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Learn about power engineering and HV/MV/LV substations. Study specialized technical articles, electrical guides, and papers.

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 all documents in this section are free to download. Navigate through sub-pages to discover all documents.

Best practice in power substation grounding

The substation grounding system is an essential part of the every electrical system. The proper grounding of a substation is essential and very important for the following two reasons. First,… Read more

Released on Jan 14, 2019

Best practice in substation grounding systems

New Technologies in Substation Automation Systems

The performance of a substation automation system depends on the implementation of an effective communication system to connect all the protection, monitoring and control devices within the substation. There are… Read more

Released on Dec 23, 2018

New Technologies in Substation Automation Systems

132 KV substation basic training for students

The equipment required for a transformer substation depends upon the type of substation, service requirement and the degree of protection desired. 132KV substation has the following major equipment. When a… Read more

Released on Dec 19, 2018

132 KV substation basic training for students

55 Comments


  1. Nanle bitrus
    Sep 14, 2020

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  2. Rex Gasinore
    Jul 09, 2020

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  3. B.H. Merzayi
    Jun 03, 2020

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


  4. DAVIS CHESOLI
    Mar 21, 2020

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    May 10, 2019

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  10. Anoop Kumar Sharma
    Apr 25, 2019

    Can we consider one VCB with metering and protection system for one transformer?


  11. Alfredo Padamo
    Mar 13, 2019

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  12. Mphumzi Kleinbooi
    Jan 24, 2019

    Good day sir/madam,
    I’m working for BCMM Municipality-electricity.Im a clerk of works here.i need you to help me understand the heavy current components,specificaly the substation equipment and each its components and use.Breakers,transformers,auxiliary transformers,isolators,current transformers,voltage transformers,surge arrestors,neutral earthing compensator(NEC),neutral earthing compensator resistor(NECR),HYpact unit Line,cubular bus bars and conductor bus bar.132 and 66kv bus couplers,HYpact bus coupler,132kv and 11kv bus section breaker,panels,DC system,DC supply for inverter.
    Thank for the assistance in advance.


  13. Willem du Toit
    Nov 07, 2018

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  14. Javier Meza
    Aug 15, 2018

    I am looking for literature related with Substation Ground Grid Connectors for Below Grade Applications


  15. ADEKUNLE UTHMAN
    Aug 09, 2018

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    Jul 11, 2018

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    May 29, 2018

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  18. Balone
    May 23, 2018

    hello i am experiencing a 95% stator earth fault on my generator protection .relay its an REG670 please assit


  19. Ms Lee Wan Ling
    Apr 11, 2018

    Kindly quote to us building cost for 1 unit substation in industrial area of integrated oil and petrochemical refineries at Rapid PTD 5319 H.S.D 36874, Mukim Pengerang, Daerah Kota Tinggi, Johor, West Malaysia
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    Thank you


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      Apr 24, 2018

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  20. baseemnasir
    Jan 12, 2018

    Hello dear
    please i want to get the calculation design on a capacitores in electrical substation and and how can we calculate the size of capacitance to instull in electrical power system


  21. Manikandan
    Dec 18, 2017

    How to calculate the substation fault level and what are the inputs are required


  22. vijaya manikanta
    Dec 15, 2017

    Can we consider parallel runs in determining short circuit rating of feeder?

    Example: 33KV incoming feeder has to be designed for 33KV, 31.5KA, 1sec rated Panel to feed 20MW, feeder length is about 2000 m to be laid in RCC Trenches.

    2Runs 33KV, 300 Sqmm, AL Cond., XLPE Cable is recommended to cater 20MW, 350A & fault current of 31.5KA, 1 Sec.

    1Run of 300 Sqmm, AL Cond., XLPE Cable can carry 310A in duct @ 30 deg C and about 28KA for 1 sec as per manf. catalog.

    Considering De-rating Factors for temperature & grouping etc. actual capacity 237Amps/ Run

    So 2 runs cater 474 Amps i.e. more than sufficient to cater required 350A.

    As 2 Runs are considered it is supposed to cater 31.5KA, 1sec considering current sharing in parallel runs.

    Kindly give your advice on the above.


  23. AKRAM FLITI
    Dec 13, 2017

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  24. Md. Ashraful Alom
    Oct 09, 2017

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  25. 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.


  26. 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.


  27. Thabiso Boase
    Jan 24, 2017

    This site makes me a better person daily


  28. ABDELMALIK FARIS
    Jan 03, 2017

    Hello;

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

    email: [email protected]


  29. 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 ….


  30. 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


  31. 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)?


  32. Saadat
    Mar 26, 2016

    Hello.
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    It is very Urgent.
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    My email: [email protected]


  33. zaya
    Dec 11, 2015

    Thank you,7


  34. sathish
    Aug 30, 2015

    I’m a substation supervisor in Bangalore.


  35. Nicks Mutuku
    Jul 13, 2015

    This quite helpful. Keep it up.


  36. Local Sydney Electricians
    Jul 03, 2015

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


  37. George
    Oct 23, 2014

    how to make electric motor solo run procedure


  38. Elvis Mulowa
    Jul 24, 2014

    thanks for the good works we are really updated


  39. letlhogonolo mogorosi
    Mar 27, 2014

    I am working as a technician in eskom, i like knowing about different protection we found in our substation,different relays how they operate when flacked what fault to be expected.more especially in distribution substations.i hope ill learn a lot from you thanks.if posible can you send me theorytical guardes.


  40. AIDIL ARIFIN, E Eng.
    Mar 21, 2014

    Thanks & Regards,


  41. B.Venkat Reddy
    Feb 16, 2014

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  42. cristian
    Jan 19, 2014

    Thanks for your documentations ,my job is electrical technician ,vendor position for italian provider LV & MV electrical equipment.

    thanks


  43. Aljan24uson
    Oct 25, 2013

    Thanks for this kind of portal site. It is very informative and helps a lot to our fellow electrical practitioners….keep it up guys!!!


  44. DONDON
    Mar 03, 2013

    Can anyone show me the Fault Current Calculation of Transmission Lines?


  45. namnguyen
    Mar 02, 2013

    Thanks for useful technical paper, keep the good works.


  46. alhana89
    Jan 27, 2013

    Thanks for making these references available for us. Keep up the good work, guys!


  47. lollo
    Jan 08, 2013

    Hi the people iv just finished my studies and am currently working,and I have been learning on how to use the new software “Janitza GridVis software” and this software monitors power from High to Low voltage systems and currently i have been tasked yo write a programm that will be used for valves have any of you people got maybe some idea on this new jasic programming??
    thanks

    • Edvard
      Edvard
      Jan 08, 2013

      To be honest I never heard of it. Can you share with me some information about it, some links.


  48. Rateb Fares
    Oct 25, 2012

    thank you very much


  49. Jones
    Jun 16, 2012

    kindly provide substation earth mat calculation …


  50. engrwaqas_11
    Nov 20, 2011

    dear,
    thank you very much for such nice work..if possible please upload field testing date e.g. transformers testing, under ground cable testing, relays testing..etc

    Regards,

    Waqas Ahmed


  51. subhransu
    Nov 13, 2011

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  52. ANANDAN
    Aug 01, 2011

    DEAR SIR
    I WANT A PROGRAMME FOR BUSBARS AMPACITY CALCULATION
    PL HELP
    ANANDAN


  53. diamond
    Jul 27, 2011

    thanks a lot

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