13.3.7 Operation principle
GUID-06BC0CC0-8A4F-4D84-A0B1-506E433F72F3 v4
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 (
Vdif Main
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 (
Vdif Pilot
alarm
), an alarm signal will be initiated to indicate the pilot fuse failure and also the faulty phase
where the voltage reduction occurred.
When
SealIn
is set to
Enabled
and the fuse failure has last for more than 5 seconds, the blocked
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.
BLOCK
vPilotA
0
Vdif Main block
Vdif Pilot alarm
OR
MAX
MIN ABS
ANSI12000144-3-en.vsd
AND
AND
MAINFUF
V1AFAIL
V1BFAIL
V1CFAIL
PILOTFUF
V2AFAIL
V2BFAIL
V2CFAIL
vMainA
vPilotB
vMainB
vPilotC
vMainC
+
-
a
b
a<b
a
b
a>b
a
b
a>b
SealIn=0
AND
OR
OR
VSealIn
OR
Phase B, same as Phase A
Phase C, same as Phase A
ANSI12000144 V3 EN-US
Figure 397: Simplified logic diagram VDSPVC (60)
1MRK 502 066-UUS B Section 13
Secondary system supervision
745
Technical manual
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