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7SR10 Description of Operation
©2018 Siemens Protection Devices Limited Chapter 1 Page 31 of 77
3.2.2 Instantaneous Derived Earth Fault Protection (50N)
Two instantaneous derived earth fault elements are provided in the 7SR1002/7SR1003 relay and four elements
are provided in the 7SR1004 relay.
50N-1, 50N-2, (50N-3 & 50N-4 – 7SR1004)
Each instantaneous element has independent settings for pick-up current
50N-n Setting
and a follower time
delay
50N-n Delay
. The instantaneous elements have transient free operation.
Where directional elements are present the direction of operation can be set using
50N-n Dir. Control
setting.
Directional logic is provided independently for each 50N-n element e.g. giving the option of using two elements
set to forward and two to reverse.
Operation of the instantaneous earth fault elements can be inhibited from:
Inhibit 50N-n
A binary or virtual input.
79 E/F Inst Trips:
50N-n
When ‘delayed’ trips only are allowed in the auto-reclose sequence
(
79 E/F Prot’n Trip n
=
Delayed
).
50N-n Inrush Action: Block
Operation of the inrush current detector function.
50N-n VTSAction:
Inhibit
Operation of the VT Supervision function.
50N-n
>
c
50N-n
Setting
If directional elements are not present this block is
omitted and the '50N-n Dir En' signal is set TRUE.
Forward
Reverse
50N-n Dir
Non-Dir
≥
1
&
&
50N-n Dir En
67N Fwd
67N Rev
50N-n Delay
50N-n VTS Action
Off
Non Dir
Inhibit
VT Fail
&
&
&
≥
1
IL1
IL2
IL3
I
N
Inhibit 50N-n
&
50N-n Element
Enabled
Disabled
81HBL2
50N-n Inrush
Action
Off
Inhibit
&
50N-n Dir En
General Pickup
&
79 P/F Inst Trips
= 50N-n
79 P/F Prot’n Trip n
= Delayed
AUTORECLOSE
Figure 3-6 Logic Diagram: Derived Instantaneous Earth Fault Element
Summary of Contents for 7SR10 Argus Series
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