Abstract
Microbial contamination of in-use and unused electrical power transformer oils obtained from Onitsha, Nigeria was studied using cultural techniques. The average bacterial and fungal counts of the in-use oil were 1.2 x 10 2 cfu/ml and 0.7 x 10 2 cfu/ml respectively while the mean bacterial and fungal counts of the unused oil were 0.5 x 10 2 cfu/ml and 0.3 x 10 2 cfu/ml respectively. The microorganisms from the in-use oil were Micrococcus luteus, Pseudomonas aeruginosa, Serratia marcescens, Corynebacterium bovis, Bacillus subtilis, Klebsiella aerogenes, Aspergillus niger, Aspergillus flavus and Mucor pusillus while those from the unused oil were Micrococcus luteus, Serratia marcescens, Bacillus subtilis, Klebsiella aerogenes and Aspergillus fumigatus. Bacillus subtilis occurred most frequently in both oils. The P H of the medium decreased to the acidic level while there was an increase in the viable counts, indicating the utilization of the transformer oils by the isolates. These isolates may cause the deterioration in the oils quality leading to the failure of the transformer with its attendant economic losses. Regular inspection and maintenance of the transformer as well as periodic changing of its oil is recommended to curb the economic losses.
Highlights
An electrical power transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two windings
The bacterial counts ranged between 0.7 x 102 cfu/ml and 1.7 x 102 cfu/ml while the fungal counts were between 0.3 x 102 cfu/ml and 1.2 x 102 cfu/ml. microorganisms were isolated from all the in-use samples examined
This work indicated that the microorganisms in the transformer oils are bacteria and fungi and that in-use oil is a better substrate for their growth than the unused one
Summary
An electrical power transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two windings. Transformer oil known as mineral insulating oil is normally obtained by fractional distillation and subsequent treatment of crude petroleum. It provides liquid insulation and dissipates the heat generated by the transformer. Ten samples of in-use electrical power transformer oil were collected from step-down transformers in various locations in Onitsha, Nigeria into sterile screw-capped bottles. The un-used oil samples (ten in number) were obtained from an electrical power distribution company at Onitsha, Nigeria
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