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We are performing some oil test like Dissolved Gas Analysis (DGA) and Oil Screening Test

So, basically, we (TDL) lab

Oil Health Assessment

Are performing some oil test like Dissolved Gas Analysis (DGA) and Oil Screening Test (OST). OST tests are distributed in three parameter like Physical Test, Electrical Test, and Chemical Test which is as follows –

Physical Parameters
  • Appearance
  • Interfacial Tension
  • Kinematic Viscosity
Chemical Parameters
  • Water Content
  • Total Acid Number
  • Sediment and Sludge
Electrical Parameters
  • Breakdown Voltage
  • Specific Resistance
  • Dielectric Dissipation Factor
Transformer Condition
  • Dissolved Gas Analysis (DGA)
  • Furanic Compound Analysis (Furans)

Other Special Test as Per Customer Requirement

Oil test results provided within 3 working days from sample receipt.
All tests done under controlled temperature and humidity, to maintain test integrity.
All testing data records maintained for a period of 2 years.
Special request on customer we are giving Statistical trending & analysis, of report.
Experienced and well qualified persons handling test operations.
Single point communication window established for all customers.
How it works

Appearance

In Appearance test – Oil may show cloudiness or sediment

Why Appearance test – Which is indicate the presence of free water, insoluble sludge, carbon particles, fibres, dust, or other contaminants.

Interfacial Tension

In Interfacial tension test - The interfacial tension between oil and water provides a means of detecting soluble polar contaminants and products of degradation. Interfacial Tension (IFT) test is performed to measure the level of polar contaminants and oxidation by-products in transformer oil, which indicates oil cleanliness and helps detect early signs of oil degradation before sludge formation, thus ensuring reliable transformer health and preventing insulation damage. Why IFT test - IFT is a tool for detection of deterioration.

Flash Point

In Flash Point test - of transformer oil is important because it measures the temperature at which the oil can vaporize to produce flammable vapours, helping to ensure the oil’s safety by minimizing fire hazards and maintaining reliable transformer operation. Regular flash point tests confirm the oil’s quality and suitability for use under operating conditions, protecting the transformer from potential fire risks and extending its service life. Why Flash Point test - It ensures the oil’s fire safety by identifying the temperature at which flammable vapours form.

Pour Point

In Pour Point test - It is a measure of the ability of the oil to flow at low temperature. Pour Point test is performed to ensure transformer oil remains fluid and can circulate freely at low temperatures, which is critical for reliable cooling and transformer operation in cold climates. If the oil solidifies or becomes too viscous in cold weather, effective cooling is compromised, leading to overheating or failure of transformer components.

Why Pour Point test - It ensures the oil can circulate and provide effective cooling during cold weather, preventing transformer overheating in low-temperature environments.

Density

In Density test – Mass per unit volume expressed in either kilogram per cubic meter or grams per millilitres. In cold climates, the density of oil may be important in determining its suitability for use. For example, ice crystals formed from separated water may float on oil of high density and lead to flashover on subsequent melting. However, density is not significant in comparing the quality of different samples of oil.

Why Pour Point test - May be useful for discriminating mineral insulating oil from other fluid types.

Kinematic Viscosity

In Kinematic Viscosity test – It is a measure of the resistance to gravity flow of a fluid the pressure head being proportional to its density. Viscosity is an important controlling factor in the dissipation of heat. Ageing and oxidation of the oil tend to increase viscosity. Viscosity is also affected by temperature. Normal ageing and oxidation of the oil will not significantly affect its viscosity. Only under extreme conditions of corona discharges or oxidation may this occur.

Why Kinematic Viscosity test – Transformer oil serves as both an insulator and a coolant. If the oil is too viscous (thick), it won’t flow efficiently, leading to poor heat dissipation and potential overheating. Viscosity also indicates the health and aging of the oil.

Water Content

In Water Content test – of transformer oil is done to measure the moisture level in the oil, which is critical because excessive water reduces the oil’s insulating properties, accelerates aging of insulation materials, and can lead to transformer failure. Keeping water content low ensures the transformer’s safe operation, reliability, and longevity. The Water Content Test measures moisture levels in transformer oil to prevent insulation breakdown, extend transformer life, and ensure safe, reliable operation.

It is a test that measures the amount of moisture present in transformer oil to ensure safe insulation and reliable performance.

Why Water Content test – Moisture reduces the insulating strength of oil and paper, accelerates aging, and may cause transformer failures. High moisture can lead to dielectric breakdown, overheating, and reduced transformer life. In such cases, oil filtration or dehydration is required.

