7SR45 Description of Operation
© 2017 Siemens Protection Devices Limited Chapter 1 Page 22 of 34
The following are the 51G-n supported Curve Characteristic:
• DTL, IEC-NI, IEC-VI, IEC-EI, IEC-LTI, ANSI-MI, ANSI-VI, ANSI-EI
Table 3-6 Instantaneous Measured Earth Fault Protection (51G-n)
Parameters Description Default Value Min Max
Step
Change
51G-n Element 51G-1 Block Disabled - - -
51G-n Setting Current Set point 0.5xIn 0.1xIn 0.80xIn 0.01
51G-n Char Characteristics DTL - - -
51G-n Time Mult
Time Multiplier
(other than DTL)
1 0.01 10 0.01
51G-n Delay
Delay
(Applicable only for
DTL)
5 s 0 s 15 s 0.01
51G-n Min
Operate
Minimum Operate
Time
0 s 0 s 20 s 0.01
51G-n Follower
DTL
Follower DTL 0 s 0 s 20 s 0.01
51G-n Reset Reset 0 s 0 s
60, IEC/
ANSI
DECAY
0.01
3.7 Switch-On-To-Fault (50LC/SOTF)
SOTF provides high-speed tripping when the relay is energized with short-circuit current or fault current.
SOTF function monitors the phase current for 10 AC cycles from the start-up of relay with CT power and trips
when any fault is detected as per the user settings. After 10 AC cycle, SOTF will not monitor current and does not
operate.
SOTF can be inhibited by assigning binary input.
Operation of the Switch-On-To-Fault elements can be inhibited from:
Inhibit 50LC A binary input.
≥1
Inhibit 50LC
50LC
Gn
50 LC Setting
c
Gn 50LC /SOTF
Enabled
Disabled
>
>
>
IL1
IL2
IL3
Gn 50 LC/
Measurement
≥1
General Pickup
&
10 cycles
Figure 3-7 Logic Diagram: 50LC Overcurrent Element
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