7SR45 Description of Operation
© 2017 Siemens Protection Devices Limited Chapter 1 Page 16 of 34
Section 3: Protection Functions (50, 51, 50N, 51N, 50G,
51G, 50LC)
3.1 Instantaneous Overcurrent Protection (50)
Two Instantaneous overcurrent elements are provided in the 7SR45 self powered overcurrent and earth fault
relay.
50-1, 50-2
Each instantaneous element (50-n) has independent settings. 50-n Setting for pick-up current and
50-n Delay definite time delay.
Operation of the instantaneous overcurrent elements can be inhibited from:
Inhibit 50-n A binary input.
Figure 3-1 Logic Diagram: Instantaneous Overcurrent Element
Table 3-1 Instantaneous Overcurrent Protection (50-n)
Parameters Description Default Value Min Max Step Change
50-n Element 50-n Block Disabled - - -
50-n Setting Current Set point 1 0.2xIn 20xIn 0.1
50-n Delay Delay time 0 0 600 s 0.01
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