MAINTENANCE OPTIMIZATION FOR POWER TRANSMISSION SYSTEMS: A CASE STUDY OF GHANA GRID COMPANY LIMITED

ABSTRACT
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.


CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND
The Ghana Grid Company (GRIDCo) was established in accordance with the Energy Commission Act, 1997 (Act 541) and the Volta River Development (Amendment) Act, 2005 Act 692, which provides for the establishment and exclusive operation of the National Interconnected Transmission System (NITS) by an independent Utility and the separation of the transmission functions of the Volta River Authority (VRA) from its other activities within the framework of the Power Sector Reforms. GRIDCo was established to undertake economic dispatch and transmission of electricity from wholesale suppliers (generating companies) to bulk customers, which include the Electricity Company of Ghana (ECG), Northern Electricity Department (NED) and the Mines (GRIDCo,2009). It is therefore incumbent upon GRIDCo to ensure the transmission network operates effectively and efficiently to achieve its core mandate. GRIDCo must ensure power transmission assets are optimally maintained in order to maximize their efficiency while minimizing maintenance cost.

Maximum asset performance is one of the major goals of GRIDCo.To achieve this goal, minimal life cycle cost and maintenance optimization become crucial while meeting demands from customers and regulators. Condition-based maintenance implies planning the future maintenance actions based on the technical state of the system, the state being assessed on the basis of the estimated reliability indices of the system at the planning moment.

The objective of maintenance optimization is to maximize grid reliability, subject to system constraints such as financial resources or crew resources. The preventive maintenance policies adopted by electric utilities are aimed at apt detection of equipment deterioration for timely interventions. The maintenance activities undertaken by the utility companies can involve equipment inspection, repair, replacement, vegetation inspection, tree trimming, and installation of animal guard and washing of insulators. The cost of preventive maintenance activities performed on a system or system element is determined on the basis of existing statistical information available at each operating unit.

1.2 PROBLEM STATEMENT
Ghana’s current energy crisis is mainly due to inadequate electricity production from the generating stations to meet national demand. This has adversely affected all facets of national development. The crisis, codenamed Dumsor, to wit, off and on, places more demand on the other operators in the electricity value chain to ensure the already bad situation does not get worse through ineffective and inefficient maintenance and operation of power equipment. Transmission assets must therefore be effectively and efficiently maintained otherwise the grid will also become unreliable for the evacuation of the already inadequate power produced from the generating sources. The Ghana Grid Company, (GRIDCo) has a medium term goal of achieving 99.9 per cent reliability on the National Transmission System by the year 2019 (GRIDCo, 2015). This set target requires a careful evaluation of the existing maintenance practices with the aim of improving it to enhance the reliability of the transmission network at a low cost while meeting stakeholder expectations. The optimization of maintenance schedules is one possible technique to reduce maintenance costs while improving reliability. The Ghana Grid Company (GRIDCo) is relatively new in the power industry and has no doubt inherited vestiges of the old ways of doing things from its mother company, the Volta River Authority. GRIDCo therefore needs to review the outdated maintenance protocols in order to re-strategize for a more effective preventive and corrective maintenance regime. Proper asset management methods also need to be implemented. The huge investment in the transmission sub-sector does require that the equipment are maintained and operated efficiently and effectively to increase uptime and grid reliability. Can the adoption of condition-based maintenance strategy address the shortfalls in the time-based maintenance approach?

1.3 RESEARCH QUESTIONS
Can GRIDCo manage its assets to achieve the optimum life cycle cost which will deliver the required availability, performance, efficiency and quality to meet the asset’s business goals and objectives?

Can GRIDCo’s existing maintenance regime facilitate the achievement of its medium term reliability target of 99.9 %?

What are the challenges that account for the shortfalls in the time-based maintenance approach?

What will be the impact of optimized maintenance management on GRIDCo’s operations?

1.4       MAIN OBJECTIVES
The focus of this research work is on the maintenance optimization for transmission systems at GRIDCo.The overall objective of the research work is to carry out an evaluation of GRIDCo’s maintenance strategy to improve the reliability and availability of the transmission network. This is intended to reduce risk of catastrophic failures, lower total cost of asset ownership and reduce costs from unplanned outages. A case study on GRIDCo’s maintenance strategy will be carried out to determine the asset maintenance challenges with respect to maintenance planning and work scheduling. The ultimate purpose of the research work is to achieve the optimum life cycle cost which will deliver the required availability, performance, efficiency and quality to meet the expectations of GIDCo’s stakeholders.

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Item Type: Ghanaian Project Material  |  Attribute: 82 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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