What is Breather in power Transformer-Electronicsinfos

What is Breather in Transformer?

A breather is a device installed on a transformer to filter out the moisture from the air. The purpose of a breather is to prevent the ingress of moisture, dust, and other contaminants. 

What is Breather in power Transformer?
Breather in Power Transformer

In a transformer, a breather is installed on the conservator tank, which is used to compensate for the expansion and contraction of the transformer oil. As the oil level in the conservator tank changes, the air is either drawn into the tank or expelled.

The breather allows this air exchange without allowing moisture, dust, or other contaminants to enter the transformer oil.

Construction of Breather

A breather is a simple device that consists of a housing, a desiccant material, and a filter. The housing of a breather is made of metal or plastic. The housing contains a desiccant material to absorb moisture from the incoming air. 

The desiccant material is made of silica gel and activated alumina.

Construction of Breather
What is a breather?

The housing also contains a filter, which is used to remove dust, dirt, and other contaminants from the incoming air. The filter is made of a porous material, such as paper or synthetic fibres.

Types of Breathers in Transformers

There are different Types of  Breathers in the transformer Including
  • Conventional Silica Gel Breathers

  • Self-Dehydrating Breathers

  • Molecular Sieve Breathers

  • Oil-Sealed Breathers

  • Hybrid Breathers

Conventional Silica Gel Breathers


These are the most common type of breathers.it filled with silica gel crystals that absorb moisture from the air.The silica gel changes color from blue to pink as it absorbs moisture. it indicating the need for replacement of Silica gel. 

Self-Dehydrating Breathers


These breathers have a built-in heating element that periodically regenerates the silica gel by removing the absorbed moisture.The regeneration process can be automatic or manually controlled.


Molecular Sieve Breathers


These breathers use molecular sieves which are synthetic materials. it is a uniform pore structure to absorb moisture. Molecular sieves have higher adsorption capacity.it can operate effectively over a wider temperature range.

Oil-Sealed Breathers


These breathers have an oil chamber that traps moisture.The oil acts as a first line of defense, increasing the effectiveness and life of the desiccant material.

Hybrid Breathers


These breathers combine different technologies, such as silica gel with molecular sieves or oil sealing with silica gel, to maximize moisture absorption and filtration efficiency.

Advantages of Breather in Transformer

Breathers provide several advantages when installed on transformers, including

  • A breather prevents moisture from entering the transformer oil by absorbing moisture from the incoming air. 
  • A breather helps to maintain the quality of the oil by preventing moisture and other contaminants from entering the transformer oil.
  • A breather can help to reduce maintenance requirements by maintaining the quality of the transformer oil.
  • A breather can help extend the lifespan of the transformer.
  • A breather can help reduce the risk of equipment failure, oil leaks, and fires.

Selecting a Breather in Transformer

Selecting the appropriate breather for a transformer involves various factors including performance, protection, and reliability.First You Need to Identify Which type of Breahter are Suitable for your Application !
  1. Breather Type

    • Conventional Silica Gel Breathers: This is Suitable for standard applications where periodic maintenance is Required.
    • Self-Dehydrating Breathers:This is Ideal for environments requiring minimal maintenance and longer operational life.
    • Molecular Sieve Breathers: Best for high-performance requirements.
    • Oil-Sealed Breathers: This is Useful for additional particulate filtration and extended desiccant life.
    • Hybrid Breathers: it Is a Customized solutions for specific operational and environmental needs.
  2. Transformer Rating and Size

    • Select a breather based on the transformer’s power rating and oil volume. Larger transformers with higher oil volumes will require breathers with greater moisture absorption capacity.
  3. Moisture Absorption Capacity

    • Consider the desiccant material's moisture absorption capacity,.it is typically measured in grams of water per unit weight of the desiccant. Higher capacity breathers are needed for transformers in high-humidity environments.
  4. Airflow Requirements

    • You need to Determine the airflow rate through the breather. Air flow depends on the transformer's breathing rate. it Ensure the breather can handle the maximum airflow without significant pressure drop.
  5. Environmental Conditions : Ensure the breather can operate effectively within the expected temperature range.

