In Germany alone there are about 560,000 local networks, worldwide there are probably umpteen million. Unregulated local network transformers are still largely the standard in the distribution network and VRDTs are the exception. But this is likely to change in the foreseeable future when electricity comes entirely from climate-neutral sources and the heat and mobility sectors are also electrified. Franco Pizzutto, Business Development Manager at Reinhausen, explains: " New feeders and new loads will continue to increase voltage fluctuations, and local grids must be prepared for this to avoid mass outages and voltage band violations." For the distribution network expert, there are consequently four key reasons why VRDTs are gaining in importance.

The volatile feed-in of large wind and solar farms places varying loads on the high and medium voltage grids. This also has consequences for the local grids, which are conventionally rigidly connected to the respective higher grid level. And if there are larger fluctuations there, the scope for the local network, which shares the available voltage band of +/- 10 percent with the upstream network, also dwindles. VRDTs decouple the medium-voltage level from the low-voltage level, which is why the voltage band no longer has to be subdivided, but is available for each voltage level.

Huge wind farms on land and at sea as well as large-scale solar parks alone can’t do the job. On the one hand, there is not enough space in a densely populated country like Germany, and on the other hand, there is a lack of acceptance among the population for large-scale interventions in the landscape. The solution is smaller local producers who are also consumers. For example, solar panels on the roofs and facades of private households or commercial participants offer enormous potential without having to clear new land for them. The expansion is therefore progressing rapidly; in the next five years, according to the industry association Solar Power Europe, the number of rooftop solar installations worldwide will increase by 60 percent. Without VRDTs, new lines would have to be laid. With VRDTs, existing power lines can be used to a greater extent – thus significantly reducing the scope of conventional grid expansion, which will of course still be necessary.

On the other hand, the new producers are confronted with new consumers, which further mix up the interplay of supply and demand. The number of electric cars is still manageable, but it is already growing rapidly. But when more and more people drive electrically and recharge their batteries at home in the evening, consumption will skyrocket. As a result the already low voltage in the evening drops additionally. Another key technology of the energy transition leads to an additional burden: Heat pumps. Instead of fossil fuels, heat is generated electrically. The grid must also cope with these new loads. VRDTs also help here to ensure that the voltage does not fall below the permissible values despite the increased load. 

What actually happens in the local grid? While the extra-high voltage grid is monitored and controlled very closely, operators know very little about the exact state of local distribution grids. Until now, this was not necessary. But if the complexity increases due to new feeders and consumers, it cannot stay that way. Local grids must become intelligent and sensors must collect data on the exact operating status. But the information collected in this way only helps if operators can also intervene. And this is where VRDTs come into play again: digitally connected, they not only provide valuable status information, but also enable the operator to actively influence network events.