Ice detecting and measuring technologies used and developed for high voltage transmission lines are introduced in this paper. The Icing Rate Meter developed by Hydro-Quebec, working with the magnetostriction principle and regulated by an electronic control system is analyzed and the resonant piezoelectric transducers operated by a microprocessor-controlled electronic circuitry is also analyzed in great detail. It shows that the Icing Rate Meter (IRM) developed by Hydro-Quebec can record the occurrence and duration of icing events, but has two limitations: information on changes in the rate of icing within each hour is lost and the amount of time consumed during heating cycles is not taken into account.A resonant piezoelectric ice detector can automatically and distinctly sense ice and water films up to 0.5mm thick. It is a smart ice detection system, which might be used widely.