2Nd Harmonic Block/Inrush Restraint (81Hbl2) Phase Elements Only; Figure 5.6-1 Functional Diagram For Harmonic Block Feature (81Hbl2) - Siemens 7SR18 Solkor Manual

5.6 2nd Harmonic Block/Inrush Restraint (81HBL2) phase
elements only
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.
81HBL2 Element
Enabled
Disabled
Inhibit 81HBL2

Figure 5.6-1 Functional Diagram for Harmonic Block Feature (81HBL2)

Unrestricted ©2018 Siemens Protection Devices Limited
81HBL2 Setting
&
81HBL2 Bias
c
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IL1
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IL2
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IL3
7SR18 Description Of Operation
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L1 81HBL2
L2 81HBL2
L3 81HBL2
81HBL2
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