ABB Relion REG670, Technical Manual

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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 (vMainL1 <
vPilotL1 or vMainL2 < vPilotL2 or vMainL3 < vPilotL3) and the voltage difference
exceeds the operation level (
Ud>MainBlock ), 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 (vPilotL1 <
vMainL1 or vPilotL2 < vMainL2 or vPilotL3 < vMainL3) and the voltage difference
exceeds the operation level (
Ud>PilotAlarm ), 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 On 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
USealIn setting. Fuse failure outputs are deactivated when normal
voltage conditions are restored.
BLOCK
vPilotL1
0
Ud>MainBlock
Ud> PilotAlarm
OR
MAX
MIN ABS
IEC12000144-1-en.vsd
AND
AND
MAINFAIL
U1L1FAIL
U1L2FAIL
U1L3FAIL
PILOTFAIL
U2L1FAIL
U2L2FAIL
U2L3FAIL
vMainL1
vPilotL2
vMainL2
vPilotL3
vMainL3
+
-
a
b
a<b
a
b
a>b
a
b
a>b
SealIn=0
t
AND
OR
OR
USealIn
OR
Phase L2, same as Phase L1
Phase L3, same as Phase L1
5s
å
IEC12000144 V1 EN
Figure 295: Simplified logic diagram VDSPVC
Section 13
1MRK502052-UEN B
Secondary system supervision
622
Technical manual