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Lifetime extension for sea cables

The steel armouring of a sea crossing power cable is vulnerable to corrosion attacks, especially at the landfall sections. A cathodic protection system will prolong the lifetime and save maintenance cost.

LIFESPAN EXTENSION

A certain way to extend the lifetime of sea crossing power transmission cables is to install a cathodic protection system.

At several locations in Norway, from mainland to islands, across fjords, etc., power transmission is very often arranged by sea crossing power cables. These types of cables are equipped with a steel armouring for mechanical strength. Especially in shallow water, as the landfall sections, the steel armouring is exposed to corrosion attacks due to higher oxygen concentration in the electrolyte, and higher risk of damages of the outer cover.

Cathodically protected and non protected sea crossing power transmission cables
Protected and non protected sea cable

Cathodic protection of sea crossing power cables is commonly arranged by installation of an impressed current system. The anodes are generally located 50-100 m away for the power cable and energised by a control unit located nearby the landfall area. A zinc reference cell may be installed to monitor the effect of the cathodic protection. This reference potential signal can also be used for controlling the output current from the control unit.

By correct operation and maintenance of such system, the risk of steel armour corrosion will be considerably reduced.

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