Parallel Operation; Master/Slave Principle; Minimizing Circulating Current - ABB SPAU 341 C User Manual

Parallel
operation
Master/slave
principle
Negative reactance
principle
Minimizing
circulating current
The voltage regulator SPAU 341 C is able to
operate parallel transformers in three ways: ac-
cording to the master/slave, the negative reac-
tance or the minimizing circulating current prin-
ciple. The master/slave principle needs direct
wiring between the regulators. The negative re-
actance principle does not require any connec-
tion between the regulators at all, whereas the
The master/slave parallel operation is suitable
for power transformers with identical ratings and
step voltages.
One voltage regulator (master) measures and
controls and the other regulators (slaves) follow
the master i.e. all tap-changers connected in
parallel are synchronized. The init situation is,
that the tap-changers are manually operated into
The negative reactance principle implemented
in SPAU 341 C is modified from previous regu-
lator designs. The expected phase-shift of the
load supplied by the transformers operating in
parallel is entered as a setting value. The regula-
tors correct their control voltage according to
the difference between the expected load phase-
shift and the phase-shift measured. This paral-
lel control scheme is suitable for power trans-
The minimizing circulating current principle is
the optimal solution for controlling parallel
transformers of different ratings or step voltages
in substations with varying reactive loads. Since
this control scheme allows exchange of data be-
tween the regulators, the circulating current can
be calculated more exactly than with other
minimizing circulating current principle is
achieved by using the serial communication
devices SPA-ZC 100. A maximum of three
transformers can be operated in parallel when
the minimizing circulating current principle is
used. The other principles can be used with an
unlimited number of transfomers in parallel.
the same step, and then the master takes com-
mand. This parallel operation is obtained by
connecting the master's outputs raise and lower
to the corresponding inputs of the slave. If sev-
eral regulators shall act as masters (one at a time),
their outputs also have to be routed to the other
regulators' inputs. To start parallel operation,
the master regulator is set to automatic mode,
and the slaves remain in manual mode.
formers with different ratings and step voltages.
Since no connection between the regulators is
required, transformers in separate substations
can also be operated in parallel. To start parallel
operation, parallel status has to be set for all the
regulators included in the connection. Parallel
status can be set via serial communication, a
binary input, or the push-button on the front
panel.
schemes. However, a maximum of three regula-
tors can be connected in parallel. To start paral-
lel operation, parallel status has to be set for all
the regulators of the connection. The serial com-
munication, a binary input, or the push-but-
ton on the front panel is used for setting paral-
lel status.
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