“Electric transmission line” means any electric powerline carrying electric power from a thermal powerplant located within the state to a point of junction with any interconnected transmission system. “Electric transmission line” does not include any replacement on the existing site of existing electric powerlines with electric powerlines equivalent to such existing electric powerlines or the placement of new or additional conductors, insulators, or accessories related to such electric powerlines on supporting structures in existence on the effective date of this division or certified pursuant to this division.