Staying safe during a blackout

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Net­ze Duis­burg ensures the city’s sup­ply secu­ri­ty with elec­tric­i­ty, gas, water, and dis­trict heat­ing around the clock. Near­ly 700 employ­ees make sure the lights stay on, water flows, and heat­ing sys­tems keep homes warm. In a large, dense­ly pop­u­lat­ed, and indus­tri­al city like Duis­burg, this is a com­plex task. Added to this are ever-chang­ing demands from the grid itself. With the ener­gy tran­si­tion, the num­ber of decen­tral­ized pow­er sources is ris­ing, and these sources are also volatile  – some­times feed­ing in a lot, some­times noth­ing at all. The need for greater oper­a­tional reli­a­bil­i­ty and intel­li­gent grid man­age­ment is grow­ing, but the tech­nol­o­gy in sub­sta­tions or gas trans­fer sta­tions must first make this pos­si­ble; at the same time there is a short­age of skilled work­ers. “To over­come these chal­lenges, we need to posi­tion our­selves to be cri­sis-proof in many areas,” says Michael Har­ing, Head of Oper­a­tions Engi­neer­ing at Net­ze Duis­burg. He over­sees the elec­tri­cal sys­tems for gas, water, elec­tric­i­ty, and dis­trict heat­ing. “We main­tain a total of 26 facil­i­ties and approx­i­mate­ly 5,000 kilo­me­ters of medi­um-volt­age lines.”

Power outage, backup power solution on

Cri­sis resilience means, first and fore­most, that Net­ze Duisburg’s crit­i­cal infra­struc­ture can con­tin­ue to oper­ate inde­pen­dent­ly in the event of a black­out. “Whether it’s hos­pi­tals, super­mar­kets, indus­try, or drink­ing water at home  –  the emer­gency sup­ply ensures that life can con­tin­ue as usu­al for the time being.” Here, Har­ing relies on back­up pow­er solu­tions that seam­less­ly step in to pro­vide gas and water in the event of a pow­er out­age. In many parts of Duis­burg, diesel gen­er­a­tors and lead-acid bat­ter­ies are still used for this pur­pose.

At trans­fer sta­tions, these ensure the gas sup­ply by keep­ing the sys­tems oper­a­tional and con­trol­lable until pow­er is restored. But the back­up solu­tion is also essen­tial for ensur­ing that the pow­er sup­ply can be restored at all: When the grid is restart­ed, loads must be con­nect­ed to sub­sta­tions in a tar­get­ed and grad­ual man­ner, because oth­er­wise it could col­lapse again imme­di­ate­ly due to high inrush cur­rents.

Switching to the future

But with the gen­er­a­tors and lead-acid bat­ter­ies that Net­ze Duis­burg has relied on so far, Har­ing and his team are increas­ing­ly reach­ing their lim­its. While the old sys­tems are proven, they are no longer suf­fi­cient for today’s chal­lenges, explains Har­ing: “Labor costs are high because diesel fuel degrades over time and must there­fore be replaced reg­u­lar­ly. The lead-acid bat­ter­ies also require exten­sive safe­ty mea­sures.”

Oper­a­tional reli­a­bil­i­ty also needs to be improved: “The back­up pow­er solu­tion only kicks in dur­ing a com­plete grid out­age, but even a par­tial fail­ure can cause the sys­tem to run unsta­bly. The gen­er­a­tors then need 70 sec­onds to start up and syn­chro­nize. That’s too long  –  in both cas­es, we want to react faster. Self-suf­fi­cien­cy was also lim­it­ed to just ten hours, but our goal is 72.” Michael Har­ing there­fore select­ed a gas trans­fer sta­tion as a pilot project to test a new solu­tion that is also suit­able for sub­sta­tions. The task: to define, for the first time, a new back­up pow­er solu­tion that is fast, dig­i­tal, and future-proof

Established and reliable

Timo Kahl is respon­si­ble for elec­tri­cal sys­tems in the gas and water sec­tor with­in Haring’s depart­ment. There­fore, the mod­ern­iza­tion of the gas trans­fer sta­tion fell under his purview. “We were look­ing for a tech­ni­cal­ly flaw­less sys­tem con­sist­ing of bat­tery stor­age and an invert­er, but also for a part­ner we trust who would sup­port us in a solu­tion-ori­ent­ed and prac­ti­cal way,” explains Kahl. He opt­ed for nick­el-man­ganese-cobalt bat­ter­ies: “Com­pared to oth­er sys­tems, they are more space-effi­cient and have a longer ser­vice life.”

What Kahl still need­ed was an invert­er capa­ble of pro­vid­ing back­up pow­er that met the high stan­dards for prod­uct qual­i­ty, data secu­ri­ty, and sys­tem per­for­mance. He found what he was look­ing for at Rein­hausen: the GRIDCON^® PCS invert­er from Reinhausen’s Pow­er Con­vert­ers port­fo­lio. This invert­er oper­ates in grid-fol­low­ing mode, mean­ing it adapts to the volt­age, fre­quen­cy, and phase angle of the pow­er grid, there­by pro­vid­ing the trick­le charge for the bat­tery. Thanks to its inte­grat­ed bat­tery man­age­ment sys­tem, it mon­i­tors opti­mal oper­a­tion. If just one of the phas­es fails, the GRIDCON PCS^® auto­mat­i­cal­ly switch­es to grid-form­ing mode with­in just 100 mil­lisec­onds – mean­ing the bat­tery and invert­er autonomous­ly take over the pow­er sup­ply. Even in the event of a par­tial phase fail­ure, every­thing now runs sta­bly. The con­trol, switch­ing, and com­mu­ni­ca­tion sys­tems of the gas trans­fer sta­tion remain oper­a­tional, remote­ly con­trol­lable, and inte­grat­ed into the con­trol cen­ter for up to 72 hours. The return to reg­u­lar grid oper­a­tion is just as fast and the bat­tery is then recharged.

Training included

Inte­gra­tion with the bat­tery stor­age sys­tems was no prob­lem. “These are estab­lished, cer­ti­fied solu­tions whose safe­ty we can rely on. Our con­tacts at Rein­hausen were always quick to respond and are just as com­mit­ted to the long-term vision as we are. That’s how a true part­ner­ship works,” says Kahl, sum­ma­riz­ing the deci­sion to choose Rein­hausen. The con­ver­sion at the gas trans­fer sta­tion was then com­plet­ed quick­ly with­in a week. And as an added bonus, the new solu­tion sig­nif­i­cant­ly reduces the envi­ron­men­tal foot­print com­pared to the old diesel sys­tem. “This helps us enor­mous­ly in achiev­ing our sus­tain­abil­i­ty goals.”

The fit between Net­ze Duis­burg and Rein­hausen was also a good one on a per­son­al lev­el. Par­al­lel to com­mis­sion­ing, the pow­er qual­i­ty experts con­duct­ed train­ing ses­sions on the new sys­tem. “It’s impor­tant to us that we have the nec­es­sary know-how in-house and can oper­ate the sys­tems safe­ly our­selves,” explains Har­ing. “That, too, means cri­sis resilience for us.” With the com­bi­na­tion of mod­ern tech­nol­o­gy and the asso­ci­at­ed exper­tise, Net­ze Duis­burg has found a future-proof solu­tion – and one that can now be applied to many oth­er gas trans­fer sta­tions and sub­sta­tions through­out the city.