SPT12_Power Transformers, Breather
Miguel Martínez Pe?as
Electrical Infrastructure Lead Expert-Technology en EDP Renewables
Let's talk about an accessory, which sometimes is not given much attention; but it has great importance, the “Breather” ??
Why do we use it?
The service life of transformers is closely related to the service life of the oil-paper insulation system; the reason is that if the mechanical stability of the oil-paper insulation is lost, there is a risk of electrical failure and, consequently, general failure of the transformer.
There are different measures in this regard, but there are two that allow avoiding external influence, such as the conservative and the breather.
Focusing on the Breather ??, the one we know as the type has commonly been used “Silica Gel Breather”
When an electrical power transformer is loaded, the temperature of the transformer insulating oil increases, consequently the volume of the oil is increased. As the volume of the oil is increased, the air above the oil level in conservator will come out. Again at low oil temperature; the volume of the oil is decreased, which causes the volume of the oil to be decreased which again causes air to enter into conservator tank
Note that natural air contains moisture that can mix with transformer oil and harm its insulation. It is crucial to filter this moisture out. A silica gel breather is the most common method for this purpose.
Silica gel breather for transformer is connected with conservator tank by means of breathing pipe. It is a container filled with silica gel that air passes through. Silica gel absorbs moisture very well ??
Silica gel crystals change color; note that the color of the silica gel crystals is generally used as an indicator of when the silica should be replaced. It is dark blue when dry; when the gel absorbs moisture and becomes saturated ?, the color changes to pink (see Figure 1).
Adsorption capacity ?over a period of 3 – 12 months, after that the Silica Gel ?must then be replaced ??
?Why? Due to as the silica gel will be completely saturated with water and therefore no longer able to absorb any additional moisture.
It is a very simple device based on a great idea, but it has the problem mentioned above, of having to do very rigorous maintenance; something that we all know is complicated, nobody is going to be looking at the transformer every day.
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Currently, this has been solved with new devices, which are becoming more and more common: Maintenance-free dehydrating breathers that avoid frequent replacement of silica gel by measuring the humidity level of the air in the pipe system and forward the results to control unit.
How do they work ?
In normal operation, the air flowing to the oil expansion vessel is dried by passing it over the silica gel and the moisture content of the air in the pipe to the expansion tank is constantly monitored. When the moisture content reaches the defined limit value, regeneration of the desiccant is activated, depending on the behavior of the operating equipment.
To summarize the main advantages would be:
? Reduces maintenance
? Reduced operating costs and increases operating reliability
? Active protection of the insulation medium against moisture
? Condition dependent and self-learning algorithm
? Easy retrofitting
There are different models of manufacturers on the market, however we must choose the specific model depending on the main parameter such as oil volume, for example we have different types for OLTC, Main Tank Power Transformer up to 40-50 MVA, Main tank PT above 200 MVA, Reactors, etc..
Below figures you can see a model from one of the usual suppliers as MESSKO (MR)
Finally, one extra advantage of these devices that I find very interesting ?? is that they are known as e-devices, allowing monitoring through an integrated transformer control system. They contribute to optimizing monitoring and would be a necessary part of future digital substations.
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I share with you some links about interesting videos and information about it.
I hope you find it interesting
Best wishes and be happy friends
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