A loadability policy established on the basis of the Overhead Transmission Lines (OHLs) static thermal rating is referred to the worst-case conditions (i.e. zero wind speed). Whilst it reduces the potential misoperations, at the same time it implies an underuse of the electrical infrastructures. The transition towards smart grids architectures calls for a reliable exploitation of these assets in order to improve the power system efficient operating. Such considerations are at the basis of the so called Dynamic Line Rating (DLR) paradigm which is incorporated in the smart grid vision. An open issue in this topic is the need to take under control the weather conditions and hence the OHL temperature along the entire OHL length. To overcome the pointed out issue, thanks also to the quick development of Wide Area Measurement System (WAMS) technology, an innovative approach can be pursued. OHL thermal dynamic can be derived from the measurement of the voltage and current synchrophasors at the OHL ends, so overcoming the need of spatially distributed sensors DLR system. It is worth noting anyway that in this case it deals with an average estimate of the OHL conductor temperature and not a punctual one as obtained by using distributed devices. With regard to the described framework, the present paper presents the first experimental findings obtained in an in-field DLR campaign carried out on the Italian power system. A recently proposed DLR estimation algorithm, never applied in reallife WAMS environment, is selected for the purpose. From its response, interesting considerations and valuable modifications to apply to the estimation algorithm mathematical framework are suggested in the work. The fundamental characteristics that the latter needs to have are well posed in evidence. The discussed experimental outcomes are referred to a real-life OHL included into the Italian WAMS monitoring program.