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Marine Electronics


November 2011 Issue

MacArtney Designs Cables to Bring Tidal Power Onshore
Earlier this summer, Scotrenewables (Orkney, Scotland) launched its prototype 33-meter-long, 100-tonne floating tidal turbine, the SR250, a platform designed to minimize installation and maintenance costs of tidal energy compared to seabed-mounted tidal turbines.

Unlike seabed-mounted turbines, the device is fixed to a mooring turret tethered to the seafloor, allowing the turbine to move with the direction of water movement. Scotrenewables chose MacArtney (Esbjerg, Denmark) to provide the infrastructure for this 250-kilowatt prototype.

The turbine has a turret and a vertical swivel. At the turret, a 6.6-kilovolt wet-mate connector acts as a stab plate. As the turbine turns about this axis to face the water flow, this swivel turret holds the dynamic unit on the anchoring, and the swivel ensures that the signal and power connections in the cable remain intact and prevents them from twisting during the 360° movement.

Scotrenewables and MacArtney worked together to custom design the 6.6-kilovolt umbilical that can carry the required 250 kilowatts. For this prototype, the 3,500-meter cable also has two signal screened twisted pairs that transfer data to and from the turbine to shore.

At the point of contact between cable and turbine, a steel stress termination on the high-voltage wet mateable connector pair takes the strain off the cable. The point where the cable exits the stress termination is also vulnerable, as vibrations in the cable can weaken it over time. A bend stiffener was designed to dampen the vibrations, to help protect the cable from fatigue and to extend its working life.

The system will be tested in the waters off Orkney for two years, providing experience for the planned full-scale one- to two-megawatt versions. For more information, visit www.macartney.com.

DCNS Measures Sea Swells to Help Predict Ship Movements
DCNS (Paris, France) has completed a sea swell field measurement campaign as part of a study contract on swell lull period prediction techniques, the company announced in September.

The Direction Générale de l'Armement (DGA) awarded the 15-month study, which was carried out with DCNS subsidiary Sirehna (Nantes, France). The study is part of a project to predict ship movements several minutes in advance, in order to define the optimum moment for carrying out a tricky operation. This knowledge will be particularly useful for deck landings by aircraft, helicopters or UAVs; launch and recovery of surface boats or USVs; and embarkation of amphibious vehicles, DCNS said.

The measurements were made off the Talut signal station at the French island Belle-Île. A sea wave radar and wave measurement buoys were used to record the sea state over many hours. A French Navy ship, the Tigre, equipped for the occasion by the DGA with an inertial unit, sailed near the buoys in order to correlate ship movements with swell measurements. For more information, visit http://en.dcnsgroup.com.

Kongsberg Solution Displays Seismic Streamers Over AIS
Kongsberg Seatex (Trondheim, Norway) has developed a solution to display the size and shape of seismic streamers over standard AIS. Kongsberg, which announced the new system in September, said making this information available to all vessels in the survey area has the potential to enhance safety and streamline operations.

Seismic operations in areas of high shipping activity can be a challenge, as a seismic survey vessel has restricted maneuverability due to the large size of a 3D or 4D streamer spread, which are typically six to 12 kilometers in length and up to about one kilometer in width. Traditionally, chase or guard boats are used to contact conflicting vessels to secure the operation.

By utilizing AIS and the Kongsberg solution, the vessel can broadcast its coordinates in the area where the vessel actually operates, together with the size and shape of the actual streamer spread. A key element of this concept is that only AIS standard compliant functions are utilized, meaning the vessel and spread will be visible on AIS-compatible ECDIS displays aboard surrounding vessels. For more information, visit http://www.km.kongsberg.com.

Milford Port Begins Trial of GeoVS 3D Surveillance System
Milford Haven Port Authority in October started a trial of C-Vu 3D VTS display software from GeoVS Ltd. (Cardiff, England). The system has been installed to establish whether its clarity of presentation and viewing versatility can enhance situational awareness and ease of interpretation for the port's vessel traffic controllers.

The technology is unique in that it transforms a traditional 2D radar display into a 3D panorama that shows vessels as they appear, meaning tankers look like tankers and tugs look like tugs. Relative sizes and locations are drawn accurately and shown in real time, GeoVS said.

The display may be said to look like a simulator when it is, in fact, a real-time presentation of radar, ECDIS and AIS data. GeoVS said it should drastically reduce the risk of radar targets being misidentified and give port controllers a clarity of vision.

Milford Haven, located in Wales, is one of the world's largest LNG terminals and is the first port in the world to try the technology. Milford Haven harbormaster Mark Andrews said he was optimistic that the C-Vu would bring benefits to the port. "The key is for us to know whether the users in our port control room will find it of value on a regular basis."

Automated surveillance is available with the C-Vu's virtual cameras that can, for example, give a port controller the same view that would be available from a distant aircraft or from the bridge of a ship.

Bathymetric data and C-Vu 3D models are created automatically from ENC S57 ECDIS charts and can be enhanced with features such as port buildings and landmarks. Hydrographic data can also be quickly updated from a port's own survey boats to create a display for the controller that is technically accurate while also being more visually accessible than when it is presented on an ECDIS.

The system was developed from studies made at Cardiff University that looked at the ways in which displays can be made more easily understood by their users.


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