7SR10 Description of Operation
©2018 Siemens Protection Devices Limited Chapter 1 Page 63 of 77
5.2 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.
NOTE:
The output should be configured as either "Pulse output" or "Hand-reset output" only.
81HBL2 Element
Enabled
Disabled
IL1
IL2
IL3
81HBL2 Bias
L2 81HBL2
81HBL2 Setting
c
>
>
>
L1 81HBL2
L3 81HBL2
81HBL2
> 1
Inhibit 81HBL2
&
Figure 5-2 Logic Diagram: Harmonic Block Feature (81HBL2)
5.3 Total Harmonic Distortion Supervision (81THD)
Single stage THD supervision element is provided in the 7SR10 Overcurrent Relay.
THD calculates the 2
nd
to 15
th
harmonic currents presents in line current and displayed in the ‘THD Meter’ window
as a percentage of fundamental frequency current.
81THD
Total harmonic distortion supervision (81THD) has independent settings.
81THD Setting
for pick-up current and
81THD Delay
follower time delay.
Operation of the Total harmonic distortion supervision elements can be inhibited from:
Inhibit 81THD
A binary or virtual input.
81THD Inrush Action:
Block
Operation of the inrush current detector function.
Summary of Contents for 7SR10 Argus Series
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