Transformer DGA & Other Diagnostics

Trafoexperts Transformer Consulting Services

Common transformer diagnostic services include:

  • Dissolved Gas Analysis (DGA)
  • Frequency Response Analysis (FRA)
  • Dielectric spectroscopy
  • Polarization/Depolarization Current Analysis (PDC)

Acceptance criteria for all these methods are developed observing large populations of power transformers using simplified models, essentially treating a transformer as a black box.

Such generic interpretations may not be suitable for your transformers because of their unique characteristics in design, application and operation (power, generator step up, furnace, rectifier, cycloconverter, etc.).

Our added value

Because of our transformer consultants’s experiences in transformer design, construction and failure analyses, we can:

  • Interpret transformer diagnostics tests results taking into account the peculiarities of your transformer.
  • Identify follow up actions to solve the transformer’s issue revealed by the diagnostic tests.


Our DGA interpretation service

Most DGA service providers are chemical labs that treat transformers as black boxes. This is not surprising since they are competent in chemical analyses but not in transformer design. They use criteria that are developed through statistical analysis of large populations of similar power transformers.

Our transformer consultant’s knowledge of transformer design and operation allows us to understand the true relationship (not simple correlation) between gasses and the transformer’s possible faults. Therefore, we can support you in getting your problem solved instead of only advising you to make a new DGA after a specific amount of time.

FAQ on our DGA service

Initial transformer fault diagnosis, how does it work?

We determine whether your transformer has a problem by examining its DGA values along with its design, quality issues, and service conditions. We then provide a clear assessment of your situation and give you a set of recommended actions to follow. The process step-by-step: We will then ask you to provide detailed information about your unit and its DGA history. Once we receive this, we will give you a time estimate for our delivery. Our experts will assess the condition of your unit considering all information provided and suggest follow up action if necessary. Our initial assessment service is complete at this point. If you need additional consultation then we will send you a separate quote.

Do you handle online monitor diagnosis too?

Yes!. We provide an initial assessment your transformer and then interpret your online monitor DGA daily (as soon you send us the data). We give you early warning if the situation deteriorates and we discuss with you a course of action to minimize chances of catastrophic failure.

What about transformer fleet health and risk assessment?

We start the assessment of your fleet by calculating custom DGA limits based on your fleet’s designs, unit types, operation conditions, and known issues. This allows us to identify the units in need of further attention. We can then assist you in monitoring critical units, inspecting them, and discussing with the manufacturer to find a solution.

I know DGA delivers best results when using limits customised to my fleet. Can you determine custom gas limits for my transformer fleet?

Yes, this is something we normally do. We use both statistical tools and our transformer knowledge to determine limits tailored to your transformers.

Others provide DGA interpretation tools so that I can get results immediately. Can you do the same?

No. With us, you will always have transformer experts looking at your data. Your data won’t be just automatically processed by a pre-programmed report generator. Our experts will take the time to go through them so it may take a few days to get back to you.

Why do you ask so many more questions about my transformers than other DGA service providers?

Others treat transformers as black boxes, so this additional information would be of little use to them. We understand transformers. Therefore, any information you can give us about their designs and service conditions is a useful piece of the puzzle for us.

How quickly will I receive your assessment of my transformer(s)?

It depends on the number of transformers you wish us to assess, the information available, our workload, and whether we receive payment in a timely manner. We will communicate our delivery time after we receive information about your transformers.

Can I send you an oil sample to analyze?

No. We are not chemical engineers. We do not have the expertise and equipment to determine dissolved gas values. Many competent labs already provide this service quickly and economically. Our added value is in the interpretation of the results reported by the labs.

Why do you give me a spreadsheet to fill with my DGA results? Can’t I just send you the lab reports?

We want to deliver maximum value at minimum cost. When you provide us with clear data in a format defined by us, we can focus on the interpretation and keep cost to a minimum. If you would like us to enter your data in the spreadsheet for you, we can do it for a flat fee of CHF 200 (up to 20 analysis points) per unit.

How can I benefit from custom limits you developed for my fleet if my oil chemical analysis lab uses an automatic DGA interpretation software that cannot apply these custom limits?

This is a very common situation. Their software may also be using out of date interpretation methods. This is not surprising since these labs are staffed by chemical engineers whose focus is on carrying out chemical analyses. We can offer you a subscription service where you forward your DGA results to us. The results will be interpreted by our transformer experts taking into account your custom DGA limits. Please contact us for a quote.

My transformer’s DGA looks fine but I am concerned about its other diagnostic results (FRA, PD, DFR, power factor, etc.). Can you help?

Sure, our transformer experts are experienced in assessing multiple diagnostics. Please contact us. We will ask you to fill a form on your unit, tell us what your problem is, and we will come back to you with a custom quote.

Please contact us if you need our service on other transformer diagnostics.

Dr. Ing. Ugo Piovan

Dr. Ing. Ugo Piovan

Transformer Consultant
Trafoexperts GmbH

Turbinenweg, 4
8610, Uster, Switzerland