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.