7SR224 Argus Description of Operation
5.7
Inrush Detector (81HBL2)
Inrush restraint detector elements are provided, these monitor the line currents.
The inrush restraint detector can be used to block the operation of selected elements during transformer
magnetising inrush conditions.
The
81HBL2 Bias
setting allows the user to select between
Phase
,
Sum
and
Cross
methods of measurement:
Phase
Each phase is inhibited separately.
Sum
With this method the square root of the sum of the squares of the second harmonic in each
phase is compared to each operate current individually.
Cross
All phases are inhibited when any phase detects an inrush condition.
An output is given where the measured value of the second harmonic component is above the
81HBL2
setting.
Figure 5.7-1 Logic Diagram: Harmonic Block Feature (81HBL2)
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Chapter 1 Page 61 of 70