Test specialists in action

Final check: Before the test system is switched on, all contacts are checked using the dual-control principle. In addition, a safety circuit is set up to close off the hazardous area.

Repairs to cable sys­tems cost time and mon­ey. There­fore, a HIGHVOLT high-volt­age test is car­ried out direct­ly after final assem­bly.

The load on cable systems in Germany is constantly increasing. Repairs to cable systems are associated with high cost and time factors. In order to control proper cable production and assembly after installation, a standard-compliant, high-voltage test is therefore carried out after final assembly.

In the course of main­te­nance and net­work expan­sion, high-per­for­mance pow­er engi­neer­ing com­po­nents are upgrad­ed and new ones are built. At the Lichter­felde com­bined heat and pow­er plant in Berlin, the grid con­nec­tion is real­ized by means of 110 kV cable sys­tems. The net­work oper­a­tor Strom­netz Berlin wants to expand its infra­struc­ture in order to be able to reli­ably sup­ply the Ger­man cap­i­tal with elec­tri­cal ener­gy in the future. In doing so, grid oper­a­tors in Ger­many are fun­da­men­tal­ly faced with a major chal­lenge: the grid must both sup­ply the grow­ing demand for elec­tric­i­ty as well as inte­grate the volatile decen­tral­ized ener­gy pro­duc­ers in a sta­ble man­ner. The increase in net­work­ing required as a result neces­si­tates an increase in the num­ber of buried high-volt­age cable con­nec­tions.

Dur­ing lay­ing, dam­age to the sheath and the main insu­la­tion as well as qual­i­ty defects in the instal­la­tion of fit­tings can occur. These can man­i­fest them­selves in par­tial dis­charges and lead to a fail­ure of the cable sec­tion or an entire sub­sta­tion dur­ing oper­a­tion. Such a fail­ure can inter­rupt the pow­er sup­ply of an entire region. Dam­age reme­di­a­tion in the form of cable fault loca­tion as well as repair and con­struc­tion mea­sures are time-con­sum­ing and cost-inten­sive for net­work oper­a­tors. In addi­tion, dam­age events can jeop­ar­dize grid sta­bil­i­ty. There­fore, high-volt­age tests with option­al accom­pa­ny­ing par­tial dis­charge mea­sure­ment after cable lay­ing are an invest­ment in qual­i­ty assur­ance.

“For net­work oper­a­tors, it becomes expen­sive when laid cables fail and pow­er fail­ures are the result. With HIGHVOLT’s test­ing sys­tem, we can pre­vent this sce­nario and test cables reli­ably and direct­ly on site.” Alexan­der Lüp­schen, KOOPMANN Com­pa­ny

With the HIGHVOLT res­o­nance test sys­tem, engi­neers of the Koop­mann Group have a mod­ern and mobile tech­nol­o­gy at their dis­pos­al to test and diag­nose cable sys­tems on site. The core com­po­nent of the sys­tem is a 23-ton res­o­nance reac­tor, which is pow­ered by state-of-the-art con­vert­er and con­trol tech­nol­o­gy as well as an exciter trans­former. The test cir­cuit is round­ed off with an addi­tion­al high-volt­age mea­sur­ing divider, par­tial dis­charge cou­pler and reverse imped­ance.

The start: The reli­a­bil­i­ty of installed com­po­nents is to be ensured with regard to main­te­nance and net­work expan­sion. This includes test­ing after instal­la­tion. With­in the scope of high-volt­age test­ing, the Koop­mann Group from Clop­pen­burg, as a spe­cial­ist in the field, takes care of this, using a mobile high-volt­age test­ing sys­tem from HIGHVOLT with up to 260 kV.

Safe­ty first: Before start­ing the con­struc­tion of the high-volt­age cir­cuit, a ground­ing sys­tem is set up and con­nect­ed to all com­po­nents of the test cir­cuit. Work safe­ty always comes first.

Pow­er sup­ply: Not only the net­work oper­a­tor but also the HIGHVOLT test sys­tem requires a pow­er­ful pow­er sup­ply. This is done by means of a feed-in of up to 320 kVA.

Test-cir­cuit set­up: The engi­neers install the test cir­cuit. This includes in par­tic­u­lar the high-volt­age mea­sur­ing divider and the par­tial dis­charge cou­pler. A block­ing induc­tance is also used to pro­tect against tran­sients in the event of a flashover dur­ing the test.

“Test­ing high-volt­age cables after they have been laid is essen­tial to check whether the cable and the nec­es­sary con­nec­tion sleeves are func­tion­ing prop­er­ly. With our per­fect­ed tech­nol­o­gy of fre­quen­cy-vari­able res­o­nance test cir­cuits, this can be real­ized in an uncom­pli­cat­ed way.“ Dr. Alexan­der Win­ter, HIGHVOLT

Con­nec­tion of the test cable: Direct con­tact to the test object is not always pos­si­ble. In the case of test­ing via a gas-insu­lat­ed switchgear, the test volt­age is fed in with the aid of a tem­porar­i­ly laid test cable.

Instal­la­tion of the PD sen­sors: The small­est weak points can lead to a dam­age event dur­ing oper­a­tion. The accom­pa­ny­ing par­tial dis­charge mea­sure­ment dur­ing the test detects these weak points at an ear­ly stage.

Final check: Before the test sys­tem is switched on, all con­tacts are checked using the dual-con­trol prin­ci­ple. In addi­tion, a safe­ty cir­cuit is set up to close off the haz­ardous area.

Test in progress … After one hour per phase, the cable test is com­plet­ed. The engi­neers ana­lyze the mea­sured data on site in the test con­tain­er.  … and passed: The cable shows no abnor­mal­i­ties. The net­work oper­a­tor can put the cable sys­tem into oper­a­tion and inte­grate it into the net­work.

Info

Even if a high-volt­age cable has been suc­cess­ful­ly test­ed and laid on site, the insu­la­tion can suf­fer dam­age over the years. With the HiMON® mon­i­tor­ing sys­tem from HIGHVOLT, how­ev­er, it is pos­si­ble to keep a per­ma­nent eye on kilo­me­ter-long stretch­es of under­ground cable and to gen­er­ate dam­age fore­casts thanks to arti­fi­cial intel­li­gence.

Find out more about the mon­i­tor­ing sys­tem.

YOUR CONTACT

Do you have any ques­tions about the project?
Dr. Alexan­der Win­ter is there for you:
 A.Winter@highvolt.com

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