mva-metho.pdf

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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:

11KV Bus

10MVA Transformer:

Page 2 of 12MVA Method Load Flow Calculation – Ver Pangonilo - Filipino Engineer

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4MVA Generator:

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

II. Upstream Values:

At 400V Bus:

At 6.6KV Bus:

2MVA Transformer:

5MVA Transformer:

At 11KV Bus:

5MVA Transformer:

10MVA Transformer:

4MVA Transformer:

At 33KV Bus:





10MVA Transformer:

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 thiscalculation for you to do).

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By Ver 8:48 AM

8 Responses

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tiong says

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

August 16, 2010, 3:36 PM

1.

Ver says

Hi Tiong,

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

August 16, 2010, 4:18 PM

2.

artem says

@ 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.

3.





February 1, 2011, 6:39 PM

Ver says

Hi artem,

Here is how the values were taken.

Upstream Values:

The sum will be:

Downstream Values:

The sum will be:

Hope this helps.

February 2, 2011, 4:47 AM

4.

artem says

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

February 2, 2011, 10:56 AM

5.

artem says

I’m sorry sir Ver but i have additional query about the voltage dip or voltage drop upon startingthe motor 150kva on the system which draws a power of 0.9 MVA..I have a result by handcalculations at 400V Bus: 77.22%, at 6.6kV: 87.72%, at 11kV: 89.28% which is a littledifferent result on your MVA Diagram as shown that at 400V Bus: 76.7% (shown calculation),

6.





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..


Ver says

Hi artem,

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

Thanks


7.

artem says

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

February 3, 2011, 10:36 AM

8.

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