Guide to understanding "Transformer Failure"

Author: Aaron Chen  Date Posted:30 June 2019 

Transformers provide an important link between the creation and supply of the energy. They are prone to be overused during operation which can lead to terrible failure.

Monitoring the performance of a transformer is one of the effective techniques in avoiding an unexpected breakdown. Early diagnosis also assures the competent performance of the transformer in the long term.

The most common malfunction considered is the contamination of the insulating fluids in the transformer which can be caused by exposure to heat, moisture or chemicals.

This is a guide on the important facts to consider in treating insulating oil in the transformer including the process of condition monitoring.

Condition Monitoring of Transformers

Nowadays, the reliability of power supply has become a challenge. This is why the infrastructure of the equipment should be proven and reliable. When it comes to transformers, the repair is definitely costly and tedious. Henceforth, observing the condition of the transformer is needed so repair can be minimised.

Condition monitoring is the process of getting data. The data needs to be related to the different kinds parameters specified for the transformer so that it is easier to foresee a trend and prevent failure.

The failure of transformers can cause power outages, environmental threats and expensive buying of power from other suppliers. Thus, understanding the significance of condition monitoring for transformers must be considered.

Why Is Transformer Condition Monitoring Important?

  • To detect early failures of the transformer
  • To prevent catastrophic power outage
  • To provide basis for economic decision for repairs
  • To help with management of maintenance
  • To control the ageing process of transformer
  • To promote safety to personnel and environment

With the use of advanced techniques, researchers are able to utilize relevant data for detecting transformer faults. Moreover, it also enables them to understand and describe aspects of condition monitoring.

What Are The Important Aspects Of Condition Monitoring?

Thermal Modelling

The life of a transformer can be known by its ability to use up the internally developed heat to the surroundings. Comparing both the actual and foreseen operating temperatures can give a diagnosis of the status of the transformer. It can also reveal defects in the operation of a transformer.

Dissolved Gas Analysis

Faults such as partial discharge, thermal heating and arcing can be identified by checking the quantities of hydrocarbon gases, hydrogen and carbon oxides in the transformer. Different kinds of gasses can serve as a basis for the different types of defects. This testing of gases will check if failure has occurred and determine the type.

Frequency Response Analysis

This technique is very sensitive. It detects failures in winding movements. It also checks deformation caused by the loss of clamping pressure or short circuit forces. This type of analysis will cover the measurement of winding impedance of the transformer.

Partial Discharge Analysis

This is a test which utilizes the partial discharge measurements in checking the integrity of equipment. This helps avoid flaws which can cause electrical stresses to exceed the insulation capacity. It can also predict which electrical equipment needs repair.

Knowing and being able to measure these characteristics, makes it a lot easier to detect potential reasons for the failure of the transformers.

What Causes a Transformer to Fail?

There are many factors which can cause a transformer to fail. Some of these factors includes the quality of materials used, how it is used, how it is designed and the likes.

One of the major contributing factors to transformer failure is the moisture contamination and it's effect on the insulating oil. Let us see the definition of "insulating oil" below first.

What is insulating/transformer oil?

Insulating oil or transformer oil is a kind of oil which is stable during high temperatures. It has a distinguished electrical insulating characteristic. These oils are used in transformers, circuit breakers and the like. The oil mainly insulates, slows down corona and arc discharging, and serves as a cooler.

The insulation oil is one of the main standards to make electrical apparatuses useful. Every parameter of the insulation oil is important therefore it should be carefully controlled during the maintenance of electrical equipment. The performance of electrical equipment depends on the purity of the transformer oil. If the oil is contaminated, it can cause the electrical equipment to fail.

Oxidation of the oil will begin when the equipment is energized. There will be a chemical reaction as soon as the oil is exposed to heat, oxygen, core and coil constituents. As the oxidation advances, the oil degrades.

What Are The Factors Affecting The Quality Of Insulating Oil?

Since there will be reactions on the insulating oil when it is exposed to certain materials, the quality will also change due to the following factors.

  1. Contamination: Moisture is the primary contaminant and likewise brings down the dielectric properties of the insulating oil.
  2. Oxidation: Oxidation is the most well-known reason for oil decay. Cautious drying and vacuum techniques must be conducted to expel air and dampness in the transformer.
  3. Excessive high temperature: Excessively high warmth will bring about decay of the oil and will expand the rate of oxidation.
  4. Static Electricity: Basically, these charges isolate at the interface of the oil and paper in any transformer; therefore, decreasing the dielectric quality of the protecting oil.
  5. Corona releases: Arcing and confined overheating can likewise separate the oil, creating gasses and water, which can prompt to the arrangement of acids.
  6. Furans: The degree of polymerization can be specifically identified with the merging of furan subordinates, which are formed in the oil.

Since the transformer oil functions as an insulator and cools the transformer, it must be free from sludge, moisture, inorganic acids and the like. Once the components of the oil have changed, the oil can no longer be of use. Therefore, transformer oil must be tested and treated since it must endure the precisions of electrical and thermal stress during its usage.

How Is the Transformer Oil Treated?

Oil Filtering

Filtering oil process will involve the transformer oil filtering at a temperature of 40 degrees Celsius. This activity will help filter small contaminated particles with the use of a filtering device.

Oil Purification

Purification of oil will involve heating the oil to a maximum of 90 degrees Celsius. It gets rid of acidic and polar components of the oil. Transformer oil purification is a process to remove mud, dissolved moisture and dissolved gases from the oil.

Oil Regeneration

This method is similar to oil purification, however, it uses extra oxidant additives. This is considered as the most effective method for regenerating oil, economically speaking. This process is also considered a potential threat to the environment.

By exploring the patterns given above, it can definitely improve the judgment of the operator with regards to the recurrence of support, and distinguish early indications of the deterioration that, if disregarded, would lead to some serious problems. With these, transformer oil must undergo maintenance with the proper selection of transformer oil filtration equipment.

Using Transformer Oil Filtration Equipment

Oil deterioration can add complications on the transformers. Thus, insulating fluids must sustain proper care and maintenance to ensure the continuous power transmission on transformers and provide guaranteed performance.

One way of treating transformer oil is by using Transformer Oil Filtration Equipment which helps transformers achieve consistent results through insulating oil filtration.


Without any monitoring system conducted, it is very difficult to predict specific faults on the transformers. Thus, it is important to perform procedures like condition monitoring.

The most common failure in the transformer is the contamination of the insulating oil. Therefore, insulating oil must be tested and treated to guarantee its efficiency. In this case, the transformer oil will then undergo treatment using specific oil filtration equipment.

For your convenience, you can check C-Mac’s Transformer Oil Filtration Equipment or Insulating Oil Treatment (IOT) and see more details about its benefits. 

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