The Giant of Amprion

Ger­man grid oper­a­tor Ampri­on want­ed the largest and most pow­er­ful phase shifter in the world. For this to work at all, there first need­ed to be a rev­o­lu­tion in on-load tap-chang­ers.

Human­i­ty wants to move more and more ener­gy simul­ta­ne­ous­ly, which requires large high-per­for­mance trans­form­ers of all types: those for HVDC trans­mis­sion across entire coun­tries, those for many indus­tri­al appli­ca­tions, such as elec­tric arc fur­naces for steel­mak­ing, or vari­able shunt reac­tors for reac­tive pow­er com­pen­sa­tion. For Ampri­on, this means pow­er­ful phase-shifter trans­form­ers or, more pre­cise­ly, the most pow­er­ful phase shifter ever.

A Emergency Call ist recieved

Ampri­on is one of four trans­mis­sion grid oper­a­tors in Ger­many. The cat­a­lyst for build­ing the giant phase shifter, and the asso­ci­at­ed ground­break­ing devel­op­ments, was an emer­gency call. A few years ago, the Ger­man Fed­er­al Net­work Agency con­tact­ed Ampri­on with the request to install high-end phase shifters at over­loaded nodes as quick­ly as pos­si­ble. Because a study had con­firmed what many sus­pect­ed at the time: Expan­sion of the pow­er grids in Ger­many is not keep­ing pace with the increased sup­ply of renew­able ener­gy.

At dimen­sions of 30 x 26 x 11 meters, this device is as large as five sin­gle-fam­i­ly hous­es, and it has a weight of 935 met­ric tons—this gigan­tic phase shifter will pay for

Rein­hard Bradt, who is in charge of grid projects at Ampri­on, goes into more detail. “This can result in indi­vid­ual max­i­mum-volt­age trans­mis­sion lines becom­ing over­loaded when ener­gy is trans­ferred from off­shore wind parks in north­ern Ger­many, for exam­ple, to the con­sump­tion cen­ters in south­ern Ger­many.” Gigan­tic phase shifters will help keep the grid durable and pow­er­ful, on an ad hoc basis, until grid expan­sion catch­es up by 2030. How­ev­er, two con­di­tions must be met to avoid dot­ting the land­scape with expen­sive emer­gency solu­tions: “Invest­ments should amor­tize with­in three years and should be sus­tain­able.”

Turbo for the VACUTAP®

A phase shifter is like a two-way valve for the grid that deter­mines whether the cur­rent flows from left to right or from right to left. Using this device, grid oper­a­tors can relieve the load on lines with­out hav­ing to inter­vene in pow­er con­sump­tion or pro­duc­tion, since that would result in hefty redis­patch­ing fees. While a phase shifter can­not increase the over­all trans­mis­sion capac­i­ty of the grid, it can move the load with­in the grid to ensure bet­ter uti­liza­tion until expan­sion can increase the grid’s over­all trans­mis­sion capac­i­ty.

A masterpiece

The first and most powerful VACUTAP® tap changer in the world for high-performance applications.

The VACUTAP® Advanced Flux Con­trol Sys­tem ensures the func­tion of vac­u­um inter­rupters in case of extreme cur­rents and mag­net­ic fields in high-end appli­ca­tions.

18—35 oper­at­ing posi­tions are pos­si­ble with the R selec­tor. TheAGIS® (Active Gas Inhi­bi­tion Sys­tem)makes it pos­si­ble to reduce gas for­ma­tion by 90 per­cent.

The highlights at a glance:

10,000 kVA switch­ing capac­i­ty**

The record tap-chang­er is up to4 Meters high*

3,200 Ampere rat­ed cur­rent*

6,000 Volt step volt­age*

Dou­bled pow­er range for VACUTAP® on-load tap-chang­er:

*The fig­ures depend on the design and indi­cate the respec­tive max­i­mum val­ues.

Ampri­on com­mis­sioned Siemens Ener­gy with the con­struc­tion of the first mega phase shifter. It will boast the fol­low­ing fea­tures: 400 kilo­volt rat­ed volt­age, 2,000 mega­volt-ampere through­put capac­i­ty and 2,992 ampere rat­ed cur­rent. But what still wasn’t clear was how oper­a­tors should per­form switch­ing oper­a­tions when such loads are present.

