Abstract
Transformers are the main component in power generation industries and play a vital part in supplying electricity all over the world. Two main insulators are used in transformers, solid insulator or cellulosic paper and liquid insulator known as insulating oil or transformer oil. Transformer oil has the function of insulation and cooling as basic function also, it is used in suppressing electrical charge and preserving inner component of transformer against corrosion. During service oil deterioration take place under the impact of thermal and electrical stresses. Chemical composition of oil changes with formation of oxidation products and oil characteristics is no longer existing, hence, Transformer oil is monitored in terms of chemical, physical and electrical properties while dissolved gases is carried out by gas chromatography. After years in service, aging of transformer oil with formation of oxidation products is mandatory, looking for solutions able to regenerate oil and remove undesired products without being harmful to original composition of oil chains is required. Treatment of aged oil get attention recently with reclaiming by variety of chemical techniques and different materials for improvement of its properties and maintain these oils in operation for next years. This study represents reclaiming procedure by means of three eco-friendly inorganic fillers: Activated Bentonite (AB), Activated Carbon (AC) and Silica Fume (SF) which used in form of mixture fillers in the sequence of (AB+AC), (AB+SF) and (SF+AC). The main scope is reclaiming aged transformer oil and using mixture technique for efficacy of two fillers despite one. Three properties acidity as a chemical property, dissipation factor and breakdown voltage as electrical properties are tested for the series of mixtures, improvement was achieved providing an environmental reclaiming procedure. Best result in acidity is attributed to mixture 1:5 (AB+SF) with 0.072 mg KOH/g oil and enhancement percentage of -30.8% while improvement in dissipation factor showed result of 0.039 and an enhancement of 61% for mixture 1:7 SF+AC. Breakdown voltage showed improvement of 122.9% of 78 KV/2.5 mm for mixtures 3:1, 5:1 and 7:1 (AB+SF).
Highlights
Transformers form a critical highly loaded and expensive part of the electricity generation and distribution networks
This study focuses on reclaiming aged transformer oil via dual mixtures of three fillers, Activated Bentonite (AB), Activated Carbon (AC) and Silica Fume (SF) to achieve the purpose of reclaiming treatment
Aged transformer oils are followed up during service according to maintenance schedule and international standards all results are referred to specifications of the same international standard (IEC 60422-2005) for evaluation of enhancement degree and effect of reclaiming process
Summary
Transformers form a critical highly loaded and expensive part of the electricity generation and distribution networks. New studies approved that toxicity of PCBs lies in their damage effect to the reproductive, neurological and immune systems, are known as carcinogenic compounds (Pelitli et al, 2015) These previous reasons were the base of new direction established by treatment of aged transformer oils via different techniques. Chemical treatments using different techniques known as reclaiming process used via the usage of surface-active fillers for the removal of undesired compounds and improvement of insulation properties. Activated Bentonite which used in many applications in industry and majorly used in treatment of aged transformer oil with satisfying results, bentonite clay was activated by addition of concentrated acid filtered, dried and added to used transformer oil, improvement in chemical and electrical properties was obtained (Nasrat et al, 2011). This study focuses on reclaiming aged transformer oil via dual mixtures of three fillers, Activated Bentonite (AB), Activated Carbon (AC) and Silica Fume (SF) to achieve the purpose of reclaiming treatment
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