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High Voltage Insulator Cleaning and Coating

May 10, 2019

  

The purpose of any effective utility maintenance program is to ensure consistent service with only planned downtimes. However, many fields overlook the importance of regular, scheduled cleanings and inspections. The power distribution and transmission industry faces significant disruptions if a cleaning regime is ignored. The results can be outages, expensive repairs, unscheduled labor overtime, and unhappy customers. A proactive maintenance program is a must.

 

However, many maintenance methods used in the electrical generation and distribution sector are ineffective due to outdated techniques that lead to several problems. High voltage insulator cleaning can circumvent the failure that contamination can cause. Inspecting and cleaning insulators is an efficient way to prevent these occurrences. In today’s marketplace, most transformers in operation at the distribution level are decades old. It is imperative their external high voltage coating be replaced with new transformer painting to protect the units from damage and corrosion. Repainting negates further impairment and extends the unit’s operational lifespan. This is an efficient method that requires only a minimal investment.

 

In addition, substation painting provides protection for other equipment including cooling equipment, bus work, and line termination. Corrosion of the steel casings can result in mechanical failure. Implementing an up-to-date preventative maintenance schedule that includes cleaning, inspection for contamination and painting the transmission equipment and substation with high voltage coating is a viable, cost-effective way to address overlooked apparatus that act as damage vectors.

 

Outdated Maintenance Techniques

 

Large swaths of the U.S. electrical grid are over five decades old. The typical maintenance methods are similar in age. Unfortunately, many of the maintenance programs were created under the assumption that modern steel structures do not succumb to corrosion that results in failure. This is false. In addition, most programs do not include adequate inspection frequency and high voltage insulator cleaning. Hence, inspecting transformers for corrosion and rust, especially in key areas like the top and seals, has been neglected for many decades. The previous assumption provided that the units would be taken out of service for a comprehensive refurbishment at regular intervals. Transformer painting was included as an element of the refurbishment. However, the frequency of refurbishments decreased with innovative technology. Knowledge of potential failures increased, which called for repainting before a transformer reaches failure mode.

 

High Voltage Insulator Contamination

 

Air pollution can cause multiple problems for high voltage insulators. Engine exhaust, acid rain, soot, smog and ash float throughout the environment and can collect on insulators. The rain will wash away some of the pollutions. However, some pollution comes in the form of oil droplets, which will remain or cause complications when mixed with water. Blown dust and soil can physically erode an insulator. They may also have mineral salts that create a conductive layer when mixed with moisture. This lays on top of the insulator and will not run off the surface if it has abrasion marks from the wind. A thorough, regular high voltage insulator cleaning is the only effective method of removing that conductive layer.

 

Contaminants may also hide the damage done to insulators. This is best addressed with high voltage insulator cleaning. In addition, non-ceramic insulators, also called NCI insulators, may incur damage from corona effects. Nitric acid may form on the insulator resulting from the corona ionizing atmospheric nitrogen, which creates a chemical soup that causes more contamination and damage to the surface. The consequence is a carbon trail in the chemical soup that causes zones of lower resistance. This leads to flashover and arcing. High voltage insulator cleaning implemented on a regular basis removes the layer of nitric acid and slows further damage.

 

Inspecting and Cleaning High Voltage Insulators

 

Any foreign substance that collects on the surface of a high voltage insulator reduces its insulating capabilities. This issue presents problems with modeling and prediction; however, two things will definitely occur if an insulator receives no cleaning: a flashover will happen or arcs will form. The result will be service disruption, potential equipment damage, and unscheduled labor expenses. Consistent high voltage insulator cleaning mitigates these impending risks and lengthens the insulator lifespan.

 

Pairing consistent inspections with high voltage insulator cleaning will circumvent the buildup of contaminants. These methods also ensure the identification of other damage, such as manufacturing defects or corona effects. It is possible to complete inspections and cleanings without service interruption, and many contractors across the U.S. offer this type of service.

 

Transformer Weathering

 

A transformer is manufactured to operate for many years. In that time, the exterior experiences the full force of the weather. Blown dust abrasion, thermal cycling, precipitation, pollution, and ultraviolet light have a negative impact on the paint protecting the steel from oxidation. Paint eventually needs to be replaced, and exposed sections of the steel must be addressed quickly to prevent damage. Transformer painting with high voltage coating should be a regularly scheduled task.

 

The sun’s ultraviolet light and the intense focusing of light through water drops atop the transformers will ruin the paint. Then rust forms a thin coat across the exposed steel and lifts off the high voltage coating as the rust advances underneath. Rust will damage sides next, especially those that face the south or sun. Parts that are unprotected from weather elements will also follow. However, by the time the rust is visible, the transformer is already greatly rusted.

 

Only a close inspection and removing the layers of iron oxide will enable a true determination of the total damage. This creates a dilemma with transformers in service. They may appear to have light rust. However, oxidation may cause pinholes that run through to the other sides. This allows water and other moisture to gain entry into the internal mechanisms of the transformer. The result is the contamination or leakage of the dielectric oil. Both of these circumstances require expensive maintenance or repairs to compromised transformers. It may even cause catastrophic failures.

