7SR45 Description of Operation
© 2017 Siemens Protection Devices Limited Chapter 1 Page 20 of 34
The following are the 51N-n supported curve characteristic:
• DTL, IEC-NI, IEC-VI, IEC-EI, IEC-LTI, ANSI-MI, ANSI-VI, ANSI-EI
Table 3-4 Time Delayed Derived Earth Fault Protection (51N-n)
Parameters Description Default Value Min Max Step Change
51N-n
Element
51N-n Block Disabled - - -
51N-n Setting Current Set point 0.5XIn 0.1xIn 0.8xIn 0.01
51N-n Char Characteristics DTL - - -
51N-n Time
Mult
Time Multiplier
(other than DTL)
1 0.01 10 0.01
51N-n Delay
Delay
(Applicable only for
DTL)
5 s 0 s 15 s 0.01
51N-n Min
Operate
Minimum Operate
Time
0 s 0 s 20 s 0.01
51N-n
Follower DTL
Follower DTL 0 s 0 s 20 s 0.01
51N-n Reset Reset 0 s 0 s
60, IEC/
ANSI
DECAY
1
3.5 Instantaneous Measured Earth Fault Protection (50G)
The earth current is measured directly via a dedicated current analogue input, I
N
.
Two instantaneous measured earth fault elements are provided in the 7SR45 self powered overcurrent and earth
fault relay.
50G-1, 50G-2
Each instantaneous element has independent settings for pick-up current 50G-n Setting and a definite time delay
50G-n Delay.
Operation of the instantaneous measured earth fault elements can be inhibited from:
Inhibit 50G-n A binary input
Figure 3-5 Logic Diagram: Instantaneous Measured Earth-fault Element
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