Idmt Characteristics According To Iec 60255-3; Time/Current Characteristic Settings; Values Of Constants Α And Β - ABB REF610 Technical Reference Manual

1MRS755535
Feeder Protection Relay
Technical Reference Manual - ANSI Version
Table 5.1.4.9.-1

Time/current characteristic settings

Value Time/current characteristic
0 Definite time
1 IEC Extremely inverse
2 IEC Very inverse
3 IEC Normal inverse
4 IEC Long-time inverse
5 RI-type
6 IEEE Extremely inverse
7 IEEE Very inverse
8 IEEE inverse
9 RD-type (RXIDG)

IDMT characteristics according to IEC 60255-3

The relay provides four time/current curve groups which comply with the
IEC 60255-3 standard: normal inverse, very inverse, extremely inverse and long-
time inverse. The relationship between time and current is expressed as follows:
β
⎛ ⎞
[ ]
= ⎟ ×
t s TD
⎜
α
−
⎝ ⎠
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.-1...Fig. 5.1.4.9.-
4) 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.
Values of constants α and β
Table 5.1.4.9.-2
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 start before the current exceeds the set pickup value by 1.3 times. At long-time
α β
0.02 0.14
1.0 13.5
2.0 80.0
1.0 120
REF610 REF610
(4)
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