ABB REF 610 Technical Reference Manual page 35

1MRS 755535
Feeder Protection Relay
Technical Reference Manual - ANSI Version
Table 4.1.4.9-2 Values of constants α and β
Time/current curve group
Normal inverse
Very inverse
Extremely inverse
Long-time inverse
According to the standard, the normal current range is 2...20 times the set pickup
value at normal inverse, very inverse or extremely inverse characteristic. The relay
is to pickup before the current exceeds the set pickup value by 1.3 times. At long-
time inverse characteristic, the normal current range is specified to be 2...7 times the
set pickup value, and the relay is to pickup before the current exceeds the set pickup
value by 1.1 times.
Table 4.1.4.9-3 Operate time tolerances specified by the standard
2)
Normal
M
2 2,22E
5 1,13E
7 -
10 1,01E
20 1,00E
1)
E = accuracy in percent; - = not specified
2)
Multiples or pickup current (a phase and ground)
Within the normal current range the inverse-time element fulfils the tolerance
requirements of class 5 at all degrees of inversity.
The time/current curve groups based on the IEC standard are illustrated in
Fig. 4.1.4.9.-1...Fig. 4.1.4.9.-4.
Note!
If the ratio between the current and the set pickup value is higher than 20, the operate
time will be the same as when the ratio is 20.
α β
0.02 0.14
1.0 13.5
2.0 80.0
1.0 120
Very Extremely
2,34E 2,44E
1,26E 1,48E
- -
1,01E 1,02E
1,00E 1,00E
REF 610
1)
Long time
2,34E
1,26E
1,00E
-
-
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