*Article* **Is the Dry-Band Characteristic a Function of Pollution and Insulator Design?** †

#### **Maurizio Albano \*, A. Manu Haddad and Nathan Bungay**

School of Engineering, Cardi ff University, The Parade, Cardi ff CF24 3AA, UK; Haddad@cardi ff.ac.uk (A.M.H.); BungayN@cardi ff.ac.uk (N.B.)

**\*** Correspondence: AlbanoM@cardi ff.ac.uk; Tel.: +44-292-087-0672

† This paper is an extended version of our paper published in 2018 IEEE International Conference on High Voltage Engineering (ICHVE 2018), Athens, Greece, 10−13 September 2018; 0-TM5-5.

Received: 22 July 2019; Accepted: 17 September 2019; Published: 21 September 2019

**Abstract:** This paper assesses the dry-band formation and location during artificial pollution tests performed on a 4-shed 11kV insulator with conventional and textured surface designs in a clean-fog chamber and with the application of a voltage ramp-shape source. The di fferent designs present the same overall geometrical dimensions, but the textured ones are characterized by the application of a patented insulator surface design. Three pollution levels, extremely high, high and moderate, were considered. A newly developed MATLAB procedure is able to automatically recognize the perimeter of the insulator, the trunk and shed areas on infra-red recordings. In addition, using the vertical axis identification, all trunks are subdivided into zones and into left and right areas, significantly increasing the capability of abnormalities detection. Any temperature increase within these areas enables to detect the appearance and the extension of dry bands. The results of the analysis of the statistical location and extension development over time of the dry bands during these set of comparative tests show a clear distinction between designs and pollution levels. These results may offer interesting design guidelines for dry-band control.

**Keywords:** insulator design; dry band; pollution
