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VAR Compensation

  1. Jan 16, 2016 #1

    How can Reactive power be physically understood?

    What is Reactive power compensation?

    Why is reactive power compensation needed?

  2. jcsd
  3. Jan 16, 2016 #2


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    Reactive power is created when ac-voltage and ac-current are phase-shifted 90°. So the power is positive for one half period and negative for the next half period. Thus the resulting power for a whole period will become zero. Reactive power cannot accumulate energy.
    Reactive power can be positive or negative. A reactance consumes reactive power and a capacitance produces reactive power. So if you have a reactive load, resulting in consumption of reactive power, you can just add a capacitive load, that produces the same reactive power ( with opposite sign ). In this way the grid doesn't have to transmit any reactive power. The reactive power has been compensated.
    Because reactive current heats transmission lines due to copper losses. When reactive power is compensated, the reactive current will be reduced, and thus the total amount of current. Thereby energy ( losses ) is saved.
  4. Jan 16, 2016 #3

    jim hardy

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    can you give a clue as to your background ?

    Hesch gave a good answer for a beginning student seeking understanding of the basic concept.

    A newbie engineer trying to figure out how to adjust var compensation for a power station voltage regulator might need a different approach to his question.

    NOT being a wise guy, but - "Who wants to know ? "
  5. Jan 16, 2016 #4
    Dear Mr. Jim

    I`m a newbie engineer [M.S In Electrical Engineering] that has been working for years in communication areas [mainly PSTN].
    I had divorced power electrical engineering/simulation/different approaches to work on mV embedded systems mainly focused on automation [micro-controllers].
    Recently I found interest on working on LV distribution substations, especially focusing on VAR compensation.

    As you can see, there is a huge gap between theoretical knowledge [M.S] and applied understanding of different engineering fields.

    What I have intention to do is to program a processor in order to [smartly] compensate VAR on L.V grids.
    First I just need to have a powerful background over all these titles, of VAR, compensation, etc...
  6. Jan 16, 2016 #5

    jim hardy

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    Many Valued Algebra? Public Switched Telephone Network?
    You're very high tech - last telephony i worked on was old Automatic Electric PAX with mechanical relays, clackety-clack ....

    Hesch is good explainer.

    Surely you remember introductory AC circuits course - phasor notation, power = VIcosθ et al...

    wikipedia has a decent review at https://en.wikipedia.org/wiki/Power_factor

    refresh what they are
    maybe we can help you with how they get pushed around
    i was in a power plant , no significant substation experience
    but PF has several "old hands" on board .
    Last edited: Jan 16, 2016
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