Inductance calculation for three-phase overhead transmission lines derives the flux linkage of each phase conductor from the currents in all conductors and their geometric mean distances, yielding an inductance formula proportional to the logarithm of the ratio between the geometric mean distance (GMD) among phase conductors and the geometric mean radius (GMR, or self-distance) of each conductor or conductor bundle. Line transposition (cyclically rotating conductor positions along the line) and conductor bundling (using multiple sub-conductors per phase to increase effective radius) are structural techniques that respectively balance mutual inductance across phases and reduce self-inductance and surface electric field stress; unbalanced ground/earth-return current is modeled via image conductors located at an empirically derived depth beneath the line. This belongs to power systems engineering (transmission line parameter modeling), a foundational component of steady-state and transient power system analysis.
Inductance calculation for three-phase overhead transmission lines derives the flux linkage of each phase conductor from the currents in all conductors and their geometric mean distances, yielding an…