ABB Relion 670 Series Applications Manual page 398

Section 14
Control
smaller than
value.
Vmax : This setting gives the upper limit of permitted busbar voltage (see section
voltage control for a single
Auto&ManBlock , then busbar voltages above Vmax will result in a partial blocking such that only
to
lower commands are permitted.
Vmin This setting gives the lower limit of permitted busbar voltage (see section
voltage control for a single
Auto Block or Auto&ManBlock , then busbar voltages below Vmin will result in a partial blocking
to
such that only raise commands are permitted.
Vblock : Voltages below Vblock normally correspond to a disconnected transformer and therefore
it is recommended to block automatic control for this condition (setting
percent of
Time
t1Use : Selection of time characteristic (definite or inverse) for t1 .
t1 : Time delay for the initial (first) raise/lower command.
t2Use : Selection of time characteristic (definite or inverse) for t2 .
t2 : Time delay for consecutive raise/lower commands. In the circulating current method, the
second, third, etc. commands are all executed with time delay
transformer in the parallel group that is tapping. In the master-follower method with the follow
tap option, the master is executing the second, third, etc. commands with time delay
followers on the other hand read the master's tap position, and adapt to that with the additional
time delay given by the setting
t_MinTripDelay : The minimum operate time when inverse time characteristic is used (see section
"Time characteristic", figure 176).
Line voltage drop compensation (LDC)
OpertionLDC : Sets the line voltage drop compensation function Enabled / Disabled .
OperCapaLDC : This setting, if set Enabled , will permit the load point voltage to be greater than
the busbar voltage when line voltage drop compensation is used. That situation can be caused by
a capacitive load. When the line voltage drop compensation function is used for parallel control
with the reverse reactance method, then
Rline and Xline : For line voltage drop compensation, these settings give the line resistance and
reactance from the station busbar to the load point. The settings for
primary system ohms. If more than one line is connected to the LV busbar, equivalent
Xline values should be calculated and given as settings.
When the line voltage drop compensation function is used for parallel control with the reverse
reactance method, then the compensated voltage which is designated "load point voltage" V
effectively an increase in voltage up into the transformer. To achieve this voltage increase,
must be negative. The sensitivity of the parallel voltage regulation is given by the magnitude of
Rline and Xline settings, with Rline being important in order to get a correct control of the busbar
voltage. This can be realized in the following way. Figure
transformer controlled in a parallel group with the reverse reactance method and with no
circulation (for example, assume two equal transformers on the same tap position). The load
392
VDeadband . Typically the inner deadband can be set to 25-70% of the VDeadband
transformer", figure 175). It is set in percent of
transformer", figure 175). It is set in percent of
VBase .
tAutoMSF and set individually for each follower.
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t2 independently of which
OperCapaLDC must always be set Enabled .
177 shows the vector diagram for a
1MRK 511 401-UUS F
"Automatic
VBase . If OVPartBk is set
"Automatic
VBase . If UVPartBk is set
UVBk ). Vblock is set in
t2 . The
Rline and Xline are given in
Rline and
L
Xline
Bay control REC670
Application manual
is