Switch-On-To-Fault (50Lc/Sotf); Figure 3-7 Logic Diagram: 50Lc Overcurrent Element - Siemens 7SR45 Argus User Manual

3.7

Switch-On-To-Fault (50LC/SOTF)

SOTF provides high-speed tripping in the event of energizing the feeder while the earth switch is closed or while
the feeder is energized when the fault current/short circuit current persists.
SOTF function monitors the phase current for a maximum duration of 25 AC cycles from the CT interrupt and trips
when any fault is detected as per the user settings. After the 25 AC cycles, SOTF function would be inhibited
automatically.
SOTF can be inhibited by assigning binary input.
Operation of the Switch-On-To-Fault elements can be inhibited from:
Inhibit 50LC
Gn 50 LC / SOTF
Enabled
Disabled
&
Inhibit 50LC
Gn 50 LC / SOTF
Measurement
IL1
IL2
25 AC cycles
IL3
Parameters
Gn 50LC/SOTF
Setting
©2018 Siemens Protection Devices Limited
A binary input
Gn 50 LC Setting
c
>
>
>
Figure 3-7 Logic Diagram: 50LC Overcurrent Element
Table 3-10
Description Default Value
Pick-up current 2xI
n
Chapter 1 - 7SR45 Description of Operation
50LC/SOTF
Min Max
1xI 20xI
n n
≥1
General Pickup
≥1 50 LC
Step Change
1
Chapter 1 Page 33 of 48