Since ever the prediction of insulator contamination has always been a hard task due to the high number of variables. The prediction is furthermore complicated by local meteorological conditions that have a not negligible impact on contamination accumulation on insulator surfaces. Contamination prediction can be assessed with two methods.

The first is based on a priori analysis without resorting contamination measurements but with specific tools that can assess for each specific location of a territory the generation of contamination by reproducing the emission of contaminants, from both anthropogenic and natural sources, the transportation in the air and then the deposition on the insulator surfaces considering cleaning effects as well. The second is based on a posteriori analysis on direct measurements with the aim to set a map of the contamination.

In this case different measurements in different periods of the years and for multiple years are necessary to have at least a significant number of specimens for each measurement point. This implies a lot of efforts in terms of times and specific statistical analysis, because samples coming from different measurements points needs to be properly processed in order to achieve the representative contamination value. Furthermore, specific spatial interpolation tools shall be used to reach the final contamination map.

Contamination of “Type A” or of “Type B” represents the two standardized contamination processes and they sometimes both occur on the same insulator, as for examples lines and stations along the coasts or near specific industrial sites where long drought periods along the year can occur. Last but not least, how to rearrange maps valid for AC to DC insulators is another aspect scarcely investigated.

In conclusion, there a few general questions that should be considered when developing a contamination map, particularly: which is the validity of a contamination map? How it can be extended to insulator types different than that used for the measurements?
In this paper an illustration of the mapping methodology used in Italy that took about 4 years is illustrated: from 2016 to 2020 considering the design stage, the in-field samplings and data post processing analysis.

This contribution will be particularly useful for the upcoming CIGRE JWG C4/A3/B2/B4.75 “Guide to procedures for the creation of contamination maps required for outdoor insulation coordination” in which one of the aims is to both collect mapping procedures and set common rules when a mapping contamination process is required.