2.15 Monitoring Functions
207
7SD610 Manual
C53000-G1176-C145-4
If a failure is detected by these criteria, the indication „Fail U absent“ (No. 168)
is output, and the device switches to emergency operation (see Section 2.9).
Figure 2-86 Logic diagram of the additional measured voltage failure monitoring
2.15.1.4 Monitoring the Phase Angle of the Positive Sequence Power
This monitoring function allows to determine the direction of power flow. You can
monitor the phase angle of the complex power, and generate an indication when the
power phasor is inside a settable segment.
One example of this application is the indication of capacitive reactive power. The
monitoring indication can then be used to control the overvoltage protection function.
For this purpose, two angles must be set, as shown in Figure 2-87. In this example,
ϕA = 200° and ϕB = 340° has been set.
If the measured phase angle Ï•(S
1
) of the positive sequence power is within the area
of the P-Q plane delimited by the angles ϕA and ϕB, the indication „ϕ(PQ Pos.
Seq.)“ (No. 130) is output. The angles ϕA and ϕB can be freely set in the range
between 0° and 359°. The area starts at ϕA and extends in a mathematically positive
sense as far as the angle ϕB. A hysteresis of 2° is provided to prevent erroneous in-
dications which might emerge at the threshold limits.
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