As a key component to ensure the safe and stable operation of power transformers, the transformer breather (also known as a moisture absorber) plays an irreplaceable role in maintaining the insulation performance of transformer oil and extending the service life of the equipment. This article will detail the working principle of the transformer breather, analyze the reasons for the rapid discoloration and blackening of silica gel, and deeply integrate professional knowledge with practical application scenarios, especially for 500 kva distribution transformer and isolation power transformer, to provide valuable reference for overseas users in equipment operation and maintenance. JINSHANMEN TECHNOLOGY CO., LTD, as a professional power equipment manufacturer, has rich experience in the production and R&D of transformers and supporting components. The company mainly produces oil immersed power transformers, dry-type power transformers, oil immersed three-dimensional coiled power transformers, dry-type three-dimensional coiled power transformers, mining explosion-proof dry-type transformers, mining explosion-proof mobile substations, amorphous alloy power transformers, on load capacity regulating power transformers, locomotive dry-type transformers, as well as prefabricated substations, modular substations, wind energy box type substations, high and low voltage switchgear and other transmission and distribution equipment.
I. Working Principle of Transformer Breather
The core function of the transformer breather is to balance the internal and external pressure of the transformer and filter the moisture and impurities in the air entering the transformer, so as to prevent the transformer oil from damp and deterioration, and ensure the normal operation of the transformer. Whether it is a 500 kva distribution transformer used in industrial and commercial power distribution or an isolation power transformer used in special scenarios such as precision equipment power supply, the working principle of its breather is consistent, which is mainly based on the thermal expansion and contraction of transformer oil. When the temperature of the transformer oil changes, the volume of the oil will change accordingly, leading to changes in the pressure inside the transformer oil conservator, and the breather will complete the "breathing" process to maintain pressure balance.
1. When Transformer Oil Temperature Rises
1.1 Corresponding Changes When Transformer Oil Temperature Rises: When the transformer is in operation, the load current flows through the winding to generate heat, which causes the temperature of the transformer oil to rise. As the temperature increases, the volume of the transformer oil expands, and the air in the transformer oil conservator is compressed, resulting in an increase in internal pressure. In order to maintain the pressure balance inside the transformer and avoid damage to the transformer tank due to excessive pressure, part of the air in the oil conservator will be discharged into the atmosphere through the transformer breather. At this time, bubbles will appear in the oil collection cup of the breather, and sometimes the bubbles will be very intense, which is a normal "exhalation" phenomenon of the breather. This process is particularly obvious in 500 kva distribution transformer with large load changes, because the oil temperature fluctuation of such transformers is more frequent during peak power consumption periods.
1.2 Air Flow Process: Oil Conservator → Breather Connecting Pipe → Glass Cover (Silica Gel) → Glass Cylinder → Oil Seal Sheet → Oil Collection Cup → Air Hole → Atmosphere. During the air discharge process, the silica gel in the breather will initially filter the air, removing a small amount of moisture and impurities in the air, ensuring that the discharged air does not carry harmful substances that affect the environment.
2. When Transformer Oil Temperature Drops
2.1 Corresponding Changes When Transformer Oil Temperature Drops: When the transformer load decreases or the ambient temperature drops, the temperature of the transformer oil will decrease accordingly. As the temperature decreases, the volume of the transformer oil shrinks, and the air in the transformer oil conservator is expanded, resulting in a decrease in internal pressure. In order to avoid negative pressure inside the transformer (which may cause the tank to be deformed by external atmospheric pressure), the breather will inhale air from the atmosphere to balance the pressure inside the oil conservator. At this time, bubbles will appear in the glass cylinder of the breather, which is a normal "inhalation" phenomenon of the breather. For isolation power transformer that requires high stability, the stable operation of the breather is crucial, because any pressure imbalance may affect the insulation performance of the transformer and further affect the power supply quality of precision equipment.
2.2 Air Flow Process: Atmosphere → Air Hole → Oil Collection Cup → Oil Seal Sheet → Glass Cylinder → Glass Cover (Silica Gel) → Breather Connecting Pipe → Oil Conservator. When inhaling air, the air first passes through the oil in the oil collection cup (oil seal), which can filter out most of the dust and impurities in the air; then it passes through the silica gel, which absorbs the moisture in the air, ensuring that the air entering the oil conservator is dry and clean, thus preventing the transformer oil from being damp and deteriorating.
