ABB REG670 Applications Manual page 592

Section 15
Control
586
to half of the transformer reactance, and then observe how the parallel control behaves
during a couple of days, and then tune it as required. It shall be emphasized that a quick
response of the regulation that quickly pulls the transformer tap changers into equal
positions, not necessarily corresponds to the optimal setting. This kind of response is
easily achieved by setting a high Xline value, as was discussed above, and the
disadvantage is then a high susceptibility to changing power factor.
A combination of line voltage drop compensation and parallel control with the
negative reactance method is possible to do simply by adding the required Rline values
and the required Xline values separately to get the combined impedance. However, the
line drop impedance has a tendency to drive the tap changers apart, which means that
the reverse reactance impedance normally needs to be increased.
Load voltage adjustment (LVA)
LVAConst1: Setting of the first load voltage adjustment value. This adjustment of the
target value USet is given in percent of UBase.
LVAConst2: Setting of the second load voltage adjustment value. This adjustment of
the target value USet is given in percent of UBase.
LVAConst3: Setting of the third load voltage adjustment value. This adjustment of the
target value USet is given in percent of UBase.
LVAConst4: Setting of the fourth load voltage adjustment value. This adjustment of
the target value USet is given in percent of UBase.
VRAuto: Setting of the automatic load voltage adjustment. This adjustment of the
target value USet is given in percent of UBase, and it is proportional to the load current
with the set value reached at the nominal current I2Base.
RevAct
OperationRA: This setting enables/disables the reverse action partial blocking
function.
tRevAct: After the reverse action has picked up, this time setting gives the time during
which the partial blocking is active.
RevActLim: Current threshold for the reverse action activation. This is just one of two
criteria for activation of the reverse action partial blocking.
Tap changer control (TCCtrl)
Iblock: Current setting of the over current blocking function. In case, the transformer
is carrying a current exceeding the rated current of the tap changer for example,
because of an external fault. The tap changer operations shall be temporarily blocked.
This function typically monitors the three phase currents on the HV side of the
transformer.
DayHuntDetect: Setting of the number of tap changer operations required during the
last 24 hours (sliding window) to activate the signal DAYHUNT
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
1MRK 502 071-UEN -
Application manual