Big Brothers

When a de-ener­gized tap-chang­er has to main­tain a huge test volt­age of 1,000 kilo­volts and switch 112 kilo­volts in a sin­gle step, size real­ly does mat­ter. The experts at Rein­hausen have built three of these giants for the Cana­di­an trans­former man­u­fac­tur­er PTI Trans­form­ers.

The largest de-ener­gized tap-chang­ers in Reinhausen’s port­fo­lio meas­ure three meters in length and one meter in diam­e­ter. Pro­duc­ing equip­ment on this scale has put Rein­hausen and Regens­burg firm­ly on the world map. No oth­er sup­pli­er includes tap chang­ers of this size as stan­dard in its port­fo­lio or has so much expe­ri­ence in high­ly spe­cial­ized areas of appli­ca­tion. How­ev­er, at the out­set, it wasn’t clear if the de-ener­gized tap-chang­ers PTI Trans­form­ers need­­ed would be tech­ni­cal­ly fea­si­ble even for Rein­hausen.

Switching Step of 112 kV

PTI Trans­form­ers had been com­mis­sioned by a Cana­di­an ener­gy provider to replace a trans­former for a hydro­elec­tric pow­er plant that had reached the end of its ser­vice life. The new trans­former had to be able to switch between one trans­mis­sion line at 250 kilo­volts and anoth­er at 143 kilo­volts. The test volt­age required was a mas­sive 1,000 kilo­volts.

“From our point of view, the huge chal­lenge of hav­ing to bridge a switch­ing step of 112 kilo­volts while main­tain­ing a test volt­age of this mag­ni­tude meant that there was only one sup­pli­er we want­ed to work with — and that was Rein­hausen.”George Par­ty­ka Jr, Vice Pres­i­dent at PTI Trans­form­ers

“From our point of view, the huge chal­lenge of hav­ing to bridge a switch­ing step of 112 kilo­volts while main­tain­ing a test volt­age of this mag­ni­tude meant that there was only one sup­pli­er we want­ed to work with—and that was Rein­hausen,” states George Par­ty­ka Jr., Vice Pres­i­dent of PTI Trans­form­ers. There was no doubt at all in the mind of the Cana­di­an man­ag­er that Rein­hausen could bring its tech­ni­cal know-how and its exper­tise to bear in build­ing a de-ener­gized tap-chang­er (DETC) to this spec­i­fi­ca­tion. But it was obvi­ous that it wouldn’t be easy.

Supersized DETCs

Karl-Heinz Sperg­er, who man­aged the project at Rein­hausen, said: “His­tor­i­cal­ly, we have always relied upon rotary de-ener­gized tap-chang­ers with a head design. De-ener­gized tap-chang­ers of this mag­ni­tude can only be pro­duced using this type of design. A straight-line de-ener­gized tap-chang­er would need to be more than ten meters long to achieve the kind of per­for­mance val­ues we were look­ing for.”

Installing the de-ener­gized tap-chang­er head takes a great deal of skill and dex­ter­i­ty. (© Hel­mut Koch)

One of the chal­lenges that arose dur­ing the devel­op­ment stage was that Reinhausen’s design was only able to accom­mo­date test volt­ages up to a max­imum of 750 kilo­volts. Mr. Sperg­er explains: “While these de-ener­­gized tap-chang­ers are huge, there are still cer­tain restric­tions on the space we have to work with and we can’t just increase the dis­tance between the con­tacts as much as we want. That made the physics of this project a real test. But true to our mot­to “If some­thing is doable, we’ll do it” we worked togeth­er with PTI Trans­form­ers to find the right solu­tion.”

Special Design

Anoth­er sig­nif­i­cant fac­tor con­tribut­ing to the com­plex­i­ty of the project was the trans­mis­sion ratio of 1:1.78. Switch­ing 143 kilo­volts to 250 kilo­volts in a sin­gle step requires six high-volt­age wind­ing strands—for every phase.

For PTI Trans­form­ers, this meant hous­ing 18 wind­ings and three of the mas­sive tap chang­ers with­in the trans­former, some­thing which, as PTI Trans­form­ers’ Mr. Par­ty­ka explained, was only pos­si­ble with Reinhausen’s sup­port: “The trans­former pow­er is high­ly depen­dent on the tap-chang­er capac­i­ty, so the devel­op­ment depart­ments work­ing on the tap-chang­er design and the trans­former design had to work togeth­er very close­ly.

Only as a team was it pos­si­ble for us to coor­di­nate the wind­ing con­fig­u­ra­tion with the spe­cial design of the tap chang­er.” The PTI Trans­form­ers and Rein­hausen experts com­plet­ed this com­plex devel­op­ment task in a mere three months, result­ing in the order being placed in Feb­ru­ary 2019 and allow­ing the de-ener­gized tap-chang­ers to go into pro­duc­tion. The tech­ni­cians were then able to con­struct the three spe­cial pieces of equip­ment in just five days. Mr. Sperg­er, him­self an elec­tri­cal engi­neer, said: “Because we insist on deliv­er­ing 100 % qual­i­ty, the tap chang­ers were then sent to our test lab­o­ra­to­ry.” There, it was found that the engi­neers had deliv­ered on their promis­es.

The moment of truth: A test volt­age of 1,000 kV will soon be flow­ing through the sys­tem. Then we will find out if the engi­neers have deliv­ered on their promis­es. (© Hel­mut Koch)

Sum­ming up the expe­ri­ence, Mr. Par­ty­ka said: “We are extreme­ly grate­ful to the Rein­hausen team for all their sup­port. As is typ­i­cal for this kind of devel­op­ment project, both sides involved in the process were under real pres­sure at times, but we knew that we could rely on Reinhausen’s exper­tise. For that rea­son, we also want Rein­hausen to mon­i­tor the process of installing the de-ener­gized tap-chang­ers at the site.”


PTI Transformers

Found­ed in 1989 and head­quar­tered in the city of Regi­na, PTI Trans­form­ers is one of Canada’s lead­ing com­pa­nies special­izing in trans­former tech­nol­o­gy. It employs around 300 peo­ple at pro­duc­tion sites in Regi­na and Win­nipeg, Cana­da, and is cer­ti­fied to ISO 9001:2015. The com­pa­ny prides itself on deliv­er­ing not only high-qual­i­ty prod­ucts, but also cus­tomized ser­vices for all aspects of trans­form­ers.


Do you have any ques­tions abut de-ener­gized tap-chang­ers?
Karl-Heinz Sperg­er will be delight­ed to answer them.

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