**5. Conclusions**

The paper presented a novel procedure to assess the formation, and to identify the location, of dry bands based on the automatic identification of selected areas and the calculation of the associated average temperature. In particular, the division of sub zones and left and right areas increase the detection capabilities from the IR recordings.

The proposed methodology has been applied on artificially polluted insulator surfaces under a ramp-shape voltage test in clean-fog chamber and the results of the analysis show that the two features are clearly a function of the insulator surface design and the pollution level applied to the insulator surface (ESDD). The automatic identification of the insulator boundaries allows an accurate estimation of the average local temperature, disregarding any area related to the surrounding environment. In addition, the choice of selected area on the trunks permits to take into account the presence of the sheds that can perturb the wetting action of the fog. The evaluation of local average temperature on symmetrical areas along the vertical axis permits to confirm the correct uniform application of a pollution layer and to warn about possible localized defects on the surface.

Pollution level is one of the most important parameters in insulator design selection. Any increased discharge activity caused by pollution on a specific insulator design affects the life expectancy, which is a key parameter that network operators have to asses in the adoption of a new design. Since one of the major causes of degradation is caused by continuous discharges on the polymeric insulator surfaces, this proposed new procedure based on the analysis of IR video recordings and on the spatial and time characterization of dry bands may provide an indication of the selection of the most appropriate surface design to maximize insulator-life extension.

The results show it is possible to estimate the location, extension and development-over-time of dry bands, and these features offer good indications to select the appropriate design for dry-band control. **Author Contributions:** Conceptualization, M.A. and A.M.H.; writing—original draft preparation, M.A.; writing—review and editing, M.A. and A.M.H.; visualization, N.B.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
