Functions of Transmission Lines and Distribution Lines

 Functions of Transmission Lines and Distribution Lines  

Transmission Lines: The transmission lines are mainly used to deliver bulk power from power stations to the load centres and large industrial consumers. Depending upon the operation voltage these are mainly divided into two types, namely

1.      Primary Transmission Lines: In this, the operating voltages are 132Kv, 220Kv, 400Kv (or) even 765Kv which depends upon the distance, the amount of power to be transmitted and the system stability from the generating station.

2.      Secondary Transmission Lines: The primary Transmission line transmission line terminates at the receiving station (RS) which is usually lines at the outskirt of the city. At the receiving station the voltage is reduced to 33kv (or) 66kv by using step-down transformer. From this station, electric power is transmitted at 33kv (or) 66kv to the various substations.

Distribution Lines: Distribution lines are used to deliver the power from substation, to the various consumers. Depending upon the operation Voltage, these are mainly dived into two types, namely

1. Primary Distribution Lines

2. Secondary Distribution Lines

1. Primary Distribution Lines: The secondary transmission lines terminate at the substation (SS) where the voltage is reduced from 33kv (or) 66kv to 11kv, 3-phase, 3-wire. This 11kv line is supplied to bulk industries and also run along the important road sides of the city. This whole system of arrangement is called primary Distribution  

2. Secondary Distribution Lines: The electric power from primary distribution line (11kv) is delivered to distribution substation (DS). These substations are localities and step – down the voltage to 400 Volt, 3-phase, 4-wire for secondary distribution. The voltage between any two phase is 400 Volt and between any phase and neutral is 230 Volt.

Need for Transmission and Distribution Lines

The electrical power supply undertakes the following aims, namely

1.       Supplying of electrical power to the consumer within the specified limits frequency. (49Hz – 51Hz).
2.       Supplying of electrical power within the specified limits of voltage (eg. Variation with in +5%)
3.       Supply of energy at low cost.
4.       Maximum security of supply and minimum fault duration.
5.       Supply of required amount of power to all types of consumers over’s the Specified area at all times continuously.
6.       Generally the power generating stations are far away from the urban areas where consumers are located. Hence, in order to fulfil the above tasks, an extensive network of conductors between the power station and consumers is required. This network mainly comprises of two lines called transmission and distribution lines.