The transformer oil is crucial in determining the system’s mechanical state. The world’s most considerable production process has significantly transformed in recent decades. Due to their electrochemical and insulating qualities, mineral-based oils, such as transformer oil, are often used in various transformers. The transformer’s oil serves as an insulator and a cooling factor. This post provides a general summary of transformer oil, including its purposes and wide varieties.
Transformer Oil: What Is It?
Transformer oil, commonly referred to as insulating oil, is a unique kind of oil with exceptional insulating dielectric qualities and excellent temperature stability. Oil-filled electrical energy converters use transformer oil to shield, prevent arcing and dielectric breakdown, and disperse the heat generated by the transformers (i.e., act as a coolant).
The transformer’s base and field winding, completely submerged in the oil, are likewise preserved using transformer oil. The insulating oil’s capacity to stop the oxidation of cellulose-based insulating material is another important quality. The transformer oil is a shield to prevent interactions between the oxygen in the air and the cellulose, thus reducing oxidation. Utilizing a MOG (Magnetic Oil level Gauge), the amount of transformer oil is routinely determined.
In What Ways Is Transformer Oil Important?
By 2023, it is expected that a significant increase in the global consumption of transformer oil will happen. Due to the growth of power grids and the resulting expansion in the construction and modernization of transformers, the Asia-Pacific region, particularly China and India, is where most of the transformer oils are consumed. The most significant users of transformer oil are distributing transformers, which are simple equipment.
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This oil is subjected to chemical pollution, mechanical forces, and electric strain over time. Power failures might result from limited performance. Close monitoring of the transformer oil is crucial to maintaining and prolonging the lifespan of the power transformer and preventing significant malfunctions.
What Purpose Does Transformer Oil Serve?
Transformer oil has two main functions: cooling and insulating. We are aware that many substances with varying dielectric strengths are accessible. These compounds must therefore sustain a voltage proportional to their electrical insulation. For example, if the voltage of the substance is increased over its particular electrical properties, then electricity will pass through it.
This oil quickly absorbs the humidity found in the environment. Wetness reduces the oil’s electrical resistance by absorbing it. The converter retains ambient water by using a silica gel-filled breather.
1. Insulator (Insulation medium)
The transformer’s oil primarily serves as insulation. It has solid electrical properties. Oil can easily shield against high voltage and stop temperature increases.
It is exceptionally electrically conductive (thermal conductivity and chemical stability). As a result, enhanced durability at extreme heat is ensured by this oil insulator material.
2. Coolant (Cooling medium)
In essence, transformers need oil for two fundamental reasons.
- To lower the heat caused by high voltage generation.
- To avoid the copper strands in the converter from burning.
According to iron limitations in the core and wrapping of big industrial transformers, the oil aids in the thermal dissipation and maintenance of excessive temps.
Transformers frequently employ dielectric mineral oil as insulation and cooling systems.
3. Improved Lubricating
The transformer’s interior components are well-lubricated by the oil. Among the transformer components that require oil for lubrication is the on-load tap changer (OLTC).
4. Genesis Arc
An arc is created in transformer oil if any fault conditions arise. Arc cooling is one of the better techniques when the mechanism is shielded by oil.
5. Damping
The electromagnetic theory behind the transformer’s operation constantly produces electric impulses in the central area. Noise is produced due to the vibration caused by the oscillating electromagnetic field. Oil is used in the converter as dampening to lessen sound and loudness.
What Are Transformer Oil Types?
1. Mineral Transformer Oil
It is generally accepted that oil also refers to crude oil that has undergone initial processing after being extracted. It can also be viewed as a natural output deposited far beneath the earth’s surface. We can refer to it as refined oil when it is at ambient temperature.
Crude oil is physically separated into different parts and components, then used to create diverse commodities. However, the extracted elements will be very distinct due to the numerous methods used to separate mineral oil. For instance, it will be split into petroleum products like crude gasoline and kerosene. The chemical components will maintain their optimum state as a whole.
The velocity pole of the total mineral oil will be pretty high due to the inability to remove any impurities during the various refining stages, making it unsuitable for usage in highly low-temperature conditions. Thus, it directly leads to the scope of mineral oil’s application being restricted.
The used solvent is segregated. Hydrocarbons’ structural integrity is not altered during production, which primarily depends on mechanical operations. The amount and characteristics of the optimum ingredients in the feedstock determine the base oil that is generated; the mineral oil cannot be refined to remove contaminants. Mineral oil or base oils are not suited for usage in cold climates due to the base oil’s higher flow point. Here are two major mineral oils used in transformer oil.
Naphthenic Oil
The crude oil used to make naphthenic transformer oil contains either no or very little organically existing paraffin. The pour point of naphthenic oil is likewise low. A fluid’s pour point is the point below that stops flowing when poured out of a container.
Since naphthenic transformer oil contains less paraffin than other oils, it exhibits a lower pour point without needing additions to depress it drastically. The oil’s flow characteristics and prolonged lifespan are additional benefits. Specialists should nevertheless check the oil at least once a year, notwithstanding the life span.
