Electrical Transmission and Distribution System

If you want to be an electrical engineer then knowing about the single line diagram of electrical transmission and distribution system and it’s really important in your practical life. Sometimes it can be a question while you are in an interview board. In this post, I am going to discuss all the basic for this topic.

I will provide a single line diagram for electrical transmission and distribution system by a .pdf format file and an AutoCAD .dwg format file that you can keep it with yourself.

Typical Schematic Diagram for Alternating Current (AC) Transmission and Distribution:

Now between the power station and the consumer, there is a large network of electrical conductor can be divided into two parts,

  1. The Transmission System
  2. The Distribution System

This main two parts can be subdivided by another two parts,

  1. Primary Transmission
  2. Secondary Transmission


  1. Primary Distribution
  2. Secondary Distribution

Related: GIS – Gas Insulated Substations

This figure is showing the layout for a typical AC power transmission and distribution system by a single line diagram.

Single Line Electrical Diagram for Transmission and Distribution SystemGeneration Station:

This is the very first sector for everything. And this is where we produce electricity. There are several power plant can be used to produce electricity like GAS Fuel Power Station, Nuclear Power Station, and others. In this figure that I provided, there is a part that called Generating Station where we can produce electric power by three-phase alternator operating in parallel.

Related: Underground Power Distribution System

The most common generating voltage is 11KV. But sometime 3.3KV or 6.6KV are used for industrial captive power generation. Now come to transmission. For economy in the transmission of electric power, the generation voltage is stepped up to 132KV or above by a three-phase power transformer. This type of transformer called a step-up transformer.

Primary Transmission:

The steeped up electric power 132KV or above is transmitted by three phases, three wire overhead line system to the outskirts of the city. This forms the primary transmission.

Secondary Transmission:

Where voltage will drop by a step-down power transformer.

Primary Distribution:

Form these parts all industrial consumer those who need bulk power and they can connect with this Primary Distribution parts. But they will need special permission from the government for a special occasion.

Secondary Distribution:

From this sector, all 11KV consumer and 220V single line consumer will get the power. For 220V distribution system, a transformer 3 phase or single phase will be used for step down from 11KV/440V or 220V.

Related: Primary Power Distribution Configurations

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