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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.


  1. Md. Ashraful Alom
    Oct 09, 2017

    I glade to see such a nice blog site i ever see…….and useful. Thanks again!

  2. A M Venkatesh
    May 31, 2017

    Been visiting this site for a pretty long time. Has been very useful whenever I was stuck in a problem / crisis concerning substation, distribution and transmission design engineering. Would like to contribute from my collections which will be useful to design engineers.

  3. Timothy Partasevitch
    Mar 17, 2017

    Hello, Mr. Csanyi, If you wouldn’t mind, while we are on the subject on the subject of Electrical Software, I would like to hear your opinion on custom software development for power networks. Seeing how the market is dominated by a particular number of companies, can outsiders (IT company) step in and be competitive.

    I’ve recently graduated and now I found myself in this particular business, directly connected with the marketing department. Although I can’t say much about details and particulars (NDA, I’m sure you understand), I work on adaptive coordination for overcurrent relays. I can share link to the particular article (it’s potential customer oriented, not purely technical), discussing the possibilities and advantages of implementing the adaptive OCR.

  4. Thabiso Boase
    Jan 24, 2017

    This site makes me a better person daily

    Jan 03, 2017


    Please, Can I find books about Photovoltaic systems / Substations?

    email: [email protected]

  6. Faysal
    Dec 31, 2016

    I will be benefited if you assist to know how to calculate HT CT ration for HT/VCB Panel.
    Thanks in Advance ….

  7. Qaisar Jamil Akhtar
    Apr 20, 2016

    Hi, i study your E E portal, That is good attempt to convey your syetem specs to Readers, pls i need substations details on my Email site.

    Thanks & Regards

  8. hossein
    Apr 05, 2016

    Hello my Friend.Could we omit the GCB(Generator Circuit Breaker) of a 160MW Combined Cycle unit (with a 160MW/15.75kV Genarator and a 200MVA/230/15.75kV Unit Transformer)?

  9. Saadat
    Mar 26, 2016

    How can i find the book “Substation Commissioning Training Course” written by Mr. Raymond Lee ??
    It is very Urgent.
    Thank you.
    My email: [email protected]

  10. zaya
    Dec 11, 2015

    Thank you,7

  11. sathish
    Aug 30, 2015

    I’m a substation supervisor in Bangalore.

  12. Nicks Mutuku
    Jul 13, 2015

    This quite helpful. Keep it up.

  13. Local Sydney Electricians
    Jul 03, 2015

    Using Voltage Stabilizer and UPS systems can prevent you from any kind of power mishaps.

  14. George
    Oct 23, 2014

    how to make electric motor solo run procedure

  15. Elvis Mulowa
    Jul 24, 2014

    thanks for the good works we are really updated

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