MR service technicians are deployed all over the world to maintain customers’ assets. An order for ČEPS in the Czech Republic shows how regular tap-changer maintenance supports the secure energy supply of an entire country.
Regensburg, a bright and sunny Monday in April. Service technicians Christoph Friedl and Andreas Singerer meet up at MR to load up their vehicle because they have another assignment. This time they are traveling to the Czech Republic to service the three on-load tap-changers of a phase-shifter transformer (PST). They have been commissioned by ČEPS, the Czech Republic’s only transmission system operator and therefore responsible for keeping the lights on in the country. The van travels from Bavaria to the Czech hills. Their destination is in the northwest of the country, where the river Eger flows into the Nechranice reservoir. This is where the Czech Republic’s largest transformer station, Hradec, is located.
It draws its electricity from the Prunéřov and Tušimice power plants and is connected to Germany across the border. It has had four PSTs since 2017. “Since they were installed, we have also had a direct service contract with MR,” explains Jan Lála, Head of the Transformer Department and Head of Maintenance Region West (more on this in the interview).
The gateway to the country
The Czech energy grid is largely transit-based. A large proportion of the energy which is imported and later exported comes from Germany. A significant proportion of this energy enters the country via the Hradec substation near Kadaň. It is one of the largest and most important substations in the Czech Republic and its operator ČEPS is the only transmission system operator in the country. PSTs are extremely important here because the Czech transmission grid has to cope with large and often fluctuating energy inflows from Germany, particularly due to ČEPS’ cross-border energy flows. These can be significant, especially during times of high wind-energy production in the neighboring country.
PSTs compensate for voltage fluctuations by shifting the overload in such a way that the grid as a whole is better utilized, which leads to a higher transmission capacity in the extra-high voltage grid. This also makes expensive redispatch measures unnecessary. Each of the four PST units at ČEPS has an output of 850 MVA and can regulate a phase angle of ± 30 degrees. The Hradec PSTs therefore act as a buffer for German wind power with fluctuating output, which has to pass through these transformers – and therefore also through MR’s on-load tap-changers.
Christoph (left) and Andreas are on the road with the van for this assignment. In Regensburg, they load it with their equipment such as tools and spare parts.
The team: Karel Alber (left) has been providing support for many years and uses the assignment to visit the site. The team receives a brief safety introduction at the beginning from Jan Lála, head of the Transformers Department.
The 100-kilogram, oil-blackened on-load tap-changers are carefully lifted out of the transformer by crane and taken to the workshop.
In use for all cases
When Christoph and Andreas arrive, they are welcomed to the site by Jan Lála. While Christoph was here last year to service the tap-changers of the other three phase shifters, for Andreas it is his first time working on the house-sized transformers. Safety is everything, which is why everything is done exactly according to protocol at the handover.
The transformer has already been secured and is no longer live and can therefore safely be handed over to Christoph and Andreas who start by draining the insulating oil. Only now is it time for the ČEPS employees to lift the three tap-changers, blackened by oil, out of the transformer one by one using a crane. This preparation alone takes two hours. Everything is now perfectly prepared. Christoph and Andreas take the tap-changers to the substation workshop and get to work. They could be faced with anything from simple cleaning to complex repairs. “But they probably won’t miss anything. This is standard maintenance – you could say ‘care’ – so that there are no unscheduled shutdowns in the future.”
“Our technicians are extensively trained and deliver MR quality all over the world.”
Uwe Seltsam, Head of Department
Andreas and Christoph are two of 300 service technicians who work for MR worldwide (around 55 of whom drive or fly from Germany). As Head of Global Execution & Product Services, Uwe Seltsam is responsible, among other things, for ensuring that their training is successful and that the service work is carried out to the highest quality. “Our service assignments can basically be divided into two areas. Firstly, those that involve unplanned and very time-critical cases that require quick action. Here, our specialists set off immediately and are usually at the customer’s premises within 24 hours. The problem is often so serious that the transformer is already damaged.” And if this stops production, it costs a lot of money with every hour that passes.
The more frequent jobs, however, are “routine maintenance” such as in Hradec. “The on-load tap-changer is very robust. If it is maintained as we recommend, it can theoretically even outlive its transformer.” This requires a high level of system knowledge and experience. “If maintenance is delayed or checked by workers on site who don’t know the full scope of service, then the system could of course fail completely at some point.”
The tap-changers are first given a wash in the oil pan. Christoph starts here with a visual check to see if there are any visible defects.
