Classification of Distribution System

Distribution System in Power Systems

• The purpose of the distribution system is to deliver electrical energy from the transmission system to individual consumers.
• The transmission system can be compared to the human body's arterial system, while the distribution system is comparable to the capillary system.

Function of Distribution System

• The main function of the distribution system is to receive power from the transmission system and deliver it to consumers at a safe and usable voltage.

Comparison with Transmission System

• It is difficult to distinguish between transmission and distribution systems because they are interconnected and have overlapping functions.
• The transmission system operates at a higher voltage and is used for long-distance transmission, while the distribution system operates at a lower voltage and is used for local distribution.

Circulatory System Analogy

• The equivalent of the distribution system in the circulatory system analogy is the capillary system.

Primary Objective

• The primary objective of the electrical distribution system is to provide a reliable and efficient supply of electrical energy to consumers.

Components of Distribution System

• An electrical distribution system includes components such as transformers, conductors, and distribution substations.

Role of Transformer

• The role of a transformer in the electrical distribution system is to step down the voltage to a safe and usable level for consumers.

Layout of Low Tension Distribution System

• A typical low tension distribution system has a radial or loop layout, with a transformer feeding multiple consumers.

Classifications of Distribution Systems

• Distribution systems can be classified based on the nature of current as AC (alternating current) or DC (direct current).
• Distribution systems can also be classified based on the scheme of connection as overhead or underground systems.

Overhead System

• The overhead system is generally employed for distribution due to its lower cost and ease of installation.

Underground System

• The underground system is used where overhead construction is not feasible, such as in urban areas.

AC System

• The AC system is preferred for distribution of electric power due to its ability to be transformed to different voltage levels and its lower transmission losses.

Secondary Distribution System

• The purpose of the secondary distribution system is to provide a safe and usable voltage to individual consumers.

Connection of Single Phase Domestic Loads

• Single phase domestic loads are typically connected in a secondary distribution system between one phase and the neutral wire.

Voltage Between Phases

• The voltage between any two phases in a secondary distribution system employing a 400/230 V, 3-phase, 4-wire system is 400 V.

DC Supply

• A DC supply is sometimes necessary in an electric power distribution system for specific applications, such as in telecommunications or electrolysis.

Distribution Substations

• The purpose of distribution substations in a secondary distribution system is to provide a reliable and efficient supply of electrical energy to consumers.

Connection of 3-Phase Motor Loads

• 3-phase 400 V motor loads are typically connected in a secondary distribution system between the three phases.

Two-Generator Method

• The principal disadvantage of the two-generator method in obtaining a 3-wire DC system is that it requires two separate generators, which can be expensive and inefficient.

3-Wire DC Generator

• The 3-wire DC generator has a specialized winding that allows it to provide a neutral wire for 3-wire DC systems.
• In the two-generator method, each generator supplies one half of the total voltage, with the neutral wire being the midpoint between the two generators.