P
In the protection scheme of 20MVA, 16.5/6.9kV , Delta-Star connected transformer having an impedance of 10 ohms, bushing CTs with ratio of 300/1A are provided for REF Protection. The CTs provided on the line side have an Ith rating of 2000A. The earth fault current of the transformer is limited to 300A approximately using a resistance of 13.3 ohms. (The LV side neutral is earthed)
While calculating the knee point voltage of the CTs for REF protection of the above transformer, should the full fault current of the transformer or merely the earth fault current (300A) be considered?
Regards,
Pramod
While calculating the knee point voltage of the CTs for REF protection of the above transformer, should the full fault current of the transformer or merely the earth fault current (300A) be considered?
Regards,
Pramod