ABB RELION RET670, Applications Manual

Page: 786 / 1016

For the Automatic voltage control for tap changer function, TR1ATCC (90) for single
control and TR8ATCC (90) for parallel control, three types of blocking are used:
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
60 .
Table 60: Blocking settings
Setting Values (Range) Description
OCBk
(automatically
reset)
Alarm
Auto Block
Auto&Man Block
When any one of the three HV currents exceeds the
preset value
IBlock, TR1ATCC (90) or TR8ATCC (90) will
be temporarily totally blocked. The outputs IBLK and
TOTBLK or AUTOBLK will be activated depending on the
actual parameter setting.
OVPartBk
(automatically
reset)
Alarm
Auto&Man Block
If the busbar voltage V
B
(not the compensated load point
voltage UVL) exceeds
Vmax (see figure
363 ), an alarm
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 Vmin < V
B
<
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
Vmax.
UVPartBk
(automatically
reset)
Alarm
Auto&Man Block
If the busbar voltage V
B
(not the compensated load point
voltage V
L
) is between Vblock and Vmin (see figure 363 ),
an alarm will be initiated or further VLOWER commands
will be blocked. The output VLOW will be activated.
UVBk
(automatically
reset)
Alarm
Auto Block
Auto&Man Block
If the busbar voltage V
B
falls below Vblock this blocking
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.
Table continues on next page
Section 15
1MRK 504 163-UUS A
Control
780 Transformer protection RET670 2.2 ANSI
Application manual