More volts for the transition

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Frank Woll­mann, plant man­ag­er at Siemens Ener­gy in Dres­den, has plen­ty to do: The trans­former plant’s order books are more than full. The approx­i­mate­ly 240 employ­ees at the site cur­rent­ly pro­duce around 115 medi­um-pow­er trans­form­ers and 25 shunt reac­tors every year.

And thanks to the ener­gy tran­si­tion, the equip­ment is in greater demand than ever before. The impor­tance of shunt reac­tors – also known as com­pen­sat­ing reac­tors – will con­tin­ue to grow in the future as they com­pen­sate for reac­tive pow­er, increase trans­mis­sion effi­cien­cy, and reg­u­late volt­age at the same time. In short, they keep the grids sta­ble.

In order to cope with the enor­mous increase in demand, Siemens Ener­gy plans to expand its pro­duc­tion in Dres­den. Woll­mann says: “We want to man­u­fac­ture more trans­form­ers and at the same time increase the pro­por­tion of shunt reac­tors. To achieve this, we are expand­ing the plant step by step.”

Comprehensive testing program

A cen­tral com­po­nent of this is the expan­sion of the exist­ing test bay. Because whether it’s a trans­former or a shunt reac­tor – before the colos­si weigh­ing sev­er­al tons are sent to cus­tomers, they have to pass an exten­sive cat­a­log of tests. “Depend­ing on what addi­tion­al require­ments the cus­tomers have, these fac­to­ry accep­tance tests can take between two days and a week and a half,” says Woll­mann. This is absolute­ly nec­es­sary because any unde­tect­ed error could have fatal con­se­quences lat­er in oper­a­tion.

How­ev­er, the test facil­i­ty in Dres­den was not pre­vi­ous­ly designed to car­ry out these tests on shunt reac­tors. High three-phase test volt­ages must be pro­vid­ed for them and the require­ments for the tests with high­er test fre­quen­cies are more com­plex. Pre­vi­ous­ly, the accep­tance tests were car­ried out at the sis­ter plant in Nurem­berg, but the process involved was too com­pli­cat­ed and too expen­sive.

Siemens Ener­gy there­fore decid­ed to upgrade the test field in Dres­den. Woll­mann only had to walk across the yard once to find a suit­able solu­tion: HIGHVOLT, a spe­cial­ist in high-volt­age test­ing tech­nol­o­gy and mem­ber of the Rein­hausen Group, which is based on the same site as Siemens Ener­gy. “There are only a hand­ful of man­u­fac­tur­ers in the world who can even build such sys­tems,” says Woll­mann.

Unique upgrade

Andreas Thiede is the expert for such AC volt­age test sys­tems at HIGHVOLT. Even though the basic prin­ci­ple of these sys­tems is the same, every test sys­tem that he and his team design is unique.

How­ev­er, the test sys­tem at Siemens Ener­gy was also some­thing spe­cial for Thiede: “We nor­mal­ly offer a con­tain­er solu­tion, but that was out of the ques­tion due to the struc­tur­al con­di­tions.” So space had to be cre­at­ed first: Two old gen­er­a­tors were tak­en out of the base­ment, ceil­ings were lift­ed, and new floors were installed to accom­mo­date com­po­nents such as con­vert­ers, capac­i­tor banks, and, above all, the new 200 MVA extra-high volt­age adapt­ing trans­former which sup­plies the test volt­age of up to 360,000 volts required for the shunt reac­tors and was man­u­fac­tured by Siemens Ener­gy based on HIGHVOLT’s design spec­i­fi­ca­tions.

One spe­cial fea­ture that HIGHVOLT has devel­oped espe­cial­ly for Siemens Ener­gy is a so-called DC exten­sion which can be used to test how the induc­tance behaves with a grad­ual increase in volt­age: “This addi­tion­al device can be used to charge the shunt reac­tor with a direct cur­rent and thus sim­u­late 150 per­cent oper­a­tion, that is, even above the pow­er lim­its of our AC volt­age sys­tem,” explains Thiede.

More shunt reactors

When the test­ing sys­tem was final­ly ready for oper­a­tion after just eleven months of con­struc­tion, the shunt reac­tors were already queu­ing up. The sys­tem worked straight away and Woll­mann is very sat­is­fied: “With such a com­plex sys­tem, that’s not a giv­en.

Of course, some fine tun­ing had to be done, but in the end the shunt reac­tors and trans­form­ers suc­cess­ful­ly left the fac­to­ry and that’s what counts.” Grid oper­a­tors can also be pleased: Siemens Ener­gy can now offer sig­nif­i­cant­ly more shunt reac­tors.