Better for the climate: synthetic air

Challenge

Sul­phur hexa­flu­o­ride (SF₆) is an ide­al insu­lat­ing gas for gas-insu­lat­ed switchgear (GIS) sys­tems, which con­trol the flow of ener­gy in sub­sta­tions or indus­tri­al plants, switch off cir­cuits when required and pro­tect the high-volt­age grid from over­loads. Com­pared to out­door switchgear, GIS sys­tems take up sig­nif­i­cant­ly less space and are there­fore par­tic­u­lar­ly suit­able for use in urban areas. And thanks to the out­stand­ing prop­er­ties of SF₆, very com­pact designs are pos­si­ble. How­ev­er, this pop­u­lar insu­lat­ing gas has a seri­ous dis­ad­van­tage: a cat­a­stroph­ic cli­mate foot­print. It is around 23,500 times more harm­ful to the cli­mate than CO_² and remains in the atmos­phere for 3,200 years.  

In 2024, a new F‑gas reg­u­la­tion there­fore came into force in the EU, which increas­ing­ly restricts the use of flu­o­ri­nat­ed gas­es and com­plete­ly bans SF₆ gas in new elec­tri­cal instal­la­tions start­ing from 2032. This also affects HIGHVOLT’s gas-insu­lat­ed test­ing and mea­sur­ing sys­tems, which man­u­fac­tur­ers and oper­a­tors need to test GIS sys­tems. Dr. Tobias Gabler from HIGHVOLT explains: “The chal­lenge is that there is no oth­er gas that has sim­i­lar­ly good prop­er­ties to SF₆.” Although there are already alter­na­tives on the mar­ket that have a sig­nif­i­cant­ly bet­ter car­bon foot­print, some of them also con­tain flu­o­ri­nat­ed gas­es, which the EU also wants to ban. “We want­ed a future-proof solu­tion for our sys­tems. We want our cus­tomers to be able to rely on the assur­ance that they will still be able to use their test­ing sys­tems in ten years’ time,” explains Gabler. 

Solution 

So, what is the alter­na­tive? The answer sounds very sim­ple: syn­thet­ic air. It con­sists of nitro­gen and oxy­gen, has a glob­al warm­ing poten­tial of zero and is there­fore com­plete­ly harm­less to the cli­mate. The catch: syn­thet­ic air has sig­nif­i­cant­ly poor­er insu­lat­ing prop­er­ties and can­not replace SF₆ gas on a one-to-one basis. “How­ev­er, the dis­ad­van­tages can be over­come if we revise the design of our test­ing and mea­sur­ing sys­tems,” explains Gabler. The test­ing experts at HIGHVOLT are there­fore grad­u­al­ly scru­ti­niz­ing all mea­sur­ing and test­ing sys­tems and inves­ti­gat­ing how they can adapt the com­po­nents to the new require­ments. For exam­ple, the insu­lat­ing capac­i­ty of syn­thet­ic air can be sig­nif­i­cant­ly improved by almost dou­bling the oper­at­ing pres­sure in the sys­tems from four to sev­en bar. This in turn requires thick­er walls for the ves­sels so that they can with­stand the high­er pres­sure. 

“We also have to increase the insu­la­tion dis­tances and adapt the elec­trode geome­tries. Over­all, these mea­sures make our sys­tems around 20 per­cent larg­er, but oth­er­wise all func­tion­al­i­ties remain the same,” says Gabler. As more and more GIS man­u­fac­tur­ers are also increas­ing­ly rely­ing on syn­thet­ic air, HIGHVOLT’s sys­tems are com­pat­i­ble with them. How­ev­er, exist­ing sys­tems that are still oper­at­ed with SF₆ can also con­tin­ue to be test­ed if appro­pri­ate adapters are used. “Our sys­tems are very flex­i­ble in this respect,” empha­sizes Gabler. 

In addi­tion to the envi­ron­men­tal aspect, syn­thet­ic air also has oth­er advan­tages for oper­a­tors such as much eas­i­er gas han­dling. As Gabler explains: “Main­te­nance is much more com­plex with SF₆ because the gas has to be extract­ed at great expense and a num­ber of safe­ty pre­cau­tions are also nec­es­sary, for exam­ple dur­ing trans­port – all of this is elim­i­nat­ed or sim­pli­fied with syn­thet­ic air.” The require­ments for syn­thet­ic air are also less strict, and syn­thet­ic air is more read­i­ly avail­able and sig­nif­i­cant­ly cheap­er than SF₆. 

The HIGHVOLT engi­neers have already adapt­ed the first res­o­nant reac­tor coil for its AC volt­age test sys­tems to the new insu­lat­ing medi­um. “This means we are cur­rent­ly one of the first man­u­fac­tur­ers to bring test­ing tech­nol­o­gy with syn­thet­ic air onto the mar­ket.” Fur­ther test­ing and mea­sur­ing sys­tems will grad­u­al­ly fol­low so that all HIGHVOLT prod­uct series will be able to oper­ate with syn­thet­ic air from 2028 onwards. .