Time Delayed Overcurrent Protection (51); Figure 3-11 Logic Diagram: Instantaneous Overcurrent Element - Siemens 7SR105 Rho User Manual

Gn 50- n Element
Disabled
Enabled
Inhibit 50-n
Gn 50
Measurement
I
A
I
B
I
C

Figure 3-11 Logic Diagram: Instantaneous Overcurrent Element

3.3.2 Time Delayed Overcurrent Protection (51)

Two time delayed overcurrent elements are provided in the 7SR105 Rho Motor Protection Relay.
51-1, 51-2
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 curves 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.
Alternatively, a 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 if the reset is selected as (IEC/ANSI) DECAYING reset the associated reset curve will be used. The reset
mode is significant where the characteristic has reset before issuing a trip output.
A minimum operating time for the characteristic can be set using 51-n Min. Operate Time setting.
A fixed additional operating time can be added to the characteristic using 51-n Follower DTL setting.
Operation of the time delayed overcurrent protection elements can be inhibited from:
Inhibit 51-n
©2018 Siemens Protection Devices
&
Gn 50 n Setting
En
>
>
>
A binary or virtual input.
7SR105 Rho Description of Operation
Gn 50- n Delay
≥
1
General Pickup
50-n
Chapter 1 Page 34 of 57