Transformer oil filtration - Transformers, which support the power industry, depend on the health and efficiency of transformer oil for their own performance. Transformer oils are maintained through a plethora of methods to support the efficacy of transformers and enhance longevity of the instrument. One of these methods is transformer oil filtration.

Contamination of transformer oil - Transformer oil accumulates acids, gases, moisture and metal particles owing to which they deteriorate over course of time. Not only used oil, even new oil may have pollutants which emphasize the need of transformer oil filtration. Some dissolved water is absorbed by paper insulation of transformer and affects the insulating attributes of the oil.

BDV and purity of transformer oil - BDV is breakdown voltage of the transformer oil is its dielectric strength.  Impurities in the oil can be detected through BDV or Breakdown Voltage. Dry and clean transformer oil has better BDV value than that with impurities. Minimum BDV of safe transformer oil is between 30 kV and 40 kV. Moisture content in BDV test must be less than 10 ppm or parts per million. PPM indicates moisture content in the oil and maximum allowed content is 35 ppm. BDV value of transformer oil is directly proportional to its quality. The lower the BDV value is, the quality gets lower.

Electrical stress of transformer oil - Due to frequent change in voltages, transformer oil gets deteriorated. The increased requirements on the oil result in increased electrical stress on the insulating fluids. To handle such stresses the oil must ensure good dielectric strength and low water residue, so that the oil is also an effective coolant. Oxidation of transformer oil results in sludge formation.

Oxidation of transformer oil - Rise in temperature results in oxidation of transformer oil, thus giving by products such as acids and sludge. Though oxidation cannot be stopped, it can definitely be mitigated.

To mitigate oxidation, oxygen must be removed from the oil as the gas reacts with inner functioning of the transformer.

Purification of transformer oil - These contaminations are removed employing purification and filtration methods. Transformer oil filtration is a part of the purification process. Transformer oil is purified by raising the temperature so that the viscosity is decreased, thereby separating oil from moisture and gases. Consequently sludge and dirt are removed from the oil by using filter candles and through filtration process.

Transformer oil degasification - Solid particles are partially removed from the oil through filters. Centrifugal forces are employed to separate oil from water and solid particles after which vacuum treatment separates gases and dehydrates oil. In centrifugal system, the solids or dirt are settled in the bottom and oil is filtered from the top. However solids sized below 10 microns could not be removed through centrifuging for which edge and depth filters are employed. Besides centrifugation, adsorption and vacuum drying processes remove contamination from transformer oil. In adsorption method, mineral and synthetic adsorbents are employed to remove moisture and other impurities dissolved in oil.

Vacuum drying - Vacuum drying, where oil is heated up and pumped through degasifier, is a popular method to remove impurities. After removing moisture content, the heated oil passes through filters of different sizes. The first filter does not allow particles above 1 mm and second filter does not allow those above 50 microns. The filters are enabled with exclusively designed cartridges and let the refined oil pass through an ionic chamber where acid contents are removed.

Benefits of the filtration process - Besides improving insulation and lifespan of the oil, filtration mitigates chances of transformer breakdown and adds to profits by reducing repairs and ensuring proper maintenance.  Insulating oils, if not maintained are sensitive to arcing, overheating, corona discharges and damage to insulating attributes, which result in breakdown of system.