Current Protection: Under-Current (37); Figure 1-41 Logic Diagram: Negative Phase Sequence Overcurrent (46Nps); Figure 1-42 Logic Diagram: Phase Current Inputs Undercurrent Detector (37) - Siemens 7SR11 Manual

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

Figure 1-41 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.
Operation of the under-current elements can be inhibited from:
Inhibit 37-n
37U/I Guard Setting

Figure 1-42 Logic Diagram: Phase Current Inputs Undercurrent Detector (37)

©2012 Siemens Protection Devices Limited
46IT Setting
46IT Char
46IT Time Mult
46IT Delay (DTL)
46IT Reset
c
& Pickup
I2
46DT Setting
>
&
c
A binary or virtual input.
0.05,0.1..5xIn
7SR11 & 7SR12 Description Of Operation
trip
46DT Delay
c
General Pickup
46IT
General Pickup
46DT
Chapter 1 Page 44 of 76