UK: Cathelco to Supply Corrosion Protection for Two Transformer Platforms

Cathelco have won contracts to supply impressed current corrosion protection (ICCP) systems for two transformer platforms, HelWin Alpha and SylWin Alpha, which are being built for Siemens Energy in Germany for offshore wind farm applications.

When completed the HelWin Alpha will be positioned near Helgoland as part of the HelWin1 offshore wind farm project where it will convert and transfer power from the North Sea East and Meerwind offshore wind farms.

The support structure for the HelWin Alpha is based on a self elevating platform which will be floated into position next to a cable tower to receive power lines from the surrounding wind turbines.

On commissioning the platform and the cable tower will be physically and electrically connected and will be protected as a single unit by the Cathelco ICCP system. The design of the system involves protecting the extended tidal areas, the uncoated submerged areas and the buried areas or foundations of the structure.

 “The design parameters for uncoated structures are very different to that of coated structures. Therefore it is very important to optimise the ICCP system performance to provide effective and reliable corrosion protection”, said Aneel Mumtaz, a corrosion engineer with Cathelco.

The ICCP system will consist of a 900amp control panel connected to eight anodes mounted on the legs and cross bracings, whilst the output will be monitored by 3 reference electrodes.

Cathelco have developed special anodes for wind turbine applications. The elements are mounted in an epoxy casting with an ABS plastic backing sheet which also acts as an integral di-electric shield. Provision of a di-electric shield ensures the current attenuation to the maximum as well as minimising the high negative potentials adjacent to anodes.

The zinc reference electrodes which measure the electrical potential at the metal/seawater interface are also robustly constructed for long and reliable performance. Installation of the anodes and reference electrodes is simplified by the use of self-torqueing snap-nuts, eliminating the need for the use of torque wrenches.

Cathelco have also won an order from Siemens Energy to supply an ICCP system for the SylWin Alpha offshore transformer platform. The platform is the largest of its type to be constructed by German based Nordic Yards and measures 80m high, 56m wide and 82m long. When completed it will be positioned 70km west of Sylt Island where it will transfer power to the German mainland.

Because of the complexity of the structure, Cathelco have designed an ICCP system with four zones. Each of the areas has a separate transformer/control panel connected to six anodes and three reference electrodes per zone. The anodes are located to optimise the distribution of the ICCP current with anodes covering the top to bottom levels of the structure. The arrangement ensures effective corrosion protection over the entire structure by avoiding the ‘shadowing’ effect of structural members which can interfere with the flow of current.

An important aspect of Cathelco offshore wind power systems is that they can be monitored and controlled remotely. Using an Ethernet connection, all of the parameters of the ICCP system can be supervised and regulated from a land based control room.

The design of the Cathelco ICCP system conforms to international standards such as DNV, Germanischer Lloyd and NACE specifications for offshore installations.

Cathelco are world leading manufacturers of ICCP systems for ships and offshore structures. With this background of experience, they have now developed corrosion protection systems which are specifically designed to protect offshore wind farms.

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Press release, November 12, 2012; Image: cathelco