Transformer oil dehydration
Drying of transformers is mandatory when deviations of the numerical value of the insulation resistance from the normalized value are downwards. To calculate the current insulation resistance, a special formula is used that takes into account the rated power and voltage of the transformer, as well as a special correction factor that characterizes the effect of temperature on the insulation resistance.
Drying the power transformer should not cause a sharp change in the temperature of the insulation and windings, as this can lead to damage caused by thermo-mechanical stresses. The temperature of the windings should not increase faster than 5 … 7 ºС per hour.
Due to the variety of needs in the field oil dehydration, GlobeCore manufactures cabinets with a vacuum system, cabinets for heating windings (without vacuum), as well as cabinets for drying various raw materials and materials (powders, pastes, foodstuffs, wood, etc.)
Drying insulation of transformers can also be control. It is performed in such cases when:
● there are signs of wetting the oil and (or) a leakage of the transformer has occurred;
● the maximum storage period of the transformer without oil was exceeded or timely refilling was not carried out;
● the active part of the transformer was unsealed for longer than the allowable time;
● a deterioration in the insulation condition was found as a result of planned tests.
Control drying of transformers can be implemented by creating a high vacuum and using a low-temperature vapor trap, using direct current or short-circuit currents to heat the windings.
Drying of oil-free transformers is necessary when the insulation is strongly wetted, traces of water appear on the active part or tank, and also when insulation performance has become much worse than normalized values. Technically, such a procedure can be carried out using a drying cabinet, a special chamber, or drying in its own tank. The best results in terms of quality are obtained by drying the active part of the transformer under vacuum in a special drying cabinet.
The oil dehydration unit for transformers UVS-6S includes an automated control of the drying process, performed by automatically registering the following parameters:
● heating temperature;
● the degree of vacuum in the installation;
● change in the degree of moisture of the insulation during the drying process;
● the presence of condensate in the chamber.
The drying process parameters are automatically registered on electronic media in the memory of the installation control device with file recording and the subsequent possibility of generating a report and protocol.