Increasing transformer longevity by curbing oil deterioration

Removing or minimizing acidity content of transformer oil is important because acidity hampers the longevity of the oil and causes ageing. Acidity accentuates formation of insoluble deposits or x waves and generates colloids, which mitigate dielectric strength of the insulating material. Controlling acidity improves efficiency and reliability of the transformer oil. Insoluble suspensions caused by acidity mitigates cooling efficiency of the transformer.
When transformer ages, carboxylic acids are formed and these acids are absorbed by the paper insulation thus initiating the degradation of the entire system. Ageing may be divided into three types Pyrolysis (due to heat), hydrolysis (due to water) and oxidation, which are all accelerated by heat, by products, contamination, work overload and voltage waves.
Transformer oil deterioration occurs due to overheating, electrical stress, contamination and oxidation. Tiny water droplets and water settled in the bottom of the transformer causes oil deterioration.
When acid content increases its quantity enough to become a sludge and oxidation is developed. Oxidation produces low molecular weight acids which hamper or degrade the entire insulation system. High molecular weight acids do not dissolve in the oil and are not that aggressive in oil degradation. As a result, the electric and chemical properties of the insulating oil suffer a setback. To mitigate oxidation, oxygen must be removed.
Oil deterioration is detected by BDV of the transformer oil. The BDV or breakdown voltage of the transformer throws light on the dielectric attributes which in turn show the moisture content in the oil.
Potassium hydroxide, also known as caustic potash, is employed for transformer oil acidity removal. When added in transformer oil, it neutralizes the acidity effect. 0.3 milligram of potassium hydroxide is sufficient to neutralize one gram of transformer oil.
When a given amount of alkali is added to the transformer oil, the oil becomes acidic, neutral or alkaline based on the pH value previously existing in the oil.
Transformer oil deterioration is averted by removal of dissolved gases and moisture in the transformer oil. A degassing and dehydration chamber is employed for this purpose and oil deterioration is eradicated with the help of vacuum pumps which purify contaminated oil which is passed three to five times in the filtration chamber.
Dehydration of transformer oil also removes solid particles and sludge deposited. The transformer oil acidity removal process is complete only when the transformer oil meets standards including OEM and IEC among other equivalent standards.
Transformer oil deterioration is also mitigated by centrifuging, where centrifuges are used to discriminate dirt from the oil. Centrifugation is applied in voltages more than 35 kV.
Oil deterioration is also curbed by employing mineral and artificial adsorbents, which remove water and impurities in the oil. Single use Fullers Earth regeneration and multiple use reactivation regeneration enables to restore the ‘new’ or ‘better than new’ status of the transformer oil.
On a concluding note, preventive maintenance, by regular oil sampling and analysis and electrical measurements are important routine while using transformers. Such caution averts losses and repairs which could be translated as a part of the profits.


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