Total Acid Number / Naturalization Value

In Total Acid Number / Naturalization Value – It measures the acid content in transformer oil, indicating the level of oil oxidation and degradation.

The acidity (neutralization value) of oil is a measure of the acidic constituents or contaminants in the oil. The acidity of a used oil is due to the formation of acidic oxidation products. Acids and other oxidation products will, in conjunction with water and solid contaminants, affect the dielectric and other properties of the oil. Acids have an impact on the degradation of cellulosic materials and may also be responsible for the corrosion of metal parts in a transformer. The rate of increase of acidity of oil in service is a good indicator of the ageing rate. The acidity level is used as a general guide for determining when the oil should be replaced or reclaimed.

Why Total Acid Number / Naturalization Value – High acidity can cause sludge formation, corrosion, and deterioration of insulating properties, leading to transformer failure.

Sediments and Sludge

In Sediments and Sludge – testing measures the number of insoluble particles accumulated in transformer oil, which may result from oil oxidation or contamination. The transformer oil is performed to detect insoluble deposits that form due to oil oxidation and aging, which can block cooling ducts, reduce heat dissipation, and accelerate insulation breakdown. Identifying and measuring these contaminants helps prevent transformer overheating, improves reliability, and guides timely maintenance or oil replacement to ensure continued efficient transformer operation.

Why Sediments and Sludge – The presence of sediment and/or sludge may change the electrical properties of the oil, and in addition, deposits may hinder heat-exchange, thus encouraging thermal degradation of the insulating materials.

Breakdown Voltage / Dielectric Strength

In Breakdown Voltage / Dielectric Strength – It is the average voltage gradient at which electric failure occurs under prescribed conditions. The dielectric strength or breakdown voltage of oil is its ability to withstand electric stress.

It is a measure of the ability of oil to withstand electric stress and has primary importance for the safe operation of electrical equipment. It is strongly dependent on the sampling temperature.

Why BDV test – The Breakdown Voltage (BDV) test is crucial for transformer oil because it measures the oil’s ability to act as an insulator and withstand electrical stress without breaking down. This ensures the safety and reliable operation of transformers by preventing electrical faults like short-circuiting or sparking. Regular BDV testing helps detect contamination or moisture in the oil early, reducing the risk of equipment failure, costly repairs, and unplanned downtime. It also supports preventive maintenance and compliance with industrial standards, extending the transformer’s lifespan and maintaining stable power supply.

Dielectric Dissipation Factor / Tan Delta

In Dielectric Dissipation Factor / Tan Delta test – is performed on transformer oil to monitor its insulation quality by detecting the presence of contaminants, moisture, and aging by-products that can degrade performance and safety. This test helps identify early signs of insulation deterioration, ensures reliable transformer operation, and informs maintenance or oil replacement decisions to prevent failures and extend operational life.

The DDF test, measures energy losses in transformer oil due to the presence of contaminants, moisture, or aging products, providing a sensitive indication of insulation deterioration and Resistivity test are performed

Why DDF / Tan Delta test – It helps assess the insulation quality and purity of the oil. A high DDF value indicates increased dielectric losses and greater risk of oil breakdown or transformer failure.

Specific Resistance / Resistivity

In Specific Resistance / Resistivity test – the volume resistivity of an insulating material is the quotient of a d.c. electrical field strength and the steady state current density within the material.

It is performed on transformer oil to monitor its insulation quality by detecting the presence of contaminants, moisture, and aging by-products that can degrade performance and safety. This test helps identify early signs of insulation deterioration, ensures reliable transformer operation, and informs maintenance or oil replacement decisions to prevent failures and extend operational life

Why Specific Resistance / Resistivity test – It helps assess the insulation quality and purity of the oil. A low resistivity value indicates increased dielectric losses and greater risk of oil breakdown or transformer failure.

Furanic Compound Analysis (Furan)

Furanic Compound Analysis (Furan) test – Basically this test performs to detect the transformer winding paper condition which is how much deteriorates.

Furan analysis of transformer oil measures the concentration of Furanic compounds, which are byproducts of the breakdown of the transformer’s paper insulation, to assess its degradation. This non-invasive test provides a reliable indicator of the solid insulation’s health, allowing for early detection of aging or faults and enabling predictive maintenance to prevent transformer failure. The concentration of furans, particularly 2-furaldehyde, correlates with the insulation’s condition and can be used to estimate its lifespan and the need for intervention.  

How it works

Breakdown product

As paper-based cellulosic insulation ages or is subjected to thermal and oxidative stress, it breaks down into oil-soluble compounds called furans.

