Arbitrary cross-section conductor

Schelkunoff s impedance assumes that a conductor is circular or cylindrical. In reality, there exist many conductors of which the cross-section is not 

Reference [21] shows an approximation of a conductor with T or hollow rectangular shape by a cylindrical shape conductor. Although the internal impedance of a conductor with an arbitrary cross-section can be accurately evaluated by a finite-element method of numerical calculation, it requires a lot of time and memory. Either an analytical formula or an efficient numerical method needs to be developed. 

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It is clear that this equation becomes identical to Equation 1.3 in a low-frequency region when assuming a small co and to Equation 1.6 when assuming a large co. It is noteworthy that Equation 1.7 is applicable to an arbitrary cross-sectional conductor, not necessarily to a circular or cylindrical conductor, because the equation is defined by the cross-sectional area S and the circumferential length of the conductor / but not by the inner and outer radii. 

Schelkunoff s impedance assumes that a conductor is circular or cylindrical. In reality, many conductors exist withcross sections are not circular or cylindrical. The internal impedance of a conductor with an arbitrary cross section was derived in Reference 19, which has been implemented in the EMTP cable parameters program [20]. 

Ametani, A. and I. Fuse. 1992. Approximate method for calculating the impedances of multi conductors with cross-section of arbitrary shapes. Elect. Eng. Jpn. 111(2) 117-123. 

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