7SR18 Description Of Operation
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Page 69 of 78
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.
Figure 5.6-1 Functional Diagram for Harmonic Block Feature (81HBL2)
81HBL2 Element
Enabled
Disabled
IL1
IL2
IL3
81HBL2 Bias
L2 81HBL2
81HBL2 Setting
c
>
>
>
L1 81HBL2
L3 81HBL2
81HBL2
> 1
Inhibit 81HBL2
&
Summary of Contents for 7SR18 Solkor
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