For RI and RD inverse time delay characteristics the possible delay time settings are instantaneous
and IEC constant time reset.
GUID-F7AA2194-4D1C-4475-8853-C7D064912614 v4
When inverse time overcurrent characteristic is selected, the trip time of the stage
will be the sum of the inverse time delay and the set definite time delay. Thus, if
only the inverse time delay is required, it is important to set the definite time delay
for that stage to zero.
26.3 Inverse characteristics
IP15797-1 v2
M12388-1 v23
Table 1076:ANSI Inverse time characteristics
Function Range or value Accuracy
Operating characteristic:
( )
= + ×
-
æ ö
ç ÷
ç ÷
è ø
1
P
A
t B td
I
EQUATION1651 V1 EN-US
Reset characteristic:
EQUATION1652 V1 EN-US
I = I
measured
/I
set
0.05 ≤ td ≤ 999.00
1.5 x I
set
≤ I ≤ 20 x I
set
ANSI/IEEE C37.112 ,
±2.0% or ±40 ms
whichever is greater
ANSI Extremely Inverse A=28.2, B=0.1217, P=2.0 , tr=29.1
ANSI Very inverse A=19.61, B=0.491, P=2.0 , tr=21.6
ANSI Normal Inverse A=0.0086, B=0.0185, P=0.02, tr=0.46
ANSI Moderately Inverse A=0.0515, B=0.1140, P=0.02, tr=4.85
ANSI Long Time Extremely Inverse A=64.07, B=0.250, P=2.0, tr=30
ANSI Long Time Very Inverse A=28.55, B=0.712, P=2.0, tr=13.46
ANSI Long Time Inverse A=0.086, B=0.185, P=0.02, tr=4.6
Section 26 1MRK 502 066-UUS B
Inverse time characteristics
1388
Technical manual
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