Under current protection of rotor winding
One undercurrent protection level with definite time delay is available within the
function. It can be used to either alarm or trip for low-excitation/loss-of-excitation
condition of the machine. This built-in feature monitors the level of the measured
current. As soon as it is lower than the pre-set value (i.e. parameter
I<
) it will start a
timer (i.e defined by parameter
tTrip_I<
). Once this timer has expired the signal
TRIPUC will be given. In order to avoid unwanted tripping of this undercurrent
feature when machine is disconnected from the network it shall be supervised by
appropriate signal (e.g. blocked when generator CB is open). Simplified logic
diagram of this feature is given in Figure
.
IEC12000021-1-en.vsd
BLOCKUC
BLOCK
AND
<
I<
MeasurCurrent
Operation_I<
IBase
tTrip_I<
t
TRIPUC
x
NOT
NOT
IEC12000021 V1 EN
Figure 223:
Undercurrent protection feature
Tripping logic
This tripping logic provides some additional features regarding blocking and tripping
options available within the function. The list below describes functionality of every
binary input and output from the function which influence the trip logic.
Available binary inputs:
BLOCK prevents operation of overload and undercurrent features, at the same time all
binary outputs are forced to zero.
BLOCKUC prevents operation of undercurrent feature only
SETLKOUT forces lockout operation (output LOCKOUT) by external signal
RESET resets lockout and forces Theta value to zero
Available binary outputs:
TRIP, operation of the overload feature
1MRK502052-UEN B
Section 8
Current protection
473
Technical manual
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