A transformer breather works by filtering moisture from the air that enters the transformer, protecting the insulating oil from degradation.
Transformers often use oil for insulation and cooling. As the transformer heats and cools with load variations, the oil expands and contracts. This change in volume requires the transformer tank to 'breathe', meaning it takes in air when the oil cools and expels air when the oil heats up. This breathing process occurs via a component called a breather.
The Breather's Primary Function
The main function of the breather is to filter out the moisture from the air before it comes into contact with the transformer's insulating oil. Moisture in the oil can significantly reduce its insulating properties and cause damage to the transformer over time.
How It Works: The Role of Silica Gel
The breather achieves this moisture filtration using a desiccant material.
- Silica Gel Core: Breathers consist of silica gel, a granular, porous form of silicon dioxide.
- Moisture Absorption: Silica gel is a highly effective drying agent because its structure allows it to absorb and hold a significant amount of water vapor from the air.
- Air Passage: As air is drawn into the transformer during the cooling cycle, it passes through the silica gel in the breather. The silica gel absorbs moisture from the air, ensuring that only dry air reaches the conservator tank and subsequently the main transformer tank.
Based on the reference: "The breather is used in the transformer to filter out the moisture from the air. Breather consists of silica gel which absorbs moisture from the air."
The Role of the Conservator Tank
The reference also mentions: "Conservator tank present at the top of the transformer which allows adequate space for expansion of oil." The breather is typically connected to the conservator tank. The breathing action (inhalation and exhalation of air) happens primarily through the breather connected to the conservator tank, which acts as a buffer for the oil's volume changes.
Why is Moisture Control Important?
Moisture is detrimental to transformer oil for several reasons:
- Reduces Dielectric Strength: Water significantly lowers the oil's insulating capability, increasing the risk of electrical breakdown.
- Accelerates Aging: Moisture promotes the degradation of both the oil and the paper insulation within the transformer.
- Corrosion: It can lead to corrosion of internal metal parts.
By removing moisture, the breather helps maintain the lifespan and reliability of the transformer.
Practical Aspects: Monitoring the Breather
Silica gel often contains an indicator that changes color as it absorbs moisture.
| Silica Gel State | Color Indicator (Common) | Moisture Absorption Level |
|---|---|---|
| Dry | Blue (or Orange) | Low |
| Partially Moist | Purple/Pink | Medium |
| Saturated | White/Pale Pink | High |
- When the silica gel turns pink or white, it indicates that it is saturated with moisture and can no longer effectively dry the air.
- At this point, the silica gel needs to be replaced or reactivated (by heating to remove the absorbed moisture) to ensure the breather continues to function correctly.
Regular inspection and maintenance of the breather, particularly checking the silica gel color, are crucial for the health of the transformer.
