Maintenance optimization for power transmission systems: A case study of Ghana Grid Company Limited

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February 2016
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The focus of this research work is on the optimization of transmission assets at the Ghana Grid Company Limited (GRIDCo). The company’s maintenance planning and work schedules are currently anchored on time-based maintenance strategy.GRIDCo has had a number of equipment breakdowns and catastrophic failures since its operationalization in August 2008.These catastrophic failures and the vulnerability of the transmission assets to unpredictable breakdowns have adverse impact on the reliability of Ghana’s electricity transmission network. Can GRIDCo manage its assets to achieve the optimum life cycle cost which will deliver the required availability, performance, efficiency and quality to meet business goals and objectives? Can the current method of equipment maintenance in GRIDCo be optimized to improve equipment and grid reliability? To answer these questions, the researcher sought to evaluate GRIDCo’s asset management systems and maintenance records on selected power equipment. Data on eight power transformers which failed catastrophically from 2008 to 2015 in the organization was obtained to facilitate the assessment of the existing maintenance strategy. The results of the research work on the eight failed transformers indicated that prior time-based preventive maintenance activities carried out on the power equipment failed to give asset health and warning of imminent catastrophic failure. The research work carried out to investigate cause of 12T3 20MVA 161/11.5/6.6kV power transformer failure revealed prior maintenance activities carried out in October 2008 before the transformer failed in December 2008 without giving early warnings. The results of my work at Buipe substation also revealed that prior planned, maintenance activities were conducted on the 33MVA 161/34.5kV power transformer power transformer codenamed 55T1 before it failed catastrophically in 2013. On the other hand the research work carried out at Kumasi substation using condition-monitoring maintenance approach on five power transformers indicated alarming levels of carbon dioxide and ethylene gases in the transformer oil of 13T5 33MVA 161/34.5kV power transformer. The results of the dissolved gas analysis (DGA) on the transformer oil was used to schedule a timely maintenance on the transformer codenamed 13T5 to avert the catastrophic failure of another power transformer in GRIDCo. The results of the research work indicate that if GRIDCo had used condition-monitoring approach for the maintenance of the eight failed power transformers, early warnings of upcoming failure would have been detected.
A thesis submitted to the School of Graduate Studies Kwame Nkrumah University of Science and Technology, Ghana in partial fulfilment of the requirement for the Degree of Master of Engineering in Industrial Operations.