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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