ABB RET615 - Page 43

Table 44. Numerical stabilized low impedance restricted earth-fault protection (LREFPNDF)
Characteristic Value
Operation accuracy Depending on the frequency of the current measured: f
n
±2 Hz
±2.5% of the set value or ±0.002 x I
n
Start time
1)2)
Minimum Typical Maximum
I
Fault
= 2.0 x set Operate
value
38 ms 40 ms 43 ms
Reset time < 40 ms
Reset ratio Typical 0.96
Retardation time < 35 ms
Operate time accuracy in definite time mode ±1.0% of the set value or ±20 ms
Suppression of harmonics DFT: -50 dB at f = n x f
n
, where n = 2, 3, 4, 5, …
1) Current before fault = 0.0, f
n
= 50 Hz, results based on statistical distribution of 1000 measurements
2) Includes the delay of the signal output contact
Table 45. Stabilized restricted earth-fault protection (LREFPNDF) main settings
Parameter
Function Value (Range) Step
Operate value LREFPNDF 5...50 % 1
Restraint mode LREFPNDF None
2nd harmonic
-
Start value 2.H LREFPNDF 10...50 % 1
Minimum operate time LREFPNDF 40...300000 ms 1
Operation LREFPNDF Off
On
-
Transformer Protection and Control 1MRS756891 F
RET615
Product version: 4.0
ABB 43