Process for controlling dryer capable of dehumidifying air entering the oil expansion vessels used in electrical appliances

Abstract

Process for controlling a dryer (10), suitable of dehumidifying air entering oil expansion vessels used in electrical appliances, in which a protective casing of the dryer (10) surrounds at least two dehumidifying tanks or vessels (S1, S2) containing means suitable to absorb air humidity coming from the outside and which can be thermally regenerated by resistors (R1, R2),the resistors (R1, R2) are connected with a load cell (C1), suitable to determine the state of saturation of the absorption means, so that detecting by the load cell (C1) of a measured mass value (M) greater than a predefined threshold value (MFS) operates the resistors (R1, R2) in order to regenerate the absorption means to the original state.

Description

technical field [0001] In general, the present invention relates to a method of controlling a dryer capable of dehumidifying air entering an oil expansion tank in electrical appliances, in particular oil-insulated electrical appliances such as transformers, load switches, etc.; the invention It also relates to a dryer using this control method. Background technique [0002] Appliances containing insulating oil usually contain an oil expansion tank that has the function of counteracting the oil volume changes that inevitably occur in the appliance due to sudden temperature changes; this oil expansion tank is supplied in advance Air treated in a specific dryer to remove or substantially reduce its humidity to measure the correct value of the breakdown voltage of the insulating oil. [0003] The prior patent document WO 2005 / 055255 discloses a known type of dryer in which a dehumidification box has an inlet for dehumidifying air, an outlet for dehumidified air and suction mean...

AI Technical Summary

Problems solved by technology

[0006] However, depending on the method of operation for this function, the resistance is not activated when air flows into the oil expansion tank, unless an orientation sensor suitable for detecting air flow and / or its control is used, or suitable for measuring dehumidification Pressure sensors for the pressure difference between the oil expansion tank and the oil expansion tank; however, such sensors need to have sufficient measurement accuracy because the airflow through the oil expansion tank is typically between 0.5 and 2.5 L / min, so they are very expensive

[0007] Furthermore, the detection of the humidity of the dry air does not always provide a complete regeneration of the absorption means, because sometimes the air entering the dehumidification box follows its preferred path, which distorts the detection itself and passes the high frequency Resistivity results in humidity sensor operation and failure, with attendant reliability issues related to the aforementioned resistance caused by continuous switching cycles

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