We rely on software like PLS-CADD for transmission line design, but understanding the underlying math makes you a better engineer. In this post, we break down the exact hyperbolic catenary equations and 4th-order stress-strain polynomials used in the Experimental Plastic Elongation (EPE) method. Follow a step-by-step hand calculation for a Drake ACSR conductor under NESC extreme loading, and see exactly how the fundamental math compares to industry-standard software outputs.