ABB RELION REX640 Technical Manual page 1208

Protection related functions
actual installation configuration. This minimizes the fault location errors caused by
inaccurate settings.
The positive-sequence reactance per unit and per phase can be calculated with a
following approximation equation which applies to symmetrically transposed three-
phase aluminium overhead lines without ground wires.
≈
X
1
ω
n
a
en
a
xy
r
Figure 689: Typical distribution line tower configurations
Example values of positive-sequence impedances for typical medium voltage
overhead-lines are given in the following tables.
Table 1152: Positive-sequence impedance values for typical 11 kV conductors,
"Flat" tower configuration
Name
ACSR 50 SQ.mm
ACSR 500 SQ.mm
Table 1153: Positive-sequence impedance values for typical 10/20 kV conductors,
"Flat" tower configuration
Name
Al/Fe 36/6 Sparrow
Al/Fe 54/9 Raven
Al/Fe 85/14 Pigeon
Table continues on the next page
1208
 
a
−
⋅ ⋅ + Ω
4
en
10  2 ln 0 5 . [ / 
ω
n
 
r
2 × π × f , where f
n
( )
⋅ ⋅
3
a a a
12 23 31
the geometric average of phase distances [m]
distance [m] between phases x and y
radius [m] for single conductor
km ]
= fundamental frequency [Hz]
n
R1 [Ω/km]
0.532
0.0725
R1 [Ω/km]
0.915
0.578
0.364
1MRS759142 F
(Equation 306)
X1 [Ω/km]
0.373
0.270
X1 [Ω/km]
0.383
0.368
0.354
REX640
Technical Manual