Step-up Transformer Sizing
Step-up Transformer Sizing
(OP)
What is the sizing criteria or standard for selecting kVA rating of a Gas Turbine and Steam Turbine Generator?
Equal kVA rating of Generator and Transformer creates temperature rise problems in some cases as per my previous experiance.






RE: Step-up Transformer Sizing
for selecting kVA rating of a Gas Turbine and Steam Turbine Generator Step-up Transformer?
RE: Step-up Transformer Sizing
RE: Step-up Transformer Sizing
In my case Steam Turbine rating is 32125 kVA with 0,8 pf.
11/31,5 kV transformer will be used. Alternatives are 35000 kVA ONAN or 25000/35000 kVA, 32000/40000 kVA.
Of course 25000/35000 kVA is the best solution in terms of investment cost. But I coulnt find any standard or criteria giving the calculation method.
No chance to calculate and prove it without computer based load flow calculation?
RE: Step-up Transformer Sizing
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Step-up Transformer Sizing
RE: Step-up Transformer Sizing
C57.116-1989
IEEE guide for transformers directly connected to generators
RE: Step-up Transformer Sizing
In C57.91, the predicted nominal life of a transformer at 110C hot spot temperature ranges from 7.4 years to 20.55 years depending on which end of life criteria is selected.
We have a fairly conservative policy for temperature limits that trips the banks if they get above 110C, thus the our banks have to be a bit over sized to have some operating margin and to account for measurement inaccuracies.
Also be sure to include the higher auxilary and load losses in your calculation for the smaller bank sizes.
If your transformer has taps, be sure that the capacity is not derated on the tap you are planning to use.
RE: Step-up Transformer Sizing
No one ever got fired for making this transformer a little too large.
"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)