Bradt con­sid­ered the two conditions—amortization in three years and sustainability—and rea­soned that he need­ed main­te­nance-free on-load tap-chang­ers, mean­ing those with vac­u­um tech­nol­o­gy. The down­side was that there were no such on-load tap-chang­ers in this pow­er rat­ing class. “So we asked MR to devel­op a VACUTAP for this pur­pose.” And MR was not ful­ly unpre­pared to con­front this chal­lenge since this type of VACUTAP had already been in pre­lim­i­nary devel­op­ment for years. But once it became much more of a real­i­ty, MR start­ed focus­ing all its ener­gy and work­ing at full force to get the new, mighty VACUTAP ready for oper­a­tion.

Development no longer an winding road

The rat­ed-cur­rent lim­it for VACUTAP tech­nol­o­gy was pre­vi­ous­ly at 1,300 amperes with­out forced cur­rent split­ting. MR engi­neers worked to raise this lim­it to a tremen­dous 3,200 amperes with­in a very short time, sur­pass­ing even the 3,000 ampere lim­it cur­rent­ly applic­a­ble to high-main­te­nance oil tech­nol­o­gy. The peo­ple at MR have devel­oped a spe­cial gadget—the Advanced Flux Con­trol System—to man­age the high lev­els of cur­rent and the mag­net­ic fields in the on-load tap-chang­ers.

The phase shifter will become a prof­itable invest­ment over the first three years and will con­tin­ue to oper­ate main­te­nance-free for anoth­er 50 years.

Now, noth­ing stands in the way of the planned, giant phase-shifter trans­former. But how gigan­tic does it need to be? Here, MR had a nice sur­prise ready for Siemens and Ampri­on: The new VACUTAP does not fea­ture any cur­rent split­ting. The on-load tap-chang­er can car­ry all the cur­rent with­in one sec­tor, which has major con­se­quences for the trans­former design because the man­u­fac­tur­er does not need to install a com­pli­cat­ed wind­ing that takes up a lot of space on the coils, which them­selves are the size of a VW bus. This allowed Siemens to think sim­pler and small­er. Due to this VACUTAP fea­ture alone, the phase­shifter trans­former is sub­stan­tial­ly small­er than the ver­sions with cur­rent split­ting. Small­er means less mate­r­i­al, lighter, and less insu­lat­ing oil. Sim­ply put: more afford­able.

Rein­hard Bradt, Head of Grid Projects at Ampri­on

And it is eas­i­er to trans­port. Ship­ping such a gigan­tic device on land can only be done using trains, for which there are weight and size lim­its that need to be observed for the trans­port goods. How­ev­er, this is not a prob­lem for this slim giant.

Money througRedispatching

One ques­tion remains: How can such a high-tech hunk amor­tize in no more than three years? The answer is sur­pris­ing: through saved redis­patch­ing costs. In the Euro­pean grid, espe­cial­ly in Ger­many, many redis­patch­ing mea­sures can be traced back to con­trac­tu­al agree­ments that stip­u­late who can con­sume and sup­ply how much elec­tric­i­ty and when they can do so. These agree­ments are defined down to the minute, and every minute over or under the defined time lim­its results in enor­mous con­trac­tu­al penal­ties. With phase shifters at the right interfaces—usually on the bor­ders between coun­tries or sup­ply areas—Amprion can car­ry out all of these con­trac­tu­al mea­sures eas­i­ly and prompt­ly.

“We expect sav­ings of one hun­dred mil­lion euros over the next three years.”

Rein­hard Bradt, Head of Grid Projects at Ampri­on

Rein­hard Bradt says, “Use sim­u­la­tions at a suit­able loca­tion showed sav­ings of more than one hun­dred mil­lion euros after deduc­tion of the invest­ment costs aris­ing over the first three years of oper­a­tion.” Com­mis­sion­ing is sched­uled for 2023. The phase shifter will become a prof­itable invest­ment with­in the first three years and will then con­tin­ue to oper­ate main­te­nance-free for anoth­er 40 to 50 years. Bradt adds, “Using this device will make sense for opti­miz­ing the pow­er flow near the bor­ders in the Ampri­on grid even after the ongo­ing grid expan­sion is com­plet­ed.”


The first vac­u­um tap chang­er for all high-end appli­ca­tions:

  • HVDC trans­form­ers for long elec­tric­i­ty high­ways
  • Vari­able shunt reac­tors (VSR) for reac­tive pow­er com­pen­sa­tion
  • Phase-shifter trans­form­ers (PST) for active con­trol of pow­er flowin ener­gy grids
  • Indus­tri­al trans­form­ers for high-per­for­mance appli­ca­tions


If you have any ques­tions about VACUTAP® VRL®,
please con­tact Chris­t­ian Hillinger:

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