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  • Users: vranac
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  1. vranac

    underfrequency protection for GSU

    Hi, thanks for replay.... Now when you mentioned that ''GSU is faster saturated than generator...'', is it possible to get some information or dana about how long it takes for transformer to be saturated. On what does it depends (exept on frequency). Is ther any formula how to calculate this...
  2. vranac

    Short circuit current for transformers in serial....

    usually I calculate like this (for may example), but I had some doubts so thanky all for your help: Xt1=(sqr(20kV)/40MVA)*(8/100)=0.8ohm Xt2=(sqr(20kV)/20MVA)*(6/100)=1.2ohm Xtotal=Xt1+Xt2=2ohm -for injection of 400V on 20kV: I=400/(sqrt(3)*Xtotal)=115A -and then recalculate this on 10kV...
  3. vranac

    Short circuit current for transformers in serial....

    thx for detail calculation. Now it's more clear to me. So, if we have transformes connected on this way, we can calculate currents on both sides without taking into concideration 10kV voltage level, and without thinking that we have transformers with different MVA? And that means, on 10kV we...
  4. vranac

    Short circuit current for transformers in serial....

    thx waross for your reply... You confused me a little bit with your pu calculation, but I manage to get it. But, If I calculate the current on 10 000V, I get 577A. Should you take in to concideration sqrt(3)? And, one more thing, if you will find time to calculate to the end...the thing I would...
  5. vranac

    Short circuit current for transformers in serial....

    Hello everybody... Let say we have two transformers (please don't bother with transformers data, they are only to get the pricipal on how to calculate): 1. 20/10kV, uk=8%, S=40MVA, YNd1 2. 10/6.6kV, uk=6%, S=20MVA, DYn11 If we would like to make stability test of 20/10kV transformer on way that...
  6. vranac

    underfrequency protection for GSU

    Hi... I am wondering about few things regarding unnderfrequency Protection for genrator stepup transformer...So, if somebody could give some comments... - is setting for trip is 47,5Hz for 1 second to short. Means should we give more time to try to come back in normal frequency - is it necessary...
  7. vranac

    generator neutal connection for stability

    Thank you ScottyUK. Now it's clear for me.
  8. vranac

    generator neutal connection for stability

    Hello.... Can anybody tell me is it neccessary to connect neutral of the Diesel generator if we want to use diesel generator as a source to inject 400v on three phase transformer on delta side. The point is to test stability of transformer injecting 400v from generator. Fault on the high...

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