Inrush Detector (81Hbl2); Figure 5.6-1 Logic Diagram: Harmonic Block Feature (81Hbl2) - Siemens 7SR224 Description & Operation

5.6 I D
NRUSH ETECTOR
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.
With this method the square root of the sum of the squares of the second harmonic in
Sum
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.
©2009 Siemens Protection Devices Limited
(81HBL2)
Figure 5.6-1 Logic Diagram: Harmonic Block Feature (81HBL2)
(1) Description of Operation 7SR224
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