7SR11 & 7SR12 Description Of Operation
©2012 Siemens Protection Devices Limited Chapter 1 Page 44 of 76
Inhibit 46IT
46IT
46IT Setting
46IT Char
46IT Time Mult
46IT Delay (DTL)
46IT Element
Enabled
Disabled
&
46IT Reset
IL1
IL2
IL3
NPS
46DT
>
c
46DT Setting
46DT Delay
c
Inhibit 46DT
46DT Element
Enabled
Disabled
&
I2
General Pickup
General Pickup
c
Pickup
trip
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 A binary or virtual input.
37U/I Guard Setting 0.05,0.1..5xIn
Figure 1-42 Logic Diagram: Phase Current Inputs Undercurrent Detector (37)
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