Transformers play a vital role in the effective functioning of power system transmission and distribution network . Therefore the operating condition of the transformers have to be checked periodically to ensure reliable service. The efficiency of transformer depends on the insulation materials used during the manufacturing of the transformer . The oil insulation deployed in the power transformers is used to transfer the heat developed inside the transformer core and windings and also be able to withstand the stress due to heavy loading and short circuit.
Transformer oil Deterioration –
Overtime due to continued operation of the transformer the insulating oil in the transformer gets deteriorated by oxidation and thermal byproducts that get deposited in the oil. These ageing products formed may cause severe breakdown of the transformer leading to heavy interruptions in the power supply. There arise the demand of preventative maintenance actions to be taken timely to avoid any unexpected outages in the network. The maintenance of the transformer includes the fact of improving the quality of the insulating oil which in turn increases the life span of the transformer.
Effects in the oil quality –
The quality of the insulating oil gets deteriorated over years and it’s necessary to analyse the contaminated oil. Most likely the mineral oil which is used as insulation oil in the transformers known to be contaminated by moisture content, sludge and acid products. The transformer oil filtration system is a method of removing the suspended sludge materials present in the oil. The impurities of the transformer oil also affects the solid insulation material and hence decreases the performance characteristics of the transformer. The condition of the transformer can be assessed by analyzing the transformer insulating oil present in it. The amount of dissolved gases and acid content in the oil speaks about the quality of the oil.
Need for Oil Filtration System –
The contaminated transformer oil contains approximately 60 ppm of moisture content and considerable amount of oxygen that gets dissolved in it. To remove these impurities high vacuum transformer oil filtration machine is engaged to purify the oil and restore the standard quality values of the oil.
Before the oil enters the filtration system the temperature of the oil is increased and then the oil is made to pass through the highly designed filter where the oil impurities are eliminated and then the oil is further treated for dehydration and degassing. After all this process the standard quality values of the transformer insulating oil can be restored by a considerable extent.
High Vacuum oil filtration machine –
Now a days high rating transformer oil filtration machines are available to process the contaminated oil in the onsite itself . These machines are highly sealed to avoid any abnormalities due to environment exposure. The transformer oil is pumped in to the high vacuum oil filtration machine by means of the inlet pump provided. The filtration process starts with the heating up of the oil which later separates the moisture content and the dissolved gases present in the insulating transformer oil. The heaters are operated by specifically designed controllers in order to avoid any overheating inside the machine and the pressure values are also at check by suitable arrangements.
The heated oil is now made to pass through series of filters. First a preliminary filter is fixed through which particles of size 1mm and above cannot pass through, thus eliminating suspended particles from the oil. Then the oil is found to be moved to filter press where sludge impurities of approximately 50microns are got filtered. Filters with special cartridges are constructed within the equipment which again finely filters the oil. Then the oil enters an ionic chamber where the acidic substances are made to react and gets eliminated.
The next step in purifying the insulating liquid is to remove the moisture content and dissolved gases developed in it. This can be done by subjecting the oil to high vaccum in the dehydration chamber made of steel in order to withstand the high pressure dropped in it. Then the oil is made to pass through a thin layer of oil made of copper or aluminum to get rid of the dissolved gases present in it. The filtered oil is pumped out through the discharging chamber. The whole process is repeated for four to five times in order to restore the standard quality values of the oil. Now the filtered oil can be tested for its quality and the values before and after oil filtration system can be compared and it would be found to be improved.