Short Circuit when we do not have R X of T/F and Source
Short Circuit when we do not have R X of T/F and Source
(OP)
I have a Transformer (11/.4kV) 1000kVA 3Phase, Dyn11, Dry Type, Secondary which can supply 25kA Short Circuit Current. Now Secondary is connected to a Bus Bar whose R = 0.48mOhm and X=0.265 Ohm which is connecting a panel. From panel a cable is connected R= 5.3mOhm X=2.6 mOhm.
My concern is how to arrive at SC Current at the end of Busbar and at the end of Cable. What will be the formula?
Normally when I calculate Sc currents I take V and Divide it by over all Z (Source+ Transformer+ Busbar+ cable+ etc +etc) this gives me the Isc. But this time I am not having Source and Transformer R and X. Please help.
My concern is how to arrive at SC Current at the end of Busbar and at the end of Cable. What will be the formula?
Normally when I calculate Sc currents I take V and Divide it by over all Z (Source+ Transformer+ Busbar+ cable+ etc +etc) this gives me the Isc. But this time I am not having Source and Transformer R and X. Please help.






RE: Short Circuit when we do not have R X of T/F and Source
Refer to IEEE Red Book or some authentic book on the subject for formulas.
Rafiq Bulsara
http://www.srengineersct.com
RE: Short Circuit when we do not have R X of T/F and Source
Am I doing correct things? And Is there any reason why X/R value stated as 12?
RE: Short Circuit when we do not have R X of T/F and Source
Rafiq Bulsara
http://www.srengineersct.com
RE: Short Circuit when we do not have R X of T/F and Source
What will be Single Phase MVA and X/R?
ETAP help file gives following formula.
MVA3P = Ö3 * kV * I3P
MVA1P = Ö3 * kV * I1P
I am confused what values to substitute for 1 Phase.
RE: Short Circuit when we do not have R X of T/F and Source
Since the single phase SC MVA or the Thevenin's driving point impedance is not given you can reasonably assume the 3-ph SC MVA to be equal to the 1-phase SC MVA at the source (swing)bus.Because your 3-ph and 1-ph sc currents at secondary of the transformer will not make a "huge" difference to your objective.
Sorry for this question please.Are you not familiar with the theory part behind the SC calculation method or you "JUST" playing with the software?
RE: Short Circuit when we do not have R X of T/F and Source
Thanks for your reply.