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Dielectric Oil Regeneration The four functions of transformer oil ? Oil provides dielectric strength and acts as a dielectric and insulating medium ? Oil provides heat transfer - acts as a cooling medium ? Oil protects solid insulation - acts as a barrier between paper and the damaging effects of oxygen and moisture ? The oil can be tested to give an indication of conditions inside the equipment - it acts as a diagnostic tool to assess solid insulation Purification of dielectric oil Oil purification is an important part of regular transformer preventive maintenance. In the purification process, water and contaminants such as solid particles and gases are removed from transformer oil . UVM - 6 / 7 MOBILE DEGASSING UNIT ? Meets international standards for transformer oil purification quality ? Water removal to 3 ppm ? Gases removed to 0.1 % by volume ? Dirt and particles removed to 0.2 micron ? Stationary or mobile plants ? Very effective and simple to operate Dielectric oil regeneration • There are different international regulations pertaining to the regeneration process . • IEC 60422 -2013. • IEEE C57.637 -2015 The importance of oil regeneration Oil regeneration • IEEE Std C57.106 -2015 • Defines regeneration is the removal of contaminants and decomposition products, such as polar, acidic or colloid materials from electrical insulation fluids with the help of chemical or adsorbing materials. Regeneration commonly includes treatment with clay or other adsorbents . Oil treatment methods To change or to regenerate ? Oil Acidity . • Acidity of used oil is caused by the formation of oxidation products . • Acids and other products of oxidation, as well as water and other impurities, influence the dielectric properties of oil . • Acids have an impact on cellulose degradation and may cause corrosion of transformer metal parts . How does transformer oil oxidize ? • Thermic and electrical stress • Cellulose decomposition • Chemical reactions due to impurities Chain breaks + Molecular regrouping Oil chain molecule CH 2 CH 3 CH 3 n Acids Peroxides Alcohols Soap Cetone Aldehydes Epoxy . Oxygen Oil acidity . Oil oxidation Experiment Catalyst Water Hours Acid number Control None Low 3500+ 0,17 Humidity None High 3500+ 0,9 Iron Iron Low 3500+ 0,65 Humidity and iron Iron High 400 8,1 Copper Copper Low 3000 0,89 Humidity and copper Copper High 100 11,2 The tests ended when they saw the first sign of sludge Source: Dobble Laboratories Interfacial tension ASTM 971 • The interfacial tension between oil and water provides a means of detecting soluble polar impurities and decomposition products. This parameter changes quite rapidly in the early stages of aging, but stabilizes while the deterioration is still moderate . Interfacial tension ASTM 971 • Presence of polar impurities has a direct effect on interfacial tension . Acceptable Problematic Unacceptable mN/m Over 32 Between 32 and 28 Below 28 Interfacial tension ASTM 971 • Polar contaminants dissolved in oil (not polar), increase its affiliation with water (polar substance) . Oil regeneration Oxidation inhibitors • The most common types of inhibitors used in transformer oils are of phenol type : 2 ,6 -di -tret -butyl - paracresol (DBPC) and 2 ,6 -di -tret - butyl phenol (DBP) . The efficinc of the inhibitor depends on the chemical composition of the base oil . Inhibitor content. • The amount of inhibitor is recommended as a percentage of the total amount of the insulation fluid . Acceptable Problematic Unacceptable Over 0.2% Between 0.1% and 0.2% Less than 0.1% Problems caused by lack of inhibitor . Parameters of regenerated oil • Oil regeneration influences three parameters : • Physical. • Viscosity. • Color. • Interfacial tension. • Electrical. • Dielectric strength. • Power factor. • Chemical. • Neutralization number. • Resistance to oxidation . Fuller’s earth • Fuller’s earth is an active medium which contains internal and external polar centers, which allow the non - polar oil components to pass, but capture polar contaminants and decomposition products solved in the oil . IEC 60422 -2013 Fuller’s earth types LVM Clay • Activates at high temperature. • High water absorption. • High acid absorption. • Low efficiency of bleaching RVM Clay •Activates at lower temperature. •Lower absorption capabitily. •Higher bleaching ability. •Higher acid absorption Fuller’s earth types AARVM • Maximum bleaching in a system without moisture AALVM • For optimum acid removal from oil with high water content http://www.jaxonfiltration.com/ How to quickly lower acidity ? The amount of acid removed depends on many factors, since adsorption is a process of dynamic equilibrium . • Temperature. • Flow rate • Oil viscosity. • Retention time. • Initial acidity . How much oil can be regenerated with fuller’s earth ? • Example Example #1 Regeneration CapacityQuantity Unit Inicial Neutralisation number 0.8 mg/KoH Final Neutralisation number 0.05 mg/KoH Number of Columns FEES By Column Total Unit 2 Quantity of Fullers Earth 130,00 260,00 Kilagrams Quantity of Fullers Earth 286,60 573,20 Pounds Quantity of Oil that can be treated 168,59 337,18 Gallons Quantity of Oil that can be treated 638,18 1.276,36 Litres Filterung Capacity of the machines GlobeCore FEES Example If the machine can reactivate fuller ’ s earthInicial Neutralisation number 0.8 Final Neutralisation number 0.05 Number of Columns CMMPES By Column Total Unit 2 Quantity of Fullers Earth 130,00 260,00 Kilograms Quantity of Fullers Earth 286,60 573,20 Pounds Number of regenerations 300,00 Unit Quantity of Oil that can be treated 50.576,64 101.153,27 Gallons Quantity of Oil that can be treated 191.453,40 382.906,79 Litres Regeneration process Equipment Types of regeneration Contact method Percolation Regeneration of dielectric oil GlobeCore CMM -R class transformer oil regeneration plants Oil regeneration process Fullers earth reactivation process Thank you.