Some transformer oils continue to have a muck issue. But there is a somewhat soluble muck in the naphthenic fluid. Because of this, quality won’t cause deposits on the transformer’s coils and interfere with its ability to cool. Additionally, this advantage avoids transformer temperature-rise issues that can reduce the unit’s life expectancy.
Paraffinic Oil
Paraffinic transformer oil contains more paraffin than naphthenic transformer oil, which is made from crude oil. The material’s pour point may need to be lowered with additions because the higher wax content rises at that point.
Water will inevitably emerge when a transformer must be used in icy conditions as permafrost melts. However, if that moisture enters a transformer’s circuit region, the liquid will significantly lower the oil’s breaking voltage or dielectric strength. A low electrode potential indicates that the oil contains humidity or other conductive materials.
In colder temperatures, paraffinic transformer oil is less dense than naphthenic oil. Similarly, the viscosity of paraffinic oil and ice differs significantly. As a result, it’s frequently used for low-temperature operations where ice on the surface could affect a transformer’s performance.
High antioxidant stability in this oil is a quality that reflects its oxidation resistance. Due to this characteristic, the fluid has a long service life even under heavy use.
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2. Vegetable Oil or Ester-Based Transformer Oil
Despite advancements throughout time, one drawback of some of the most popular transformer oils is that they harm the planet. Therefore, those who utilize them must employ basins or other comparable devices to control the fluid. However, employing ester-based oils, which are frequently recyclable, is an increasing trend.
Esters also aid in reducing the risk of flame, which is another benefit. According to statistics, organic ester oil rather than mineral oil is used in more than 2.5 million transformers worldwide. Esters’ ability to function at temperatures more than 30 degrees Celsius higher than mineral-based oils is one of the factors contributing to this transition.
Some experts expect more decision-makers to favor ester oils due to warmer weather and a rising propensity for transformer overloading. Fluids will burn at a specific temperature if an outside source heats them is known as the material’s flash point. The flashpoint of organic ester, apparently the greatest of the substitute fluids applied in transformers, is 360 degrees Celsius. So selecting an ester-based oil might be a wise choice to avoid flames that rapidly expand to the nearby forest.
Another advantage of employing ester oils in transformers is that much smaller devices, such as those that could supply backup power in emergencies, can now be produced. These transformers, for instance, might be up to one-third more diminutive than those that use other forms of oil.
Beneficial to the Ecology
The organic ester transformer is extremely eco-friendly since it uses insulation oil made of non-toxic, safe, and recyclable organic esters. Organic esters degrade at over 97% after 28 days, compared to less than 30% for mineral oils. Organic ester is safe for organisms and does not impact oral ingestion. The organic ester transformer won’t pollute the environment even if it spills. Organic esters are greener thermal insulation oils that are made from sustainable energy plants and do not depend on petrochemical raw resources. They also have reduced greenhouse gas emissions.
Transformer vegetable oil and flame security
The combustion temperature of organic ester surpasses 300°C, which is substantially greater than that of mineral oil. Organic ester is more demanding to fire than mineral oil and exhibits self-extinguishing properties once it does, which can significantly lower the risk likelihood of transformer flame and blast.
Increased Insulating Life
Organic ester molecules exhibit great hydrophilic nature and are more magnetic than mineral oil molecules. Organic ester has comparative water absorption of roughly 4–30 times more than mineral oil at the same temperatures. Organic esters are better able to collect water from the insulator sheet than mineral oil throughout the aging cycle, helping to preserve the proper equilibrium of humidity in the oil-paper insulators and postponing the getting older of the insulation material paper. Second, the hydrolysis reaction of the organic ester can metabolize the humidity present in the insulating form, preventing humidity from adversely affecting the paper’s deterioration. Additionally, organic esters stop insulator paper’s cellulose from being hydrolyzed, slowing down how quickly it ages.
High Thermal Tolerance Threshold
Organic ester has a thermal endurance level of B (130 °C), which is better than mineral oil’s thermal endurance level A (105 °C), and when combined with cellulose sheet, can enhance thermal resistance. It is possible to create a hybrid insulating method and high-temperature insulating technology by mixing organic ester with a thermally sensitive firm insulating layer (120°C and beyond) to increase the heat flow limitation of organic ester transformers.
3. Silicone Oil
The most significant drawback of silicone oil is its excessively high cost. Compared to transformer oil, silicone oil costs nearly six times as much globally as domestically. The value of the transformer will rise as a result. However, given the relatively straightforward production procedure, excellent interactive and heat consistency, and electrical insulating materials characteristics, silicone oil transformers can decrease a significant amount of daily upkeep, mainly because of the rising flash point and more excellent combustion point of black wire, as well as the self-resistance of silica degradation products. The era performs well in terms of flame security because of its combustibility. Silicone oil transformers are still highly potent despite the growing reduction of the cost differential between silicone oil and mineral oil.
Although silicone oil transformers are less likely to ignite the fire, they are not ideal for moist settings. Due to the inability to currently resolve the local silicone oil availability, this product’s large-scale manufacturing and growth are now restricted. Underground railroads and electric trains will initially use silicone oil transformers before being used in other applications.
