South Africa recently passed 200 consecutive days without load shedding. Eskom credited disciplined planned maintenance as the primary driver of that milestone. Scheduled insulator washing is a core part of that maintenance discipline. In KwaZulu-Natal and Gauteng, utilities wash insulators during planned winter outages to remove contamination before the wet season. However, insulator washing alone does not change the surface behaviour of the insulator. Once contamination returns, the electrical risk returns with it.
What Insulator Washing Actually Achieves
Insulator washing removes accumulated contamination from porcelain, glass and composite insulator surfaces during a planned maintenance outage. In South Africa, this typically occurs as a scheduled winter programme, with stations taken offline in KwaZulu-Natal and Gauteng ahead of the summer rains. The process removes coastal salt deposits, industrial fallout, dust from mining operations and other surface contaminants that accumulate throughout the year.
Consequently, surface conductivity drops immediately once contamination is removed. A clean insulator surface cannot activate leakage current, and flashover risk drops sharply following a thorough wash. For utilities operating under Eskom’s maintenance recovery framework, scheduled insulator washing is therefore a non-negotiable element of the annual maintenance programme.
However, washing is a corrective intervention rather than a preventative one. Once the station returns to service, contamination begins to accumulate again. In coastal environments like the KwaZulu-Natal coast, industrial zones on the Highveld, and mining regions in the Northern Cape and Limpopo, contamination can return to significant levels within weeks of washing.
Why Contamination Returns Faster Than Wash Cycles Allow
The fundamental limitation of insulator washing as a standalone strategy is that it does not change the surface properties of the insulator. Porcelain and glass insulators are inherently hydrophilic — they attract and spread moisture across their surfaces in a continuous film. This surface behaviour does not change regardless of how thoroughly or how frequently washing is performed.
When contamination redeposits on a hydrophilic insulator surface and moisture contacts it, dissolved soluble salts create a conductive electrolytic film. Rain, fog, dew or condensation all trigger this process. Leakage current flows. Dry band arcing develops. In severe contamination events, this progression culminates in flashover even on recently washed insulators.
Furthermore, South Africa’s contamination environments are aggressive. Coastal salt aerosol from the KwaZulu-Natal coast and the Western Cape deposits rapidly on insulator surfaces. Industrial pollution from the Highveld power corridor, cement dust, and mining fallout all contribute to elevated surface conductivity well before the next scheduled wash cycle.
Specifically, the period between annual wash cycles represents the highest risk window for contamination-induced flashover. Washing reduces the risk at the start of that window. However, the insulator’s hydrophilic surface means that risk rebuilds continuously as contamination accumulates and wet weather events occur.
The Surface Behaviour Problem That Washing Cannot Solve
Flashover does not occur because contamination exists on the surface alone. Instead, it develops when contamination becomes electrically active in the presence of moisture. The critical condition is water film formation — when moisture spreads across the insulator surface as a continuous conductive layer rather than as discrete droplets.
Insulator washing removes the contamination that drives this process. However, it does not address the surface property that enables it. A freshly washed porcelain insulator remains hydrophilic. As a result, the next rain event or fog episode will form a water film across the surface regardless of how recently it was cleaned. If contamination has already begun to redeposit, that water film will activate it.
This is why utilities that rely on washing alone remain in a reactive maintenance position. The wash programme resets the contamination level but does not reduce the insulator’s susceptibility to water film formation. Therefore, the risk cycle repeats regardless of how disciplined the washing schedule is. For a detailed explanation of how flashover develops and why hydrophobicity prevents it, read our article on silicone insulator coating flashover prevention.
How Hydrophobic Coatings Reduce the Need for Insulator Washing
The solution is not to abandon insulator washing. Scheduled washing remains a sound maintenance practice for heavily contaminated environments. Rather, the opportunity is to change the surface behaviour of the insulator so that contamination struggles to bond in the first place, and so that the cleaning that does occur happens naturally.
When an insulator surface repels water, moisture forms discrete droplets rather than a continuous film. Consequently, contamination remains electrically inactive even when present. Leakage current does not develop. Dry band arcing cannot occur. Critically, because nothing bonds easily to a hydrophobic surface, even light rainfall effectively self-cleans the insulator — washing loose contamination away without a maintenance team, without a planned outage, and without cost.
Silicone-based high voltage insulator coatings achieve this by altering the surface energy of the insulator. The cured silicone film creates a permanently hydrophobic surface that causes water to bead and run off rather than spreading into a conductive film. Additionally, low molecular weight silicone components migrate from the cured coating into contamination deposits that accumulate on the surface over time. This transfers hydrophobicity into the contamination layer itself, maintaining protection as pollution builds. Technical guidance on RTV silicone coating chemistry and performance standards is available from CSL Silicones, the manufacturer of the SI-COAT 570 HVIC.
