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Booster transformer topology for transmission application

  1. Jul 16, 2017 #1
    Hi,
    Regarding transmission line booster transformer topologies I'm curious as to what would happen over all the possible permutations.

    I refer you to the following:
    BT.PNG
    http://top10electrical.blogspot.com.au/2015/03/booster-transformer.html

    I presume that in real life the booster transformers are all 1:1, but for this discussion imagine that all the primaries and secondaries have tap changes, so all buck-boost configurations are possible.

    For this thought exercise I'm defining the power flow of left to right (through the regulating transformer) as forward, as well as down to up (through the booster transformer) as forward. As well as defining the primary as being on the left of the regulating TX and the primary as being the top of the booster transformer.

    I haven't yet put in the values for if the polarity of the secondary of the booster transformer being swapped. But I am curious as to what would happen if you reversed this as well, so in good time I want to record the effects of swapping the dot on the secondary of the booster transformer as well.

    Please see the following table I have attached the .xlsx of:
    permutatiosn pic.PNG

    I have just used 1;2 as short-hand for a boost ratio, and 2;1 for bucking ratio.
    I have inputted a couple of the resulting power flow and voltage changes, as I expect they would occur. If someone could help me understand the operation and fill in the rest, that would be wonderful.

    Thank you!
     

    Attached Files:

  2. jcsd
  3. Jul 17, 2017 #2
    In general these will be a % of the total ratio, like 1% to 5%.

    They are almost always boost - to account for line drop in the feeder, and that is dependent on current.

    You should note - the effect of the Main Transformer's set up and the Regulating/Booster configuration are the SAME. It just happens one is all in one transformer and one is built as two. (If you "stack" the booster on top of the regulator it looks the same as the main). Since it is labeled as Boost - then I doubt it is bucking, but having the separate winding does allow for this possibility - but I have not seen it.

    The Main and Regulating / boost can be evaluated separately. Eg. Input to point A. Ideally it would then have function (calculation) of Line drop in the feeder based on current load. And THEN Reg/Boost input to point B.

    You are not mapping the topologies - I do not know what Topo #1 is.

    Ideally - evaluation goes beyond basic voltage analysis, but the purpose is generally just to boost voltage.
     
  4. Jul 17, 2017 #3
    Thanks for the reply.

    I'm aware that they're almost always boost, to prop up the feeder voltage. But this is mostly an academic exercise, I want to play with all possible permutations (useful in real life or not, if necessary please re-read my OP, any questions about it, please ask me). So it would be helpful if I could rearrange this in another way to better think about and understand it. When you say that the main TX is effectively the same as the regulating/boost transformer, this is a step in the right direction for my understanding. I've arranged this as a picture illustration:
    rearranged.png
    However, because the feeder is in between parts of the primary coil (on the left) of this hybrid 'regulating and boosting transformer', I'm not quite sure how to treat this.

    When I say topologies, as per the table in my OP, I mean the turns ratio of the regulating TX is 1:1 and the ratio of the BT is 1:1;
    I further define topology 2 as: the turns ratio of the right side (secondary) is larger than the left side (primary), of the regulating TX and the BT ratio is 1:1
    topology 3 is: the turns ratio of the left side (primary) is larger than the right side of the regulating TX, and the BT ratio is 1:1
    topology 4 is the turns ratio of the regulating TX is 1:1, the turns ratio of the primary (top coil) is smaller than the secondary (bottom coil) of the Booster TX. N.B. the "top coil" of the BT is now on the left of the 'Regulating and Booster transformer.
    topology 5...and so on...

    Thanks!
     
  5. Jul 18, 2017 #4
    OH - yes, I spoke too soon. But here you see the separate loop can, essentially be at any voltage ( for example, a high voltage will have lower current in the loop and then lower I2xR losses. The Boost does not have to be 1:1. The effect of the Regulating + boost will probably yield 100%, + 105% +110%... but assuming 1:1 fro just the Boost is putting values in, and assuming something that you do not know.

    I would make this all generic and assign a Ratio (M = N2/N1) term like "MR1" and "MBoost"

    Example on the Main you have one case

    Vout = Vin X Mmain1

    Then construct a spreadsheet with Variables (inputs and ratios) in the header and then Calculations(outputs).

    You could actually build a pretty slick calculator in excel like this - using a slider to input the load, and the excel calculates the best Transformer Tap combination.
     
  6. Jul 19, 2017 #5
    Agreed.

    Okay, I'll try to make the excel into a calculator, and I'll used the initial table as input values for the ratio values.

    So
    VReg_secondary = Vout*MR1
    But how do I calculate the voltage of VB?
    Would VB = Vout + VReg_secondary*MBoost?

    Cheers!
     
  7. Jul 19, 2017 #6
    That is how I would do it ..

    I know I used Vout - probably should be VA - just nomenclature

    I would probably include a Vfeeder

    So then there are 5 voltages defined, 1 input and 4 calculated.
     
  8. Jul 20, 2017 #7
    At this point I want to understand how the regulation TX and BT relationship works first, I'll get to Vfeeder and VA in time. As will I moving the dot polarity of the BT (so it becomes a buck-transformer).

    So I've made a [quick] similar attempt, please see attached excel sheet. However I gave the turns numbers and Va (240V) as inputs and got Vb as the output.

    But I'm not quite sure if this is a correct representation, I think it could use some verification of the formulae.

    Thanks!
     

    Attached Files:

  9. Jul 20, 2017 #8
    Overall this does not seem too different then your original spreadsheets.

    "Regulation" - indicates the voltage is being controlled / maintained close to a nominal voltage. While for the math the ratios do not matter, you have this like a step up arrangement.

    In reality - it may be common or Va to be low ( generator voltage) feeder to be high to reduce losses, and the the regulating Trans actually be a step down to distribution or end user voltage.

    As this point I am kind of lost as to what you are trying to do, what is the objective. The math should be straightforward and for the Main there are 3 options, for the regulating/boost set up there are 3 options, you have 9 permutations.
     
  10. Jul 25, 2017 #9
    Sorry for the delayed reply.

    The reason it didn't look too different from my original spreadsheet was because I wasn't really evaluating it for it's line regulation properties. As for what my objective is, is that I am trying to get my bearings of the concept because I was considering a three phase bucking system where the booster is fed from other phases, to shift the voltages and currents and balance the load and correct the power factor. But that would be a very complex system, needing to account for currents etc.
     
  11. Jul 25, 2017 #10
    Seeing your other post - the challenge with transformer based set up is changing taps under load, this introduces a number of "real world" problems. If the load is static and does not require adjustment in operation than a simpler system can be developed. If it requires a dynamic adjustment, then stepped caps ( PF and Filtering) or an active ( power electronics) solution is the most practical.

    Developing significant magnetic solutions is practically and art and expensive to make. Adding load to a primary phase, will affect that phases "other" secondary windings. Not that simple.
     
  12. Jul 26, 2017 #11
    I completely agree and am under no illusions about the difficulty/impossibility of this idea. But as an academic exercise (when I have the time) I want to play around with the concept (for static loads).

    Thanks again for your help
     
  13. Jul 26, 2017 #12
    Magnetic solutions TYPICALLY add costs and losses - that can be reduced in active solutions. Like the computer has replaced the adding machine, Digital Power ( SMPS) is replacing analog (passive) power elements.
     
  14. Jul 28, 2017 #13
    I appreciate the brilliance of active solutions, and in good time I want to build in the basics of power electronics I once learnt. But I also still like to meditate on magnetic solutions because of their robust construction and the nature of having the potential to be incredibly reliable. This really appeals to me on a more emotional level.
     
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