ABB RELION 670 Series Technical Manual page 751

1MRK 502 066-UUS B
13.3.7 Operation principle
VDSPVC requires six voltage inputs, which are the three phase voltages on main and pilot fuse
groups. The initial voltage difference between the two groups is theoretical zero in the healthy
condition. Any subsequent voltage difference will be due to a fuse failure.
If the main fuse voltage becomes smaller than the pilot fuse voltage (vMainA < vPilotA or vMainB <
vPilotB or vMainC < vPilotC) and the voltage difference exceeds the operation level (
block ), a blocking signal will be initiated to indicate the main fuse failure and block the voltage-
dependent functions. In addition, the function also indicates the phase in which the voltage
reduction has occurred.
If the pilot fuse voltage becomes smaller than the main fuse voltage (vPilotA < vMainA or vPilotB <
vMainB or vPilotC < vMainC) and the voltage difference exceeds the operation level (
alarm ), an alarm signal will be initiated to indicate the pilot fuse failure and also the faulty phase
where the voltage reduction occurred.
SealIn is set to Enabled and the fuse failure has last for more than 5 seconds, the blocked
When
protection functions will remain blocked until normal voltage conditions are restored above the
VSealIn setting. Fuse failure outputs are deactivated when normal voltage conditions are restored.
VSealIn
vPilotA
+

vMainA -
Vdif Main block
0
Vdif Pilot alarm
BLOCK
vPilotB
Phase B, same as Phase A
vMainB
vPilotC
Phase C, same as Phase A
vMainC
ANSI12000144 V3 EN-US
Figure 397: Simplified logic diagram VDSPVC (60)
Technical manual
a
a<b
AND
b
SealIn=0
a
MAX
a>b
b
a
MIN ABS
a>b
b
5 s
t
OR
0
OR
Secondary system supervision
GUID-06BC0CC0-8A4F-4D84-A0B1-506E433F72F3 v4
Vdif Main
Vdif Pilot
V1AFAIL
AND
MAINFUF
OR
AND
V2AFAIL
PILOTFUF
OR
V1BFAIL
V2BFAIL
V1CFAIL
V2CFAIL
ANSI12000144-3-en.vsd
Section 13
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