To reach the electricity from the production center to a receiver, a huge network of conductive wire establishes. This network is called transmission and distribution system. The transmission system is used to transmit the electricity from the production center to load center and distribution line is used to distribute electricity from sub center to receiver. The power transmission and distribution of electricity can be in any system of A.C. or D.C. In A.C. system, the transmission is three phases, three wires and in case of distribution, there are usually three phases four wires used. In a modern A.C. power system, the elements are usually is like as follows-

  • Generating Station
  • Generating Station
  • Step-up Sub Station
  • Transmission line
  • Switching Station
  • Step-down Sub-station
  • Primary distribution line/Network
  • Service Transformer Bank or Distribution transformer
  • Secondary Distribution line

All transmissions and distribution systems may have all the components or may not.

Transmission line for electrical energy

What is the transmission line?

To transmit high power from power plant a huge circuit or network of high voltage creates, that is transmission line. The transmission lines become single circuit, double circuit, a triple circuit for conducting more power. A transmission line is divided into two based on the operating voltage. Such as-

  • Primary transmission: (230KV, 132KV)
  • Secondary transmission: (66KV, 33KV)

What is the distribution line?

To reach or distribute electrical energy to the customer level, such as- shops, houses, industries etc, a circuit or network is created. which is a distribution line. It has many branches and the service is connected through huge taping.
Depending on the voltage distribution lines are two types, such as-

  • Primary distribution – 11KV, 6.6KV and 3.3KV (very much used 11KV)
  • Secondary distribution – 400V, 230V

What is electrical Feeder?

To distribute electricity in a various populated area, industrial or residential area, an electric line is built for supplying electricity to different load center from high voltage epicenter or grid epicenter is called feeder. Therefore, the feeder is a connected electric line between high voltage electric epicenters to the low-pressure electric epicenter. There is no taping in the feeder. As a result, the current density is the same everywhere. In the case of feeder design, the main considering thing is the current density of line. It is a thick type of cable.

Electric power Distributor

The Distributor is an electric line, which is set for supplying the electricity in various areas, industrial areas, residential areas or in case of other necessity. Therefore, it can be said that supplying electricity through an electric line to the customer level is called a distributor. The supplying voltage in general customer level, or in houses is 230/400V volt and for this usually: three phases four wire distribution system uses.
But most popular and most used distribution system of 11KV primary distribution, the secondary distribution of 400 volts, both lines are drawn on the same pillar support.
Since the distributor, distributed electricity is to the customer level, so there have many tapings in the line. Usually, the current density is never the same. In both ends of the line, the voltage is often unequal. That is to say, voltage drops occur in the line. In distribution, the acceptable voltage drop should not be more than 6%. The voltage of the distribution line should not be more than (+- 60%) of the declared line. In that case of distribution design, a voltage drop is given more consideration.
Service main: By the service main, the electricity has distributed to the customer from the distribution line.

Various System of transmission and Distribution of electrical energy

In the case of electric power transmission, A.C. three-phase three-wire system is most common. In the case of distribution, A.C. three-phase four-wire system is mostly used. Without these, those systems are used in electric power transmission and distribution are as follows-

D.C system

  • D.C two wire
  • The D.C two-wire main point earthed
  • Three-wire system (D.C)

Single phase A.C system

  • Single-phase two wire
  • The Single-phase two wire with mid-point earthed
  • Single-phase three-wire

Two phase A.C system

  • Two-phase three wire
  • Two-phase four wire

Three phase A.C system

  • Three phases of the three-wire system
  • Three phases of the four-wire system

Among the mentioned systems, it is better to use a system after determinant that, in which system the length of the conductor will be less. For that, copper saving is to compare.

When transmission is by overhead system

It has seen that, in case of overhead transmission, the maximum disruptive stress falls between conductor and earth or neutral wire for the same power, same distance, and sending same loss in case of savings.

When the transmission is by an underground system

When power is transmitted through the underground cable, then much pressure falls on the insulation of two conductors. In this case, it is better to consider the maximum voltage between the two conductors for saving copper.

Types of Distribution system

Mainly based on the supply, distributor system are two types, such as-

  • A.C Distributor
  • D.C Distributor


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