High voltage is used in electrical transmission primarily for two reasons: to minimize power losses and to increase efficiency.

1. Minimize Power Losses: When electricity is transmitted over long distances, there are inherent resistance losses in the transmission lines due to the electrical resistance of the conductors. These losses lead to a drop in voltage along the transmission lines, resulting in wastage of power and reduced efficiency. According to Ohm’s law (V = IR), for a given current (I), higher voltage (V) results in lower power loss (P = I^2R). Therefore, by transmitting electricity at high voltages, the current can be reduced, which in turn reduces the power losses due to resistance in the transmission lines.
2. Increased Efficiency: Power loss in transmission lines is directly proportional to the square of the current and inversely proportional to the voltage. By transmitting electricity at high voltage, the current can be decreased, which leads to lower resistive losses in the transmission lines. This results in more efficient transmission of electricity over long distances, as a greater portion of the generated power reaches its destination.

In summary, high voltage transmission reduces power losses, increases efficiency, and allows for the economical transmission of electricity over long distances. However, it’s important to note that stepping up the voltage for transmission requires transformers, and stepping it down again for distribution at the consumer end, which incurs additional costs and infrastructure.

High voltage transmission offers several advantages over low voltage transmission:

1. Reduced Power Losses: As I mentioned earlier, power loss in transmission lines is directly proportional to the square of the current and inversely proportional to the voltage. By transmitting electricity at high voltage, the current can be reduced, which in turn reduces resistive losses in the transmission lines. This results in more efficient transmission of electricity over long distances, as a greater portion of the generated power reaches its destination.
2. Efficient Use of Conductors: High voltage transmission allows for the use of smaller conductors (thinner wires) for a given amount of power transmission compared to low voltage transmission. This is because higher voltage allows for lower current, and lower current means less heat generated in the conductors. Therefore, the size and cost of conductors can be reduced, making high voltage transmission more economical.
3. Economies of Scale: High voltage transmission lines can carry larger amounts of power over long distances, which enables the creation of large interconnected electrical grids. These grids benefit from economies of scale, allowing for more efficient generation, transmission, and distribution of electricity. Additionally, high voltage transmission lines can be used to transport power from remote generation sources, such as hydroelectric dams or wind farms, to population centers where electricity demand is high.
4. Voltage Regulation: High voltage transmission systems offer better voltage regulation capabilities compared to low voltage systems. Voltage regulation is important for maintaining the quality and stability of the electrical supply, especially during periods of high demand or fluctuating loads.
5. Reduced Infrastructure Costs: While the initial cost of building high voltage transmission lines and associated infrastructure may be higher compared to low voltage systems, the overall cost per unit of transmitted power is often lower due to reduced losses and the ability to transmit larger amounts of power over longer distances.

In summary, high voltage transmission offers advantages such as reduced power losses, efficient use of conductors, economies of scale, improved voltage regulation, and reduced infrastructure costs, making it the preferred choice for transmitting electricity over long distances.