“Our insulators can support 100 metric tons”

What made the request from Siemens so unusual?

To begin with, the ITER project itself, which is aim­ing to find noth­ing less than the ener­gy source of the future. 35 nations are work­ing togeth­er at Cadarache in south­ern France to demon­strate the tech­ni­cal fea­si­bil­i­ty of nuclear fusion. The high-volt­age deck from Siemens, which is cur­rent­ly being test­ed in Pad­ua, plays a key role in the project. Its tech­nol­o­gy pro­vides the sup­ply volt­age required for the neu­tral beam injec­tion which heats the plas­ma to up to 150 mil­lion degrees. It is only at this tem­per­a­ture that nuclear fusion becomes pos­si­ble, and it takes one mil­lion volts to get there. The deck there­fore needs to be insu­lat­ed rel­a­tive to ground poten­tial. This is no easy task—and that’s where we come in.

What did Siemens need from you?

In total, they need­ed eight hol­low sup­port insu­la­tors to sup­port and insu­late the hun­dred-ton deck, which hous­es trans­form­ers, cab­i­nets, and con­vert­er cab­i­nets among oth­er com­po­nents.

What were the challenges you faced?

First­ly, the sta­t­ic load is very high. The hol­low insu­la­tors have to sup­port a weight of 100 met­ric tons. Sec­ond­ly, Cadarache is sit­u­at­ed in an area which expe­ri­ences seis­mic activ­i­ty. The tubes there­fore also have to be able to with­stand dynam­ic forces with a wall thick­ness of just twelve mil­lime­ters. And they could only be six meters tall because the deck is in a hall. That’s real­ly short—for volt ages of this mag­ni­tude they would nor­mal­ly be eleven meters tall.

What solution did RPC provide?

The sta­bil­i­ty of the glass-fiber rein­forced plas­tic (GRP) in the hol­low insu­la­tors is cru­cial. Our spe­cial­ists used finite-ele­ment cal­cu­la­tions to deter­mine the opti­mum angle and lay­er struc­ture to ensure that the GRP tube can with­stand the mechan­i­cal loads. And the way in which the glass fibers are wrapped around the tube also deter­mines the insu­lat­ing capac­i­ty. That’s how we were able to achieve the lim­it­ed height. The GRP tubes are filled with nitro­gen to ensure that no mois­ture can get inside them. The inter­nal pres­sure is mon­i­tored at all times using pres­sure sen­sors from MESSKO and ISM tech­nol­o­gy from MR. In this way, exper­tise from across the Rein­hausen Group has been incor­po­rat­ed into the hol­low insu­la­tors.

The ITER project has extremely strict safety requirements. How were you able to meet the high quality standards?

Admit­ted­ly it was a very com­pli­cat­ed process. The hol­low insu­la­tors were sub­ject­ed to count­less tests by an inde­pen­dent lab­o­ra­to­ry as well as by the MR and RPC labs. Numer­ous mate­r­i­al sam­ples were stud­ied and test­ed to assess their suit­abil­i­ty. Ulti­mate­ly, the tests showed that the stan­dard mate­r­i­al that we also use for the tubes in on-load tap-chang­ers already meets the high require­ments.

Are the hollow insulators also suitable for other applications?

Yes. For exam­ple, for the thyris­tor and rec­ti­fi­er tow­ers in HVDC appli­ca­tions, some of which are sup­port­ed by 16 insu­la­tors. With our GRP tubes, you only need four. There is also grow­ing demand for HVDC sys­tems with com­pos­ite insu­la­tors. We are there­fore con­stant­ly expand­ing our port­fo­lio in this direc­tion.