Table 516: Positive-sequence impedance values for typical 10/20 kV conductors, “Flat” tower
configuration assumed
Name R1 [Ω/km] X1 [Ω/km]
Al/Fe 36/6 Sparrow 0.915 0.383
Al/Fe 54/9 Raven 0.578 0.368
Al/Fe 85/14 Pigeon 0.364 0.354
Al/Fe 93/39 Imatra 0.335 0.344
Al/Fe 108/23 Vaasa 0.287 0.344
Al/Fe 305/39 Duck 0.103 0.314
Table 517: Positive-sequence impedance values for typical 33 kV conductors, “Flat” tower
configuration assumed
Name R1 [Ω/km] X1 [Ω/km]
ACSR 50 sq.mm 0.529 0.444
ACSR 100 sq.mm 0.394 0.434
ACSR 500 sq.mm 0.0548 0.346
Zero-sequence impedance values
Location of earth faults requires both positive-sequence and zero-sequence
impedances. For short circuit faults, zero-sequence impedances are not required.
The positive-sequence impedance per unit values for the lines are typically known or
can easily be obtained from data sheets. The zero-sequence values are generally not as
easy to obtain as they depend on the actual installation conditions and configurations.
Sufficient accuracy can, however, be obtained with rather simple calculations using
the following equations, which apply per phase for symmetrically transposed three-
phase aluminium overhead lines without ground wires.
R Hz R km
0
50 1 0 14804[ ] . [ / ]≈ + Ω
GUID-087D1F51-4C8C-4CF4-ACE5-9F43AF0DD3FC V1 EN (Equation 60)
R Hz R km
0
60 1 0 17765[ ] . [ / ]≈ + Ω
GUID-C33EC003-0DA2-4FFC-9496-586D7342DAF6 V1 EN (Equation 61)
X
w
r
km
n
en
0
4
2 10 3 0 25≈ ⋅ ⋅ ⋅ +
−
ω
ln . [ / ]Ω
GUID-6850481D-094B-4FA0-9E73-39DCC6C49BCC V2 EN (Equation 62)
R
1
conductor AC resistance [Ω/km]
Section 5 1MRS758755 A
Protection related functions
494 REC615 and RER615
Technical Manual
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