9.5.7 Operation principle
SEMOD153866-61 v4
The Voltage differential protection function VDCPTOV (60) is based on comparison of the
magnitudes of the two voltages connected in each phase. Possible differences between the ratios
of the two Voltage/Capacitive voltage transformers can be compensated for with a ratio
correction factors
RF_X
. The voltage difference is evaluated and if it exceeds the alarm level
VDAlarm
or trip level
VDTrip
signals for alarm (ALARM output) or trip (TRIP output) is given after
definite time delay
tAlarm
respectively
tTrip
. The two three phase voltage supplies are also
supervised with undervoltage settings
V1Low
and
V2Low
. The outputs for loss of voltage V1LOW
resp V2LOW will be activated. The V1 voltage is supervised for loss of individual phases whereas
the V2 voltage is supervised for loss of all three phases.
Loss of all V1 or all V2 voltages will block the differential measurement. This blocking can be
switched off with setting
BlkDiffAtULow
=
No
.
VDCPTOV (60) function can be blocked from an external condition with the binary BLOCK input. It
can, for example, be activated from Fuse failure supervision function FUFSPVC.
To allow easy commissioning the measured differential voltage is available as service value. This
allows simple setting of the ratio correction factor to achieve full balance in normal service.
The principle logic diagram is shown in figure
352.
Section 9 1MRK 502 066-UUS B
Voltage protection
650
Technical manual
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