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Participant

Join Date: Mar 2014
Posts: 3

Positive, Negative, Zero Sequence Resistance/Reactance

03/10/2014 10:08 AM

Is it possible to calculate the the following parameters;

1. positive sequence reactance and resistance, in ohms

2. negative sequence reactance and resistance, in ohms

3. zero sequence reactance

from the following given nameplate data;

5 MVA, power transformer, 69 kv - 13.8 kv, DYn1, %IR = 0.62, %IX = 7.10, %IZ= 7.13, 3-legged core construction

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Guru
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#1

Re: Positive, Negative, Zero sequence resistance/reactance

03/10/2014 10:30 AM

Yes, it is possible, and very easy. What exactly are you having difficulty with? We don't do homework here, but here's a place that you can start your research. The first page provides plenty of examples.

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Participant

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#2
In reply to #1

Re: Positive, Negative, Zero sequence resistance/reactance

03/10/2014 11:04 AM

Thank you for caring to send your comment. Unfortunately, I am just a trader of electrical products like power transformer and have a very little technical know-hows and know-whys of this product so I may not understand the references you suggested. I wish I could just get the answers I need so I can pass the same to my customer who asked for it. (This is as good as asking you to do the homework for me.)

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#3
In reply to #2

Re: Positive, Negative, Zero sequence resistance/reactance

03/10/2014 11:59 AM

...then the correct thing to do is, when the method has been discovered, embrace the method in a local procedure within the operation so that the information and techniques learned remain within the organisation and can be passed on to others yet to come. Having a fluid response to such enquiries will boost sales in the future.

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Participant

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#4
In reply to #3

Re: Positive, Negative, Zero sequence resistance/reactance

03/10/2014 12:05 PM

Well noted. Thanks

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Guru
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#5
In reply to #2

Re: Positive, Negative, Zero sequence resistance/reactance

03/10/2014 12:31 PM

PWS will remember Jackanory, a children's TV show in the UK telling entertaining stories.

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Power-User

Join Date: Jul 2013
Location: Faridabad Near New Delhi India
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#7
In reply to #2

Re: Positive, Negative, Zero sequence resistance/reactance

03/11/2014 1:33 AM

Just a simple and straight answer to your post.

1. Positive, Negative and Zero sequence reactance and resistance are same for Transformers.

2. From the parameter given in your post one can calculate Overall Impedance (which is vector sum of reactance and resistance).

3. You can find equivalent resistance of Transformer winding from Factory Test Report. If you have values of resistance of primary and secondary separately then one can compute equivalent resistance.

4. Once equivalent resistance is known then from overall impedance reactance can be computed.

But Resistance is hardly used in fault level calculations as it is negligible when compared with reactance.

Best of luck

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Active Contributor

Join Date: Dec 2013
Posts: 10
#6

Re: Positive, Negative, Zero Sequence Resistance/Reactance

03/10/2014 10:38 PM

5, this is the data calculated by the manufacturer.

to your other question, i connt undertand the positive sequence reactance and resistance, in ohms? we will checked to electrical engineering data guide to check this formulas.

have a fomula to calculate the reactance, resistance of the high voltage transformer

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Guru

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#8

Re: Positive, Negative, Zero Sequence Resistance/Reactance

03/11/2014 8:01 PM

Yes! It is very much possible.

But you have given the notations incorrectly. It is not %IR, %IX & %IZ; it should be %R, %X & %Z only.

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Power-User

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#9

Re: Positive, Negative, Zero Sequence Resistance/Reactance

03/11/2014 10:44 PM

Sorry I did not noticed that you have stated percentage values of Resistance inductance and Impedance.

Here is the method of working:

kV 69
MVA 5
Amp (1000 x MVA/1.732/kV) 41.8382
% ristance 0.62
PU Resistance (100 x %age resistance) 0.0062
Nominal Impedance (kV x1000/1.732/Amp) 952.2
Equi. Resistance (PU Resistance x Nominal Impedance) 5.90364

Above is equivalent value of Resistance of Transformer when viewed from 69kV

Similarly you can calculate value from 13.8kV side.

As said before Zero negative and positive sequence values are same for a Transformer.

And also you can covert % reactance and impedance using above working.

Check - Sq root (Resistance Square + Reactance Square) = Impedance.

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Apol (1); electricalexpert65 (1); fnv1217 (2); powersolutionsFBD (2); PWSlack (1); RAMConsult (1); TonyS (1)

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