still learning
Electrical
- Jul 12, 2017
- 1
Hi....
Can somebody explain me (math or by words)...
If we have differential protection of transformer 132/33kV, YND5 with differential protection setting 0.3Ibase (where Ibase is 137A), with CT ratio on HV side of 200/1, and on LV side of 800/1.
Pick up value of differential on HV side is (0.3*137)/200= 0.205A -> this is for 3ph fault.
Pick up value on HV side for 1ph fault is 0.205*1.5=0.3075A
Question is....why it is 1ph fault 1.5times more than for 3ph fault (on Y side)?
Same for delta (LV) side, why is there factor sqrt3 between 1ph and 3ph fault?
Thanks
Can somebody explain me (math or by words)...
If we have differential protection of transformer 132/33kV, YND5 with differential protection setting 0.3Ibase (where Ibase is 137A), with CT ratio on HV side of 200/1, and on LV side of 800/1.
Pick up value of differential on HV side is (0.3*137)/200= 0.205A -> this is for 3ph fault.
Pick up value on HV side for 1ph fault is 0.205*1.5=0.3075A
Question is....why it is 1ph fault 1.5times more than for 3ph fault (on Y side)?
Same for delta (LV) side, why is there factor sqrt3 between 1ph and 3ph fault?
Thanks