Negative sequence inverse time characteristic
Negative sequence current
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I2
tMax
tMin
IEC08000355-2-en.vsd
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0.01 0.1 1 10 100
IEC08000355 V2 EN
Figure 202: Inverse Time Delay characteristic, step 1
The example in figure 202 indicates that the protection function has a set minimum
operating time t1Min of 5 sec. The setting t1Min is freely settable and is used as a
security measure. This minimum setting assures appropriate coordination with for
example line protections. It is also possible to set the upper time limit, t1Max.
9.12.3.2 Start sensitivity
The trip start levels Current I2-1> and I2-2> of NS2PTOC are freely settable over a
range of 3 to 500 % of rated generator current IBase. The wide range of start setting
is required in order to be able to protect generators of different types and sizes.
After start, a certain hysteresis is used before resetting start levels. For both steps the
reset ratio is 0.97.
9.12.3.3 Alarm function
The alarm function is operated by START signal and used to warn the operator for an
abnormal situation, for example, when generator continuous negative sequence
current capability is exceeded, thereby allowing corrective action to be taken before
removing the generator from service. A settable time delay tAlarm is provided for the
alarm function to avoid false alarms during short-time unbalanced conditions.
Section 9 1MRK 502 071-UEN -
Current protection
392 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
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