ABB RELION RET670 Applications Manual page 806

Section 15
Control
800
• a is a safety margin that shall cover component tolerances and other non-linear
measurements at different tap positions (for example, transformer reactances
changes from rated value at the ends of the regulation range). In most cases a
value of a = 1.25 serves well.
This calculation gives a setting of Comp that will always initiate an action (start timer)
when the transformers have n tap positions difference.
OperSimTap: Enabling/disabling the functionality to allow only one transformer at a
time to execute a Lower/Raise command. This setting is applicable only to the
circulating current method, and when enabled, consecutive tap changes of the next
transformer (if required) will be separated with the time delay t2.
OperUsetPar: Enables/disables the use of a common setting for the target voltage VSet.
This setting is applicable only to the circulating current method, and when enabled, a
mean value of the VSet values for the transformers in the same parallel group will be
calculated and used.
OperHoming: Enables/disables the homing function. Applicable for parallel control
with the circulating current method, as well for parallel control with the master-
follower method.
VTmismatch: Setting of the level for activation of the output VTALARM in case the
voltage measurement in one transformer bay deviates to the mean value of all voltage
measurements in the parallel group.
tVTmismatch: Time delay for activation of the output VTALARM.
T1RXOP.......T8RXOP: This setting is set Enabled for every transformer that can
participate in a parallel group with the transformer in case. For this transformer (own
transformer), the setting must always be Disabled.
TapPosOffs: This setting gives the tap position offset in relation to the master so that
the follower can follow the master's tap position including this offset. Applicable when
regulating in the follow tap command mode.
MFPosDiffLim: When the difference (including a possible offset according to
TapPosOffs) between a follower and the master reaches the value in this setting, then
the output OUTOFPOS in the Automatic voltage control for tap changer, parallel
control TR8ATCC (90) function block of the follower will be activated after the time
delay tMFPosDiff.
tMFPosDiff: Time delay for activation of the output OUTOFPOS.
1MRK 504 163-UUS A
Transformer protection RET670 2.2 ANSI
Application manual