ABB RET670 Applications Manual page 683

1MRK504116-UUS C
Application manual
Partial Block: Prevents operation of the tap changer only in one direction (only
VRAISE or VLOWER command is blocked) in manual and automatic control mode.
Auto Block: Prevents automatic voltage regulation, but the tap changer can still be
controlled manually.
Total Block: Prevents any tap changer operation independently of the control mode
(automatic as well as manual).
Setting parameters for blocking that can be set in TR1ATCC (90) or TR8ATCC (90)
under general settings in PST/local HMI are listed in table 161.
Table 161: Blocking settings
Setting Values (Range)
OCBk Alarm
(automatically Auto Block
reset) Auto&Man Block
OVPartBk Alarm
(automatically Auto&Man Block
reset)
UVPartBk Alarm
(automatically Auto&Man Block
reset)
UVBk Alarm
(automatically Auto Block
reset) Auto&Man Block
Table continues on next page
Description
When any one of the three HV currents exceeds the
IBlock , TR1ATCC (90) or TR8ATCC (90) will
preset value
be temporarily totally blocked. The outputs IBLK and
TOTBLK or AUTOBLK will be activated depending on the
actual parameter setting.
If the busbar voltage V (not the compensated load point
B
Vmax (see figure 277), an alarm
voltage UVL) exceeds
will be initiated or further VRAISE commands will be
blocked. If permitted by setting in PST configuration, Fast
Step Down (FSD) of the tap changer will be initiated in
order to re-enter the voltage into the range
Vmax . The FSD function is blocked when the lowest
voltage tap position is reached. The time delay for the
FSD function is separately set. The output VHIGH will be
activated as long as the voltage is above
If the busbar voltage V (not the compensated load point
B
Vblock and Vmin (see figure277),
voltage V ) is between
L
an alarm will be initiated or further VLOWER commands
will be blocked. The output VLOW will be activated.
If the busbar voltage V falls below
B
condition is active. It is recommended to block automatic
control in this situation and allow manual control. This is
because the situation normally would correspond to a
disconnected transformer and then it should be allowed to
operate the tap changer before reconnecting the
transformer. The outputs VBLK and TOTBLK or
AUTOBLK will be activated depending on the actual
parameter setting.
Section 3
IED application
Vmin < V
<
B
Vmax .
Vblock this blocking
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