Time Delayed Overcurrent Protection (51); Figure 3-2 Logic Diagram: Time Delayed Overcurrent Element - Siemens 7SR45 Argus User Manual

7SR45 Description of Operation
3.2

Time Delayed Overcurrent Protection (51)

One time delayed overcurrent element is provided in the 7SR45 self powered overcurrent and earth fault relay.
51-1
51-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, ANSI using 51-n Char. A time multiplier is applied to the characteristic curves using the 51-n
Time Mult setting. Alternatively, a definite time lag delay (DTL) can be chosen using 51-n Char. When Definite
Time Lag (DTL) is selected the time multiplier is not applied and the 51-n Delay (DTL) setting is used instead.
The 51-n Reset setting can apply a definite time delayed reset, or when the operation is configured as an IEC
or ANSI and 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 51-n MinOperate setting.
A fixed additional operate time can be added to the characteristic using 51-n Follower setting.
Operation of the time delayed overcurrent elements can be inhibited by assigning binary inputs.
Inhibit 51-n A binary input.
Figure 3-2 Logic Diagram: Time Delayed Overcurrent Element
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