ABB RET615 Product Manual page 33

ABB
Transformer Protection and Control
RET615
Product version: 2.0
Table 34. Numerical stabilized low impedance restricted earth-fault protection
(LREFPNDF)
Characteristic
Operation accuracy
1)2)
Start time
Reset time
Reset ratio
Retardation time
Operate time accuracy in definite time mode
Suppression of harmonics
1) Current before fault = 0.0, f
2) Includes the delay of the signal output contact
Table 35. Numerical stabilized low impedance restricted earth-fault protection
(LREFPNDF) main settings
Parameter
Operate value
Restraint mode
Start value 2.H
Minimum operate
time
Operation
I = 2.0 x set
Fault
Operate value
= 50 Hz, results based on statistical distribution of 1000 measurements
n
Function
LREFPNDF
LREFPNDF
LREFPNDF
LREFPNDF
LREFPNDF
Value
Depending on the frequency of the current
measured: f ±2Hz
n
±2.5% of the set value or ±0.002 x I
Minimum Typical
38 ms 40 ms
< 40 ms
Typical 0.96
< 35 ms
±1.0% of the set value or ±20 ms
DFT: -50dB at f = n x f
n
...
Value (Range)
5...50 %
None
2nd harmonic
10...50 %
40...300000 ms
Off
On
1MRS756891 B
Issued: 01.10.2009
n
Maximum
43 ms
, where n = 2, 3, 4, 5,
Step
1
-
1
1
-
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