Measurement

Furan analysis involves detecting and quantifying these compounds in a sample of transformer oil, typically using High Performance Liquid Chromatography (HPLC).

Primary indicator

The most common Furanic compound measured is 2-furaldehyde (2-FAL), as it is the most stable and abundant byproduct of cellulose breakdown.

Health assessment

The amount of Furanic compounds in the oil is directly proportional to the degradation of the paper insulation.

How it works
Non-invasive assessment

It allows for the assessment of the transformer's solid insulation without taking the unit offline for physical inspection.

Life extension

By tracking furan levels over time, it is possible to determine if the insulation is aging normally or if the process is accelerating due to other factors.

Failure prevention

High furan levels can warn of serious insulation deterioration and impending transformer failure, prompting necessary maintenance or replacement.

Informs maintenance

Data from furan analysis helps in planning maintenance, such as determining if other interventions like fuller earth’s filtration are needed or if the unit should be retired.

Dissolved Gas Analysis

Dissolved gas Analysis test – Basically DGA test perform to find transformer internal condition. DGA is a sensitive and reliable technique for monitoring the internal health of oil-filled transformers. It helps identify and diagnose faults early, enabling preventive maintenance and avoiding unplanned outages. Interpreting the results involves looking at the concentration and ratios of specific gases, often with the aid of graphical tools. Regular DGA testing allows for condition-based maintenance, helping to prevent catastrophic failures by detecting problems before they become severe. 

How it works

Fault detection

When a transformer experiences electrical or thermal stress, the oil and insulation break down, releasing specific gases.

Gas analysis

The concentration of these gases in the oil provides critical diagnostic information.

Diagnostic interpretation

Different gases and their ratios point to specific issues:

Diagnostic interpretation- Different gases and their ratios point to specific issues:

Thermal faults

Overheating generates gases like methane (𝐶𝐻4), ethane (𝐶2𝐻6), and ethylene (𝐶2𝐻4). Higher temperatures Favor ethylene production.

Electrical faults

Partial discharges can produce hydrogen (𝐻2) and methane (𝐶𝐻4), while arcing can produce more acetylene (𝐶2𝐻2).

Insulation paper degradation

Overheating of paper insulation can be indicated by elevated levels of carbon monoxide (𝐶𝑂) and carbon dioxide (𝐶𝑂2).

Why DGA test – DGA is a most critical and crucial test in transformer oil testing which is find and prevent unwanted or unplanned failure and maintenance to reduce major accidents.

Properties and deterioration/degradation of transformer oil

The reliable performance of mineral insulating oil in an insulation system depends upon certain basic oil characteristics that can affect the overall performance of the electrical equipment. To accomplish its multiple roles of dielectric, coolant and arc-quencher, the oil needs to possess certain properties, in particular:

  • High dielectric strength to withstand the electric stresses imposed in service
  • Sufficiently low viscosity so that its ability to circulate and transfer heat is not impaired
  • Adequate low-temperature properties down to the lowest temperature expected at the installation site
  • Resistance to oxidation to maximize service life

 

In service, mineral oil degrades due to the conditions of use. In many applications, insulating oil is in contact with air and is therefore subject to oxidation. Elevated temperatures accelerate degradation.

The presence of metals, organo-metallic compounds or both may act as a catalyst for oxidation. Changes in colour, the formation of acidic compounds and, at an advanced stage of oxidation, precipitation of sludge may occur.

Dielectric and, in extreme cases, thermal properties may be impaired.

In addition to oxidation products, many other undesirable contaminants, such as water, solid particles and oil-soluble polar compounds can accumulate in the oil during service and affect its electrical properties. Testing and analysis of the transformer oil gives us the assessment of oil as well as transformer condition in its running state, enabling us to take better preventive actions and avoid failures / breakdowns

Hence this oil must be periodically tested to ascertain its basic electrical properties, and make sure it is suitable for further use or initiate necessary actions like filtration/regeneration. Transformer Oil is not only subject to its own degradation but is also a carrier of gasses emanated during arcing or flashovers between paper and winding insulations.

Oil and other insulating liquids suffer from electrical and mechanical stresses while a transformer is in operation. In addition, there are contaminations caused due to chemical interactions with windings and other solid insulations, catalysed by high operating temperature. As a result, the original chemical properties of transformer oil changes gradually, rendering it ineffective for its intended purpose after many years. Transformer Oil Testing and Analysis provides important information regarding any such incipient faults, without the need to pull down the equipment from its running condition. We are India’s leading private laboratory for Transformer Oil testing as per ISO/IEC 17025:2017

Our next project is providing emergency on site transformer oil testing services with our NABL accredited Mobile Lab.

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