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22.02.2024 CompanyEvents

10,000 VRDT - the new standard in the distribution grid?

The use of on-load tap-changers in voltage regulating distribution transformers (VRDT) has proven to be a particularly economical solution both in Germany and internationally. Thanks to its compact design, maintenance-free operation and simple installation, ECOTAP® VPD® from Maschinenfabrik Reinhausen has established itself with many grid operators as one of the cornerstones for increasing the hosting capacity for generators and loads in the distribution grid. In February 2024, MR will deliver the 10,000th ECOTAP® VPD®, underlining the statement that the third generation of the ECOTAP® VPD® makes voltage regulation for distribution transformers.

Top-class panel discussion

Top-class panel discussion

During the energy industry fair e-world energy & water 2024, Maschinenfabrik Reinhausen (MR) organized a panel discussion on the topic of "Are voltage regulating transformers still an innovation or already standard?" How can the capacities of medium and low-voltage grids be best utilized through active voltage regulation without costly grid expansion? How can renewable generators or new types of loads such as electric vehicles or heat pumps be efficiently integrated into the distribution grid? How is the VRDT integrated into the grid development strategy? What hurdles had to be overcome when introducing this asset into the grid planning toolbox?

The following experts from the world of distribution grids answered these questions and reported on their practical experience:  

  • Michael Bühnert, Head of Sales, Sächsisch-Bayerische Starkstrom-Gerätebau GmbH 
  • Michael Pink, Network Planning, KNG - Kärnten Netz GmbH 
  • Marvin Reiting, Head of Asset Management, EAM Netz GmbH
  • Bianca Renner, Asset Strategy and Innovation, Avacon Netz GmbH 

Moderation: Armin Vielhauer, Head of Distribution Grid Applications, MR GmbH 


Participants in the panel discussion from left to right: Armin Vielhauer, Head of Distribution Grid Applications, Maschinenfabrik Reinhausen GmbH; Marvin Reiting, Head of Asset Management, EAM Netz GmbH; Bianca Renner, Innovation and Strategy, AVACON Netz GmbH; Michael Pink, Grid Planning, KNG-Kärnten Netz GmbH; Michael Bühnert, Head of Sales, Sächsisch Bayerische Gerätebau GmbH.

The participants covered a wide range of perspectives. Mr. Pink from Kärnten Netz GmbH (KNG), for example, sees the VRDT as "rather innovative, as we have to check each application individually and the standard is a long way off." For EAM Netz GmbH, the voltage regulating distribution transformer is "not an innovation," according to Mr. Reiting, “ it is standard. But it has to share the space with the conventional transformer." Avacon Netz GmbH, on the other hand, is fully committed to the VRDT. According to Ms. Renner, it has been "standard for 4 years" and covers 100% of the annual procurement of distribution transformers. As sales manager at transformer manufacturer Sächsisch-Bayerische Starkstrom-Gerätebau GmbH, Mr Bühnert has a broader view of the market and knows: "As a self-regulating transformer, the VRDT is a standard that is still unrecognized by many."

The participants began by explaining their application strategies. These range from individual calculation of each low-voltage grid with a comparison of measures in individual cases, to a regional roll-out of VRDT based on continuous monitoring, as used by EAM Netz GmbH in the medium-voltage grid, to the exclusive installation of voltage regulating distribution transformers at AVACON Netz GmbH.  

The second exciting block of topics was the exchange of experiences regarding the introduction of the equipment into the processes of the respective companies. The most important aspects here were, on the one hand, the adaptation of processes, such as the change in planning guidelines and the commissioning initially accompanied by internal specialists. On the other hand – as is usual with changes – the skepticism of individuals had to be countered and uncertainties and questions from affected departments had to be answered. Mr. Bühnert confirms that some customers are reluctant to introduce new technologies even though the VRDT is a mature technology. After all, the transformer is essential for operational reliability, “so innovation is difficult at first.” A decisive key to introducing this new technology was to familiarize employees with VRDTs in use. The participants fully agreed with Ms. Renner’s statement “with experience comes acceptance”. According to Mr. Reiting, this was also due in particular to the very low incidence of faults with VRDT: “The VRDT was convincing in itself.” In order to make the roll-out of VRDTs to the extent necessary for the energy transition independent of the openness or reservation of individuals towards technologies, Avacon Netz GmbH has also introduced a kind of "reversal of the burden of proof": Employees would no longer have to justify why they wanted to use an VRDT but would have to explain their motives should they not do so.

