The aim of this paper is to investigate the various effects of climate conditions on outdoor insulators in coastal areas as a result of saline contamination under acidic and normal cold fog, determining significant electrical and physico-chemical changes on the insulator surface and considering the effect of discharge current, electric field distribution and surface roughness. To replicate similar conditions near the shoreline, experimental investigations have been carried out on insulation materials with the combined application of saline contamination and acidic or normal cold fog. The test samples included silicone rubber (SiR), ethylene propylene diene monomer (EPDM) and high-density polyethylene (HDPE), which were used as reference. The materials are of the same composition as those used in real-life outdoor high voltage insulators. All samples were aged separately in an environmental chamber for 150 h for various saline contaminations combined with acidic and normal cold fog, and were generated by means of the adopted experimental setup. This analysis represented conditions similar to those existing near the shoreline exposed to saline and acid spray during winter and early spring. Electric field and discharge current along polymeric samples were examined under acidic and normal cold fog. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopic (SEM) were used to probe the physico-chemical changes on the samples surface and investigate the hydrophobicity recovery property after aging tests. Finally, a comparative study was carried out on polymeric samples before and after being exposed to the acidic and normal cold fog based on the results obtained from the experiment. Research data may provide references for the better prediction of surface degradation as well as for the better material coating and design of external insulation.

A suitable, non-standard method for artificial pollution testing using simulated acid rain pollution in a laboratory was developed in this work. The method is applicable to a wide range of climatic conditions and rain acidities. The established method adopts the solid layer principle in the preparation and application of acid rain of various pollution severities to test insulators. Glass cap and pin insulators were contaminated, assembled into strings of two discs and flashover tests carried out on the strings at different orientation angles. The frequency of flashover occurrence, maximum withstand degree of pollution, effect of pollution severity, and effect of orientation angle were investigated. Test results showed that the orientation angle plays little or no role in the flashover of the insulators under dry conditions. Under wet conditions, the insulators performed better when inclined. Flashover voltage was observed to be inversely proportional to time while the time to flashover was inversely proportional to the pollution severity. The probability of flashover increases with an increase in voltage for a fixed pollution severity or increase in pollution severity for a fixed voltage level. This indicates that the probability of flashover is a function of the product of pollution severity and voltage.