
13Theory of Distributed-Parameter Circuits and Impedance
1.2.2.2.3 Carson’s Earth-Return Impedance
There were no computers in the 1920s; thus, it was impossible to use
Pollaczek’s impedance [8]. Carson derived the same formula as Pollaczek,
neglecting the earth permittivity (i.e., ε
e
= ε
0
in Equation 1.23), and he fur-
ther derived a series expansion of the innite integral in Equation 1.21. The
details of Carson’s expansion formula are explained in many publications,
for example, Reference 11.
1.2.2.2.4 Admittance
Almost always, the following well-known admittance is used in steady-state
and transient analyses of overhead lines:
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nYjCjPP
D
d
ij ...