Remote/Local Control - ABB SPAU 341 C User Manual

Negative reactance
principle
Minimizing
circulating current

Remote/local control

6
If the software switch SGF1/2=1 and parallel
operation has been selected, the regulator starts
operating according to the modified negative
reactance principle. By comparing the actual
phase-shift measured with the set load phase-
shift value, and measuring the current, the com-
pensating value U can be calculated. The com-
ci
pensating value U affects the regulator con-
ci
trol voltage U in such a way, that a stable volt-
p
age control of parallel operating transformers is
obtained once the reactive load is relatively sta-
ble.
The compensating value U
the following expression:
I stability
ci
U = x x U
ci
I 100
nt
If the software switch SGF1/2=0 and parallel
operation has been selected, the regulator starts
operating according to the minimizing circu-
lating current principle. Each voltage regulat-
ing module transmits its own current and phase-
shift values to the other modules operating in
parallel. Then the modules calculate the total
value of the busbar current and the phase-shift
and compare it with its own values measured.
If the software switch SGF1/3=1, the module
can be switched between remote and local con-
trol via the external control input BLOCK.
When the external control input is energized,
the regulator mode and operation is controlled
remotely using the serial communication param-
I
I
U
stability = percentage setting value
If the parallel operating transformers have dif-
ferent rated currents, the regulator stability set-
ting value should be proportional to the rated
currents, i.e. the higher the rated current the
higher the stability setting value.
is obtained from
ci
n
This calculation gives the circulating current to
be minimized. The same formula as for the nega-
tive reactance principle is used for calculating
the compensating value U
same stability setting value can be set for the
separate regulators, since the regulators take into
account differences in the transformers's rated
currents.
eters I6, I7, I9, I10 and V152. When the exter-
nal control input is deenergized, local push-but-
ton control is enabled. Control of regulator
mode and operation via external control inputs
MAN', AUTO', RAISE', LOWER' and RSV is
always enabled.
= circulating current [kA]
ci
= rated current of the power trans-
nt
former [kA]
= rated phase-to-phase voltage of the
n
power transformer
. In this case, the
ci