All Aboard

On board the ships of the Ger­man fed­er­al police force, prob­lems with har­mon­ics reg­u­lar­ly inter­fered with the elec­tron­ic equip­ment. But since active fil­ters from the GRIDCON® ACF series were installed on board, their pow­er sup­ply has been free from inter­fer­ence.

The Bayreuth glides almost silent­ly into the har­bor at Neustadt in Hol­stein on a bright and sun­ny morn­ing. The silence is only bro­ken by the Baltic Sea gen­tly lap­ping against the side of the police ship that mea­sures almost 66 meters in length and ten meters in width. Almost the full crew is stand­ing at the ship’s rail in their blue uni­forms. The offi­cers look to their col­leagues wait­ing patient­ly on the quay for their shift on board.

They have been at sea for six days, patrolling the 140-nau­ti­cal-mile coastal stretch between the Flens­burg Firth and Buk­spitze cape in the Bay of Meck­len­burg. Fol­low­ing a 360-degree turn, the Bayreuth slow­ly approach­es the quay wall. The lines are sent fly­ing through the air and the ship is secure­ly moored up by 10 a.m. Right on time. Now it’s time for the crews to change over and pro­vi­sions to be restocked for the next few days at sea.

Com­mand­ing Offi­cer Frank Rogat­ty can usu­al­ly be found stand­ing up on his bridge. He has been travel­ing to sea for the Ger­man fed­er­al police force since 2002. He says: “We are one of three coast­guard ships that cov­er the North and Baltic Seas.” It is their job to per­form checks on ships cross­ing over inter­na­tion­al sea bor­ders, emer­gency res­cue oper­a­tions at sea, har­bor inspec­tions, and stan­dard traf­fic checks, just like the ones per­formed by offi­cers on land. After all, there are speed lim­its and pri­or­i­ty rules at sea too.

Com­mand­ing Offi­cer Frank Rogat­ty needs to be able to rely ful­ly on the tech­nol­o­gy when out at sea. (© Jens Umbach)

Sum­mer is the busiest time of year, as com­mer­cial ships have to share the water with motor­boats, yachts, and stand-up pad­dle boards. The crew is made up of 14 police offi­cers, who work in three shifts to ensure that the coast­guard patrol is always in action. Some­times the crew is even big­ger.

“We have to be out­side no mat­ter what the wea­ther is like and we need to be able to rely ful­ly on the tech­nol­o­gy we have on board—especially when we need to maneu­ver quick­ly when vis­i­bil­i­ty is poor and the sea is rough,” says Rogat­ty, point­ing at the on-board equip­ment. “This is a com­plex sys­tem. All the elec­tri­cal com­po­nents have to work per­fect­ly in sync.”

Problems with harmonics

This is exact­ly the prob­lem that they were encoun­ter­ing two years ago. The crew’s cell phone charg­ers kept break­ing, the dish­wash­er and individ­ual com­put­ers were reg­u­lar­ly out of action, and key func­tions per­formed by the elec­tron­ic equip­ment in the bridge were being dis­rupt­ed.

It took quite some time until the cause of these issues was iden­ti­fied. The cul­prit was actu­al­ly a few floors beneath the crew in the ship’s bel­ly. It was the fre­quen­cy con­vert­er of the ship’s elec­tric engine. Head Machine Oper­a­tor Volk­er Uhlen­brock shouts above the noise com­ing from the engine room: “We kept notic­ing inter­fer­ence once we had hit a cer­tain speed. This led us to the idea that har­mon­ics could be inter­fer­ing with the oth­er elec­tri­cal com­po­nents. We always have around 50 elec­tri­cal instal­la­tions on board.”

The oth­er Ger­man police force ships were expe­ri­enc­ing the same phe­nom­e­non. While each of the ships still has a diesel engine, this is only real­ly intend­ed for use in emer­gen­cies or when real­ly high speeds are need­ed. For stan­dard oper­a­tion, the elec­tric engine is used since it con­sumes less fuel, pro­duces few­er emis­sions, is qui­et, and doesn’t dis­rupt the crew’s sleep. And the main­te­nance costs are low­er when the diesel engine is used less often. “Two diesel gen­er­a­tors sup­ply the pow­er required for the dri­ve and on-board elec­tri­cal equip­ment, with a con­tin­u­ous out­put of 450 kilo­watts each,” says Uhlen­brock.

