SCFF Corrosion

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Mitigating Corrosion on a 345kV SCFF Submarine Cable Circuit
Project for New York Power Authority

One of ECE's cable engineers worked with a team of Russian scientists to study corrosion on the New York Power Authority's 345kV Self-Contained Fluid-Filled (SCFF) submarine cables running from New Rochelle, NY to Hempstead Harbor, Long Island. During this project, sensors were placed along the 4 submarine cables (3 phases plus a spare) to measure stray electrical currents that exist in Long Island Sound.

Each sensor consisted of an "array" to measure the stray current voltage potential along east-west and north-south axes using two pairs of silver-silver-chloride electrodes.

Sensor locations were monitored using differential global positioning satellite (GPS) equipment so that measurements could be repeated using the same locations at a later date. The locations were also important for calculations. Rusty Bascom was responsible for the project and is shown here recording sensor positions.

In addition to evaluating stray current measurements, cable samples were tested at laboratories located in St. Peterburg, Russia to evaluate the phenomenon that could result in deterioration of the cable's outer layers, including the armor and copper return conductor.

Results of the analysis showed that stray DC currents in Long Island Sound would cause corrosion of the cable armor and deterioration of the semiconductive polyethylene jacket between the armor and return conductor, leading to electrolytic corrosion on the return conductor. A cathodic protection system was designed, manufactured and supplied to protect the cables from damage. NYPA installed this equipment in April and May 1999.
The active impressed cathodic current protection (ICCP) system included current density sensors to monitor stray electrical currents in Long Island Sound. The figure at left shows one of the current density sensors being installed. The cathodic protection system included an array of anode beds - 24 in total - on either end of the 13.2km cable circuit. Each anode bed included magnetite anodes and some special design features to allow them to operate for the full design life - 40 years - of the 345kV SCFF cables.