Instantaneous Sensitive Earth Fault Protection (50Sef); Time Delayed Sensitive Earth Fault Protection (51Sef); Figure 3-12 Logic Diagram: 7Sr10 Sef Instantaneous Element; Figure 3-13 Logic Diagram: 7Sr10 Sef Instantaneous Element - Siemens 7SR10 Argus Series Manual

3.4.2

Instantaneous Sensitive Earth Fault Protection (50SEF)

Two sensitive earth fault elements are provided in the 7SR1002/7SR1003 relay and four elements are provided in
the 7SR1004 relay.
Each instantaneous element has independent settings for pick-up current 50SEF-n Setting and a follower time
delay 50SEF-n Delay. The instantaneous elements have transient free operation.
Where directional elements are present the direction of operation can be set using 50SEF-n Dir. Control setting.
Directional logic is provided independently for each 50SEF-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 50SEF-n
79 SEF Inst Trips: 50SEF-n
50SEF-n VTSAction: Inhibit
Directional elements will not operate unless the zero sequence voltage (V
Voltage setting i.e. the residual voltage is greater than 3 times this setting and the phase is in the
Forward/Reverse operating range.
50SEF-n Element
Disabled
Enabled
AUTORECLOSE
Inhibit 50SEF-n
79 P/F Inst Trips
= 50SEF-n
&
79 P/F Prot'n Trip n
= Delayed

Figure 3-12 Logic Diagram: 7SR10 SEF Instantaneous Element

50SEF-n Dir.
Control
Non-Dir
Forward
Reverse
67SEF Fwd
67SEF Rev

Figure 3-13 Logic Diagram: 7SR10 SEF Instantaneous Element

3.4.3

Time Delayed Sensitive Earth Fault Protection (51SEF)

Two sensitive earth fault elements are provided in the 7SR1002/7SR1003 relay and four elements are provided in
the 7SR1004 relay.
51SEF-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 51SEF-n Char. A time multiplier is applied to the characteristic curves
using the 51SEF-n Time Mult setting. Alternatively, a definite time lag (DTL) can be chosen using 51SEF-n Char.
When DTL is selected the time multiplier is not applied and the 51SEF-n Delay (DTL) setting is used instead.
©2018 Siemens Protection Devices Limited
50SEF-1, 50SEF-2, (50SEF-3 & 50SEF-4 – 7SR1004)
A binary or virtual input.
When 'delayed' trips only are allowed in the auto-reclose sequence
(79 SEF Prot'n Trip n = Delayed).
Operation of the VT Supervision function.
&
I (I )
4 SEF
50SEF-n VTS Action
Off
Non-Dir
Inhibit
VT Fail
&
≥1
&
51SEF-1, 51SEF-2, (51SEF-3 & 51SEF-4 – 7SR1004)
) is above the 67SEF Minimum
0
50SEF-n Setting
50SEF-n Delay
c
>
& &
&
7SR10 Description of Operation
General Pickup
50SEF-n
≥1
50SEF-n Dir En
Chapter 1 Page 38 of 77