ABB Relion 670 Series Applications Manual page 377

1MRK 511 401-UUS F
1. that the busbar or load voltage is regulated to a preset target value
2. that the load is shared between parallel transformers in proportion to their ohmic short
circuit reactance
If the transformers have equal percentage impedance given in the respective transformer MVA
base, the load will be divided in direct proportion to the rated power of the transformers when the
circulating current is minimized.
This method requires extensive exchange of data between the TR8ATCC (90) function blocks (one
TR8ATCC (90) function for each transformer in the parallel group). TR8ATCC (90) function block
can either be located in the same IED, where they are configured in PCM600 to co-operate, or in
different IEDs. If the functions are located in different IEDs they must communicate via GOOSE
interbay communication on the IEC 61850 communication protocol. Complete exchange of
TR8ATCC (90) data, analog as well as binary, via GOOSE is made cyclically every 300 ms.
The busbar voltage V
associated TR8ATCC (90) function. These measured values will then be exchanged between the
transformers, and in each TR8ATCC (90) block, the mean value of all V
The resulting value V
thus assuring that the same value is used by all TR8ATCC functions, and thereby avoiding that one
erroneous measurement in one transformer could upset the voltage regulation. At the same time,
supervision of the VT mismatch is also performed. This works such that, if a measured voltage V
differs from V
than a pre set time (setting parameter
The calculated mean busbar voltage V
under Main menu/Test/Function status/Control/TransformerVoltageControl(ATCC,90)/
TR8ATCC:x.
Measured current values for the individual transformers must be communicated between the
participating TR8ATCC (90) functions, in order to calculate the circulating current.
The calculated circulating current I
ICIRCUL under Main menu/Test/Function status/Control/
TransformerVoltageControl(ATCC,90)/TR8ATCC:x.
When the circulating current is known, it is possible to calculate a no-load voltage for each
transformer in the parallel group. To do that the magnitude of the circulating current in each bay,
is first converted to a voltage deviation, V
=
C I
V
di i
EQUATION1979-ANSI V1 EN-US
where X
Comp which serves the purpose of alternatively increasing or decreasing the impact of the
circulating current in TR8ATCC control calculations. It should be noted that V
values for transformers that produce circulating currents and negative values for transformers
that receive circulating currents.
Now the magnitude of the no-load voltage for each transformer can be approximated with:
Bay control REC670
Application manual
is measured individually for each transformer in the parallel group by its
B
will then be used in each IED instead of V
Bmean
with more than a preset value (setting parameter
Bmean
× ×
X
cc _ i i
is the short-circuit reactance for transformer i and C
i
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tVTmismatch ) an alarm signal VTALARM will be generated.
is shown on the local HMI as a service value BusVolt
Bmean
for transformer "i" is shown on the HMI as a service value
cc_i
, with equation 124:
di
values will be calculated.
B
for the voltage regulation,
B
VTmismatch ) and for more
, is a setting parameter named
i
will have positive
di
Section 14
Control
,
B
(Equation 124)
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