The Perfec Weather For Cable Testing!

In the future, the only way to test long sub­ma­rine cables in off­shore wind farms will be via res­o­nance test­ing. HIGHVOLT has there­fore devel­oped a new test­ing sys­tem capa­ble of with­stand­ing the harsh con­di­tions out at sea.


Consid­er this sce­nario: Short­ly before the win­ter sea­son, an unknown prob­lem aris­es at an off­shore wind farm. With so lit­tle time before the end of the test­ing season—and in this wea­ther—no one is able to vis­it the site to car­ry out a high-volt­age test. So the win­ter storms rage for months and the rotors are in per­ma­nent motion—but it all goes to waste.

The elec­tri­cal pow­er that is gen­er­at­ed can­not be used on land. The bad weath­er and low tem­per­a­tures mean that no work can be car­ried out on site, so the engi­neers have to wait until at least April before they can vis­it the wind farm and find out what the prob­lem is. In the mean­time, the wind farm oper­a­tor keeps star­ing at the cal­en­dar: For every day that they are unable to sup­ply pow­er to the grid, they lose more and more mon­ey. When will it final­ly be sum­mer again?

So what is need­ed are prac­ti­cal, weath­er-proof off­shore test­ing sys­tems.

Con­ven­tion­al test­ing sys­tems for inspect­ing cables are not designed for the con­di­tions at an off­shore plat­form. When exposed to the salt in the air, as well as rain, snow, and rough seas, they can­not oper­ate reli­ably. Solu­tions that have proved use­ful for on-site test­ing on land—the use of tents, for example—are not going to be much help here. Fur­ther­more, trans­port­ing mate­ri­als and peo­ple with spe­cial ships or heli­copters is dif­fi­cult and has to be planned well in advance. The win­dow of oppor­tu­ni­ty where the wind farms are actu­al­ly acces­si­ble amounts to only a few months of the year. So what is need­ed are prac­ti­cal, weath­er-proof off­shore test­ing sys­tems.

Resonance testing

In response to these two factors—the weath­er at sea and the IEC standardization—HIGHVOLT has devel­oped an off­shore test­ing sys­tem which ful­fills the require­ments for on-site test­ing on the high seas. The tech­nol­o­gy is based on the tried-and-test­ed HIGHVOLT res­o­nance test­ing sys­tems, which have long been in use in hun­dreds of appli­ca­tions all over the world.

RESONANCE TESTING

The res­o­nance test­ing method repro­duces the load on a cable in nor­mal oper­a­tion at nom­i­nal volt­age and at approx­i­mate­ly grid fre­quen­cy. A res­o­nant cir­cuit com­pris­ing a test induc­tor (induc­tance) and test cable (capac­i­tance) is estab­lished for this pur­pose. The vari­able fre­quen­cy (10–500 Hz) of the test sys­tem sup­ply is auto­mat­i­cal­ly set to the res­o­nance fre­quen­cy of the test cir­cuit, which min­i­mizes the required feed-in pow­er.

Over half of all prob­lems are due to instal­la­tion errors. These can be reli­ably detect­ed by means of res­o­nance test­ing.

The nec­es­sary adap­ta­tions have been made with out­stand­ing atten­tion to detail: The engi­neers in Dres­den checked the suit­abil­i­ty of every sin­gle com­po­nent for off­shore use and upgrad­ed or redesigned them as nec­es­sary. Exam­ples include the use of cor­ro­sion-free mate­ri­als which are extreme­ly resis­tant to salt water spray, shield­ed and off­shore-cer­ti­fied plug con­nec­tors, and a gas-insu­lat­ed mod­ule for reli­able, fault-free con­nec­tion of the sys­tem com­po­nents and volt­age mea­sure­ment.

With this test­ing sys­tem, HIGHVOLT pro­vides wind farm oper­a­tors, cable man­u­fac­tur­ers, and test­ing ser­vice providers with the flex­i­bil­i­ty they need to safe­guard the func­tion­ing of com­plex off­shore elec­tri­cal infra­struc­tures on a contin­uous basis.

The engi­neers in Dres­den checked the suit­abil­i­ty of every sin­gle com­po­nent for off­shore use.

And if some­thing should go wrong short­ly before the end of the next test­ing sea­son, this solu­tion will enable them to test the sys­tems quick­ly, rec­ti­fy the prob­lem and har­ness the pow­er of the win­ter winds to the fullest pos­si­ble extent.


YOUR CONTACT


If you are look­ing to increase the reli­a­bil­i­ty of your off­shore cable infra­struc­ture,
Kat­ja Vogt will be hap­py to answer your ques­tions.
 k.vogt@highvolt.com


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