How’s the transformer? The grid operator MITNETZ STROM wants to know exactly and is equipping two power transformers at the Meuselwitz substation with ETOS®. With this central control and monitoring system, the condition of transformers can be continuously monitored, and their service life increased through predictive maintenance.
Sometimes it’s the little things that get on your nerves. For Jan Schönfeld, Asset Manager at MITNETZ STROM, and his colleagues at the Meuselwitz substation in Thuringia, it was the protective devices on two power transformers that kept tripping–seemingly for no reason–during the summer months. All attempts to get to the bottom of the problem failed.
“The tripping has no effect on the power supply,” explains Jan Schönfeld, but adds “While the transformer continues to run despite irregularities, we of course still have to investigate such malfunctions.” When Maschinenfabrik Reinhausen presented the ETOS® system to him in the fall of 2023, it came at just the right time. The ability to quickly locate irregularities with the help of sensor-based, real-time monitoring of transformers awakened his hopes of being able to get to the bottom of problems without much effort in the future. It soon became clear that this is by no means the only advantage offered by ETOS®.
“The feed-in of renewable energies, the increasing demand for electricity for the charging infrastructure of electric vehicles or new heating systems often exceed the capacity of our transformers.”
Jan Schönfeld, Asset Manager at MITNETZ STROM.
A Digital Twin for the Transformer
ETOS®–an open system solution for power transformers–enables the intelligent real-time monitoring of operation as well as the control of power transformers. Sensors on the transformer collect all relevant operating data, which is then evaluated by the CPU in the ETOS® control cabinet. This also allows maintenance work to be planned in a targeted manner. “ETOS® serves as a data source for implementing a digital twin of the power transformer, so to speak,” summarizes Christian Hofmeister, Project Manager Service Solutions.
This was fascinating to Jan Schönfeld and his colleagues, and together with MR they launched a transformer service project at the Meuselwitz substation: two transformers that convert the 110 kV of the high-voltage grid into 20 kV for the medium-voltage grid were equipped with intelligent sensors and the existing motor drives were replaced with two intelligent ETOS® drive cabinets.
Two transformers, which convert the 110 kV of the high-voltage grid into 20 kV for the medium-voltage grid, were equipped with intelligent sensors before the ETOS® control cabinets were installed.
The MR team prepared every step of the retrofit in advance.
Good Care, Long life
MITNETZ STROM is the largest distribution grid operator in eastern Germany. The electricity grid has a length of almost 72,000 kilometers, spread over an area of more than 29,000 square kilometers and the company supplies around 2.2 million people in Brandenburg, Saxony, Saxony-Anhalt and Thuringia with energy. MITNETZ STROM is a wholly-owned subsidiary of envia Mitteldeutsche Energie AG, which in turn belongs to the EON Group.
“We are struggling with the same problems that are affecting the entire industry,” says Jan Schönfeld: “The feed-in of renewable energies, the increasing demand for electricity for the charging infrastructure of electric vehicles, new heating systems and the ever-increasing energy requirements of data centers often exceed the capacity of our transformers.” And the transformers at MITNETZ STROM, as in the rest of Germany, are often getting on in years.
“Transformers have an average life expectancy of around 50 years,” explains Schönfeld and adds: “We have a whole range of years of construction in our 250 or so transformers. Some date back to the 1970s, others we have already replaced as part of the grid expansion. However, we are always keen to keep transformers connected to the grid for as long as possible.” The reasons for this are obvious: delivery times for new transformers are currently several years and prices have gone through the roof. At the same time, the prices for monitoring systems have fallen significantly. “In addition, retrofitting with electronics and sensors is much less expensive than dismantling and removing an old transformer and installing a new one,” says Schönfeld.
“The demands on the ETOS® system can vary depending on the workload, which is why we design each cabinet individually.”
Christian Hofmeister, Project Manager Service Solutions at MR.
It contains everything you need
The ETOS® system has a modular structure, as Christian Hofmeister explains: “It is important to us that customers get exactly the functions they need. Depending on the workload, the demands on the system can vary, which is why we design each cabinet individually.” The two transformers for the Meuselwitz substation, for example, were equipped with sensors for bushing monitoring–after all, defective bushings are responsible for 17 percent of all transformer failures. “Temperature management is also carried out by ETOS®, which continuously determines and records the winding temperature. This makes it possible to minimize the hot-spot temperature at an early stage,” explains Hofmeister.
For optimized cooling, the MR experts networked the existing cooling system control cabinets with the ETOS® drive cabinets. “Based on the measured values, we can start pre-cooling at a certain load current value,” says Hofmeister. Electronic dehumidifiers will also reduce maintenance costs in future.
“Previously, our maintenance staff had to replace the silica gel beads every six months,” says Schönfeld and explains, “This is no longer necessary because the new dehumidifiers dry the silica gel beads automatically on a cyclical basis.” The so-called VAM sensor for vibro-acoustic measurements in the on-load tap-changer was also very important to Schönfeld and his team. “It records the vibrations during the switching processes and compares them with stored reference values,” says Schönfeld. “An alarm is triggered in the event of deviations.” The advantage: no time-consuming removal of the on-load tap-changer is necessary, and an analysis service provides a detailed report with recommendations and measures to rectify the irregularity. “That’s exactly what I was looking for,” says Schönfeld with satisfaction.
Two intelligent ETOS® control cabinets replace the old motor drives.
Ready for the future: it took just five days to set up and commission the ETOS® control cabinets.
With Individuality, Expertise and Care
In order to design the ETOS® drive cabinets for MITNETZ STROM, Christian Hofmeister dug deep into the circuit diagrams, the transformer data and the ventilation control data. “Of course, you can expect expertise from a market leader like MR,” says Schönfeld, but adds, impressed. “Our contacts are often employees from sales departments which makes everything more complicated because information always goes via detours to the real experts. However, we communicated with Christian Hofmeister directly and at eye level and he really looked at every wiring, every cross-section, all connections and cable bushings as well as all interfaces in detail.” Schönfeld also liked the unconventional but time-saving way of finding solutions via virtual meetings and a cell phone camera: “Instead of having a cumbersome meeting on site, a colleague went out to the transformers with a cell phone to show the MR experts the local conditions.”
Into the future in fice days
It took just five days to set up and commission the ETOS® drive cabinets. “Two weeks before we started, I prepared and reviewed all the commissioning documents,” says Hofmeister. In a meeting, he then carefully briefed all the service technicians and went through every step of the conversion with them. He was on site himself for the commissioning. “Now I know the transformers in Meuselwitz inside and out,” he says with a grin. A new era is beginning for the team at the Meuselwitz substation, and their ETOS® drive cabinets are the pilot for other MITNETZ STROM substations. And Jan Schönfeld is optimistic. “In the future, transformer faults can be detected and rectified at an early stage, which will hopefully put an end to unplanned maintenance work on Sunday evenings,” he says.
Reinhausen Inside
The open ETOS® operating system is easy and intuitive to use. MR also offers practice-based online training courses for beginners and advanced technicians who are entrusted with the commissioning or use of ETOS®. The free live training courses each focus on a specific topic, which experienced trainers explain in a compact format.
YOUR CONTACT PERSON
Do you have any questions about the retrofit project? Bastian Auerbach is there for you: B.Auerbach@reinhausen.com