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Figure 3. 50 y 50/51 IEEE xtremely Inverse
If overcurrent fault is 24xI
n
=12000 Ap, IEEE Extremely inverse curve defines a tripping value of
0.376 s (Figure 3) for 50/51 function. It is considered that this time is too high, so when current
fault reaches 24xI
n
, definite time overcurrent function will be work. 50 function tap is adjusted at
14xIn so definite time overcurrent function will trip when current fault is higher than 14xIn (50
function does not wait to reach 24xIn)
The figure below (Figure 4), shows the tripping curve of the relay:
Figure 4. Relay tripping curve