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4.3.1.3 ANSI / IEEE Inverse Time Protection Curves
-2006: IEEE
Standard Inverse-Time Characteristic Equations for Overcurrent Relays -
standard describes the protection curves named as below.
1. IEEE MI: IEEE Moderately Inverse Curve.
2. IEEE VI: IEEE Very Inverse Curve.
3. IEEE EI: IEEE Extremely Inverse Curve.
Universal trip time delay formula is given above, while ANSI / IEEE constants for various
curves are given on the below table.
t Trip delay (s).
A A constant for the characteristic (s).
I Momentary current (A).
Is Set current threshold (A).
-).
B A constant for the characteristic (s).
TMS Time Multiplier Setting (-).
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