Subsea power cables are among the most risky components in offshore wind farms. Damage to the difficult-to-access cable systems is a burden on both the budget and operating costs of wind farm operators and their insurers. Insurance data shows, for example, that in recent years 70 to 80 percent of all payouts for offshore wind projects were spent on damage to cable systems.
The permanent condition monitoring of subsea energy cables – also known as structural health monitoring (SHM) – offers opportunities to transform the necessary maintenance and servicing of offshore wind turbines from damage-based to condition-based maintenance. Defects are detected immediately. Safety-relevant measures are initiated more quickly. Downtimes are reduced because the damaged areas are known. Lengthy troubleshooting can be dispensed with. Repairs are carried out more quickly. Operating costs are reduced and the service life of systems is extended in the long term by limiting damage and optimizing maintenance intervals.
In order to permanently monitor underwater power cables, Fraunhofer IKTS is further developing its ultrasonic method, which emits low-frequency ultrasonic waves, so-called guided waves, to detect defects in dynamic power cables at an early stage.
With power cable monitoring, sensors are arranged in a ring around the cable sheathing. The sensor ring is permanently installed and remains on the cable duct so that the condition of power cables that are difficult to access can be continuously monitored via remote maintenance.
The sensor ring contains all the necessary electronic components for carrying out the measurements. The electronics and sensors are protected by various barrier layers that permanently prevent the ingress of seawater. Data evaluation is carried out by means of image-based Fresnel zone migration. The data is stored in a cloud. A digital twin is created in conjunction with AI algorithms and physical models. This allows the effects of operation on the components and the system to be evaluated and displayed via a handheld device or an augmented reality environment.
Fraunhofer Institute for Ceramic Technologies and Systems IKTS