Cable damages in the wind farm lead to high costs. If they remain undetected, short circuits may occur, leading to turbine standstills. Usually, it takes several days until the wind farm is back in operation. “This depends on the type of the damage and on the availability of the service personnel. For a normal damage, operators can expect some five days of yield loss,” Oliver Klausch, head of technical management at wpd windmanager GmbH & Co. KG explains. For an average wind turbine generator, down time yield losses amount to some 5,000 Euros a day. “At an average, we have five turbines to a wind farm, this means, we are speaking of 125,000 Euros of yield loss,” so Klausch’s calculation. If the wind farm is beyond the warranty period, costs for localization of the damage and repairs must be added. Money, that the wind farm operator could save by cable testing, says the head of technical management: “According to experience, the reasons for a cable damage are always due to improper cable construction prior to commissioning of the wind farm – around 80 per cent based on faulty mounting of the fittings and the remaining 20 per cent based on incorrect installation in the ground”. Since most operators check the cables at commissioning only by VLF and cable sheath measurements, the majority of damages remain undetected.
Detecting partial discharges
Wind farm operators may protect themselves – for instance – by partial discharge measuring. This will uncover weak points, such as incorrectly installed fittings. The exchange will then be done during low-wind periods – even before down-times occur. Evaluations from the wind manager data bank show, that – on an average – every other wind farm will be affected by cable damage during its operating time. Especially prior to expiration of the warranty period, operators are advised to check their wind farm for cable damages, enabling them to claim compensation from the cable builder for possible faults. “Time and cost involved for such a test are absolutely manageable,” says Klausch, “especially in relation to a possible yield loss.”
With their cable test van, wpd windmanager is assisting wind farm operators in localizing and diagnosing of cable faults. At the HUSUM Wind fair, September 12 to 15, operators will be able to gain information on the different measuring methods at Booth A02 in Hall 4. On top of that, the Bremen-based company will take care of all other topics concerning the commercial and technical management of wind farms during the fair.