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
79 E/F Inst Trips: 50G-n
50-n Inrush Action: Block
50G-n VTSAction: Inhibit
Figure 1-32 Logic Diagram: Measured Instantaneous Earth-fault Element
©2012 Siemens Protection Devices Limited
7SR11 & 7SR12 Description Of Operation
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).
Chapter 1 Page 35 of 76