Calculations:
REF Function
This setting is used to select the principle used for the differential protection.
Transformer Rating = 2.00 MVA
Primary side (HV) = 33.00 kV
Secondary side (LV) = 0.415 kV
Impedance = 6.390 %
Rated current = 2782.89 Amps
CT ratio = 2782.89 Amps
CTRp = 3200
CTRs = 1
Therefore a current of 2782.49 Amps in Primary will reflect in secondary as
= 2782.41 / (3200 / 1)
= 0.87 Amps
Pick-up of the High Imp REF function in
secondary
= 20% of 0.87
Is1 = 0.17 A