ABB RELION Series Technical Manual page 501

1MRS758755 A
REC615 and RER615
Technical Manual
W
ρ
earth
658
f
n
GUID-2FE803A9-203E-44ED-8153-4F5903233736 V1 EN
the equivalent depth [m] of the earth return path
ρ earth resistivity [Ωm]
earth
r
en
2 2
3
r 3 a a
⋅ ⋅ ⋅
12 23
GUID-F7698D7C-ADCC-4555-A3C7-05DAEB3FBA70 V2 EN
the 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-4FEEEF83-D0D7-49A8-90F6-453E28AE27B2 V2 EN
Figure 256: 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
protected feeder is known, the setting value can be calculated.
Ph capacitive React
=
(
ω
n
GUID-3D723613-A007-47ED-B8D7-F9D55C5FBF38 V2 EN
Protection related functions
2
a
31
1
)
C
⋅
0 F
Section 5
= Ph leakage Ris.
L0F
of the
0F
(Equation 63)
495