OFFSHORE CABLE TESTING

They are growing in number and getting bigger and bigger: Offshore wind parks make a signif­i­cant contri­bu­tion to increasing the propor­tion of envi­ron­men­tally friendly elec­tricity in the energy mix. At the same time, the gener­a­tive perfor­mance of wind turbines is constantly increasing. For new wind parks, for example, the oper­ating voltage of the connec­tion cables from the wind turbines to the collec­tion and connecting plat­forms is now being increased to 66 kV.

The experts at the Inter­na­tional Elec­trotech­nical Commis­sion (IEC) there­fore decided to permit — in addi­tion to the SOAK test (a 24-hour test at nominal voltage) — only reso­nance testing for oper­ating volt­ages greater than 36 kilo­volts in the new stan­dard IEC 63026 for subma­rine cables up to 72.5 kV.

HIGHVOLT is the only provider of a testing system that is weather-proof and there­fore always avail­able offshore despite adverse condi­tions.

MOBILE CABLE TESTING

HIGHVOLT is a pioneer when it comes to testing cables based on polymer insu­lating mate­rials, such as cross-linked poly­eth­ylene (XLPE) in high-voltage appli­ca­tions. The engi­neers from Dresden built the first-ever mobile testing system, which fits on a semi truck trailer. It can there­fore be trans­ported to almost any loca­tion without special permits, even where there is no space for large testing systems.

This includes cities and densely popu­lated regions where more and more cables are being routed under­ground. The testing trailer is designed for cable lengths of up to 10 kilo­me­ters; for longer cables, multiple testing systems can also be connected in parallel and in series.

HEALTH CHECK 120 M ABOVE THE GROUND

Mechan­ical vibra­tions of the rotors, light­ning strikes, frequent load changes and a high number of switching oper­a­tions — the trans­formers in the nacelles of wind turbines are exposed to enor­mous loads. If they fail, it is a time-inten­sive and costly feat to repair or even replace them.

What can be done? Ideally, check the trans­formers regu­larly in order to iden­tify impending damage at an early stage. The stan­dard method for doing this is the induced voltage test with partial discharge diag­nos­tics. But how does that work at more than a hundred meters above the ground, with little space in the nacelle? HIGHVOLT has devel­oped a portable testing system that oper­a­tors or service providers can use to inspect the condi­tion of the trans­former insu­la­tion directly in the nacelle itself.

XXL REACTORS FOR THE BACKBONE OF THE ENERGY TRANSITION

Renew­able energy sources are often far away from popu­lated areas. Ever larger distances need to be trav­eled to trans­port the elec­tricity to where it is needed. Projects with subma­rine and land cables of several hundred kilo­me­ters are there­fore increasing around the globe. Promi­nent projects include the A-Link, Südlink and SüdostLink in Germany, which form the back­bone of the energy tran­si­tion.

The cable sections must be tested in advance so that nothing goes wrong when oper­ating these cable systems. The number one failure source are the joints that connect the cable sections to each other. Since conven­tional testing systems soon fall short in testing power, HIGHVOLT devel­oped special XXL reac­tors. They provide four times as much power at only twice the volume of previous reac­tors for the reso­nance testing method. The power can be further increased through series and parallel connec­tion, meaning that cable lengths of up to 200 kilo­me­ters can be tested.

OPERATION AT THE HEART OF THE ENERGY SUPPLY

Power trans­formers are reaching a crit­ical age around the world, and at the same time, power grid loads are increasing due to bidi­rec­tional load flows caused by the supply of renew­able ener­gies. Oper­a­tors can check whether the equip­ment needs servicing with tests such as the induced voltage test and loss measure­ments in a no-load state and under load.

Often, this neces­si­tates disman­tling the power trans­former, draining the oil and then trans­porting it to a repair site — at signif­i­cant logis­tical effort and expense. However, there’s an easier way.

HIGHVOLT has devel­oped a testing system for this purpose that can be trans­ported on a semi truck trailer, enabling this kind of high-voltage testing right in the primary substa­tion. This way, the oper­ator can decide based on the measure­ments whether removal is even neces­sary, or if cheaper on-site repairs will suffice.

BIG BROTHER IN THE CABLE DUCT

When malfunc­tions occur during oper­a­tion, the HiRES Locator can help. This online measuring device is connected to medium- and high-voltage cables during oper­a­tion and locates a break­down in real time, imme­di­ately raising an alarm.

As a result, oper­a­tors know where they have to fix the problem. Conven­tional testing methods, in contrast, the fault is only located once the malfunc­tion has occurred. Then, after the event, a suit­able, powerful voltage source must be brought to the cable and measure­ments made in a costly and time-inten­sive proce­dure. The HiRES Locator is there­fore a cost-effec­tive solu­tion for moni­toring cable sections in real time.