Figure 479: MNSPTOC Inverse Curve B
If the fault disappears, the negative-sequence current drops below the
Start
value
setting and the START output is deactivated. The function does not reset
instantaneously. Resetting depends on the equation or the
Cooling time
setting.
The timer is reset in three ways:
• When the negative sequence current drops below start value the subtraction in
the denominator becomes negative and the cumulative sum starts to decrease.
The decrease in the sum indicates the cooling of the machine and the cooling
speed depends on the value of the negative-sequence current. If the sum reaches
zero without a fault being detected, the accumulation stops and the timer is
reset.
• If the reset time set through the
Cooling time
setting elapses without a fault
being detected, the timer is reset.
• If ST_EMERG_ENA is activated, the timer is reset.
1MRS759142 F
Protection functions
REX640
Technical Manual
847
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