Siemens 7SR224 - Instantaneous Overcurrent Protection (50); Figure 3.1-2 Logic Diagram: Instantaneous Over-Current Element

(1) Description of Operation 7SR224
Page 20 of 66 ©2009 Siemens Protection Devices Limited
3.1.2 Instantaneous Overcurrent Protection (50)
Four elements are provided e.g. giving the option of using two elements set to forward and two to
reverse.
Each instantaneous element (50-n) has independent settings. 50-n Setting for pick-up current and 50-
n Delay follower time delay. The instantaneous elements have transient free operation.
For the directional elements the direction of operation can be set using 50-n Dir. Control setting.
Directional logic is provided independently for each 50-n element.
Operation of the instantaneous overcurrent elements can be inhibited from:
Inhibit 50-n A binary or virtual input, or function key.
79 P/F Inst Trips: 50-n When ‘delayed’ trips only are allowed in the auto-reclose
sequence (79 P/F Prot’n Trip n = Delayed).
50-n Inrush Action: Inhibit Operation of the inrush current detector function.
50-n VTS Action: Inhibit Operation of the VT Supervision function.
Figure 3.1-2 Logic Diagram: Instantaneous Over-current Element