The initial question "Are VRDTs still innovative or already standard?" can therefore be answered with "Both!". Technologically, they are mature and standardized in many respects. At the same time, they represent an innovation in the processes of the companies that want to introduce them. When asked whether pilots are still needed, the participants were unanimous: pilots help to gain operational experience and create acceptance. All the companies were also consistently positive in their outlook for the further intensified use of VRDT in the future, particularly because the increasing dynamization of the energy transition and the grid reinforcement required for it demands for approaches that are more efficient than conventional grid expansion.  

The panel discussion ended with a large number of questions from the audience. It was then possible to talk directly to the panelists and take a look at the different development stages of the on-load tap-changer for voltage regulating distribution transformers.

How VRDTs work

How VRDTs work

The changes in the course of the energy transition are massive in the distribution grids: On the one hand, decentralized power generation, e.g. through photovoltaic systems, is increasing, while on the other hand heat pumps and EV charging stations are increasing the load on the grid. Measures are therefore required to maintain the necessary voltage quality. Depending on the grid conditions, a VRDT can increase the hosting capacity for additional loads and feeders by a factor of two to four without having to lay new lines. How does it work? The control and regulation unit continuously measures the secondary voltage and automatically sends a signal to the on-load tap-changer when it needs to adjust the transformation ratio. This reliably decouples the low-voltage grid from the fluctuations in the medium-voltage grid. The VRDT therefore shifts the last voltage control point from the substation to the local grid station. As a result, far greater voltage increases and decreases can be permitted in both the medium and low-voltage grids than in conventional grid planning. The impact on the public space is minimal: replacing an existing unregulated local grid transformer with a VRDT one takes around one day. The control and regulation unit can also be connected to SCADA systems. This means that more complex grid control is also possible and important operating parameters and measured values are now available online for grid management purposes.  

Proven technology from the pioneer

With ECOTAP® VPD®, MR has adapted the know-how gained from several decades of experience with on-load tap-changers to the specific requirements of distribution network transformers and continuously developed it further. In 2009, the effectiveness of voltage regulating distribution transformers was demonstrated for the first time in real operation in field trials. Conventional on-load tap-changers with oil switching technology were still used in these pilot projects. In 2012, MR introduced GRIDCON® iTAP®, the first maintenance-free and very compact vacuum on-load tap-changer for distribution transformers. The system consisted of an on-load tap-changer, motor-drive unit and voltage regulator and was the first series solution for VRDTs. Finally, in 2016, MR introduced the ECOTAP® VPD®, the first high-speed resistor type tap-changer for distribution transformers with direct drive. It solved the problem of additional losses in the transformer, which its predecessor generated due to the reactors required for the function. Just two years later, the second generation of ECOTAP® VPD® was launched on the market. It is even more economical than its predecessor and is suitable for a wider range of applications.  

The third generation of ECOTAP® VPD® followed in 2021 with the aim of making voltage regulation the standard in local grid transformers. The design volume has been reduced by a further 50 percent compared to its predecessor and the OLTC, including motor, weighs 30 percent less. The third generation is designed in such a way that it is suitable for high-volume production. This means that costs can be significantly reduced, making the VRDT even more economical. The ability to increase the grid’s hosting capacity for generators and innovative consumers without reinforcing the cable network is convincing: MR will deliver the 10,000th ECOTAP® VPD® in February 2024. More than 150 transformer manufacturers have already installed it and over 300 operators worldwide are using it.

More about VRDT in the podcast and video
The control of distribution grids plays a major role in the efficient and sustainable use of energy. Franco Pizzutto, Business Development Manager at MR, shares his knowledge of technical advances and strategic approaches in the Reinhausen podcast POWER ON

Podcast POWER ON

Renewable energies as well as new loads such as those arising in the mobility and heating sectors pose major challenges for distribution grids worldwide. Voltage regulation in distribution grids has therefore become a key technology for efficiently managing the increased requirements in the grids. The video on the YouTube channel "Reinhausen TV" clearly summarizes the most important facts about the third generation of the ECOTAP® VPD®:

Reinhausen TV

Panel discussion 10.000 VRDT – E-world Essen

Please click on the link to activate the video. Please note that after activation data will be transmitted to Youtube.


Otmar Reichmeyer

Head of Communications Maschinenfabrik Reinhausen GmbH

Phone +49 941 4090-648
E-Mail o.reichmeyer@reinhausen.com

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