ABB Relion REC670 Applications Manual page 337

1MRK 511 358-UEN A
Comp a
EQUATION1941 V1 EN-US
where:
•
DU is the deadband setting in percent.
• n denotes the desired number of difference in tap position between the transformers,
that shall give a voltage deviation U
p is the tap step (in percent of transformer nominal voltage).
•
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
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
OperUsetPar : Enables/disables the use of a common setting for the target voltage USet . The
common setting for target voltage is mainly used for the circulating current method, but can
also be applied to the master follower method. When enabled, a mean value of the
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 On 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
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
function block of the follower will be activated after the time delay
tMFPosDiff : Time delay for activation of the output OUTOFPOS.
Application manual
´ D
2 U
= ´ ´
100%
´
n p
Off .
which corresponds to the dead-band setting.
di
Comp that will always initiate an action (start timer) when
t2 .
Section 13
Control
(Equation 129)
USet values
tMFPosDiff .
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