Thanks davidbeach.
After searching the forum and further reading, for most of the transformers we deal with (3 phase Dyn, most likely with core-type cores, i.e. not shell), R0=R1 and X0=(0.85 to 0.9)X1 will be suitable (NER values to be added separately).
Merry Christmas to all.
Can anyone please offer tips in modelling transformer zero sequence impedance of transformers in SKM Powertools. We mostly encounter three-phase delta-grounded wye units, some of which have neutral earthing impedances installed at the star point.
I have seen information stating none should be...
When performing fault current calculation study on a system with a motor controlled by a VSD, I am of the understanding that, for an overcurrent fault upstream of the VSD, fault contributions by this motor need not be considered as the VSD will not allow them to pass. Is this correct ?
With...
How does one calculate the required CT class such that the CT will not saturate at the maximum fault level with the new CT standard (AS60044.1-2003). There is no guidance, as was provided by App B of AS1675-1986.
From what I understand, AS60044.1 is similar to the corresponding IEC standard...
Thanks everyone for your input. :-)
In Australia, MV resistors are often used on power transformers to limit EF current to 10A (11kV txf secondary voltage), for which normally only 50/51 protection is used. Apart from the difficulty of employing 27/59 protection, is there a specific reason why...
Thanks for the reply alehman. We are investigating replacing the earthing transformers (which have LV resistors across the secondary terminals), with HV resistors.
We have a client looking to replace his earthing transformers with new transformers. These transformers are to be connected to 3 parallel 11kV generators (one per generator), with resistors on the secondaries.
Our normal preference (w.r.t. power transformers) is for earthing resistors, as they...
