of the new traffic characteristics.The signal circuits need to be ìimmunized from the traction power circuits.
- Tracks might need upgrade to allow OLE interfaces and Speed increases, including new track work or re-alignment.
- The overall railways add high electric shock risk to the staff working in the Railways or public using railwayswhich will need a complete bonding of the system to earth to avoid fatal results of electrification.
- Also, if the power conducting wiring breaks down in some way, all trains can be brought to a standstill until such fault is rectified.
Tunnels may be suitable for electrification, or may require costly remedial work,enlargement.
Integration of the electrification support structures with existing station canopiesmust be considered. Station canopies that project over platform edges may needmodification.