Interview with Dr. Michael Krüger, OMICRON electronics GmbH
TM: Mr. Krüger, thank you for your time and interview. I am sure it is not easy for you at the moment as you are...
byTransformers Magazine
TM: Mr. Krüger, thank you for your time and interview. I am sure it is not easy for you at the moment as you are attending the CIGRE 2014 conference in Paris. How do you see this conference?
MK: Well, you must know, the CIGRE takes place only every 2 years. It is one of the most important central conferences in the field of high voltage electricity which leading experts and decision makers attend regularly. First of all, I expect, of course, some interesting conversations, new contacts and drivers for the future. I am currently working in five different CIGRE working groups on the topic of transformers. And some of these working groups use the conference‘s off-peak times to meet and discuss concepts and ideas for the future. That‘s another important reason for me to attend this conference.
TM: What do you think are the major things that came out of this year‘s conference?
MK: A striking number of papers in this year‘s agenda deal with the ‘Health Index for Power Transformer’. This is obviously an important topic of current interest and it is also interesting for me – one of my working groups has the same focus.
TM: How did you become a member of the CIGRE and what benefits do you see in being a member?
MK: I became a member of CIGRE through the working group A2.26 ‘Mechanical Condition Assessment of Transformer Windings using Frequency Response Analysis’ (FRA). If you work in such a working group, it is usual to be a personal member of CIGRE. The publications they produce, especially the brochures, are really useful. Every working group aims to put together a brochure on their topic. If the working group has the right members, including leading experts, their experience and expertise is influential in producing brochures of a high professional standard. Members can download the brochures and many other trade publications from www.e-cigre.org free of charge. For example, the working group A2.26 published the FRA brochure 342 in 2008, whose findings formed the basis for the new IEC norm 60076-18 established in 2012. The standardisation of the FRA method has resulted in becoming mandatory when carrying out final testing of transformers in the factory.
TM: You have been working in the power supply industry for a long time now. Looking back, what has changed the most over that time?
MK: I have been in the industry for 35 years and the biggest changes have been brought about by the arrival of computers as well as better calculation methods of electric equipment and above all, by new electronic measurement procedures which were previously unimaginable. Meanwhile, there is an increasing change from time-based to condition-based testing and permanent online monitoring. This is exciting for working on new approaches and, thus developing new test systems.
TM: Could you give an example?
MK: Sure. Have a look at partial discharge (PD) measurements. It is something that has been around for many years. I carried out my first PD measurement in 1977 with a SIEMENS radio interference voltage (RIV) measuring device. If I compare that with our MPD 600 and its software today, they are worlds apart. Especially considering that you can now make sensitive PD measurements even in areas with high electromagnetic interference as you might find in a substation. Monitoring systems have undergone a lot of changes too and are used more and more. That also affects diagnostics measuring on site. Offline diagnostic measurements are now often only carried out when the monitoring systems show abnormal readings. For example, through a DGA (dissolved gas analysis) system, we were able to detect raised hydrogen levels in a transformer. This often indicates a presence of PD. At the same time, the PD monitoring system also allowed us to detect and confirm strong PD activities around 2 bushings. To investigate further, a PD localisation was carried out with our PDL 650. We were able to locate the faults. Therefore, we could also reduce repair costs as we directly knew where to attempt for repairs.
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