7SR11 & 7SR12 Description Of Operation
©2012 Siemens Protection Devices Limited Chapter 1 Page 35 of 76
3.3.2 Instantaneous Measured Earth Fault Protection (50G)
Two instantaneous derived earth fault elements are provided in the 7SR11 relay and four elements are provided
in the 7SR12 relay.
50G-1, 50G-2, (50G-3 & 50G-4 – 7SR12)
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 e.g. giving the option of using two elements
set to forward and two to reverse.
Operation of the instantaneous measured earth fault elements can be inhibited from:
Inhibit 50G-n A binary or virtual input.
79 E/F Inst Trips: 50G-n When ‘delayed’ trips only are allowed in the auto-reclose sequence
(79 E/F Prot’n Trip n = Delayed).
50-n Inrush Action: Block Operation of the inrush current detector function.
50G-n VTSAction: Inhibit Operation of the VT Supervision function (7SR1205 & 7SR1206).
Figure 1-32 Logic Diagram: Measured Instantaneous Earth-fault Element
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