4.5 Earth Fault Overcurrent Protection in Earthed Systems (optional)
457
7SA522 Manual
C53000-G1176-C155-3
Figure 4-4 Trip time caracteristic of the inverse time overcurrent stage with logarithmic-
inverse characteristic
Logarithmic inverse t = T
3I0p Max T-delay
— T
3I0p Time Dial
·ln(I/,S3,&.83)
Note: For I/,S3,&.83 > 35 the time applies for I/,S3,&.83 = 35
Figure 4-5 Trip time characteristics of the zero sequence voltage protection U
0 inv.
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