Drive Elec­tric

E.ON study: Smart equip­ment, such as voltage regu­la­tion distri­b­u­tion trans­formers, can ensure that grids are able to cope with people charging their elec­tric cars.

Marten Bunne­mann is the CEO of Avacon AG. He is convinced that VRDTs are the way forward when it comes to over­coming the chal­lenges asso­ci­ated with e-mobility.

Electro­mo­bility is on the rise all around the world. But this raises the ques­tion whether our power grids can cope with this trend. E.ON, Germany’s largest distri­b­u­tion grid oper­ator, recently pub­lished a high-profile study looking into the grids of its four regional grid oper­a­tors (Avacon Netz, Bayern­werk Netz, E.DIS Netz, and Schleswig-Holstein Netz). And the results confirmed that it would be possible to charge all cars elec­tri­cally within the area served by the grids by 2045.

Voltage regu­la­tion distri­b­u­tion trans­formers (VRDTs) are an impor­tant part of the tech­nical infra­struc­ture required. Leading the way in the use of this equip­ment, which was devel­oped in part­ner­ship with Maschi­nen­fabrik Rein­hausen, Helm­stedt-based Avacon Netz GmbH has a partic­u­larly impres­sive reper­toire of expe­ri­ence in terms of imple­men­ta­tion and oper­a­tion. We talked with CEO Marten Bunne­mann about what the study covered and the tech­nical solu­tions

Mr. Bunne­mann, what do you see as the main prob­lems when inte­grating elec­tro­mo­bility into the grid?

All of our research into grid inte­gra­tion has revealed that the main prob­lem is how drivers will go about charging their vehi­cles since we have to predict these patterns of behavior 15 or 20 years in advance. The key ques­tions to consider are: How many cars will real­is­ti­cally be charged at once and how can we make sure that the grids are able to cope with this level of demand? We looked into this as part of the large-scale study mentioned above, but also in many other studies. We gave partic­ular emphasis to those looking at rural grids since our rural spaces (villages and small and medium-sized towns) have the most cars.

Propo­si­tion one:
A full switch to e-mobility is a possi­bility

And we deter­mined that, on the basis of the knowl­edge avail­able to us now, there won’t be any major prob­lems for our grids if we are smart in our prepa­ra­tions for elec­tro­mo­bility and stay ahead of the game. We want to be able to stand out from the crowd and not force specific charging times on our customers. They should all be able to charge their vehi­cles at home when­ever they wish to. This is the promise we have made to ourselves.

To what extent do voltage regu­la­tion distri­b­u­tion trans­formers (VRDTs) feature in your plans for the upgrade work required in the future?

Trans­formers and lines are known for being the main compo­nents of power grids. According to our find­ings, prob­lems mainly occur in the trans­formers and lines in the low-voltage grid, which is the part of the grid that is closest to the customers. Here, the first prob­lems that almost always arise are trans­formers being overload­ed and line volt­ages being too low. Any other issues are much less common.

What this means is that we will replace small, unreg­u­lated trans­formers with larger voltage regu­la­tion distri­b­u­tion trans­formers (VRDTs). And we will also make them intel­li­gent. This largely cuts out the need for line rein­force­ments, which often used to be required to the detri­ment of the general public.

A lot of demand would be placed on the power grid if everyone were to start charging their cars at the same time. VRDTs help to keep the voltage constant. (© Timo Müller)

What bene­fits do you expect from the use of voltage regu­la­tion distri­b­u­tion trans­formers?

To put it simply, the use of VRDTs large­ly rules out voltage prob­lems in the low-voltage grid, and poten­tially also the medium-voltage grid, depend­ing on the spec­i­fi­ca­tions. This is a very quick and effi­cient way of ensuring that we don’t have to subject the gen­eral public to unnec­es­sary cable in­stallation work.

Propo­si­tion two:
There are no longer any tech­nical obsta­cles standing in the way of full e-mobility.

Instead, we can limit ourselves to work that is usually required as a result of age and to major new connec­tions that have always required grid devel­op­ment. This is how we can fit elec­tro­mo­bility into the existing grid—especially when we are able to look ahead and make plans for the future.

But we mustn’t forget that costs are still involved. We included cost consid­er­a­tions in our study with the results showing a one-time charge of around EUR 400 on average per vehicle for expanding the grid. But as far as we are concerned, these invest­ments are absolutely worth­while. It’s all rela­tive, after all: Around EUR 25,000 has to be invested in a car every seven years on average.

Which specific measures does the study call for?

Perhaps we should cover one thing first of all: We are often asked why we assume that the auto­mo­tive segment will become fully elec­tric. We know that this is a bold assump­tion but it is based on internal and external analyses of the mobility sector, with a partic­ular focus on sustain­ability and effi­ciency. The crucial thing for us is what we now take away from the results. And we have to say that we have put together an excel­lent package.

Propo­si­tion three:
Grids can be made fit for the future without having to undergo major restruc­turing.

What this means for our customers and commu­ni­ties first off is that we will be supporting elec­tro­mo­bility in every way. Instead of complaining, we’ll be moti­vating because we believe this is the right direc­tion to be heading in and we take the issue of CO2 very seri­ously. As far as our grids are concerned, we will be focusing on intel­li­gent secondary substa­tions with VRDTs and on larger line cross-sections. But this will only be when replace­ments are needed, usually owing to age. This requires an incred­ibly strategic approach when allo­cating expan­sion work but it stops us pressing pause on a future issue that we don’t want to abandon.

The ECOTAP® VPD® is the key compo­nent in the quest to have e-mobility rolled out exclu­sively. (©Timo Müller)

That was sadly what many grid oper­a­tors did ten years ago when the first solar boom occurred before this VRDT tech­nology even existed. And we don’t want to be faced with an impos­sible task in ten years’ time. Another point worth mention­ing is that we will also have more solar power within our grids, poten­tially including heat pumps, and VRDTs are ideal here. This tech­nology there­fore helps move the energy tran­si­tion in all direc­tions.

VRDTs are still quite rare around the world. What’s your expe­ri­ence with using them?

Our oper­ating expe­ri­ence has been very posi­tive. It goes without saying that there were a few start-up and devel­op­ment prob­lems with the first series deliv­ered years ago. But the VRDTs we have today work in exactly the same way as stan­dard trans­formers. But, figu­ra­tively speak­ing, they can do twice as much!

Propo­si­tion four:
VRDT tech­nology is key to the energy revo­lu­tion.

And there is not even much more mate­rial required—just the regu­lator. For us this means effi­ciency, intel­li­gence, and sustain­ability. Obvi­ously all of that cannot replace strategy and exper­tise, including on the part of colleagues working on the grid. But our expe­ri­ence has been so posi­tive that over 90% of our new trans­former acqui­si­tions in 2019 have been VRDTs.


A full switch to elec­tro­mo­bility repre­sents a major chal­lenge for distri­b­u­tion grids—especially if the power has to come from sustain­able sources. The tech­nology needs to compen­sate for fluc­tu­a­tions in medium voltage and must be able to respond dynam­i­cally to changes in feed-in and load at the low-voltage level. In both cases, grid oper­a­tors can rely on the ECOTAP® VPD®.

It combines the exper­tise that MR has accu­mu­lated over decades of working with vacuum on-load tap-changers in high-speed resistor-type tap-changer tech­nology with expe­ri­ence in voltage regu­la­tion distri­b­u­tion trans­formers to guar­antee a stable, main­te­nance-free perfor­mance of 500,000 tap-change oper­a­tions. The ECOTAP® VPD® is so compact that it does not make the distri­b­u­tion trans­former any larger.


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