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1. fgm
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## How design autotransformer in ETAP?

I have autotransformer consisting of 3 single-phase auto transformers 400/220 / 31.5 kV and 267 MVA unit capacity or total capacity of 800 MVA

Modeling it with a 3-Winding Transformer * but I can't understand in the section for "impedance" resistance for a 800 MVA оr for a 267 MVA should I enter?

Last edited by fgm; 03-04-2016 at 01:10 AM.

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You need to read symmetrical components by blackburn to know the basics. You need to go back the basics of per unit calculations.

Let's always remember that:
ETAP is just a tool. A garbage input results in a garbage output.

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Hi*

when dealing with single phase transformers to be connected to form a bank of three phase power transformer* the impedance per transformer should be used. this is independent when it is connected as an auto transformer bank. But* since the auto transformer is like a three-winding transformer* the nameplate of the transformer will have illustrated three values of impedances measured with respect to each other (i.e. H-X* H-Y* X-Y). In this case* you have to solve the value of impedance per side of transformer (H* X* Y) because these data are needed in the power flow software. the formula for that is usually written in several excellent texts in power system. In the case of PSS/E* you will have to just input the nameplate parameters and the software engine will solve the required impedances.

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Hi*

when dealing with single phase transformers to be connected to form a bank of three phase power transformer* the impedance per transformer should be used. this is independent when it is connected as an auto transformer bank. But* since the auto transformer is like a three-winding transformer* the nameplate of the transformer will have illustrated three values of impedances measured with respect to each other (i.e. H-X* H-Y* X-Y). In this case* you have to solve the value of impedance per side of transformer (H* X* Y) because these data are needed in the power flow software. the formula for that is usually written in several excellent texts in power system. In the case of PSS/E* you will have to just input the nameplate parameters and the software engine will solve the required impedances.

7. fgm
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Thank's.
I will use the impedance for a 267 MVA in p.u %

8. fgm
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Last edited by himmelstern; 09-12-2017 at 11:05 PM.

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thanks himmelstern

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I found an autotransformer on GIS or geoespatial diagram* for railway applications* it used for etrax module.

and

Last edited by himmelstern; 09-14-2017 at 08:06 PM.

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## Re: How design autotransformer in ETAP?

Originally Posted by fgm

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I have autotransformer consisting of 3 single-phase auto transformers 400/220 / 31.5 kV and 267 MVA unit capacity or total capacity of 800 MVA
Modeling it with a 3-Winding Transformer * but I can't understand in the section for "impedance" resistance for a 800 MVA ذ¾r for a 267 MVA should I enter?
OK so 3W TX

If LV winding = 800 kva and if Teritry winding = 200 kva then HV winding will = 1000kva (sum) in most cases.
Now you must check impedance Z% from manufacturer nameplate. With Z% and kva you can calculate R* X *X/R ratio.

*very important*: depend on software make sure you calculate above values on correct base power (usually winding kva). I see many mistake from this error.

Edit: i misread your best* what i say above is for three winding transforner* autotransformer might be different.
Last edited by user82; 09-15-2017 at 08:00 PM.

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