Deshumecedor de transformador, Esquemas y mapas conceptuales de Eficiencia Energética

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File : ESSICC VE UNCONTROLLED COPY Rev. 4 dtd 09/10/

AIR DEHYDRATING BREATHERS

threaded and/or flanged connection, single unit and modular assy

type VE 05 - 10 - 15 - 30 - 50 - 80 - 100 - 150

for power transformers

1. GENERAL INFORMATION

Air dehydrating breathers are transparent hollow cylinder tubes which contain chemically pure silicium salt (silicagel) with coloured indicator. The air breathed inside the transformer due to the thermal contraction of the oil mass, passes through the silicagel. The silicagel absorbs the humidity, indicating the saturation degree by changing colour as follows: ORANGE silicagel completely dry WHITE silicagel saturated with humidity The salt contained in the breather, when saturated, may be easily removed and regenerated by heating it, inside a ventilated oven, at 120° - 150°C, until the colour becomes orange again. The specific property of the silicagel is its high absorption power of humidity. This is total until the salt has absorbed water for about 15% of its weight, and saturation is reached when the salt has absorbed water for 30 to 40 % of its weight.

2. TECHNICAL FEATURES The upper and lower parts are made in a non-porous corrosion-proof aluminium alloy casting. The hollow cylinder is made of plexiglas and it is protected by a stainless steel cylinder, with windows which allow the visual control of the silicagel colour. In the bottom side of the breather, an hydraulic valve prevents continuos air contact with the silicagel and allows the air to pass in both direction (inlet or outlet) only when there is pressure deficiency or excess inside the transformer. Pressure values for air passage into the dehumidifier are:

0.003 kg/cm^2 inlet , or 0.005 kg/cm^2 outlet The hollow container and the hydraulic valve are separated by a drilled plate with a labyrinth system, which have the double purpose of diffusing inlet air uniformly, and of avoiding that any salt dust may damage the closing system.

3. DRAWINGS AND TECHNICAL DATA A table on the drawings in the following pages shows, the general overall dimensions, the silicagel contained inside the cylinder, the max oil quantity, contained inside the transformer on which the breather must be installed, calculated for normal conditions, as below indicated, using the formula at paragraph 5: Average air temperature 20°C Average air humidity 60% Average thermal cycle “∆ t “ 20°C Average duration of thermal cycle T 8 hours Maintenance interval M 90 days Different environment conditions of the site where the transformer is installed may influence the maintenance interval, when the choice of the size of the breather has been made.

4. PROTECTION OF OUTER SURFACES

Outer surfaces in aluminium alloy are covered with a double coat of high protective paint against all weather conditions, and temperature between - 40°C and + 100°C. All the screws are made in mild steel zinkplated; upon request in stainless steel.

5. CHOICE OF THE BREATHER SIZE (or of the maintenance interval) The choice of the breather size (or maintenance interval) is directly related to the quantity of the breather silicagel contain. The mass of silicagel necessary for the proper functioning is given approximately by a function of 6 variable quantities, listed here following:

• Mass of oil “V” inside the transformer , denominated in dm3 or in litres.
• Average temperature of the air in the environment where the transformer is installed, denominated in °C
• Average Humidity of the air in the environment where the transformer is installed, denominated in %.
• Average thermal cycle “∆t“ of the transformer, denominated in °C, to be calculated as difference between the minimum and the maximum temperatures reached by the oil inside the transformer within a time period.
• Average duration of thermal cycle “T“ denominated in hours, to be calculated as the time interval between two thermal cycles.
• Maintenance interval “M“ denominated in days.

File : ESSICC VE UNCONTROLLED COPY Rev. 4 dtd 09/10/

9. SATURATED STEAM TABLE FOR WATER

Showing the mass of water, in gram (10-3 kg), contained in one cubic meter of air (related to the air temperature and the air humidity).

AIR TEMPERATURE AIR HUMIDITY [%]

°C 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

10. AIR DEHYDRATING BREATHER TYPE TV75 & VE05 (page 5.40) They are small sized dehydrating breathers, particularly fit for assembling on small distribution transformers The type VE05 follows the same manufacturing principles of the bigger sizes like the type VE10. The type TV75 (or TV74) is the cheapest model of our breathers: its top flange is made in corrosion proof aluminium alloy. The silicagel housing is made of cellulose triacetate (cellidor by Bayer), suitable for mineral oil; only upon request, this breather can be fitted with a stainless steel cylindrical protection.