ABB RELION RET670, Applications Manual

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equal to
D
V
in
. The setting shall be smaller than VDeadband . Typically the inner
deadband can be set to 25-70% of the VDeadband value.
Vmax : This setting gives the upper limit of permitted busbar voltage (see section
"Automatic voltage control for a single transformer" , figure 363 ). It is set in percent of
VBase . If OVPartBk is set to Auto&ManBlock , then busbar voltages above Vmax will
result in a partial blocking such that only lower commands are permitted.
Vmin This setting gives the lower limit of permitted busbar voltage (see section
"Automatic voltage control for a single transformer" , figure 363 ). It is set in percent of
VBase . If UVPartBk is set to Auto Block or Auto&ManBlock , then busbar voltages
below Vmin will result in a partial blocking 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
UVBk ). Vblock is set in percent of VBase .
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 t2
independently of which 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
t2 . The followers on the other hand read the master’s
tap position, and adapt to that with the additional time delay given by the setting
tAutoMSF and set individually for each follower.
t_MinTripDelay : The minimum operate time when inverse time characteristic is used
(see section "Time characteristic" , figure 364 ).
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
OperCapaLDC must always be set Enabled .
1MRK 504 163-UUS A
Section 15
Control
Transformer protection RET670 2.2 ANSI 793
Application manual