Transformers are critical components in the power grid, converting voltages of electricity from the power plants into suitable voltages for homes and businesses. Their reliable operation is essential for preventing power outages, expensive repairs, and other safety hazards.
However, organisations are often faced with challenges around transformer health where moisture accumulates in the transformer and significantly degrades the insulation and oil quality of transformers. To prevent this occurrence, desiccant breathers are incorporated into the transformers to prevent moisture from entering the transformer and averting a transformer failure.
This article will provide details into the role of desiccant breathers in transformers, including their functionality, the different options, maintenance tips, and the best ways to use them.
Desiccant Breathers for Transformers
Desiccant breathers are devices that prevent moisture from entering the transformer through the air-breathing mechanism of the conservator tank.
Because they are not hermetically sealed, transformers need to “breathe” as the oil’s temperature rises and falls. Unless appropriately filtered, the air that is inhaled and exhaled during this breathing action might introduce moisture into the transformer.
How Desiccant Breathers Operate in a Transformer
The operating mechanism of a desiccant breather in a transformer is straightforward yet effective. A tube or pipe connects the desiccant breather to the transformer’s conservator tank.
When the transformer heats up, the oil inside expands, causing air to be expelled. When it cools, the oil contracts, drawing air into the transformer conservator tank. The air enters through the breather.
As air passes through the desiccant material (typically silica gel) in the breather, the desiccant absorbs moisture from the air. This prevents moisture from entering the transformer, which could degrade the insulation oil and internal components. Some advanced breathers also include particulate filters that trap dust, dirt, and other airborne contaminants, ensuring only clean, dry air enters the transformer.
In some designs, a check valve ensures that air flows in only one direction, preventing oil vapours from escaping the conservator tank, which could otherwise lead to contamination. Through these processes, desiccant breathers maintain the integrity of the transformer’s oil and prevent moisture and contaminants from causing damage or reducing the transformer system’s efficiency.
Key Components of a Desiccant Breather
Desiccant breathers are typically equipped with the following components to ensure the effective removal of moisture from the transformer. When the transformer cools, the oil contracts and the air is drawn into the conservator tank through the breather.
As the air passes through the desiccant material within the breather, moisture from the incoming air is absorbed, and only filtered dry air enters the tank. Conversely, when the oil expands, and the air is expelled, the check valve prevents the desiccant from being exposed to potentially moist air outside the transformer.
| Component |
Description |
| A Form of Dehydrant |
Silica gel is the most used desiccant in breathers due to its high moisture absorption capability and self-indicating mechanism. It changes colour from orange to green, indicating when replacement is needed. |
| Housing for Breather |
This forms a seal around the desiccant and allows air to flow through it before reaching the transformer’s conservator tank. |
| Outlet for Air |
The breather’s air intake is located here. Advanced breathers may include particulate filters to trap dust and airborne contaminants for further air purification. |
| Check Valve |
Some breathers are equipped with check valves that allow air to flow in only one direction, preventing oil vapours from escaping the conservator tank. |
Different Types of Desiccant Breathers for Transformers
Desiccant breathers come in a variety of types, each with its own unique characteristics and applications such as size, operating conditions, and specific requirements.
Silica Gel Desiccant Breathers: Silica gel breathers are the most widely employed type of breathers. They are often utilised in small to medium-sized transformers and feature a simple enclosure filled with silica gel. Regular maintenance, including desiccant replacement and inspection, are also necessary to ensure the breather’s optimal performance.
Self-Generating Desiccant Breathers: These breathers are equipped with a heating element that periodically evaporates the absorbed moisture from the desiccant material. This process allows the breather to regenerate continuously and eliminates the need for manual desiccant replacement. This breather is also ideal for transformers located in remote or hard-to-reach areas where regular maintenance is challenging or impractical.
Venturi Desiccant Breathers: These breathers utilise the Venturi effect to enhance air flow and desiccant performance. The Venturi tube creates a low-pressure zone that draws air away from the breather, increasing the desiccant’s moisture absorption capability. These breathers are often used in applications requiring high airflow rates or high-humidity conditions, as the risk of moisture ingress is higher in such environments.
Hybrid Desiccant Breathers: Hybrid desiccant breathers combine the advantages of multiple desiccant materials to enhance the effectiveness of moisture removal in transformers. This breather type is employed when precise control over moisture is crucial. Desiccant materials such as silica gel, molecular sieve, and activated alumina may be further included to achieve superior moisture absorption and removal so the transformer can function optimally.
Maintenance and Replacement of Desiccant Breathers
Regular maintenance and prompt replacement of desiccant material are needed for the consistent operation and effectiveness of the desiccant breathers. Here are some maintenance and replacement guidelines for optimal breather performance.
- Look at the Color of the Desiccant: Regularly check the desiccant material for signs of saturation and the time for replacement. Self-indicating desiccants such as silica gel change colour from orange to green when saturated, signalling the need for replacement. The desiccant material may require more frequent replacement in humid conditions because of the increased moisture load.
- Check Breather Housing: Ensure the breather housing is intact and free from damage to prevent unfiltered air from bypassing the desiccant material.
- Make Sure There Is No Oil Contamination: Ensure the conservator tank is securely sealed to prevent oil from leaking into the breather and contaminating the desiccant. If oil leakage occurs, replace the desiccant and thoroughly clean the breather.
- Replace Damaged Components: To ensure optimal breather performance, regularly inspect the valves and replace the particle filters as needed.
Ensuring Proper Desiccant Breather usage
It is important to follow these guidelines to ensure that the right desiccant breather is selected and used according to its set-up to ensure optimal performance and protection for transformers.
Select the Appropriate Breather: It is important to choose a breather that matches the transformer’s size, location, and operating conditions. Advanced or hybrid breathers should be considered for their moisture control capabilities for transformers placed in high-humidity environments.
The transformer’s size and load profile influence the breather’s required capacity and design. Large transformers or those operating under heavy loads may need breathers with greater desiccant capacity or faster moisture absorption rates to provide adequate protection.
Consistent Monitoring: Establish a system for regularly monitoring the desiccant and the breather’s overall condition. This proactive approach helps prevent unexpected breakdowns and failures caused by moisture ingress.
Further, the availability of staff and maintenance resources should be evaluated when selecting a desiccant breather. Self-regenerating breathers that require less frequent maintenance may be more cost-effective in the long run, especially if regular maintenance is challenging.
Consider the Environment: In challenging environments, such as coastal areas or regions with extreme weather, it may be necessary to take extra precautions, such as utilising heated breathers or erecting weather shields, to protect the transformer from damage.
Follow Manufacturer Guidelines: Install the breather according to the manufacturer’s instructions. If the desiccant material is not properly installed, the breather will not be effective, as air may bypass it.
Conclusion
Desiccant breathers are crucial for maintaining transformers and protecting the insulating oil and internal components from moisture-related damage.
By understanding the various types of desiccant breathers, their operation, and maintenance requirements, organisations can maintain the transformer’s performance and extend its lifespan. Implementing regular monitoring, proper maintenance, and best practices also ensures a reliable and efficient power distribution system with moisture-related risks minimised over the long run.
At Stream Peak International, we offer a range of desiccant breathers for safeguarding both equipment and stored fluids from harmful moisture and contamination. We provide guidance on product selection as well as support with installation to ensuring optimal transformer performance and functioning. Connect with our engineers to explore the ideal solution for your requirements.
