Unlike overhead line systems, which use wires suspended above tracks to provide power, third rail systems deploy an additional rail on the tracks. This third rail carries electrical power directly to the train. Here's an exploration of the different types of third-rail train equipment prevalent today.
The conductor rail, often simply termed the third rail, is the backbone of this power system. Typically made of steel or aluminum, these rails run parallel to the main train tracks. There are mainly two types:
In an over-running system, the third rail is positioned at its top level with the running rails, and the train picks up power from the top of the rail.
For an under-running system, the third rail is positioned lower than the running rails, and the train picks up power from the bottom. This design tends to be safer, as the electrified part of the rail is less exposed, minimizing the risk of accidental contact.
Collector shoes are components attached to the train, sliding along the third rail to draw power. Given the need for consistent and efficient power collection, these shoes are made of robust, conductive materials, ensuring smooth electricity transfer while minimizing wear and tear.
Ensuring safety and efficiency, insulators are crucial in third rail systems. Positioned at regular intervals, they support the third rail and keep it elevated from the ground, preventing short circuits and potential electricity leakage. Modern insulators are crafted from high-strength materials, offering durability while maintaining electrical resistance.
Safety is paramount in any electrified system, and third-rail systems are no exception. Protective boards serve as physical barriers, shielding the third rail from accidental contact by personnel, animals, or debris. Made from non-conductive materials, they provide an added layer of safety, especially in stations and other high-traffic areas.
While not exclusive to third rail systems, substations play a pivotal role in regulating and supplying power. Positioned strategically along the rail network, they transform and distribute electricity to the third rail, ensuring trains receive consistent and optimal power.
Equipment within these substations, like transformers and circuit breakers, is crucial for the reliable operation of third rail systems.
End Ramps and Section Breaks
Transitions and interruptions in third rail systems need to be handled with precision. End ramps taper off the third rail at its endpoints, allowing collector shoes to smoothly exit without jarring impacts. Meanwhile, section breaks divide the third rail into different electrical sections.
This design allows for maintenance work or isolates faults without shutting down the entire rail line.