Wheeler incremental inductance rule

The incremental inductance rule, attributed to Harold Alden Wheeler[1] by Gupta[2]: 101  and others[3]: 80  is a formula used to compute skin effect resistance and internal inductance in parallel transmission lines when the frequency is high enough that the skin effect is fully developed.

Skin effect resistance is assumed to be equal to the reactance of the internal inductance.

Gupta[2]: 67  gives a general equation with partial derivatives replacing the difference of inductance.

Wadell[4]: 27  and Gupta[2]: 67  state that the thickness and corner radius of the conductors should be large with respect to the skin depth.

In the top figure, if and then the internal inductance is and the skin effect resistance is