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Newly electrified lines often show a "sparks effect", whereby electrification in passenger rail systems leads to significant jumps in patronage / revenue. A problem specifically related to electrified lines are gaps in the electrification. Maintenance costs of the lines may be increased by electrification, but many systems claim lower costs due to reduced wear-and-tear on the track from lighter rolling stock. The low-frequency AC system may be powered by separate generation and distribution network or a network of converter substations, adding the expense, also low-frequency transformers, used both at the substations and on the rolling stock, Services are particularly bulky and heavy. However, electric rolling stock may run cooling blowers when stopped or coasting, thus consuming energy. The higher power of electric locomotives and an electrification can also be a cheaper alternative to a new and less steep railway if train weights are to be increased on a system. There are some additional maintenance costs associated with the electrical equipment around the track, such as power sub-stations and the catenary wire itself, but, if there is sufficient traffic, the reduced track and especially the lower engine maintenance and running costs exceed the costs of this maintenance significantly.

The costs would be better covered by finding a way to send more than one message at a time through the single wire, thus increasing revenue per wire. Energy efficiency and infrastructure costs determine which of these is used on a network, although this is often fixed due to pre-existing electrification systems. Therefore, most long-distance lines in developing or sparsely populated countries are not electrified due to relatively low frequency of trains. NEMA connectors are power plugs and sockets used for AC mains electricity in North America and other countries that use the standards set by the US National Electrical Manufacturers Association. NEMA 8 devices are specified for three wire, two-pole, grounding devices for 480 volts. All NEMA 14 devices offer two hots, a neutral, and a ground, allowing for both 120 and 240 V when supplied by split-phase power, or 120 and 208 V if the supply is three-phase.

While it is unlikely to replace alternating current as the dominant form of electricic power, it has become more economical than AC for overhead lines exceeding 800 km and undersea or underground lines exceeding 50 km - making DC the ideal choice for especially long connections and connections to isolated power plants and consumers. Electricity for electric rail systems can also come from renewable energy, nuclear power, or other low-carbon sources, which do not emit pollution or emissions. The high power of electric locomotives also gives them the ability to pull freight at higher speed over gradients; in mixed traffic conditions this increases capacity when the time between trains can be decreased. In 1857 he published in the Engineer the whole theory of the mechanical forces involved in the laying of a submarine cable, and showed that when the line is running out of the ship at a constant speed in a uniform depth of water, it sinks in a slant or straight incline from the point where it enters the water to that where it touches the bottom. Therefore, almost all high speed trains are electric. The electric train can save energy (as compared to diesel) by regenerative braking and by not needing to consume energy by idling as diesel locomotives do when stopped or coasting.

Regenerative braking returns power to the electrification system so that it may be used elsewhere, by other trains on the same system or returned to the general power grid. The same applies to the kind of push-pull trains which have a locomotive at each end. Power conversion for a DC system takes place mainly in a railway substation where large, heavy, and more efficient hardware can be used as compared to an AC system where conversion takes place aboard the locomotive where space is limited and losses are significantly higher. These become a nuisance if the locomotive stops with its collector on a dead gap, in which case there is no power to restart. This is less of a problem in trains consisting of two or more multiple units coupled together, since in that case if the train stops with one collector in a dead gap, another multiple unit can push or pull the disconnected unit until it can again draw power. More than a third of Americans’ yearly salary is put toward household bills. However, the higher voltages used in many AC electrification systems reduce transmission losses over longer distances, allowing for fewer substations or more powerful locomotives to be used.

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