Where:
I
2
is negative sequence current expressed in per unit of the rated generator current
t is operating time in seconds
K is a constant [s], which depends on generator size and design
Current I2-1>
Operate
time
t1Min
t1Max
(Default= 1000 s)
(Default= 5 s)
K1
IEC09000691-2-en.vsd
IEC09000691 V2 EN
Figure 122: Inverse time characteristic with t1Min and t1Max
For a detailed description of inverse time characteristic, see chapter "Inverse time
characteristics".
The reset time is exponential and is given by the following expression:
ResetTime s
ResetMultip
I
I
K
NS
Start
[ ]
−
= ⋅
2
1
EQUATION2111 V4 EN
(Equation 74)
Where
I
NS
is the measured negative sequence current
I
Start
is the desired start level in pu of rated generator current
ResetMultip
is multiplier of the generator capability constant
K
equal to setting
K
1 and thus defines
reset time of inverse time characteristic
1MRK 502 048-UEN A Section 8
Current protection
247
Technical manual
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