Idmt Characteristics According To The Ieee C37.112; Values Of Constants A, B And P - ABB REF610 Technical Reference Manual

1MRS755535
Feeder Protection Relay
Technical Reference Manual - ANSI Version

IDMT characteristics according to the IEEE C37.112

REF610 provides three time/current curve groups which comply with the
IEEE C37.112 standard: extremely inverse, very inverse and inverse. The
relationship between time and current is expressed as follows:
⎛ ⎞
A
[ ]
⎜ ⎟
= + ×
t s B TD
⎜ ( ) ⎟
p
−
M 1
⎝ ⎠
t = operate time
M = multiplies of pickup current
TD = time dial
The actual operate time of the relay (see Fig. 5.1.4.9.-5...Fig. 5.1.4.9.-
7) includes an additional filter and detection time and the operate time
of the trip output contact. When the operate time of the relay is
calculated as above, approximately 30 ms should be added to the result
t.
Table 5.1.4.9.-4

Values of constants A, B and P

Time/current curve group
Extremely inverse
Very inverse
Inverse
The time/current curve groups based on the IEEE standard are illustrated in
Fig. 5.1.4.9.-5...Fig. 5.1.4.9.-7.
A B
6.407 0.025
2.855 0.0712
0.0086 0.0185
REF610 REF610
(5)
P
2.0
2.0
0.02
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