Freezing rain occurs when it rains or drizzles at temperatures below 0ºC or when precipitation falls on subcooled surfaces. The measurements of the conductor temperature and the catenary angle (inclination) must be used to detect conductor elongation caused by ice – icing. Mathematical model takes into account the mechanical properties and physical characteristics of the conductor as well as its own conductor mass, and the length of the span. The parameters of the catenary curve at the freezing rain temperature represent the initial state of the activation of the ICE-ALARM computer algorithm. The model monitors the elongation/sag of the conductor and re-calculates the data according to the change in the measured angle.