ABB Relion REG670, Technical Manual, Page: 536 / 1298

9.5.6 Monitored data
Table 296: VDCPTOV Monitored data
Name Type Values (Range) Unit Description
UL1DIFF REAL - kV Differential Voltage
phase L1
UL2DIFF REAL - kV Differential Voltage
phase L2
UL3DIFF REAL - kV Differential Voltage
phase L3
9.5.7 Operation principle
The Voltage differential protection function VDCPTOV (60) is based on comparison
of the amplitudes 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
RFLx . The voltage difference is
evaluated and if it exceeds the alarm level UDAlarm or trip level UDATrip 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 U1Low and U2Low . The outputs for loss of voltage U1LOW
resp U2LOW will be activated. The U1 voltage is supervised for loss of individual
phases whereas the U2 voltage is supervised for loss of all three phases.
Loss of all U1 or all U2 voltages will block the differential measurement. This
blocking can be switched off with setting
BlkDiffAtULow = No .
VDCPTOV 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 255 .
Section 9
1MRK502052-UEN B
Voltage protection
530
Technical manual