Update (02 February 2011):

Load Factor
Figure 2 Load Flow Calculation

Here are the steps in calculating the values in above Figure 2:

I. Downstream Values:
Note: These are the values above the arrow.
33KV Bus:

MVA_sc=250MVA

11KV Bus

10MVA Transformer:
MVA_sc={1/({1/250}+{1/111.11})}=76.87MA

4MVA Generator:
MVA_sc=35.4MVA

From here, we are not able to go any further since we need values from downstream to be able to calculate the equivalent MVA between the 5MVa transformer and the 5MVa motor.

II. Upstream Values:

At 400V Bus:

MVA_sc=({0.9}+{0.15}+{0.596}) = 1.65MVA

At 6.6KV Bus:

2MVA Transformer:

MVA_sc={1/({1/1.65}+{1/33.33})}=1.57MVA

5MVA Transformer:

MVA_sc=1.57+6.8=8.37MVA

At 11KV Bus:

5MVA Transformer:

MVA_sc=1/({1/8.37}+{1/71.43})=7.49MVA

10MVA Transformer:

MVA_sc=(7.49+5)*{76.87/(76.87+35.4)}=8.55MVA

4MVA Transformer:

MVA_sc=(7.49+5)*{35.4/(76.87+35.4)}=3.94MVA

At 33KV Bus:

10MVA Transformer:

MVA_sc={1/({1/8.55}+{1/111.11})}=7.94MVA

At this point, we have completed all the values in the upstream MVA contribution for load flow.

Let us now go back to the downstream calculation where we stopped. (Note: I will leave this calculation for you to do).

19 thoughts on “MVA Method Load Flow Calculation

  1. gillrn Reply

    PLEASE I NEED A PDF ebook with so many examples, on how to calculate load flow calculation using MVA method

  2. ver Post authorReply

    @iam:
    Do not be sorry, we encourage discussions here. It is a virtue to ask when unsure.

  3. iam Reply

    Thank you, the answer is on the article. I’m sorry i don’t read carefully.

  4. iam Reply

    Likely 0.9 from MVA Starting Motor, 0.15 and 0.596 from MVAsc Motor. where are 5.44; 2,97 ; 0,49 ; 1,98 came from?
    May I have more explanations of Voltage Drop?
    Thanks,

  5. iam Reply

    Dear Sir,
    I apologize if i do not understand at items below,
    for Vd = 2.97 / (2.97 + 0.9) = 76.7 % or 306.8 V
    Where is 2.97 come from?
    Thank you so much,

    • ver Post authorReply

      That value was taken from 5.44 * (0.9 / (0.9+0.15+0.596)) = 2.97

  6. jonner Reply

    How to find Zero Sequence MVA:

    if a synchronous motor (y/ wye and netral connected to gound ):
    synchronous motor, nameplate: 2000KW ( 2.219MVA )
    impedance ( xd”=15.38, x2=15.38, x0=15.38 )
    dynamic model equivalent ( xd=110%, Xdu=116.93%, xd’=23%, XL=11% )
    Locked rotor , LRC= 453.5%
    pf =14.8%
    grounding connection ( Y. type resistor )

    Any information you could supply would be very welcome
    Jonner

  7. Ver Post authorReply

    @orlyboy,

    as they load are in parallel, the MVAs should be added. The answer was correct, it was a typo on the formula. Thanks for picking that up.

  8. orlyboy Reply

    Sir,
    How come the upstream value at 400V bus is 1.65 MVA?
    As in the figure shows (1/0.9)+(1/0.15)+(1/0.596) = 9.4556
    1/9.4556 is approximately 0.105757.

    How come it is 1.65?

    Kindly explain

  9. orlyboy Reply

    Sir,

    What is meant by MVA?
    Is it Mega Volt Ampere or Mean Value Analysis?

    Regards,
    Orlyboy

  10. artem Reply

    I salute you sir for sharing your knowledge and expertise, thank you very much..god bless.

  11. Ver Post authorReply

    Hi artem,

    I have updated the article. I hope it will be much clearer at this time.

    Thanks

  12. artem Reply

    I’m sorry sir Ver but i have additional query about the voltage dip or voltage drop upon starting the motor 150kva on the system which draws a power of 0.9 MVA..I have a result by hand calculations at 400V Bus: 77.22%, at 6.6kV: 87.72%, at 11kV: 89.28% which is a little different result on your MVA Diagram as shown that at 400V Bus: 76.7% (shown calculation), at 6.6kV Bus: 80.6%, at 11kV Bus: 90% and 33kV Bus: 96.6%.
    Please help me sir, how did you perform this calculations.. thank you..

  13. artem Reply

    exactly sir ver, this helps a lot. thank you very much..mabuhay ka and god bless.

  14. Ver Post authorReply

    Hi artem,

    Here is how the values were taken.

    Upstream Values:
    67.33MVA = 112.27MVA*(7.49/{7.49+5})

    44.94MVA = 112.27MVA*(5/{7.49+5})
    The sum will be:
    44.94MVA + 67.33MVA = 112.27MVA

    Downstream Values:
    8.55MVA = 12.49MVA*(76.87/{76.87+35.4})

    3.94MVA = 12.49MVA*(35.4/{76.87+35.4})

    The sum will be:
    3.94MVA + 8.55MVA = 12.49MVA

    Hope this helps.

  15. artem Reply

    @ 11kv bus as per mva diagram,
    upstream values mva are 67.33 (transfo. 2) and 44.94 (motor 5mva)
    downstream values mva are 8.55 (transfo. 1) and 3.94 (generator side)..
    Please help me to explain sir how did these values came. How to perform this calculation…Thank you.

  16. Ver Post authorReply

    Hi Tiong,

    Motor MVAs in load flow calculation is the rated motor MVA, not the short circuit MVA

  17. tiong Reply

    Quoted” 1. Motor MVAs are equal to the rated Equivalent MVAs.”

    I wish to confirm that Motor MVAs is the short circuit MVA please? Thank you

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