7SR45 Description of Operation
© 2017 Siemens Protection Devices Limited Chapter 1 Page 19 of 34
Table 3-3 Instantaneous Derived Earth Fault Protection (50N-n)
Parameters Description Default Value Min Max Step Change
50N-n
Element
50N-n Block Disabled - - -
50N-n Setting Current Set point 1xIn 0.2xIn 20xIn 0.1
50N-n Delay Delay time 0 0 s 600 s 0.01
3.4 Time Delayed Derived Earth Fault Protection (51N)
One time delayed derived earth fault element is provided in the 7SR45 self powered overcurrent and earth fault
relay.
51N-1
51N-n Setting sets the pick-up current level.
A number of shaped characteristics are provided. An inverse definite minimum time (IDMT) characteristic is
selected from IEC and ANSI using 51N-n Char. A time multiplier is applied to the characteristic curves using the
51N-n Time Mult setting. Alternatively, a definite time lag delay (DTL) can be chosen using 51N-n Char. When
definite time lag (DTL) is selected the time multiplier is not applied and the 51N-n Delay (DTL) setting is used
instead.
The 51N-n Reset setting can apply a definite time delayed reset, or when the operation is configured as an IEC
or ANSI if the reset is selected as IEC/ANSI (DECAY) reset, the associated reset curve will be used.
A minimum operate time for the characteristic can be set using the 51N-n MinOperate setting.
A fixed additional operate time can be added to the characteristic using the 51N-n Follower setting.
Operation of the time delayed derived earth fault elements can be inhibited by assigning binary inputs.
Inhibit 51N-n A binary input.
Figure 3-4 Logic Diagram: Derived Time Delayed Earth Fault Protection
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