ABB RET630 - Numerical Stabilized Low Impedance Restricted Earth-Fault Protection

Table 35. Numerical stabilized low impedance restricted earth-fault protection
(LREFPNDF)
Characteristic Value
Operation accuracy At the frequency f = f
n
±1.5% of the set value or ±0.002 × I
n
Start time
1)2)
I
Fault
= 2.0 × set
Operate valueI
Fault
=
10.0 × set Operate
value
Typical 18 ms (±5 ms)
Typical 12 ms (±5 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: -50dB at f = n × f
n
, where n = 2, 3, 4,
5, …
1) Current before fault = 0.0 × I
n
, f
n
= 50 Hz
2) Includes the delay of the signal output contact
Table 36. Numerical stabilized low impedance 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 0.040...300.000 s 0.001
Transformer Protection and Control 1MRS756788 A
RET630
Product version: 1.0 Issued: 15.09.2009
32 ABB