The development of new marine infrastructures like renewable energy projects or other coastal equipments leads to the increasing necessity to evaluate the impact of these marine structures on the environment. Among the environment modifications to be studied, the electromagnetic impact of the power cables and the infrastructures themselves is an important, but hardly studied, subject.
The PASSEM system has been developped to evaluate the electromagnetic environment. It is a towed instrument capable of measuring marine electromagnetic fields (electric dipôles and a 3 axis magnetometer) with high precision and resolution. These measurements can be completed by installing seafloor instrumentation.
The PASSEM system can record the EM fields on a large surface in a short period of time.
Electromagnetic fields measurements are essential in the evaluation of the impact of marine power cables on the environment and ecosystems
The PASSEM system is derived from the MAPPEM system. The active electromagnetic source has been removed to allow high quality measurements of the electromagnetic environment.
It includes 4 electric field channels, and a 3 axis fluxgate magnetometer. All channels are recorded at 2kHz sampling rate. The system includes navigation and attitude sensors to determine its position in water (2 axis tiltmeter, pressure sensor, altimeter).
Position of the 4 Electric dipoles on the streamer.
The area is surveyed leaving the instrument in the water column or close to the installed infrastructures, while keeping a safe distance.
The PASSEM allows to visualize data in real time, for Quality Control and to adapt the survey lines if needed.
Realtime Desktop data visualisation and control
Data quality allows to record the electromagnetic signals present in the environment, and to identify their sources, such as swell, power line signals, and of course the eventual signals from the installed infrastructure or cable.
An electromagnetic environment study should include a zero-state evaluation of the EM fields, before the environment is modified, and later surveys to assess the modification of the EM fields.