  6. Breather Material and Construction

    • You must to Ensure the breather is constructed from durable materials resistant to environmental factors such as UV radiation, corrosion, and mechanical wear.

Example Calculation

For a transformer with the following specifications

  • Power Rating: 10 MVA
  • Oil Volume: 10,000 liters
  • Environmental Conditions: High humidity, tropical climate
  • Breathing Rate: 50 liters per hour
  1. Breather Type: Self-dehydrating breather for minimal maintenance.
  2. Moisture Absorption Capacity: High-capacity desiccant (e.g., molecular sieves).
  3. Airflow Requirements: Ensure the breather can handle 50 liters per hour without significant pressure drop.
  4. Environmental Conditions: Choose materials resistant to high humidity and tropical climate.

Breather Materials and Their Properties

Silica Gel

  • Composition: Amorphous form of silicon dioxide.
  • Moisture Absorption: High capacity, typically absorbing up to 40% of its weight in water.
  • Color Indicator: Often impregnated with cobalt chloride to change color from blue (dry) to pink (saturated) as it absorbs moisture.
  • Regeneration: Can be regenerated by heating to 120-150°C to drive off absorbed moisture.
  • Durability: Good mechanical strength and stable over a wide temperature range.
  • Usage: Commonly used in conventional breathers for its effectiveness and cost-efficiency.

Molecular Sieves

  • Composition: Crystalline aluminosilicates (zeolites) with uniform pore sizes.
  • Moisture Absorption: Higher moisture adsorption capacity than silica gel, especially at low humidity levels.
  • Selectivity: Can selectively adsorb water molecules due to uniform pore structure.
  • Regeneration: Can be regenerated by heating to 200-300°C.
  • Durability: Highly stable and durable, suitable for extreme conditions.
  • Usage: Used in applications requiring high moisture absorption and stability in varying environmental conditions.

Activated Alumina

  • Composition: Highly porous form of aluminum oxide.
  • Moisture Absorption: Good moisture adsorption capacity, less than silica gel but effective for certain applications.
  • Regeneration: Can be regenerated by heating to 175-200°C.
  • Durability: Chemically inert, non-toxic, and resistant to abrasion.
  • Usage: Occasionally used in breathers where moderate moisture control is required.

Oil (in Oil-Sealed Breathers)

  • Composition: Typically mineral oil or synthetic oil with specific properties.
  • Moisture Absorption: Acts as a first line of defense, trapping moisture before it reaches the desiccant.
  • Filtration: Also traps particulate contaminants, enhancing overall filtration efficiency.
  • Durability: Requires periodic replacement, but extends the life of the desiccant.
  • Usage: Used in oil-sealed breathers to enhance moisture control and particulate filtration.

Frequently Asked Questions – FAQs

What is the purpose of a breather in a transformer?

A breather in a transformer is used to absorb moisture from the air entering the transformer.

How does a silica gel breather work?

A silica gel breather contains desiccant material, such as silica gel.it absorbs moisture from the air passing through it. As the air enters the breather, moisture is absorbed by the silica gel.

When should I replace the silica gel in the breather?

The silica gel in the breather should be replaced when it changes colour.it indicating that it has reached its moisture absorption capacity. Most breathers come with colour indicators that change colour (e.g., from blue to pink).

How often should I inspect the breather?

It is recommended to inspect the breather regularly, such as during routine maintenance checks on the transformer. 

What are the benefits of using a breather in a transformer?

Using a breather helps prolong the transformer's lifespan by preventing moisture-related issues.

Can a breather be used in all types of transformers?

Breathers are commonly used in oil-filled transformers to control moisture levels.

How do I install a breather on a transformer?

Installation instructions for a breather vary depending on the breather model and transformer type. 

Are there different types of breathers available for transformers?

Yes, there are different types of breathers available, including silica gel breathers, molecular sieve breathers, and hybrid breathers. 

Can a breather reduce the need for transformer oil maintenance?

breather helps control moisture levels and maintain oil quality.

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