Understanding Probable Condition and Loading Limits for Today’s Aged Power Transformer Population
Understanding Probable Condition and Loading Limits for Today’s Aged Power Transformer Population
David J. Woodcock
Weidmann Systems International Inc
Introduction:
Privatization, deregulation and financial restructuring are driving electric generating, transmission and distribution companies to find ways of improving their competitive position. Increased equipment utilization, deferred capital expenditure and reduced maintenance expense are all a part of the guidelines for today’s electric utility engineers and managers. Although tighter operating budgets and reduced spending are not new to most utility planners, the increased need to leverage more out of existing equipment on the grid must be achieved with the majority of power transformers nearing the end of their useful life. Large power transformers are a major concern to any electric utility when it comes to reliability because each one feeds large numbers of customers and its replacement would involve a considerable amount of time and expense. Much of the contingency planning of power systems relates to concerns about transformer loading limits, and arrangements for contingency operation when one fails. On-line monitoring systems are becoming popular on major substation transformer installations to determine normal or fault conditions and warn of incipient failure.
Power transformers are the single largest capital item in substations, comprising almost 60 percent of the total investment. Utility expenditures in operation and maintenance do not normally reflect the magnitude of this investment even though the cost of premature and unexpected failure can be several times the initial cost of the transformer. There is not only the
refurbishment or replacement cost but also possible costs associated with clean-up, loss of revenue, and deterioration in the quality of power delivery.
To add to this challenge, annual reductions in capital spending over the past twenty or more years, in both North America and Europe, has resulted in a significant increase in asset utilization, or normal transformer loading. This has reduced overall system contingency margins and increased the risk of losing customer service in the event of a substation transformer failure.
This paper discusses both a rigorous method for determining the probable condition of power transformers in use, provides options for setting loading limits based on condition ranking and looks at the growing trend toward the use of transformer on-line monitoring for improving system reliability and optimizing the use of these important electric utility assets.
See detail : Understanding the Probable Condition and Loading Limits for Today’s Aged Power Transformer Population
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