HIGH VOLTAGE INSULATOR COATINGS
SI-COAT 570 HVIC High Voltage Insulator Coating for Transmission and Distribution Infrastructure
SI-COAT 570 HVIC is a room temperature vulcanising RTV silicone high voltage insulator coating manufactured by CSL Silicones and distributed exclusively across Sub-Saharan Africa by Technical Solutions Supplies. It prevents pollution induced flashover on high voltage insulators, transformer bushings, switchgear, busbars and substation equipment by maintaining a permanently hydrophobic surface that stops moisture from forming a conductive film over contamination deposits.
One application before energisation or during a planned maintenance outage delivers more than 15 years of maintenance free flashover protection in the most contaminated environments across Sub-Saharan Africa.
The Flashover Problem That Costs Utilities Millions Every Year
Pollution induced flashover is one of the most disruptive and costly failure modes in transmission and distribution infrastructure. The mechanism follows a predictable sequence that utility engineers across Southern Africa recognise well.
Contamination accumulates on insulator surfaces continuously. Coastal salt aerosol from KwaZulu-Natal and the Western Cape, industrial emissions from the Highveld power corridor, dust from mining operations and arid terrain in the Northern Cape and Namibia all deposit on porcelain, glass and composite insulator surfaces. In dry conditions this contamination presents no immediate risk. When moisture from rain, fog, dew or condensation contacts the contaminated surface, it dissolves soluble salts and chemicals to form a conductive electrolytic film across the insulator.
Leakage current flows across this film. The current generates heat, dries sections of the surface unevenly and creates dry band arcing. That arcing progressively tracks and erodes the insulator surface until it culminates in a full flashover, tripping the line, damaging equipment and in severe cases destroying insulators, transformers and associated plant.
The direct cost of a flashover event on a major substation runs from tens of thousands to tens of millions of rand depending on the equipment affected. The indirect costs in unplanned generation disconnection, emergency maintenance mobilisation and supply interruption penalties extend the total impact significantly further.
SI-COAT 570 HVIC stops this failure mechanism entirely by making the insulator surface permanently hydrophobic, preventing moisture from forming the conductive film that activates contamination into leakage current pathways.
Key Performance Properties
Permanent hydrophobicity is the fundamental performance property of SI-COAT 570 HVIC. The cured silicone film causes water to bead and run off the insulator surface rather than spreading into a continuous conductive film. Moisture cannot activate the contamination layer because it cannot spread uniformly across the hydrophobic surface. Leakage current does not develop. Dry band arcing does not occur. Flashover cannot follow.
Hydrophobicity transfer to contamination is the property that distinguishes RTV silicone coating from every other insulator protection method. Low molecular weight silicone components migrate from the cured film into contamination deposits that accumulate on the coated surface over time, making the contamination layer itself hydrophobic. The coating continues to prevent flashover as pollution builds rather than being overwhelmed by accumulating contamination.
Live-line application capability means SI-COAT 570 HVIC applies to energised high voltage equipment by trained live-line applicators without planned outages. This eliminates the outage scheduling constraints that make conventional insulator maintenance programmes difficult to execute on loaded networks.
Service life exceeds 15 years under field conditions in contaminated environments including coastal, industrial, desert and mining environments. Field performance data from utilities in South Africa, Namibia and across Sub-Saharan Africa confirm 15 year plus performance across the full range of contamination environments encountered on the continent.
Standards compliance covers IEEE 1523, the IEEE Guide for the Application, Maintenance and Evaluation of RTV Silicone Rubber Coatings for Outdoor Ceramic Insulators, and the relevant IEC standards for RTV coatings on outdoor high voltage insulators.
Where SI-COAT 570 HVIC Is Used
Transmission substations on South Africa’s national grid and the SAPP regional interconnection face contamination from coastal salt aerosol, industrial pollution and dust depending on their location. SI-COAT 570 HVIC applied before energisation on new substation builds, or during planned outages on existing infrastructure, eliminates flashover risk for 15 or more years.
Renewable energy substations on wind and solar farms in the Northern Cape, Western Cape and Eastern Cape operate in high dust and coastal salt environments. SI-COAT 570 HVIC applied from commissioning protects the generation and transmission investment for the full expected service life of the facility.
Distribution infrastructure in coastal towns, industrial zones and mining regions across South Africa, Namibia, Zambia and the broader Sub-Saharan network faces contamination that drives flashover frequency on unprotected distribution insulators. SI-COAT 570 HVIC provides cost effective protection across the full distribution voltage range from 11kV through to 765kV.
Transformer bushings are among the highest consequence insulation components in a substation. A bushing flashover can result in transformer fault, fire or destruction. SI-COAT 570 HVIC applied to transformer bushings prevents contamination induced flashover on the most expensive and difficult to replace equipment in the substation.
Switchgear and busbars in outdoor and indoor substation environments face contamination penetration through ventilation and cable entry points. SI-COAT 570 HVIC applied to insulated surfaces prevents moisture activation of internal contamination deposits and eliminates tracking and arcing failure.
Application Summary
Substrate: porcelain, toughened glass and composite high voltage insulators, transformer bushings, switchgear insulation and busbars. Application timing: pre-energisation on new builds, planned outage or live-line on existing in-service equipment. Application method: brush or spray by trained applicators. System: single component RTV silicone, no mixing required. Cure: ambient temperature moisture cure, tack free within 2 hours, full cure within 24 hours. Hydrophobicity: permanent, transfers to contamination layer over time. Live-line capability: yes, by trained live-line applicators using approved work methods. Voltage range: 11kV distribution through to 765kV extra high voltage transmission. Service life: 15 or more years under Sub-Saharan African field conditions. Standards: IEEE 1523 and relevant IEC standards for RTV insulator coatings.
SI-COAT 570 HVIC vs Conventional Insulator Maintenance Methods
Our feature on RTV silicone coating technology was published in ESI Africa’s 2026 Powering Mines & Industry Volume 6, exploring how utilities across Sub-Saharan Africa are reducing flashover incidents and maintenance burdens through protective coating solutions.
Silicone grease requires reapplication every 6 to 12 months in contaminated environments, absorbs contamination into the grease layer reducing effectiveness over time, and slumps and migrates in hot conditions.
Live line washing removes contamination temporarily but does not change the hydrophilic surface property of the insulator. Contamination reaccumulates immediately, the process carries inherent flashover risk during washing, and it generates an ongoing operational cost with no end point.
Composite insulator replacement provides equivalent hydrophobicity on new infrastructure but requires full insulator replacement including line outages, mechanical handling and structural work at a cost significantly higher than coating the existing population.
SI-COAT 570 HVIC delivers a single application with permanent hydrophobicity, hydrophobicity transfer to contamination deposits, 15 year plus service life, live-line application without outages and a fraction of the cost of insulator replacement.
For full technical specifications and application guidelines, download the Technical Data Sheet below or contact Technical Solutions Supplies directly.
Phone: 031 002 7376 Email: sales@tssupplies.co.za
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