Siemens 7SR242 - Current Protection: Under-Current (37, 37 G); Figure 3-14 Logic Diagram: Undercurrent Detector (37, 37 G)

7SR242 Duobias Description Of Operation
©2010 Siemens Protection Devices Limited Chapter 1 Page 34 of 52
3.8 Current Protection: Under-Current (37, 37G)
Optionally two under-current elements are provided for both line and measured earth current, each can be
selected to either winding 1 or winding 2.
Each phase has an independent level detector and current-timing element. 37-n Setting sets the pick-up current.
An output is given after elapse of the 37-n Delay setting.
Operation of the under-current elements can be inhibited from:
Inhibit 37-n A binary or virtual input.
Gn 37-n U/I Guarded Operation of the undercurrent guard function.
Inhibit 37G-n A binary or virtual input.
1
37-n
37-n Delay
37-n Setting
c
<
<
<
Inhibit 37-n
37-n Element
Enabled
Disabled
&
Wn IL1
Wn IL2
Wn IL3
37-n U/I
Guarded
Yes
<
37-n U/I Guard
Setting
&
<
<
1
Ig-n
37G-n
37G-n Delay
37G-n Setting
c
<
Inhibit 37G-n
37G-n Element
Enabled
Disabled
&
Figure 3-14 Logic Diagram: Undercurrent Detector (37, 37G)