 

Repaint Transformers at First Sight of Rust

 

Consistent transformer inspection, cleaning, and painting with high voltage coating will increase the lifespan and enable identification of potential problems. At first sight of rust, painting the transformer should take place quickly along with regularly planned maintenance. Signs of high voltage coating failure in one section is a clear indication that failure exists along the rest of the surfaces. Inspection of all other transformers at the location should also take place, especially equipment of similar age and wear and tear. It is more cost effective to paint all the equipment needing attention at one time.

 

This preventer deeper corrosion from forming and mechanically compromising the transformer. New high voltage coating will mitigate water and moisture intrusion, which results in a longer lifespan of the dielectric oil and longer intervals prior to a necessary refurbishment or overhaul. In addition, it decreases the instances of unscheduled service downtimes.

 

Rust removal and transformer painting also increases the efficiency of the cooling systems. Rust acts as a thermal insulator on both passively and actively cooled transformers. This reduces operating temperatures, electrical losses in the equipment and loads on pumps. Additionally, transformer painting helps to prevent future mechanical failures due to corrosion on the cooling fins and pipes in the cooling system. The most common failure in transformer cooling systems is leaking from those crucial parts.

 

Mechanical Failures in Other Equipment

 

Most of the equipment and structures in a substation are constructed of steel. If the coating is in poor condition, they will be likely to sustain mechanical failure from corrosion. A regular maintenance schedule includes inspecting, cleaning and painting with high voltage coating the other equipment found in a substation. Consistent maintenance prevents premature failure of all substation equipment and structures.

 

Large load bearing equipment, such as line originating or terminating supports or pylons, may be particularly vulnerable to mechanical disruption due to corrosion. The loads tend to be dynamic on this equipment, and weather elements shift the loads constantly across the structures. Similar to a bridge, this allows rust to deeply penetrate vital components more quickly. They are troublesome and costly to repair, so they must be consistently inspected, cleaned and painted to prevent and mitigate rust damage.

 

In fact, all metal structures in substations should be regularly inspected for rust, cleaned and repainted with high voltage coating. Instrumentation transformers incur the same difficulties from rust corrosion that power transformers incur, and they will suffer from moisture contamination or drain completely of their dielectric oil through small leaks caused by rust. This happens more quickly than with a power transformer, and it causes a service outage, thermal failure and damage to direct and adjacent circuits. Painting the substation equipment also protects circuit breakers, fuse panels, and switching gear because each has internal components that steel enclosures protect. If the sheet metal corrodes and allows leaks in moisture to the internal components, it will cause further disruption.

 

Consistent Inspection, Cleaning, and Repainting

 

When compared to the expense of a service disruption and equipment failure, a consistent maintenance plan that includes inspecting for corrosion and paint wear in transformers and substation equipment is a small cost. While some areas can be difficult to inspect, the use of drones is making that a problem of the past. Most inspection can be completed visually since rain will typically wash rust down the outsides of the structures. Equipment with flat, large tops that gather rainwater should be given particular attention.

 

High voltage insulator cleaning along transmission lines and in substations should occur on a consistent schedule. This includes inspection of the insulators too. The result will be longer service life and easier visual inspections to identify potential disruptions and flaws prior to becoming bigger problems. Cleaning substation equipment may be done through several different methods without disrupting service.

 

In order to prevent and mitigate corrosion damage, painting should be completed as soon as rust appears. The most critical step to provisioning a substation for painting is preparing the surfaces. Paint requires a clean, solid surface to adhere to. Every surface in the substation to be painted should be cleaned thoroughly of rust, dirt and loose paint. In fact, this step can be a significant percentage of the cost of painting the substation. It is labor and time intensive, and the process requires specialized equipment. If maintenance has been kept up-to-date, only a light cleaning and removal of rust will be necessary, which will keep the expense to a minimum.

 

In order to minimize the costs further of a substation painting, add in planned time for painting after specific intervals that take into account the age of the equipment as well as the age of the corrosion prevention coating. A proactive approach to planned maintenance makes its execution much more efficient.

 

After the Repairs and Repainting

 

Having current maintenance practices that meet minimum standards is a must for keeping transformers and substation equipment running at optimal levels. A regular review of the practices should also take place. Insulators have specific lifespans. Extending those lifespans through consistent methods is the safest way to keep equipment running and will save money. This takes systematic inspection as well as high voltage insulator cleaning. NCI insulators should be included on the list. The paint on a transformer has a shorter life than the transformer itself. Therefore, keeping up with painting is a highly cost-effective technique to lengthen their service life until they need a comprehensive refurbishment. Structures and equipment made from steel within a power transmission system and substation need sufficient protection from rust corrosion. Therefore, preplanned substation painting must be integrated with all other maintenance schedules. In order to stop the damage from rust corrosion to equipment, a preventative maintenance schedule must include cleaning, inspection, and repainting.

 

Final Thoughts

 

Customers rely upon reliable electrical service. Keeping service disruptions to a bare minimum means having a proactive and up-to-date maintenance schedule. High voltage insulator cleaning and painting with high voltage coating is necessary. Preventing costly repairs and refurbishments to equipment comes through thorough inspection and cleaning. Utility Service and Maintenance is available to answer any questions regarding proper maintenance of critical electrical assets.

 

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