Substation transformer asset management solutions

Patrick McShane, Cooper Power Systems

The influencers of asset management plans are numerous–shrinking capital expenditure budgets, an uncertain timetable for the nation’s economic turnaround, and a slow but steady demand growth are factors utilities consider before implementing an asset management program. In the current economic, political and media-saturated world in which utilities operate, understanding and appraising risk may be the biggest influencer of all. A direct correlation exists between risk management and asset management.

Grid concerns

Utilities are managing aging assets at a time when environmental and fire safety standards and regulations have never been stricter.

Aging substation infrastructure in the United States is increasing concerns for risk management. One report by Hartford Steam Boiler Inspection and Insurance Co. predicted substation transformer failures will rise approximately 500 percent within 10 years as many of the units installed in the heyday of the 1950s and 1960s exceed their expected operational life cycle.

In spite of established safeguards, a percentage of substation transformer failures will occur in an eventful mode, resulting in tank ruptures and/or fires. In addition to the direct costs associated with transformer failures, potential eventful failure costs include production downtime, damage to adjacent equipment and property, casualties and resulting liabilities, potential environmental risk exposures, and the resulting unfavorable publicity that accompanies such events.

Transformer risk management solutions

Often, shrinking budgets prohibit upgrading potentially faulty substation transformers with newer units. One proven, cost-effective means to reduce the risk of substation fires, while adhering to current environmental and fire safety guidelines, is to retrofill transformers filled with conventional mineral oil with ester-based fire-resistant dielectric coolants. The cost of purchasing a new transformer (including all ancillary costs associated with installation of the new unit and decommissioning of the old unit) will exceed 10 times the cost of retrofilling an existing unit.

Fire-resistant fluids are recognized fire safeguards by the National Electrical Code and National Electrical Safety Code. This recognition, along with approval by Factory Mutual (FM) and classification by Underwriters Laboratories, translates to cost savings for utilities. It enables transformers up to 10 MVA filled with less-flammable fluid to be installed indoors without the requirement for sprinklers or vaults. Factory Mutual also recently reduced the minimum spacing and other fire safeguards for substation transformers filled with FM-approved fluids.

Ester-based fire-resistant fluids also offer environmental safeguards that translate to increased risk protection. These types of transformer fluids are highly biodegradable with minimum environmental impact. Independent testing and review by public agencies show that toxicity, for example, is not a concern with ester-based fluids like Cooper Power Systems’ own Envirotemp FR3 dielectric coolant, which has achieved EPA’s Environmental Technologies Verification.

Transformer asset management solutions

Strengthening the link between risk management and asset management, certain types of ester-based dielectric fluids have been proven to extend the life of substation transformer paper insulation by more than 500 percent when compared to transformers filled with mineral oil. Water is known to be the major factor for accelerating the aging process in paper, and as paper ages it produces more water. These fluids have the ability to draw out retained moisture and absorb water created by aging insulation paper.

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Alliant Energy studied the impact of one such fluid, Envirotemp FR3, on extending the remaining life of its substation transformers. For the study, Alliant replaced the mineral oil in a 50 MVA transformer manufactured in 1957, installed at a generating plant in Cedar Rapids, Iowa. By doing so, the utility expects to extend the useful life of the transformer by several years, while upgrading the fire safety characteristics and improving the environmental profile.

“We agreed to the test,” said John Larsen, executive manager at Alliant Energy, “because this alternative would offer us and our customers significant financial relief in equipment purchases and maintenance costs, while reducing the risk of fire and environmental impact.”

Alliant has seen immediate dividends as the retrofill fluid quickly increased the flash and fire points and lowered the relative humidity. (See table.)

The most recent results of Alliant’s testing indicate the paper samples tested at the 500-hour point, 250 hours after the retrofill point, show a major difference in the moisture content. The moisture in the samples aged in oil increased to a 1.0 percent level, while the paper aged in the natural ester decreased to less than 0.4 percent. By 1,000 hours, the water content in the insulating paper aged in oil reached approximately 6.0 percent, where it began to disintegrate.

In addition to Alliant Energy, current users of Envirotemp FR3 include American Electric Power, Alabama Power, WE Energies, Seattle City and Light, and Florida Power & Light.

Conclusion

Asset management plans that don’t address the potential risks inherent with equipment that has exceeded its anticipated life are simply incomplete. Cost-effective solutions are available to utilities that address both asset and risk management programs, including ester-based dielectric fluids for substation transformers that extend the life of the equipment and allow compliance with current fire and environmental standards and regulations.

McShane is product line manager for dielectric fluids at Cooper Power Systems. Professional activities include IEEE TC task force chair for ester-based dielectric coolants. He is the principal inventor of four U.S. patents relating to dielectric fluids. Several of his safety-related proposals have been adopted by U.S. and International Codes and Standards. He can be reached at 262-524-4591 or pmcshane@cooperpower.com.

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