---

In order to manu­fac­ture a regu­lated distri­b­u­tion trans­former, you have chosen to use on-load tap-changers from Rein­hausen. Why?

BIRBACHER: For us, it was clear from the outset that we wanted to work with a strong partner, agree on the inter­faces and develop a product that was reli­able, safe to operate, and above all, could be launched on the market quickly. Both of our compa­nies have an excel­lent repu­ta­tion and stand for many years of expe­ri­ence, quality, and longevity. If we say that we combine SBG exper­tise with Rein­hausen tap-changer tech­nology, we don’t have to adver­tise much more than that.

BÜHNERT: One major advan­tage is that we offer a plug & play solu­tion that is inter­esting for all users who want to improve their network quality. In addi­tion to supply network oper­a­tors, this also applies to indus­trial compa­nies that have increased demands in rela­tion to a stable voltage band in the network due to sensi­tive processes.

What sets the VRDT with ECOTAP VPD apart?

BÜHNERT:A key advan­tage is the ability to inte­grate the VRDT into existing infra­struc­tures. The VRDT foot­print, i.e., the floor space that it occu­pies, is nearly iden­tical to that of its unreg­u­lated coun­ter­part. In addi­tion, it can switch under load and complete tap changes under all condi­tions. And we can cover the entire voltage band with a control band­width of plus/minus ten percent. For example, the VRDT can be used as a direct regu­lator in the low-voltage network, or as a support to stabi­lize the medium-voltage network. In addi­tion, the tap-changer does not cause any addi­tional losses. This is not only impor­tant in terms of effi­ciency, but also in terms of heat devel­op­ment.

Was it a compli­cated devel­op­ment process to get the VRDT ready for series produc­tion?

BIRBACHER: We are gener­ally very quick at designing a func­tional model. Ulti­mately, we were dealing with a trans­former with addi­tional taps, which we then opti­mized over the course of many devel­op­ment steps. It was there­fore possible to test various winding and reactor designs. As a result of devel­oping our own reac­tors and thanks to their instal­la­tion posi­tion, we were able to halve the addi­tional losses in bridge posi­tions, as well as further opti­mize the size and sound emis­sion. We were able to improve these aspects even more by changing to the high-speed resistor-type tap-changer prin­ciple of the ECOTAP VPD. We worked closely with Rein­hausen on all the steps, and we have both prof­ited greatly from this coop­er­a­tion. We have been supplying serial-produc­tion VRDTs since 2012. By now they are part of the stan­dard oper­ating equip­ment for energy providers.

Were there any diffi­cult obsta­cles during this opti­miza­tion phase?

BÜHNERT: There were three main points. First of all, it was diffi­cult to coor­di­nate the inter­faces between the trans­former, the tap-changer, and the control tech­nology. In addi­tion, a trans­former with a tap-changer behaves differ­ently from a conven­tional one. This was some­thing that we had to consider during the design phase. The third point was the behavior with alter­na­tive insu­lating media. Due to the internal mechanics there was a lot to consider with regard to the oper­ating temper­a­ture.

How easy was it to inte­grate the VRDT into live produc­tion?

BIRBACHER: We are used to producing special solu­tions. There­fore, series produc­tion was not a problem. The tap-changer is very easy to inte­grate without any special tools. Normally, we install de-ener­gized tap-changers, which can be switched off, in distri­b­u­tion trans­formers. These are adjusted accord­ingly to match the grid voltage. The prin­ciple is basi­cally the same, except that the ECOTAP VPD is slightly larger and heavier in compar­ison to tap-changers that can be switched off.

How do you rate the market poten­tial?

BIRBACHER:Around 70 percent of the approx. 1,000 VRDTs in Germany were produced by SBG. The emer­gence of other markets will obvi­ously depend on how the respec­tive govern­ments promote alter­na­tive ener­gies. Among other things, we see further poten­tial in the expan­sion of e-mobility infra­struc­tures. We mainly attract supply network oper­a­tors and energy supply compa­nies, and of course we also carry out projects directly with indus­trial customers and compa­nies for alter­na­tive energy gener­a­tion. For example, we can supply wind energy plants with control tech­nology, which means that the feed-in already has the optimum voltage quality. Overall, we are in a growth market with the VRDT.