SI-COAT 570 HVIC: Reducing Washing Frequency While Maintaining Protection
SI-COAT 570 HVIC is a room temperature vulcanising RTV silicone high voltage insulator coating developed by CSL Silicones and available exclusively across Sub-Saharan Africa through Technical Solutions Supplies. It applies to porcelain, glass and composite insulators, transformer bushings, switchgear and substation equipment during planned maintenance outages.
A single application of SI-COAT 570 HVIC applied during a scheduled wash outage delivers more than 15 years of hydrophobic surface protection. Unlike the insulator surface itself, which reverts to its hydrophilic state the moment washing stops, the coated surface maintains its water-repelling properties continuously throughout the service period.
This changes the risk profile of the insulator fundamentally. Rather than washing resetting a hydrophilic surface that accumulates risk again, washing combined with SI-COAT 570 HVIC resets a surface that resists water film formation for the next 15 years. Consequently, the period between wash cycles becomes a managed low-risk interval rather than a growing vulnerability window. Furthermore, because the hydrophobic surface prevents contamination from bonding, light rainfall acts as a natural cleaning mechanism. It removes loose deposits continuously without any maintenance intervention.
SI-COAT 570 HVIC complies with IEEE 1523 and the relevant IEC standards for RTV coatings on outdoor high voltage insulators. Its service life exceeds 15 years under Sub-Saharan African field conditions across coastal, industrial, desert and mining environments. For full technical specifications, visit the SI-COAT 570 HVIC FAQ or contact Technical Solutions Supplies directly.
From Reactive to Preventative: The Maintenance Shift
Eskom’s load shedding recovery was built on moving from reactive breakdown maintenance to planned, preventative maintenance discipline. The same principle applies at the insulator level. Scheduled washing is planned maintenance. However, on its own, it remains reactive to contamination that has already accumulated rather than preventing the conditions that make that contamination dangerous.
Adding SI-COAT 570 HVIC to the scheduled wash programme shifts insulator maintenance from reactive to genuinely preventative. The wash removes contamination. The coating ensures that contamination which returns cannot activate into a flashover risk until the next scheduled intervention. Together, they deliver the kind of maintenance outcome that Eskom’s recovery has demonstrated is possible across South Africa’s generation and transmission network.
For utilities and industrial operators managing high voltage infrastructure across Sub-Saharan Africa, this combination represents the most cost-effective path to sustained flashover protection with a manageable maintenance footprint.
Frequently Asked Questions: Insulator Washing and Flashover Prevention
Why is insulator washing done during planned outages in South Africa?
In South Africa, insulator washing is typically performed as a scheduled winter maintenance programme, with power stations and substations taken offline in KwaZulu-Natal and Gauteng ahead of the summer wet season. This removes accumulated contamination before seasonal rainfall activates it into leakage current pathways. Performing washing during planned outages eliminates the safety risks associated with live-line work and allows thorough cleaning of all insulator surfaces.
Does insulator washing prevent flashover permanently?
No. Insulator washing removes contamination temporarily but does not change the hydrophilic surface properties of porcelain and glass insulators. Once washing stops, contamination begins to reaccumulate. When moisture contacts the redeposited contamination, flashover risk returns. Consequently, washing must be repeated regularly to maintain acceptable risk levels.
What is the difference between a hydrophilic and hydrophobic insulator surface?
A hydrophilic surface attracts moisture and allows it to spread as a continuous film. This is the natural state of porcelain and glass insulators. A hydrophobic surface repels moisture, causing it to form discrete droplets that run off the surface. Contamination on a hydrophobic surface cannot dissolve into a conductive film, so leakage current does not develop. Silicone coatings like SI-COAT 570 HVIC create permanent hydrophobicity on treated insulator surfaces.
How long does SI-COAT 570 HVIC last after application during a maintenance outage?
SI-COAT 570 HVIC delivers more than 15 years of hydrophobic surface protection under Sub-Saharan African field conditions. A single application during a planned maintenance outage therefore covers multiple wash cycles without requiring recoating. This makes it a highly cost-effective complement to existing washing programmes.
Can SI-COAT 570 HVIC be applied during a scheduled insulator wash outage?
Yes. SI-COAT 570 HVIC is specifically suited to application during planned maintenance outages. The insulator surface is cleaned as part of the normal wash programme, and the coating is applied before the station returns to service. No additional outage time is required beyond what the washing programme already schedules.
Does using SI-COAT 570 HVIC mean washing is no longer necessary?
In many environments, SI-COAT 570 HVIC significantly reduces or eliminates the need for scheduled insulator washing. Because the hydrophobic surface prevents contamination from bonding, loose deposits are carried away by light rainfall naturally. This self-cleaning behaviour means that annual wash programmes can often be reduced in frequency or scope without increasing flashover risk. For utilities managing large insulator populations across substations and transmission lines, this translates directly into fewer planned outages, lower maintenance costs and reduced safety exposure for maintenance teams.
Technical Solutions Supplies is the exclusive Sub-Saharan Africa distributor for CSL Silicones. For more information on SI-COAT 570 HVIC and its application in scheduled insulator maintenance programmes, contact the TSS team directly.