Chapter 1 - 7SR45 Description of Operation
©2018 Siemens Protection Devices Limited Chapter 1 Page 27 of 48
3.3 Instantaneous Derived Earth Fault Protection (50N)
Two instantaneous derived earth fault elements are provided in the 7SR45 Argus Relay.
50N-1, 50N-2
Earth current is derived by calculating the vector sum of the measured phase currents.
Each instantaneous element has independent settings for pick-up current
50N-n Setting
and a definite time delay
50N-n Delay
.
Operation of the instantaneous derived earth fault elements can be inhibited by assigning binary inputs.
Inhibit 50N-n
A binary input.
50N-n
>
c
Gn 50N -n Setting
Gn 50N- n Delay
IL1
IL2
IL3
I
N
Inhibit 50N-n
Gn 50N- n Element
Enabled
Disabled
General Pickup
∑
&
Figure 3-3
Logic Diagram: Instantaneous Derived Earth Fault Element
Table 3-4
Instantaneous Derived Earth Fault Protection (50N-n)
Parameters
Description
Default Value Min
Max
Step Change
Gn 50N-n Element 50N-n Block
Disabled
-
-
-
Gn 50N-n Setting
Pick-up current
1xIn
0.2xI
n
20xI
n
0.1
Gn 50N-n Delay
Delay time
0
0 s
< 20 s
0.01
≥
20 s
< 100 s
0.1
≥
100 s
600 s
1