Smart maintenance of power transformers

Growing energy demand, increasing distributed generation and an aging asset infrastructure are all part of the major challenges facing electric utilities today. Asset and maintenance...

byMartin PFANNER


Growing energy demand, increasing distributed generation and an aging asset infrastructure are all part of the major challenges facing electric utilities today. Asset and maintenance managers need to ensure the reliability of their assets in an environment which is experiencing increasing cost pressure. Since power transformers are among the most critical and cost intensive components in electric energy networks, life-cycle management programs are becoming more and more common. Thereby, a two-step approach is often utilized to keep the lifecycle management process more cost efficient.

 

Initial screening

In an initial screening step you can evaluate power transformers by monitoring the most critical components and using test methods which can indicate a wide range of problems.

The most powerful screening method is the Dissolved Gas Analysis (DGA). Due to the fact that this method can be used to detect a very broad spectrum of problems related to the active part makes it the most widely accepted and used measurement routinely performed on power transformers. If performed frequently, it also allows detection of developing failure modes by trending over time and evaluating the rate of change of certain gas concentrations.

In many cases bushings reach the end of their life before the power transformer itself. However, the diagnostic reach of DGA related to bushings is limited. Therefore, power/dissipation factor and capacitance measurements should be included in the screening process as part of the lifecycle management program.

Based on this condition information, you can assign the probability of a failure to each asset. In the second step, you can conduct a more detailed condition assessment for the high risk assets including diagnostic testing.


Diagnostic testing

Additional test methods have to be employed to further evaluate the condition and decide on maintenance, repair or replacement measures. In addition to the above mentioned DGA and power/dissipation factor tests, you can use a variety of electrical test methods to diagnose different problems within the power transformer.

 

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