ABB RELION REX640 Technical Manual page 1118

Section 5
Protection related functions
1112
ρ Earth resistivity [Ωm]
earth
r
en
2 2
3
r 3 a a
⋅ ⋅
12 23
Equivalent radius [m] for conductor bundle
r Radius [m] for single conductor
a Distance [m] between phases x and y
xy
Ph leakage Ris and Ph capacitive React settings
The Ph leakage Ris and Ph capacitive React settings are used for improving fault
distance estimation accuracy for earth faults. They are critical for an accurate fault
location in unearthed networks. In other types of networks they are less critical. The
Ph leakage Ris setting represents the leakage losses of the protected feeder in terms of
resistance per phase. The Ph capacitive React setting represents the total phase-to-
earth capacitive reactance of the protected feeder per phase. Based on experience, a
proper estimate for Ph leakage Ris should be about 20...40 ⋅ Ph capacitive React.
GUID-C2606346-FBE5-4F8E-8B3D-B61B2152ABF9 V1 EN
Figure 603: Equivalent diagram of the protected feeder. R
The determination of the Ph capacitive React setting can be based either on network
data or measurement. If the total phase-to-earth capacitance (including all branches)
per phase C of the protected feeder is known, the setting value can be calculated.
0F
Ph capacitive React
=
( ω
GUID-3C14B012-81F4-495A-A983-E390CAB7D40C V1 EN
In case of unearthed network, if the earth-fault current produced by the protected
feeder I is known, the setting value can be calculated.
ef
Ph capacitive React
=
GUID-D97BF36F-3E8C-45BC-8567-74145719C52C V1 EN
U Phase-to-phase voltage
xy
2
a
⋅
31
1
C
)
⋅
n 0 F
⋅ 3 U
xy
I
ef
1MRS759142 C
= Ph leakage Ris.
L0F
(Equation 277)
(Equation 278)
REX640
Technical Manual