ABB RER670 Applications Manual page 333

1MRK 506 375-UEN A
Railway application RER670 2.2 IEC
Application manual
Xline equal 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.
Section 12
Control
327