HYDRO 2016 Paper 6A2
Oliver Anders, Manfred Stender
The rising number of wind parks, and thus the demand for new survey tasks, results in continuous development for companies working in the renewable energy sector. Building a wind park requires laying inter-array and export cables. Those cables are buried or covered to protect them, bringing environmental changes to a minimum. A common depth of burial ranges from 1.5 m to 3 m. The challenge of surveying those buried power cables is choosing the right method. The method involves choosing between a broad field of sensors, techniques, vehicles and software. All claiming to fulfil the task but often lacking in details.
The standard equipment used by the industry to survey alternating or direct current or out of service cables, consists of magnetometers, gradiometers, active pulsing, passive detection and acoustic systems.
Different systems are shown that are capable of detecting different types of cables. The challenging part of choosing the right method will be discussed, presenting surveys conducted by Fugro OSAE GmbH demonstrating variable survey conditions on different cable systems and the impact on results. Asymmetric EM fields, radiated by a multi-core cables system may need additional care during the processing and interpretation of data, as common survey systems assume a radial symmetric field as a signal source. The reasons and solutions will give the audience up-to-date information that comprehensive metadata information is needed beforehand to conduct and deliver reliable results. Furthermore, a new approach by determining the depth of burial is shown using seabed difference calculations that result in inverse depth of burial information. The new inversed depth of burial approach is faster and can reduce costs if planned in advance.