11
SME70, SME70-C, SME70-M-Manual-04-2020
—
Overcurrent - 51
I> threshold
(1)
100...900 A (step 10 A)
t> otime delay
0.000....1.000 s (step 0.005 s)
Start time
0.045 s
Dropout ratio
> 0.95
Reset delay
0.02 s
Duration of the fault not detected
0.04 s
Duration of the fault detected
0.08 s
Threshold accuracy
±10%
Operate time accuracy
± 10 ms
Operation
Each phase fundamental frequency current is compared with the setting threshold. Currents above
the pickup value are detected and a start is issued. After expiry of the associated operate time a
trip command is issued (51 relay); if instead the current drops below the threshold, the element it is
restored.
—
Residual overcurrent - 51N
I
E
> threshold
(1)
10...200 A (step 2 A)
t
E
> time delay
0.000....1.000 s (step 0.005 s)
Start time
0.045 s
Dropout ratio
> 0.95
Reset delay
0.02 s
Duration of the fault not detected
0.04 s
Duration of the fault detected
0.08 s
Threshold accuracy
±10%
Operate time accuracy
± 10 ms
Operation
The residual current is compared with the setting threshold. Currents above the pickup value are
detected and a start is issued. After expiry of the associated operate time a trip command is issued
(51 relay); if instead the current drops below the threshold, the element it is restored.
I
I
>
t
TRIP
0.045
General operation time characteristic for the phase overcurrent element - 51
t-int-F51N.ai
I
E
0.045
(s)
I
E
>
t
General operation time characteristic for the residual overcurrent element - 51N
TRIP