During Andreas’ second assignment in the field, Christoph stays involved as they meticulously put all the components through their paces on the open tap-changer.
Measure, clean, test
In the workshop, the service technicians go through all the necessary steps in a practiced manner. Christoph knows the tap-changers like the back of his hand: “Our products are designed for maximum efficiency. There are no extra screws and every little component has its own specific function. If I don’t know these, I can’t take good care of the tap-changer.” After cleaning the outside, he and Andreas first measure certain values such as the resistances, energy storage, contact wear, contact bridge clearance or main contact connection. They then completely dismantle the tap-changers and clean all components to remove oil and soot. The inspection also includes the technicians’ scrutinizing eye, explains Andreas: “The visual inspection may sound simple, but it is precisely our expert eye that detects abnormalities or where small wearing parts need to be replaced – such as contact wear, gaps, the contact spring and so on.”
“Although we always carry out similar work, no two jobs are the same. It remains exciting.”
Christoph Friedl, Service Technician
Jan Lála also pops in from time to time to let the professionals show him the inner workings of his tap-changers – a rare sight. The workshop in Hradec is as well equipped as a transformer factory and even has a large oil pan in which the 100 kilogram diverter switch inserts can drip dry. “It simply makes the work easier. You have to be particularly careful with these phase shifters: High currents pass through their tap-changers, so there’s a lot of wear on the contacts and more dirt,” explains Christoph. Once everything has been measured, checked, cleaned and serviced, the diverter switch inserts are reassembled. Tap-changer maintenance normally takes eight to ten hours, so there is not much room for delays. A technician normally looks after one tap-changer alone and during the three days that they are on duty at ČEPS, Christoph and Andreas also check the designated location in the transformer. This includes checking and cleaning the oil tank, servicing the linkage, checking the upper gear unit and the protective relays, and finally testing the entire on-load tap-changer to ensure that it is working properly. The work on the transformer also takes an entire working day.
Very high currents pass through the copper contacts. Andreas checks whether their condition already requires replacement or whether cleaning is sufficient for the time being.
Jan Lála (left) has Christoph show him the function and replacement of the resistor connection cables from the contact shell to the resistor pack — a rare sight for the plant manager.
Once cleaned, serviced and tested, the on-load tap-changers are returned to the transformer. The insulating oil is then refilled and test switching operations are carried out.
Finally, the job ends as it began: The tap-changers are reinstalled by crane, the oil is filled in and test switching is carried out. Once the transformer is properly running again, the service technicians officially hand it back to the operator together with their service report. Jan Lála is satisfied: “With MR Service, we are simply using the best possible service quality.” And so ends a short assignment for the MR team.
A profession for doers
Christoph is usually on the road alone, often for several weeks. As he explains: “That’s the great thing about the job – you’re your own boss. You know what you have to do, you can focus entirely on your task and your pace and look back on your work with pride at the end. You can see what you have achieved.” And the service technicians also get around a lot. “I’m always somewhere else in the world and see places that a tourist wouldn’t even get to. In no other job in the world would I have enough vacation days that I could get to know so many countries and people as through this job,” explains Christoph.
Four years ago, Christoph left his job as a trained industrial mechanic to gain this experience and independence by completing a one-year training course to become a service technician at MR. Since then, he has been on the road around 200 days a year. Andreas, who joined MR as a trained metalworker and is just finishing his training as a service technician, is also enthusiastic: “The training is very comprehensive. Despite my apprenticeship as a fitter, I was a full year into my apprenticeship at MR before going out into the field on my own for the first time. This simply makes me feel well prepared and gives me the confidence I need: I know I can do the job well and cleanly – and get to know new people and places in the process.”
“Customers rely on our expertise. I greatly appreciate this trust.”
Andreas Singerer, Service Technician
This is also MR’s recipe for success: career changers with an electrical engineering or mechatronics background are welcome, as they first have a full year of intensive training with the comprehensive expert know-how that makes MR special. And that attracts personalities, explains Uwe Seltsam. “The job is for doers and explorers. People who like to organize themselves and want to see something of the world, and who have some ‘ants in their pants’ – they’re perfect for it.” Seltsam knows what he’s talking about; after all, he worked as a service specialist for seven years himself and has fond memories of that time. Because the assignments are always different and always new, and improvisation is often required. Conditions are not always as luxurious as those in Hradec where the substation even has its own workshop with a large oil pan and perfect lighting. “But that’s exactly why we are happy to invest in the training year. After that, it’s clear that our technicians are fully trained and can deliver MR quality everywhere.”
