Admittance-Based Earth-Fault Protection Efpadm (Ansi 21Ny) - ABB RELION REX640 Technical Manual

Protection functions
4.2.3.10 Technical data
Table 563: INTRPTEF Technical data
Characteristic
Operation accuracy (Uo criteria with transi-
ent protection)
Operate time accuracy
Suppression of harmonics
4.2.4 Admittance-based earth-fault protection EFPADM (ANSI
21NY)
4.2.4.1 Identification
Function description
Admittance-based earth-fault pro-
tection
4.2.4.2 Function block
Figure 278: Function block
4.2.4.3 Functionality
The admittance-based earth-fault protection function EFPADM provides a selective
earth-fault protection function for high-resistance earthed, unearthed and
compensated networks. It can be applied for the protection of overhead lines
as well as with underground cables. It can be used as an alternative solution
to traditional residual current-based earth-fault protection functions, such as
the IoCos mode in DEFxPDEF. Main advantages of EFPADM include a versatile
applicability, good sensitivity and easy setting principles.
EFPADM is based on evaluating the neutral admittance of the network, that is, the
quotient:
Yo
=
The measured admittance is compared to the admittance characteristic boundaries
in the admittance plane. The supported characteristics include overadmittance,
oversusceptance, overconductance or any combination of the three. The
490
Io − / Uo
Value
Depending on the frequency of the measured
current: f ±2 Hz
n
±1.5% of the set value or ±0.002 × U
±1.0% of the set value or ±20 ms
DFT: -50 dB at f = n × f
IEC 61850 IEC 60617
identification identification
EFPADM Yo> ->
1MRS759142 F
o
, where n = 2, 3, 4, 5
n
ANSI/IEEE C37.2
device number
21NY
(Equation 56)
REX640
Technical Manual