The Role of Infrared Electrical Imaging
Infrared electrical imaging, or thermography, is a critical inspection tool for utilities and industrial operators. It uses thermal cameras to detect heat generated by electrical resistance. This helps spot hot spots on high-voltage equipment before they cause failures. The method requires no contact. As a result, technicians can scan live, energised equipment without shutting down a line or substation. This makes infrared electrical imaging one of the few inspection methods utilities can run on a routine schedule. It does not disrupt supply.
Engineers commonly use temperature difference, or Delta T, to judge how urgent a finding is. Industry guidance from NETA flags an immediate priority in two cases. The first is when a component runs 15°C hotter than a similar component under the same load. The second is when a component runs 40°C above ambient air temperature. At that level of temperature rise, failure probability climbs sharply within days rather than months. Consequently, infrared surveys form part of most utilities’ predictive maintenance programmes today.
What Infrared Imaging Actually Finds on Insulators
On insulators, a hot spot rarely appears at random. It usually points to one underlying cause: contamination breaking down the surface’s ability to shed moisture. Salt, industrial dust, and fog particles settle on an insulator over time. In addition, moisture on the surface combines with these particles to form a thin, conductive film. Once that film forms, leakage current begins to flow. As a result, Joule heating dries the film unevenly, leaving narrow, non-conductive dry bands between wet sections.
The voltage that would normally spread across the whole surface then concentrates across these dry bands. The local electrical field eventually exceeds the breakdown strength of air, roughly 3 kV per millimetre. Therefore, a spark bridges the gap. Engineers call this dry band arcing. Consequently, it generates heat, ultraviolet radiation, and ozone. Furthermore, repeated arcing degrades ceramic glazes and silicone rubber housings over time. Left unchecked, dry band arcing can ladder across the remaining wet surface. This can trigger a full flashover, taking a line or substation out of service.
This is precisely the sequence infrared imaging picks up. However, the camera does not see contamination directly. It sees only the heat that contamination-driven arcing produces. A thermal scan therefore flags the symptom accurately, but it cannot remove the pollution layer causing it.
Why SI-COAT 570 HVIC Addresses the Root Cause
SI-COAT 570 HVIC is an RTV silicone coating that keeps the insulator surface hydrophobic. Rather than letting contamination and moisture combine into a continuous conductive film, the coating causes water to bead and shed. In addition, it transfers hydrophobic properties into the pollution layer itself. Without a continuous film, leakage current cannot establish. Consequently, dry bands cannot form, and there is no arc for a thermal camera to detect.
South Africa does not run live insulator washing programmes. As a result, this distinction matters more locally than in regions where crews wash contamination off energised lines. TSS’s territory typically relies on scheduled outages or dry-cleaning methods to manage contamination instead. Therefore, a coating that prevents the conductive film from forming in the first place reduces how often that maintenance is needed at all.
The goal, however, is not a coating that makes infrared scans look better. It is a coating that gives thermographers fewer contamination-driven findings to flag on every subsequent survey. However, utilities in coastal and industrial zones see this benefit most clearly, since pollution accumulates fastest there. Coastal substations in South Africa remain a strong example of this. RTV silicone chemistry has already demonstrated multi-decade hydrophobicity retention at a 132kV coastal substation coated in 2004. The site recorded zero flashovers since, even through a severe pollution event two years later.
Applying This Across TSS’s Territory
Utilities and mining operators across South Africa, Zambia, DRC, Tanzania, and Namibia run infrared surveys on transmission lines and substations. They also run these surveys on mine-owned infrastructure as part of routine maintenance. SI-COAT 570 HVIC applies to porcelain, glass, and composite insulators using airless spray, brush, or roller. Technicians apply it at 300 to 500 microns DFT. In addition, it restores hydrophobicity on aged composite insulators that have already lost their water-repellent surface. Grease-based alternatives need reapplication every 6 to 12 months. SI-COAT 570 HVIC, however, delivers many years of protection from a single application.
Frequently Asked Questions
What causes dry band arcing on outdoor electrical insulators?
Dry band arcing happens when contamination and moisture form a conductive film on an insulator. Leakage current then dries that film unevenly. Therefore, the dry, high-resistance bands that form concentrate voltage and spark across the gap.
How can maintenance teams identify signs of dry band arcing?
Infrared thermography is the standard detection method. It picks up the heat that leakage current and arcing generate. Therefore, teams can act before the damage progresses to a full flashover.
Does SI-COAT 570 HVIC prevent flashover?
Yes. It keeps the insulator surface hydrophobic. Consequently, it prevents the conductive film that leads to dry band arcing and flashover in the first place.
Is dry band arcing a bigger risk in coastal areas?
Yes. Salt contamination accelerates conductive film formation. This is why coastal substations, in particular, see more frequent flashover activity without a protective coating in place.
How long does SI-COAT 570 HVIC last once applied?
SI-COAT 570 HVIC typically lasts 15+ years under severe outdoor conditions. Furthermore, hydrophobicity has been confirmed at coastal sites 18 years after application.
Ready to reduce the contamination-driven findings on your next infrared survey? Contact TSS for technical specifications and supply solutions, or visit /faq/ for answers to more questions.
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