- Silica Gel Breather Definition: A silica gel breather is a device used to filter moisture from the air entering a transformer, protecting its insulation.
- Air Flow Mechanism: Transformer oil expansion and contraction cause air to move in and out of the conservator tank, necessitating filtration.
- Moisture Absorption: Silica gel effectively absorbs moisture from the air, ensuring the air entering the transformer is dry.
- Dust Filtering: The oil seal cup in the breather traps dust particles, preventing them from contaminating the transformer oil.
- Color Change Indicator: Silica gel crystals change from dark blue to pink as they absorb moisture, indicating when they need to be replaced or regenerated.
Silica Gel Breather of Transformer
In a conservator-type electrical power transformer, changes in load and ambient temperature change the temperature and volume of the transformer insulating oil. Expanding oil displaces air from the conservator. Contracting oil draws replacement air into the conservator tank. Sealed transformers and conservators with an air cell use different arrangements, so the breathing path depends on the transformer’s design.
Ambient air contains water vapour. If moisture enters a transformer, it can reduce the dielectric strength of the insulation and accelerate the ageing of insulating paper. A breather reduces this source of moisture ingress by passing incoming air through a desiccant, but it is only one part of the transformer’s moisture-control system.
Silica gel breather for transformer is connected to the conservator’s air space by a breathing pipe.
Construction of Silica Gel Breather
A conventional transformer breather has a transparent container filled with silica gel and a connection to the conservator breathing pipe. Screens or perforated parts distribute the airflow and retain the gel. Some designs have an oil-seal cup or another closing system at the air inlet. Silica gel adsorbs water vapour on its internal surface. The humidity or dew point of the outlet air depends on the breather design, airflow, temperature and condition of the gel, so fixed values do not apply to every unit.
Working Principle of Silica Gel Breather
When the transformer inhales, ambient air flows through the silica gel before it reaches the conservator. The gel adsorbs water vapour, but its capacity is finite. Indicator colours depend on the desiccant and manufacturer: some products change from orange to green or white, while traditional cobalt-chloride indicator gel can change from blue to pink. Operators should use the colour limits and service instructions for the installed product. In designs with an oil seal, the cup limits continuous contact between the gel and ambient air when the transformer is not breathing. Its exact filtering and sealing action depends on the breather design.
A pressure difference across the breather moves the oil in a hydraulic seal and allows air to pass in the required direction. During inhalation, the incoming air passes through the desiccant. During exhalation, air from the conservator passes back through the breather. The gel condition, breather body, airflow path and oil level in the seal cup should be checked as specified by the manufacturer. Saturated gel, a low oil level, damage or a blocked breathing path can reduce protection or interfere with normal breathing.
