Time Delayed Derived Earth Fault Protection (51N); Figure 3-6 Logic Diagram: Derived Instantaneous Earth Fault Element - Siemens 7SR12 Argus Manual

Overcurrent relay energy management
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3.2.2
I
NSTANTANEOUS
Two instantaneous derived earth fault elements are provided in the 7SR11 relay and four elements are provided
in the 7SR12 relay.
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 50-n element.
Operation of the instantaneous earth fault elements can be inhibited from:
Inhibit 50N-n
79 E/F Inst Trips: 50N-n
50-n Inrush Action: Block
50N-n VTSAction: Inhibit
50N-n Inrush
Action
Off
Inhibit
&
81HBL2
AUTORECLOSE
79 P/F Inst Trips
= 50N-n
&
79 P/F Prot'n Trip n
= Delayed
50N-n Dir
Non-Dir
Forward
Reverse
67N Fwd
67N Rev

Figure 3-6 Logic Diagram: Derived Instantaneous Earth Fault Element

3.2.3
T
D
IME
ELAYED
Two time delayed derived earth fault elements are provided in the 7SR11 relay and four elements are provided in
the 7SR12 relay.
51N-n Setting sets the pick-up current level.
A number of shaped characteristics are provided. An inverse definite minimum time (IDMT) characteristic is
selected from IEC and ANSI curves using 51N-n Char. A time multiplier is applied to the characteristic curves
using the 51N-n Time Mult setting. Alternatively, a definite time lag delay (DTL) can be chosen using 51N-n
Char. When definite time lag (DTL) is selected the time multiplier is not applied and the 51N-n Delay (DTL)
setting is used instead.
©2017 Siemens Protection Devices Limited
D
E
ERIVED
ARTH
50N-1, 50N-2, (50N-3 & 50N-4 – 7SR12)
A binary or virtual input.
When 'delayed' trips only are allowed in the auto-reclose sequence
(79 E/F Prot'n Trip n = Delayed).
Operation of the inrush current detector function.
Operation of the VT Supervision function (7SR1205 & 7SR1206).
50N-n Element
Disabled
Enabled
&
Inhibit 50N-n
50N-n Dir En
IL1
I
N
IL2
IL3
&
&
D
E
F
ERIVED
ARTH
51N-1, 51N-2, (51N-3 & 51N-4 – 7SR12)
7SR11 & 7SR12 Description Of Operation
F
P
(50N)
AULT
ROTECTION
50N-n
Setting
c
>
If directional elements are not present this block is
50N-n VTS Action
omitted and the '50N-n Dir En' signal is set TRUE.
Off
Non Dir
Inhibit
&
VT Fail
&
≥1
P
(51N)
AULT
ROTECTION
General Pickup
50N-n Delay
50N-n
&
≥1
50N-n Dir En
Chapter 1 Page 37 of 88

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