Current Protection: Under-Current (37); Figure 3-18 Logic Diagram: Negative Phase Sequence Overcurrent (46Nps) - Siemens 7SR12 Argus Manual

46IT Element
Enabled
Disabled
Inhibit 46IT
IL1
IL2 NPS
IL3
46DT Element
Enabled
Disabled
Inhibit 46DT

Figure 3-18 Logic Diagram: Negative Phase Sequence Overcurrent (46NPS)

3.8 Current Protection: Under-Current (37)

Two under-current elements are provided 37-1 & 37-2 for phase currents and two for the earth or sensitive earth
fault input 37G-1 & 37G-2 or 37SEF-1 & 37SEF-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.
An output is also given to indicate the operated phase.
All under-current elements work with True RMS currents.
Operation of the under-current elements can be inhibited from:
Inhibit 37-n
37U/I Guard Setting
37-n
Enabled
Disabled
Inhibit 37-n
37 U/I Guarded
Yes
37 U/I Guard
Setting
<
<
<
IL1
IL2
IL3
©2017 Siemens Protection Devices Limited
46IT Setting
46IT Char
46IT Time Mult
46IT Delay (DTL)
46IT Reset
c
&
I2
46DT Setting
&
c
A binary or virtual input.
0.05,0.1..5xIn
&
&
&
37-n Setting
c
<
<
<
7SR11 & 7SR12 Description Of Operation
Pickup
trip
46DT Delay
>
c
37-n Start Option 37-n Delay
Any/All
General Pickup
46IT
General Pickup
46DT
37-n
Chapter 1 Page 49 of 88