High-Impedance Based Restricted Earth-Fault Protection Hrefpdif (Ansi 87Nhi) - ABB RELION REX640 Technical Manual

1MRS759142 F
4.3.4.10 Technical data
Table 687: LREFPNDF Technical data
Characteristic
Operation accuracy
Start time
Reset time
Reset ratio
Retardation time
Operate time accuracy in definite time mode ±1.0% of the set value or ±20 ms
Suppression of harmonics
4.3.5 High-impedance based restricted earth-fault protection
HREFPDIF (ANSI 87NHI)
4.3.5.1 Identification
Function description
High-impedance based restricted
earth-fault protection
4.3.5.2 Function block
Figure 431: Function block
4.3.5.3 Functionality
The high-impedance based restricted earth-fault protection function HREFPDIF
is used for the restricted earth-fault protection of generators and power
transformers.
The function starts when the differential neutral current exceeds the set limit.
HREFPDIF operates with the DT characteristic.
1
Current before fault = 0.0, f
ments
2
Includes the delay of the signal output contact
REX640
Technical Manual
1, 2
I = 2.0 × set
Fault
ate value
= 50 Hz, results based on statistical distribution of 1000 measure-
n
Value
Depending on the frequency of the measured
current: f ±2 Hz
n
±2.5% of the set value or ±0.002 x I
Minimum
Oper-
37 ms
Typically 40 ms
Typically 0.96
<35 ms
DFT: -50 dB at f = n × f
IEC 61850 IEC 60617
identification identification
HREFPDIF dIoHi>
Protection functions
n
Typical Maximum
41 ms 45 ms
, where n = 2, 3, 4, 5, ...
n
ANSI/IEEE C37.2
device number
87NHI
759