Parallel operation modes Description
Negative reactance principle
The actual phase angle setting results in a
regulating error. When the line drop compen-
sation is used, the setting should be changed
when the number of transformers in parallel
operation is changed.
+ The step voltages and short circuit impe-
dances of the transformers do not need to
be identical.
+ No communication or wiring between regu-
lators is needed, meaning that the principle
can be applied even when the parallel trans-
formers are located at different substations.
+ Supports an unlimited number of trans-
formers in parallel
Minimizing circulating current
- Requires extra configuration efforts since
this principle utilizes a horizontal communi-
cation between the regulators (the inputs
TRx_I connected from parallel transformer
controller's outputs TR0_I.
+ The step voltages and short circuit impe-
dances of the transformers do not need to
be identical.
+ The phase angle of the load current may
vary without any impact on the regulation
accuracy.
+ Automatic adjustment for the number of
transformers (for an accurate calculation of
line drop compensation term)
9.5.6 Signals
Table 1023: OLATCC Input signals
Name Type Default Description
I_A SIGNAL 0 Phase A current
I_B SIGNAL 0 Phase B current
I_C SIGNAL 0 Phase C current
U_AB SIGNAL 0
Phase-to-phase volt-
age AB
TAP_POS INT8 0 Integer value repre-
senting tap chang-
er position of own
transformer
Table continues on the next page
1MRS757644 H Control functions
620 series
Technical Manual
1073
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