function of a transformer breather
The function of a transformer breather (also known as a dehydrating breather)
A transformer breather is an important auxiliary component on the transformer's oil conservator (oil storage tank). Its core function is to prevent moisture and impurities in the external air from entering the transformer, while ensuring the pressure inside the oil conservator is balanced with the outside, thus protecting the transformer's insulation performance and operational safety. Here is a detailed explanation of its specific functions and working principles:
Absorbing moisture and preventing dampness to protect insulation
The insulating oil and insulating materials (such as insulating paper) inside the transformer are very sensitive to moisture. If moisture in the air enters the oil conservator, it will cause the insulating oil to deteriorate due to dampness (decreased breakdown voltage, increased dielectric loss), and the insulation performance of the insulating paper will also decline. In severe cases, it may even lead to short-circuit faults.
The breather absorbs moisture in the air entering the oil conservator through its internal desiccant (such as silica gel), ensuring that the air entering the transformer is dry.
Filtering impurities to avoid contamination
If impurities such as dust and particles in the external air enter the oil conservator, they will contaminate the insulating oil and affect its heat dissipation and insulation performance. The desiccant and structure of the breather can filter the air to a certain extent, blocking impurities from entering.
Balancing pressure to protect the oil tank
During the operation of the transformer, the oil temperature changes with the load, causing the volume of oil in the oil conservator to expand or contract, thereby changing the pressure inside the oil conservator.
- When the oil temperature rises, the oil volume expands, the pressure inside the oil conservator increases, and the excess air is discharged through the breather;
- When the oil temperature drops, the oil volume contracts, the pressure inside the oil conservator decreases, and external air enters through the breather.
This process prevents the oil tank from being damaged due to drastic pressure changes and avoids unfiltered air from entering directly.
A breather usually consists of the following parts: connecting pipe, silica gel tank, desiccant (silica gel), and bottom oil seal cup.
- The silica gel tank contains color-changing silica gel (usually blue, turning pink after absorbing moisture), which can visually show the moisture absorption state.
- The bottom oil seal cup is filled with transformer oil (or special sealing oil), forming an oil seal to further block moisture and impurities in the air. At the same time, when the pressure changes, air must pass through the oil seal to enter or exit, reducing the direct circulation of unfiltered air.
When external air enters, it first passes through the oil seal to filter out some impurities and water vapor, then further absorbs moisture through the silica gel, and finally the dry air enters the oil conservator; when the internal air is discharged, it also passes through the silica gel and oil seal, reducing the direct loss of oil vapor in the oil conservator.
If the breather fails (such as saturated and discolored desiccant, missing oil seal, broken silica gel tank, etc.), it will cause moist air and impurities to enter the transformer directly, accelerating insulation aging, shortening the equipment life, and even causing faults. Therefore, during operation, it is necessary to regularly check the state of the silica gel, replace the saturated desiccant in time, and replenish the oil seal oil to ensure the normal operation of the breather.
In short, the breather is a key component of the transformer's "respiratory system". It provides an important guarantee for the safe and stable operation of the transformer by drying and filtering air and balancing pressure.
