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  1. emviana

    Impedance Transformer Calculation Based on Short Circuit Tests.

    waross, This was what we were doing. Full load at secondary 2.25 MVA (half of primary winding) and use as base 2.25 MVA at primary. We was in doubt in what MVA base to use (2.25 or 4.5 MVA), but considering what 7anoter4 said, now, I really think that I should use 2.25 MVA in all three...
  2. emviana

    Impedance Transformer Calculation Based on Short Circuit Tests.

    waross, This was another pointing of discussion here, during de transformer testing. I'm not sure what base use in primary winding, 4,5MVA or 2,25MVA. Until the moment no one coul answer this for me. First I was thinking that correct is use 4,5MVA, but another guy here said do use 2,25MVA as...
  3. emviana

    Impedance Transformer Calculation Based on Short Circuit Tests.

    Thanks a lot, pwrtran. 13.89 kV was a typing error. The correct is 13.8 kV. We was calculating Zps and Zpt like in your first answer, founding 9.05% and 9.04% respectively, assuming that power base por HV winding was 2.25 MVA (half total), for a full load in secondary OR tertiary winding. My...
  4. emviana

    Impedance Transformer Calculation Based on Short Circuit Tests.

    Hi, all. We are testing a new three winding transformer (4,5 MVA 13.8 kV Delta / 2,25 MVA 0,48 kV Wye / 2,25 MVA 0,48 kV Wye) to obtain the percentual impedance of windings. We obtained the following results: -Voltage applied in 13.89 kV winding with secondary short-circuited and tertiary...
  5. emviana

    Votlage Regulator - Manufacturers

    It is a rotating rectifier.
  6. emviana

    Votlage Regulator - Manufacturers

    Hello everybody. I was looking for AVR models to install in a 25MW 13.8 kV generator, for an industrial usage. We are substituting the old AVR's units by new ones. What are good manufacturers for this products? Best Regards!
  7. emviana

    Siemens Setting Tool

    Thanks, George. I'm trying to install it on a Windows XP based PC. I think that it's really necessary to have an old version of DIGSI.
  8. emviana

    Siemens Setting Tool

    Hello. Can anyone know where I find the demo version of Siemens DIGSI 4.0? I was trying to install 4.83 demo version, but it was required de old version first. Thanks.
  9. emviana

    Low power factor tripping

    Thanks waross. Reactive power demand at induction motor starting is about 15 MVar (0.2 PF estimated at starting). I'm not sure if SM can generate 15MVar. PF protection is set with 0.7 inductive with 0.2 seconds. It was adjusted in compliance with IEEE C37.96-2000 - IEEE Guide for AC Motor...
  10. emviana

    Low power factor tripping

    Thanks, dpc. Actually, we have tried to change SM to a overexcited mode, but it didn't work. I think that SC limiter impedance is high, and so IM drains from a lower impedance source, in this case, the synchronous motor. In this way, i'm not sure if operation with generators A and B will solve...
  11. emviana

    Low power factor tripping

    Hello. In our industrial plant, we have some problems during an induction motor starting. I'd like to talk about ideas to solve this problem. The electrical diagram is attached. Describing the problem: Two generators (A and B) connected in two load bars (A and B) that connect to a...
  12. emviana

    Generator Protection

    Thanks a lot. Very useful.
  13. emviana

    Generator Protection

    What are good literatures on power generator protections besides IEEE Standars? Thanks a lot.
  14. emviana

    Generator Differential Trip

    Now, the differential currents.http://files.engineering.com/getfile.aspx?folder=f53b4c82-4766-46ed-8785-e7e8e78ec159&file=Idiff_X_Irest.JPG
  15. emviana

    Generator Differential Trip

    Thanks a lot for the ansers. Now I am uploading graphical oscilography of phase currents, differential currents ans restriction currents. Only by information, relay is a SIEMENS 7UM62.http://files.engineering.com/getfile.aspx?folder=38aaa3f7-c4e0-495d-85d8-4c1c4f982cdc&file=iA,_iB,_iC_currents.JPG
  16. emviana

    Generator Differential Trip

    I'm showing current oscilography at instant of trip. S1 = side of generator's terminal. S2 = side of generator's grounding. The CT's are of equal specefication on two sides (4000-5A). Thanks.http://files.engineering.com/getfile.aspx?folder=42de7951-21a3-4709-8c08-3ebf20258a78&file=trip.JPG
  17. emviana

    Generator Differential Trip

    We have two differential relays: 1) One protecting only generator (this one trips on energization of 100 MVA tranformer); 2) One protecting generator + 80 MVA transformer (this one doesn't trip). 230 kV bus is always energized. The problem occurs when we energize one 100 MVA transformer at no...
  18. emviana

    Generator Differential Trip

    Hello. I need some help. In my area we have a 13.8kV, 74.3 MVA generator (wye connection) connected to a 80 MVA 13.8/69 kV (delta/ground-wye) transformer. The 69 kV side of this transformer is connected to a bus fed by a 100MVA 230/69 kV (grounded wye/grounded wye). The 230 kV side of this...

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