“We can now focus all of our atten­tion on our police work with­out hav­ing to wor­ry about the on-board elec­tri­cal equip­ment.”Frank Rogat­ty, Com­mand­ing Offi­cer of the Bayreuth

As the issues with the pow­er sup­ply on board showed no signs of stop­ping, the Ger­man police force decid­ed to look for a solu­tion. And Rein­hausen had just what they were look­ing for. Thomas Zöll­ner, who works at Pow­er Qual­i­ty, is an expert in ship tech­nol­o­gy so he was able to help: “The prob­lem with iso­lat­ed grids is that they have a much low­er short-cir­cuit capac­i­ty com­pared to grids on shore.

This means that the tech­nol­o­gy is more like­ly to suf­fer from interfer­ence on the whole.” The Ger­man police force is by no means alone in expe­ri­enc­ing these prob­lems. Ship­yards are rely­ing more and more on elec­tric engines, while the use of elec­tron­ic equip­ment installed on board is also on the rise. This is also true for super yachts and spe­cial-pur­pose ships such as cable lay­ers and suc­tion dredgers.

Fighting Harmonics

Zöll­ner explains: “Unpleas­ant net­work per­tur­ba­tions caused by har­mon­ics is a famil­iar phe­nom­e­non with­in the auto­mo­tive sec­tor where dis­rup­tion to the fac­to­ry pow­er sup­ply can crip­ple the entire pro­duc­tion process.” To avoid this, grid oper­a­tors have been using active fil­ters for some time now. “That’s how we can elim­i­nate prob­lem­at­ic har­mon­ics. The active fil­ters in our GRIDCON® series auto­mat­i­cal­ly detect lim­it-val­ue devi­a­tions and emit oppos­ing waves to bal­ance out any such fluc­tu­a­tions. This same prin­ci­ple can also be applied to ships,” says Zöll­ner.

The elec­tric engine was caus­ing prob­lems on board once the ship had hit a cer­tain speed. (© Jens Umbach)

Head Machine Oper­a­tor Volk­er Uhlen­brock soon deter­mined that the fre­quen­cy con­vert­er was caus­ing all the trou­ble. But that’s all in the past now. (© Jens Umbach)

The GRIDCON® active fil­ter elim­i­nates the dis­rup­tive har­mon­ics. (© Jens Umbach)

In order to prove that har­mon­ics were in fact to blame for the prob­lems and to tai­lor the active fil­ters to the require­ments on board the ship, the Pow­er Qual­i­ty expert took a lot of read­ings and mea­sure­ments over sev­er­al days. “We basi­cal­ly per­formed an ECG on the on-board elec­tri­cal sys­tem,” explains Zöll­ner. The results were aston­ish­ing! While the stan­dard allows a pro­por­tion of har­mon­ics up to eight per­cent (with five per­cent as the rec­om­mend­ed val­ue), up to 14 per­cent was mea­sured on the ship

Zöll­ner deter­mined that the indus­trial GRIDCON® ACF would be the ide­al fil­ter solu­tion here. But it wasn’t pos­si­ble for the active fil­ter to be installed in the same way as it is on dry land: “The sway­ing and vibra­tions on the ship could dam­age the tech­nol­o­gy. And so we had to install vibra­tion absorbers under­neath the con­trol cab­i­net,” says Zöll­ner. Once the nec­es­sary tests had been passed, all three of the Ger­man police force’s ships were fit­ted with the Rein­hausen fil­ter solu­tion.

Full Steam Ahead

The GRIDCON® ACF has been in use on the Bayreuth for two years now. Head Machine Oper­a­tor Uhlen­brock is delight­ed with the results: “All the prob­lems we were hav­ing have dis­ap­peared. And I don’t have to do a thing because the fil­ter is ful­ly auto­mat­ic. The sys­tem sim­ply goes into stand­by when­ev­er we turn the engine off.”

Com­mand­ing Offi­cer Rogat­ty is just as hap­py: “We can now focus all of our atten­tion on our police work with­out hav­ing to wor­ry about the on-board elec­tri­cal equip­ment.” Both of these expe­ri­enced sea­far­ers have now end­ed their shifts and hand­ed every­thing over to the next crew. The Bayreuth is ready to set off again by 2 p.m. It departs slow­ly and heads back out onto the Baltic Sea as qui­et­ly as it arrived.


The GRIDCON® ACF active fil­ter solu­tion is ide­al for a wide range of appli­ca­tions. In addi­tion to the auto­mo­tive sec­tor and on board ships, active fil­ters can be found on wind farms, in mines, in sewage treat­ment plants, with­in the food indus­try, and in office and com­mer­cial build­ings. Active fil­ters auto­mat­i­cal­ly com­pen­sate for har­mon­ics and they can be relied upon to do so with great accuracy.The mod­u­lar design means that the solu­tion can be adapt­ed to suit each customer’s spe­cif­ic require­ments.


Want to find out more about using active fil­ters on ships?
Thomas Zöll­ner is here to help:

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