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Figure 11 shows seven typical case studies from a total of showed the added benefit of improved oil qualities for acid,
71 transformers that had online dryers installed. The table IFT, and liquid power factor.
shows that transformers treated with an online dryer also

Figure 11: oil results for acid, IFt, and power Factor (pF) before and after an online dryer was used

SoLUtIonS And FUtURE tREndS Transformer services that ensure good oil quality and healthy
Real-time remote online monitoring is becoming increasingly paper insulation have been shown to increase transformer
popular. This technology allows users to monitor moisture service life. Data presented in this paper indicated that on
and dissolved gases – all remotely via the internet. The average, oil maintenance resulted in an additional six years
remote monitors can detect a single gas or up to eight of service life each time it was performed.
gases within the transformer oil. The single gas monitors
detect hydrogen levels over time. The buildup of hydrogen
in transformer oil is a good indication of a problem, since Robert T. Rasor, Benjamin A. Hall, Andrew B. Shkolnik and Jon
hydrogen is produced to at least some extent with every Trout
transformer fault (partial discharge, hotspot overheating, SD Myers Inc., Tallmadge, Ohio, USA
arcing). For the eight gas monitoring systems, the gases CARILEC Engineering and GIS Conference
monitored are hydrogen, oxygen, methane, carbon
monoxide, carbon dioxide, ethylene, ethane, and acetylene. REFEREnCES
The remote monitors act as a “check engine light,” where
abnormal results indicate that further laboratory testing and [1] IEEE Guide for Loading Mineral-Oil-Immersed Transformers
investigation is warranted. and Step-Voltage Regulators, IEEE Std.C57.91, 2011.
[2] Processing records, SD Myers Inc. circa 1965 through
Granular clay filtering columns can now be retrofitted to present.
any filter press rig with just three small hoses. The filtering [3] IEEE Guide for Acceptance and Maintenance of Insulating Oil
in Equipment, IEEE Standard C57.106, 2006.
columns will help to remove acid and improve the interfacial [4] O. Roizman, V. Davydov, “Online Determination of Water
tension (IFT) of the transformer oil. Also, online drying units Content of Paper: Color Chart Approach.” Presented at the Spring
are now available with the ability to regenerate themselves. 2011 IEEE Transformers Committee meeting, TF on Moisture in
These online dryers can reuse their filter media over and over Oil, Nashville, Tennessee.
again. The ability to regenerate the media saves on long- [5] IEEE Guide for the Evaluation and Reconditioning of Liquid
term cost of new filtering media and shipping. Finally, online Immersed Power Transformers, IEEE Standard C57.140, 2006.
filters are now available to stay ahead of oil oxidation. While [6] R. Rasor, D. Roberts, and A. Shkolnik, “Transformer Reliability
continuously filtering the oil to remove oxidation products, – A Statistical Look.” A CIGRE Canada paper to be presented at
these online filters also monitor either one or eight gases. the September 2014 conference in Toronto.

ConCLUSIon
Transformer reliability is becoming increasingly important. At
the same time companies are looking to get the maximum
lifespan possible out of their electrical equipment. Regular
fluid testing, maintenance, and preventive measures are
always a good place to start to increase equipment life.
industry Journal 27