Question

What is disadvantages of EHVAC

Answer 1

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The main advantage of high voltage transmission is that large amounts of electricity can be transmitted at relatively low currents. This is why high voltage transmission is used in the first place! High currents require thicker cables since most energy is wasted as heat. Not only is this inefficient, but it’s expensive; the cable used on transmission lines isn’t cheap, so the smaller the diameter of the cable, the less expensive it is. By using higher voltages, less current is needed, and thus smaller conductors can be used, which economically makes sense.

Of course, high voltage transmission also has its disadvantages. While high voltage alone isn’t dangerous, transmission lines are very dangerous, considering the amount of electricity flowing through them. The high voltage allows the electricity to energize the air surrounding the conductor and causes it to “jump”, so even coming close to them is extremely risky. This is why it is never a good idea to approach a downed power line, especially if it’s energized. Because high voltage enables the electricity to arc through air, transmission lines must be properly insulated to prevent the electricity from “leaking” onto their pylons.

Another problem with high voltage transmission is the need for transformers to step voltage up and down as needed. Transformers are expensive, oil-filled, and can weigh more than 300–400 tons. Transformers, like conductors, lose some energy as heat. The oil inside them usually prevents them from overheating, but sometimes cooling fins and/or external fans are needed to maintain the transformer’s temperature. To prevent them from becoming overloaded, both the primary (incoming) and secondary (outgoing) lines must be protected by circuit breakers. These also protect the transformers from faults and damaging surges should the line voltage exceed the transformer’s insulation rating voltage. All in all, this apparatus is expensive and, like anything else, requires regular maintainance.

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