3.3 Commissioning
311
7SD610 Manual
C53000-G1176-C145-4
• With closed circuit breakers, the power values are viewed as primary and second-
ary values on the front display panel or via the operator or service interface with a
personal computer.
Here, again, the „WEB-Monitor“ is a convenient help since the vector diagrams also
show the allocation between the currents and voltages (Figure 3-25). Cyclically and
acyclically swapped phases can easily be detected.
• The measured power values on the actual device or in DIGSI enable you to verify
that they correspond to the load direction (Figure 3-26):
P positive if active power flows into the protected object,
P negative if active power flows toward the busbar,
Q positive if reactive power flows into the protected object,
Q negative if reactive power flows toward the busbar.
Therefore, the power results and their components must have opposite signs at
both ends.
It must be taken into consideration that high charging currents, which might occur
with long overhead lines or with cables, are capacitive, i.e. correspond to a negative
reactive power into the line. In spite of a resistive-inductive load, this may lead to a
slightly negative reactive power at the feeding end whereas the other end shows an
increased negative reactive power. The lower the load current for the test, the
higher the significance of this influence. In order to obtain unambiguous results, you
should increase the load current if necessary.
Figure 3-26 Apparent load power
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