ABB REF 610 Technical Reference Manual page 40

REF 610
40
Feeder Protection Relay
Technical Reference Manual - ANSI Version
IDMT (mode) characteristics according to the IEEE C37.112
REF 610 provides three time/current curve groups which comply with the IEEE
C37.112 standard: extremely inverse, very inverse and moderately inverse. The
relationship between time and current is expressed as follows:
⎛
⎜
⎜
=
t ( s )
⎝
(
where
t = operate time (in seconds)
TD = time dial
=
M multiplies of pickup
Note!
The actual operate time of the relay (see Fig. 4.1.4.9.-5...Fig. 4.1.4.9.-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.
Table 4.1.4.9-4 Values of constants A, B and P
Time/current curve group
Extremely inverse
Very inverse
Moderately inverse
The time/current curve groups based on the IEEE standard are illustrated in
Fig. 4.1.4.9.-5...Fig. 4.1.4.9.-7.
A
+
B
p
)
−
M 1
current
A B
6.407 0.025
2.855 0.0712
0.0086 0.0185
1MRS 755535
⎞
⎟
⎟
x TD
⎠
P
2.0
2.0
0.02