Chapter 1) 7SR242 Duobias Description Of Operation
©2015 Siemens Protection Devices Limited
Chapter 1 Page 28 of 60
3.2
Current Protection: Phase Overcurrent (51, 50)
The optional phase overcurrent elements have a common setting to measure either fundamental frequency RMS
or True RMS current:
True RMS current:
51/50 Measurement = RMS
Fundamental Frequency RMS current:
51/50 Measurement = Fundamental
3.2.1 Instantaneous Overcurrent Protection (50)
Optionally two instantaneous overcurrent elements are provided, each can be selected to either winding 1 or
winding 2.
Each instantaneous element (50-n) has independent settings.
50-n Setting
for pick-up current and
50-n Delay
follower time delay. The instantaneous elements have transient free operation.
Operation of the instantaneous overcurrent elements can be inhibited from:
Inhibit 50-n
A binary or virtual input.
50-n Inrush Action: Inhibit
Operation of the inrush detector function.
User Inhibit
Reylogic (graphical logic).
50-n
50-n Setting
Enable
>
c
50-n Delay
>
c
>
c
Wn-IL1
Wn-IL2
Wn-IL3
50/51
Measurement
L1 81HBL2
50-n Inrush
Action
Off
Inhibit
&
L2 81HBL2
L3 81HBL2
&
&
1
General Pickup
1
&
Inhibit 50-n
50-n Element
Enabled
Disabled
User Inhibit 50-n
Figure 3-5
Logic Diagram: Instantaneous Over-current Element
Summary of Contents for 7SR242 Duobias
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