Typical Layout of a Sub-Station by Towfiqur Rahman

(towfiq.eee@gmail.com)

What is a Sub-station?A substation is a part of an

electrical generation, transmission, and distribution system, where voltage is transformed from high to low, or low to high, or many other important functions. Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps.

Mainly Sub-station is defined as “The assembly of apparatus used to same some characteristics (e.g. Voltage, AC to DC, P.F. , Frequency etc.) of electric supply is called Substation.”

Types of Sub-station Classified by their main two features.

According to constructional features:- Are of four type.

1. Indoor Sub-station 2. Outdoor Sub-station 3. Underground Sub-station 4. Pole-mounted Sub-station

According to service requirement features:- Are of six types.

Transformer Sub-station:- Divided into two different sub types:-

i. Transmission Sub-station ii. Distribution Sub-station

Switching Sub-stations Power factor correction Sub-station Frequency Changing Sub-station Converting Sub-station Industrial Sub-station

Design Considerations

Site Considerations:- Location place, Access road, present and future load center, existing and future sources of power etc.

Environmental Considerations:- Weather, Temperature, Wind, Appearance, Public Safety, Audible Noise, Electrostatic and Electromagnetic Effects, Effluent, Ice etc.

Components of a Substation Transformer:- Main

component. It is classified by two type.

Power Transformer:-

A power transformer is used in a substation to step up or step down the voltage

Instrument Transformer

i. Current Transformer

ii. Voltage Transformer

Insulator Earthing system Isolation

Switches Circuit breakers

Surge arrestor Switchgear Relay

Sub-station Layout

A:Primary power lines' side 1.Primary power lines 2.Ground wire 3.Overhead lines 4.Transformer for

measurement of electric voltage

5.Disconnect switch 6.Circuit breaker

7.Current transformer 8.Lightning arrester

B: Secondary power lines' side

7.Current transformer

8.Lightning arrester

9.Main transformer

10.Control building 11.Security fence

12.Secondary power lines

Plan & Section of a Substation