Premium Membership ♕

Save 50% on all EEP Academy courses with Enterprise Membership Plan and study specialized LV/MV/HV technical articles & guides.

Substation theory and practice

An electrical substation is a subsidiary station of an electricity generation, transmission and distribution system where voltage is transformed from high to low or the reverse using transformers. Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps.

Power substation guides, research papers and studies
Power substation guides, research papers and studies (on photo: Ghana Aboadze 330kV substation)

A substation that has a step-up transformer increases the voltage while decreasing the current, while a step-down transformer decreases the voltage while increasing the current for domestic and commercial distribution. The word substation comes from the days before the distribution system became a grid.

The first substations were connected to only one power station where the generator was housed, and were subsidiaries of that power station.

Equipment in substation

Substations generally have switching, protection and control equipment and one or more transformers. In a large substation, circuit breakers are used to interrupt any short-circuits or overload currents that may occur on the network. Smaller distribution stations may use recloser circuit breakers or fuses for protection of distribution circuits. Substations do not usually have generators, although a power plant may have a substation nearby.

Other devices such as power factor correction capacitors and voltage regulators may also be located at a substation.

Substations may be on the surface in fenced enclosures, underground, or located in special-purpose buildings.

High-rise buildings may have several indoor substations. Indoor substations are usually found in urban areas to reduce the noise from the transformers, for reasons of appearance, or to protect switchgear from extreme climate or pollution conditions.

Where a substation has a metallic fence, it must be properly grounded (UK: earthed) to protect people from high voltages that may occur during a fault in the network.

Earth faults at a substation can cause a ground potential rise. Currents flowing in the Earth’s surface during a fault can cause metal objects to have a significantly different voltage than the ground under a person’s feet; this touch potential presents a hazard of electrocution.

Browse guides and papers

Note that not all documents in this section are free to download. Navigate through sub-pages to discover all documents.

Fault Finding Solutions Guide by MEGGER

When voltage is impressed across any insulation system, some current leaks into, through, and around the insulation. When testing with DC high voltage, capacitive charging current, insulation absorption current, insulation leakage current, and by-pass current… Read more

Jul 01, 2012

Megger - Fault Finding Solutions

Protection of electrical networks

Generally, with an HV power supply, a private distribution network comprises (see Figure 1-1): An HV consumer substation fed by one or more sources and made up of one or more busbars… Read more

May 05, 2012

Protection of Electrical Networks

Design Guide for Rural Substations

This bulletin covers rural transmission and distribution with air-insulated, outdoor substations 345 kV (phase-to-phase) and below. Possible design responsibilities of the engineer are covered, including preparation of construction drawings, material,… Read more

Mar 23, 2012

Design Guide for Rural Substations

Electric Power Substations Engineering

Today’s state-of-the-art HVDC and FACTS controls fully digitized and processor based allow steady-state, quasi steady-state, dynamic, and transient control actions and provide important equipment and system protection functions. Fault monitoring… Read more

Feb 11, 2012


  1. [email protected]
    Feb 04, 2023

    HV substation tubular switch yard transformer and other electrical equipment design and specification shall be elaborated.

  2. Stephen Ochieng' Okello
    May 11, 2022

    I appreciate and love thy modest way of skills and knowledge sharing around here!

  3. Igwe Geoff
    Aug 05, 2021

    i thank you for your desire to extend knowledge.
    Please i am working on an estate that has 64Nos 500kva 11/415kv transformers.
    I divided the transformers into four radial circuits.

    One of the circuits has 26Nos 500kva transformers. Can i use 3 x150mm2 aluminium conductor to connect them considering that cureent for 26Nos 500kva is 679A

  4. Igwe Geoff
    Aug 05, 2021

    I am working on an an estate that have 65 Nos 500kva 11/415 transformers.
    I have 27 transformers of 500kva to be feed from a sf6 1250A.
    Can i use 150mm2 aluminium conductors to feed the transformers in radial form

  5. Biswajeet Rout
    Jul 14, 2021

    Hi, I am a graduate student, working on distribution system automation and security to cyber threat. I must say that your content is so unique to explain the terminology and equipment. I am requesting you to make an document and AMI, SCADA and PMU. I hope this will help the community in a large extent. Thank you.

  6. Nanle bitrus
    Sep 14, 2020

    You really improve my ideas in power

  7. Rex Gasinore
    Jul 09, 2020

    Learn more to understand what is all about Electrical Technology..

  8. B.H. Merzayi
    Jun 03, 2020

    Hi dear!
    Please, send information about RTCC panel for a 110kV /20kv substation
    thank you.

    Mar 21, 2020

    i would like to be a regular contributor to most discussions in electrical engineering. Specifically in areas of protection, Reliability engineering and alternative energy. Am an electrical engineer by training with over 30 years of expereince both in the academic and industry.

    • Igwe Geoff
      Aug 05, 2021

      i thank you for your desire to extend knowledge.
      Please i am working on an estate that has 64Nos 500kva 11/415kv transformers.
      I divided the transformers into four radial circuits.

      One of the circuits has 26Nos 500kva transformers. Can i use 3 x150mm2 aluminium conductor to connect them considering that cureent for 26Nos 500kva is 679A

  10. Satish Bedi
    Jan 11, 2020

    i have lot of ideas for Electrical energy conservation which i had tested and result is good

  11. Godswill Essienta
    Aug 18, 2019

    you guys are unique, i want to be part of this vision, thanks.

    Aug 01, 2019

    hi am francis from bonum kenya limited
    kindly see your email and let me know what item you manufacture

  13. Agaba Emmanuel
    Jun 07, 2019

    I wish to subscribe to this portal,thanks

Leave a Comment

Tell us what you're thinking. We care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

6  ⁄    =  one

Learn How to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Enjoy learning!

Subscribe to Weekly Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and guides (PDF).
EEP Academy Courses - A hand crafted cutting-edge electrical engineering knowledge