GE Industrial Solutions Entellisys 5.0 User Manual - Manual (Page 63)

Overcurrent protection 63
5
fault where (I
RMS
/C) is 4.0, the circuit breaker will trip according to the I 2 T curve. In this case the
system will initiate a trip after approximately 1.1 seconds. On a fault where (I
RMS
/C) is 10.0, the
system will not follow the I 2 T curve and will instead initiate a trip according to the constant-time
part of the trip curve (i.e., after 0.283 seconds). In this case, if the system followed the I 2 T curve,
the trip time would have been only 0.18 seconds.
Values:
• Disabled
• Enabled
• Max Slope
Max Slope
I
2 T Max Slope limits the slope for ST delay band settings, transitioning from the I 2 T slope to the
definite time at 10x. Above 10X, the I 2 T slope is typically no longer needed for selectivity with the
I 2 T slope of smaller downstream breakers or fuses. The truncated I 2 T slope maintains selectivity
while providing superior protection.
Figure 5-3 Typical I 2 T Curves - Max slope vers normal I 2 T