2Nd Harmonic Block/Inrush Restraint (81Hbl2) Phase Elements Only; Total Harmonic Distortion Supervision (81Thd); Figure 5-2 Logic Diagram: Harmonic Block Feature (81Hbl2) - Siemens 7SR10 Argus Series Manual

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
Inhibit 81HBL2
Figure 5-2
5.3

Total Harmonic Distortion Supervision (81THD)

Single stage THD supervision element is provided in the 7SR10 Overcurrent Relay.
nd
THD calculates the 2 to 15
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
81THD Inrush Action: Block
©2018 Siemens Protection Devices Limited
81HBL2 Setting
&
81HBL2 Bias
c
>
IL1
>
IL2
>
IL3
Logic Diagram: Harmonic Block Feature (81HBL2)
th
harmonic currents presents in line current and displayed in the 'THD Meter' window
A binary or virtual input.
Operation of the inrush current detector function.
7SR10 Description of Operation
> 1
L 1 81HBL2
L 2 81HBL2
L 3 81HBL2
Chapter 1 Page 63 of 77
81HBL2