Stevenson J. Power system analysis

160

CHAPTER

SERIES IMPEDANCE OF TRANSMISSION LINES

where

m is the distance between conductors. Both Dm and Ds must be in the

same units, usually either meters or feet. The GMR found in tables is an

equivalent

s' which accounts for skin eect where it is appreciable enough to

aect inductance. Of course, skin eect is greater at higher frequencies for a

conductor of a given diameter. Values of

s listed in Table A.3 of the Appendix

are for a frequency of 60 Hz.

Some tables give values of inductive reactance in addition to GMR. One

method is to expand the logarithmic term of Eq. (4.46), as follows:

XI,

2.022

10 -

In - + 2.022 x 1



ill

Djmi

(4.47)

If both

and Dill

arc in feet, the rst term in Eq. (4.47) is th