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Home / Technical Articles / The Essentials Of Substations, Electrical Equipment and Busbar Arrangements

Introduction to substations

Electrical power systems nowadays are generated, transmitted, and distributed in the form of alternating current. The electric power is produced at the power stations which are located in suitable places, generally quite away from the consumers.

The Essentials Of Substations, Electrical Equipment and Busbar Arrangements
The Essentials Of Substations, Electrical Equipment and Busbar Arrangements (on photo: Little yellow bird and big transformer in substation behind; credit: Tomislav Bicanic via Flickr)

It is delivered to the consumers through a large network of transmission and distribution. At many places in the line of the power system, it may be desirable and necessary to change some characteristics (e.g., voltage, AC to DC, frequency, power factor [pf], etc.) of electric supply.

For that, in between the power station and ultimate consumer, a number of transformations and switching stations have to be created. These are generally known as substation.


  1. What Is the Substation?
  2. Classification of Substations:
    1. According to Service Requirement
    2. According to Constructional Features
  3. Comparison Between Outdoor and Indoor Substation
  4. Transformer Substations
  5. Equipment in a Transformer Substation
  6. Busbar Arrangements in Substations
  7. Key Diagram of 11 kV/400 V Indoor Substation

1. What is the substation?

The assembly of apparatus used to change some characteristic (e.g., voltage, AC to DC, frequency, pf, etc.) of electric supply is called a substation. Substations are important part of power system. The continuity of supply depends to a considerable extent upon the successful operation of substations.

It is, therefore, essential to exercise utmost care while designing and building a substation.

The following are the important points which must be kept in view while laying out a substation:

  1. It should be located at a proper site. As far as possible, it should be located at the center of gravity of load.
  2. It should provide safe and reliable arrangement. For safety, consideration must be given to the maintenance of regulation clearances, facilities for carrying out repairs and maintenance, abnormal occurrences such as possibility of explosion or fire, etc.
    For reliability, consideration must be given for good design and construction, the provision of suitable protective gear, etc.
  3. It should be easily operated and maintained.
  4. It should involve minimum capital cost.

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2. Classification of substations

There are several ways of classifying substations. However, the two most important ways of classifying them are according to (1) service requirement and (2) constructional features.

2.1 According to Service Requirement

A substation may be called upon to change voltage level or improve power factor or convert AC power into DC power, etc.

According to the service requirement, substations may be classified as follows:

2.1.1. Transformer substations

Those substations which change the voltage level of electric supply are called transformer substations. These substations receive power at some voltage and deliver it at some other voltage.

Obviously, transformer will be the main component in such substations. Most of the substations in the power system are of this type.

Transformer substation
Figure 1 – Transformer substation
2.1.2. Switching substations

These substations do not change the voltage level, that is, incoming and outgoing lines have the same voltage. However, they simply perform the switching operations of power lines.

2.1.3. Power factor correction substations

Those substations which improve the power factor of the system are called power factor correction substations. Such substations are generally located at the receiving end of transmission lines.

These substations generally use synchronous condensers as the power factor improvement equipment.

Power factor correction substations
Figure 2 – Power factor correction substations (photo credit:
2.1.4. Frequency changer substations

Those substations which change the supply frequency are known as frequency changer substations. Such a frequency change may be required for industrial utilization.

Frequency converter substation
Figure 3 – Frequency converter substation (on photo: SEPTA Wayne Rail Substation & Static Frequency Converter – Philadelphia, Pennsylvania; credit:
2.1.5. Converting substations

Those substations which change AC power into DC power are called converting substations. These substations receive AC power and convert it into DC power with suitable apparatus (e.g., ignitron) to supply for such purposes as traction, electroplating, electric welding, etc.

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Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.

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