7SR105 Rho Description of Operation
©2018 Siemens Protection Devices Chapter 1 Page 35 of 57
General Pickup
51-n
Gn 51- n Setting
Gn 51- n Charact
Gn 51- n Time Mult
Gn 51- n Delay (DTL)
Gn 51- n Reset
En.
Gn 51- n Follower DTL
Gn 51- n Min. Operate Time
En.
Pickup
trip
En.
Pickup
trip
En.
Pickup
trip
I
A
I
B
I
C
Gn 51
Measurement
≥
1
≥
1
Inhibit 50-n
&
Enabled
Gn 51- n Element
Figure 3-12 Logic Diagram: Time Delayed Overcurrent Element
3.4 Current Protection: Derived Earth Fault (50N, 51N)
The earth current is derived by calculating the sum of the measured line currents. The elements measure the
fundamental frequency RMS current.
3.4.1 Instantaneous Derived Earth Fault Protection (50N)
Two instantaneous derived earth fault elements are provided in the 7SR105 Rho Motor Protection Relay.
50N-1, 50N-2
Each instantaneous element has independent settings for pick-up current
50N-n Setting
and a follower time
delay
50N-n Delay
. The instantaneous elements have transient free operation.
Operation of the instantaneous earth fault elements can be inhibited from:
Inhibit 50N-n
A binary or virtual input.
I
N
&
50N-n
General Pickup
Enabled
Disabled
Gn 50N- n Element
EF In
Inhibit 50N-n
En
Gn 50N- n Setting
Gn 50N- n Delay
I
A
I
B
I
C
>
Figure 3-13 Logic Diagram: Derived Instantaneous Earth Fault Element
Содержание 7SR105 Rho
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