II. Reasons for Rapid Discoloration of Transformer Breather Silica Gel
Silica gel is the core filter component of the transformer breather, which is usually blue in the dry state and turns red after absorbing moisture. Under normal circumstances, the discoloration of silica gel is very slow, and it can be used for several months or even longer. However, in actual operation, the silica gel of the breather may discolor rapidly, which not only increases the maintenance workload but also may indicate potential faults in the equipment. This problem is common in both 500 kva distribution transformer and isolation power transformer, and the main reasons are as follows:
2.1 Long-term rainy weather leads to high air humidity. The silica gel absorbs a large amount of moisture in the air, resulting in rapid discoloration. This is an objective environmental factor, especially in areas with high humidity all year round. The silica gel of the breather needs to be replaced more frequently.
2.2 The capacity of the breather is too small. For transformers with large load changes and frequent breathing, such as 500 kva distribution transformer used in industrial parks, if the capacity of the breather is not matched, the moisture absorption capacity of silica gel cannot meet the actual demand, leading to rapid saturation and discoloration.
2.3 There are cracks or damages on the silica gel glass cover or tank. If the glass cover or tank of the breather is cracked, damp air in the atmosphere can directly enter the silica gel tank without being filtered, causing the silica gel to absorb moisture and discolor rapidly. Therefore, regular inspection of the appearance of the breather is an important part of daily maintenance.
2.4 There is no oil or the oil level is too low in the oil seal cover at the lower part of the breather. The oil in the oil seal cover plays a role of primary filtration and sealing. If there is no oil or the oil level is too low, the oil seal cannot play a good role, and damp air directly enters the silica gel tank, accelerating the discoloration of silica gel. It is recommended to check the oil level of the breather regularly and replenish the oil in time.
2.5 Improper installation of the breather. For example, the silica gel gasket is cracked and unqualified, the screws are loose, the installation is not sealed, etc. These problems will lead to damp air entering the oil conservator without passing through the silica gel filtration, resulting in rapid discoloration of silica gel. Especially for isolation power transformer that requires high sealing performance, improper installation of the breather will not only cause rapid discoloration of silica gel but also may affect the insulation performance of the transformer.
III. Reasons for Blackening of Transformer Breather Silica Gel
It is normal for the transformer breather silica gel to turn red due to moisture absorption, but sometimes the upper and lower parts of the silica gel in the breather may turn black, which is an abnormal phenomenon and needs to be paid attention to. This phenomenon may occur in both 500 kva distribution transformer and isolation power transformer, and the root cause is that transformer oil enters the breather, specifically as follows:
3.1 Blackening of the lower part of the silica gel: It is caused by excessive oil in the oil collection cup at the lower part of the breather being inhaled during the "inhalation" process of the breather. When the oil level in the oil collection cup is too high, the oil will be sucked into the silica gel tank along with the air during the inhalation process, causing the lower silica gel to be contaminated by the oil and turn black.
3.2 Blackening of the upper part of the silica gel: It may be caused by a problem with the bellows in the oil conservator. If the bellows is damaged or leaking, the transformer oil vapor in the oil conservator will enter the breather along the connecting pipe, and the oil vapor will condense on the upper silica gel, causing the upper silica gel to turn black. In summer, the temperature is high, the "breathing" of the transformer is intensified, and the amount of oil vapor exhaled is more, so the phenomenon of blackening of the upper silica gel is more obvious.
IV. Conclusion
The transformer breather is a key component to ensure the safe operation of transformers. Its stable operation is directly related to the service life of the transformer and the safety of the power supply system. Whether it is a 500 kva distribution transformer in power distribution scenarios or an isolation power transformer in special power supply scenarios, it is necessary to pay attention to the working state of the breather, regularly inspect the color change of silica gel, and timely handle the problems of rapid discoloration and blackening of silica gel. JINSHANMEN TECHNOLOGY CO., LTD has rich experience in the production of transformers and supporting breathers, and can provide high-quality transformers and professional technical support for global users, helping users reduce maintenance costs and ensure the stable operation of power equipment.