为什么中国要发展超高压输电线路

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High-voltage transmission lines are used to transmit electric power over relatively long distances,usually from a central generating station to main substations.They are also used for electric power transmission from one central station to another for load sharing.High voltage (HV) transmission lines are made of high voltage (between 138 and 765 kilovolts) overhead and underground conducting lines of either copper or aluminum.
One of the key concerns in transmission of electricity is power loss in transmission lines (called line loss or transmission loss),dissipated as heat due to the resistance of the conductors.The smaller the surface area of the conductors,the smaller the loss to heat dissipation.High voltages require less surface area,resulting in reduced line loss.With high-voltage lines,the voltage can be stepped up at the generating station,transmitted through the transmission grid to a load center,and there stepped down to the lower voltages required by distribution lines.