Power transmission system means to transmit power to electrical network. It increases the low voltage before transmission it for long distance. The higher the voltage is, the less the current is, so there will be less lost for current during the transmission.
Power transmission system is divided into two parts: 1. Power transmission lines and substation.
Most of power transmission system is consisted of aerial transmission lines, stranded aluminum conductor, ACSR, extended diameter conductor and composite overhead ground wire and so on.
Generally speaking, voltage from power plant is low. If there is no voltage increase, according to ratio of UI, there will be big current in the transmission lines. It is known that temperature of lines is related to resistance and current. The bigger the current is, the temperature in the same conductor will be higher. Then most of the power generated from power plant will be lost on the conductors. Besides, the higher the temperature of the conductor, there will be more damages to conductors. In order to avoid the negative effects caused by the above problems, we make measures to higher the voltage to reduce the power. That what substation does. Cable used for substation is generally power cables with the corresponding voltage. Meantime, according to different laying environment and methods, different cables need to be taken into account.