ABB REF 610 Technical Reference Manual page 48

REF 610 REF 610
48
Feeder Protection Relay
Technical Reference Manual
IDMT 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 inverse. The
relationship between time and current is expressed as follows:
⎛
⎜
A
⎜
[ ]
= +
t s B
⎜
P
⎛ ⎞
I
⎜ ⎜
⎟ −
1
⎜
>
⎝ ⎠
⎝
I
t = operate time
I = phase (or earth-fault) current value
n (or n ) = time multiplier
0
I> (or I >) = set start value
0
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.
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.
⎞
⎟
⎟
×
n
⎟
⎟ ⎟
⎠
A
6.407
2.855
0.0086
1MRS755310
B P
0.025 2.0
0.0712 2.0
0.0185 0.02
(5)