Instantaneous Measured Earth Fault Protection (50G); Figure 3.4-2 Logic Diagram: Measured Instantaneous Earth-Fault Element - Siemens 7SR21 Manual

3.4.2

Instantaneous Measured Earth Fault Protection (50G)

Two instantaneous measured earth fault elements are provided in the 7SR21 relay. Four elements are provided in
the 7SR22 relay e.g. giving the option of using two elements set to forward and two to reverse.
Each instantaneous element has independent settings for pick-up current 50G-n Setting and a follower time
delay 50G-n Delay. The instantaneous elements have transient free operation.
Where directional elements are present the direction of operation can be set using 50G-n Dir. Control setting.
Directional logic is provided independently for each 50G-n element.
Operation of the instantaneous measured earth fault elements can be inhibited from:
Inhibit 50G-n
79 E/F Inst Trips: 50G-n
50G-n Inrush Action: Inhibit
50G-n VTSAction: Inhibit
Disabled
50G-n Inrush
Enabled
Action
Off
Inhibit
&
81HBL2
AUTORECLOSE
79 P/F Inst Trips
= 50G-n
&
79 P/F Prot'n Trip n
= Delayed
50G-n Dir.
Control
Non-Dir
Forward
Reverse
67G Fwd
67G Rev

Figure 3.4-2 Logic Diagram: Measured Instantaneous Earth-fault Element

©2010 Siemens Protection Devices Limited
A binary or virtual input, or function key
When 'delayed' trips only are allowed in the auto-reclose sequence
(79 E/F Prot'n Trip n = Delayed).
Operation of the current inrush detector function.
Operation of the VT Supervision function (7SR22).
50G-n Element
&
Inhibit 50G-n
50G-n Dir En
51G/50G Measurement
IG
&
&
7SR21 & 7SR22 Argus Description of Operation
50G-n Setting
c
>
If directional elements are not present this block is
50G-n VTS Action
omitted and the '50G-n Dir En' signal is set TRUE.
Off
Non Dir
Inhibit
&
VT Fail
1 &
General Pickup
50G-n Delay
50G-n
&
1
50G-n Dir En
Chapter 1 Page 33 of 71