ComparisonsEE Questions / AnswersTransformer

What is the difference between Power Transformers and Distribution Transformers?

Main Difference between Power Transformer and Distribution Transformer

In brief, those transformers installed at the ending or receiving point of long and high voltage transmission lines are the power transformers (mostly Step up). At the other hand, The distribution transformers (generally pole mounted) are those installed nearby the load terminals (City and villages) to provide utilization voltage at the consumer terminals (mostly step down). difference between Power Transformer and Distribution Transformer

Below are some additional differences between power and distribution transformers.

  • Power transformers are used in transmission network of higher voltages for step-up and step down application (400 kV, 200 kV, 110 kV, 66 kV, 33kV) and are generally rated above 200MVA.
  • Distribution transformers are used for lower voltage distribution networks as a means to end user connectivity. (11kV, 6.6 kV, 3.3 kV, 440V, 230V) and are generally rated less than 200 MVA.
  • A power transformer usually has one primary and one secondary as well as one input and output setup. A distribution transformer may have one primary and one divided or “Tapped” secondary, or two or more secondaries.
  • Power transformers generally operate at nearly full – load. However, a distribution transformer operates at light loads during major parts of the day.
  • The performance of the power transformers is generally analyzed by commercial or maximum efficiency because they are designed for maximum efficiency at full load. Whereas, the performance of a distribution transformer is judged by all day efficiency of transformer because they are designed to be operated for maximum efficiency at 60-70% load as they are normally doesn’t operate at full load all the day as there are peak hours for load in 24 hrs which are not same at once all the time.
  • The rating of a high transformer is many times greater than that of distribution transformer.
  • In Power Transformer, the flux density is higher than the distribution transformer.
  • Power transformers, primary winding always connected in star and secondary winding in delta connections while in distribution transformers, primary winding connected in delta and secondary in star connection. read more about the comparison between star & delta connections.
  • In The Sub station, at the end of the transmission line, The power transformer connection is in Star-Delta.(to step down the level of voltage)
  • At the beginning of the transmission line (H-T), the connection of the power Transformer is in Delta – Star (to step up the level of voltage). Also, not that the same connection i.e Delta – Star connection is used in three phase step down distribution transformer as well

Good to Know: All day efficiency = (Output in KWhr) / (Input in KWhr) in 24 hrs. All day efficiency is less than the Power efficiency. Read more Here.

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  1. Anonymous says:

    power transformer are not always connected in star primary side, pls correct it…

  2. Mujeebullah haji abdul latif says:

    the first two lines say that power and distribution transformers have same ratings but down its written that power transformer has greater ratings as compared to distribution.

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  4. Distribution transformers rated upto 750kVA.<br />Power transformer mostly use delta star connection

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  6. manishkumar v. bhoot says:

    Its very nice general knowledge for us which is provided by this side

  7. mami zbest says:

    i really appreciated this interesting website i think this is not only for current generation but, for the next……

  8. Engr Dadiri says:

    The power rating cut off stated above is not a standard,you could have power transformer at a 132kv sub station rated 30,45,60mva .yes as low as that, also distribution transformers can be as low as 15mva.even the winding arrangement is not general cos a power transformer could have a tertiary winding 11kv in addition to the secondary which means the star delta rule is not applied here.

  9. Munif Mutahar says:

    Very nice general knowledge

  10. guys help us to add on my professional in electricity

  11. Eng Hankumba Miyanda says:

    on the last two statements,i would love you to shed more light on it, because what i know is for a step up tx- we have star delta and step down is the other way round because you want to have a neutral for distribution purposes.

  12. jresquival says:

    That’s good to know that distribution transformers are used for lower voltage distribution networks as a means to end user connectivity. I guess it doesn’t need as much voltage when it’s not traveling as far. After moving to the city and seeing transformers all over the place, I was wondering what the difference was.

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