Are you a distribution engineer? Get William Kersting's book on distribution systems:
https://www.amazon.com/gp/product/B074N2D241/ref=dbs_a_def_rwt_hsch_vapi_tkin_p1_i0
Kersting developed WindMil software. The equations of R, X, B, and G of transmission lines are derived are covered in that book, included insulated conductors.