ABB REF 610 - Page 42

ts
I
I
k
[]
=
>
−
⎛
⎝
⎜
⎜
⎜
⎜
⎞
⎠
⎟
⎟
⎟
⎟
×
β
α
1
(4)
t = operate time
I = phase (or earth-fault) current value
k (or k
0
) = time multiplier
I> (or I
0
>) = set start value
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.
Table 5.1.4.9.-2 Values of constants α and β
Time/current curve group αβ
Normal inverse 0.02 0.14
Very inverse 1.0 13.5
Extremely inverse 2.0 80.0
Long-time inverse 1.0 120
According to the standard, the normal current range is 2...20 times the set start value
at normal inverse, very inverse or extremely inverse characteristic. The relay is to
start before the current exceeds the set start value by 1.3 times. At long-time inverse
characteristic, the normal current range is specified to be 2...7 times the set start
value, and the relay is to start before the current exceeds the set start value by 1.1
times
Table 5.1.4.9.-3 Operate time tolerances specified by the standard
I/I>
a)
Normal
b)
Very
b)
Extremely
b)
Long time
b)
2 2,22E 2,34E 2,44E 2,34E
5 1,13E 1,26E 1,48E 1,26E
7 - - - 1,00E
10 1,01E 1,01E 1,02E -
20 1,00E 1,00E 1,00E -
a)
or I
0
/I
0
>
b)
E = accuracy in percent; - = not specified
Within the normal current range the inverse-time stage fulfils the tolerance
requirements of class 5 at all degrees of inversity.
42
REF 610REF 610
Feeder Protection Relay
Technical Reference Manual
1MRS755310