Transmission of Electric Power Mar06

Transmission of Electric Power...

Transmission of Electric Power Transmission of electric power is a process by which the electric power produced at power plants is transported in bulk quantities over long distances for eventual use by consumers. Electric power is sent from generating power plants to the end consumer by transmission lines. Transmission lines, when interconnected with each other, become transmission networks. This transmission network along with power stations and substations is known as ‘transmission grid’ or simply ‘grid’. A typical transmission grid is shown in Fig 1. The transmission networks which are interconnected at the national level are known as ‘National grid’. Energy is usually transmitted within a grid with three phase alternating current (AC). Due to the involvement of large quantity of electric power and due to the properties of electricity, transmission involving long distances normally takes place at high voltage (33 kV or above). Electric power is usually transported to a substation near the consuming point which is either a populated area or an industrial complex. At the substation, the high voltage electric power is converted to lower voltages suitable for consumer use, and then transported to the end users through low voltage electric distribution line Fig 1 Typical transmission grid Transmission efficiency and transmission losses Transmitting electricity at high voltage reduces the fraction of energy lost to resistance, which varies depending on the specific conductors, the current flowing, and the length of the transmission line. For a given amount of power, a higher voltage reduces the current and thus the resistive losses in the conductor. Transmission efficiency is improved by increasing the transmission voltage using a step-up transformer which has the effect of reducing the current in the conductors, whilst keeping the power transmitted nearly equal to the power input. The reduced current flowing through the conductor reduces the losses...