The fate of subsea HVDC

Submarine electricity transmission systems are increasingly being used for long and short hauls in undersea, lake, and river interconnection applications, such as in the Hudson River in New York or for connecting offshore wind farms across Europe — allowing transmission in areas where water has made underground or overhead solutions impossible. As with overhead and underground systems, many high-voltage subsea systems are moving toward high-voltage direct current (HVDC) technology and away from the historically prevalent alternating current (AC) technology.

Credit: Terry Goss/Wikimedia Commons

The market for HVDC and high-voltage alternating current submarine electricity transmission systems is large and highly specialized. A look at existing and planned systems indicates that the submarine transmission industry will continue to experience substantial growth for years to come. With at least 140 new high-voltage direct current and high-voltage alternating current systems currently being deployed or in the planning stages, Navigant Research expects this highly specialized market is expected to experience rapid growth in the near future.

In Europe, the transmission system requires extensive reconfiguration and expansion to deal with coal and nuclear generation plant retirements and the rapid growth of offshore and onshore wind generation in the Nordic region, as well as in other remote offshore areas. The European market will likely account for more than half of the global submarine cable projects over the next decade, according to Navigant Research.

Europe’s transmission system, according to Navigant, currently requires extensive reconfiguration and expansion to deal with coal and nuclear generation plant retirements and the rapid growth of offshore and onshore wind generation in the Nordic region, as well as in other remote offshore areas. Because of this, the European market — which currently represents more than 70 percent of regional market share — will likely account for more than half of the global submarine cable projects during the next decade.

“Over the past several years, two market drivers have emerged as dominant forces shaping this market: connecting offshore wind generation to the mainland and reconfiguring or expanding interconnections between states, countries, and regions,” said James McCray, senior research analyst with Navigant Research. “Submarine technologies are helping to address changing electric generation mixes and isolated national grids are also being interconnected for security, balance, and the sale of excess electricity in cross-border exchanges.”

But a surprising risk to the transmission technology exists. Last August, a YouTube video surfaced of a shark biting a subsea cable, causing a frenzy. The video appeared to have been part of a marine survey and was made infamous in the summer of 2014 on the Discovery Channel’s Shark Week. According to some, the video signified that worldwide telecommunications could come under widespread attack by sharks because submarine fiber-optic cables are the backbone of the global Internet. As strange as it sounds, the same could be true for subsea transmission systems. In fact, there is still a question whether the cable — which sustained no obvious external damage and is unlikely to have suffered internal damage — was even fiber-optic telecommunications. It could very well have been an electrical power system.

Since then, the International Cable Protection Committee (ICPC) took the initiative to review records of cable faults worldwide and, along with an assessment of the video, concluded that much of the concern was unfounded. Essentially, sharks and other fish were responsible for less than 1 percent of all cable faults up to 2006 — and, since then, no such cable faults have even been recorded.

Overall, ICPC studies have seen a marked decline in faults caused by fish bites, including sharks. From 1901 to 1957 — a period dominated by subsea telegraphic cables — at least 28 cables were damaged. From 1959 to 2006 — a span that encompasses coaxial cables, which were replaced by fiber-optic systems in 1988 — around 11 cables needed repair, and fish bites accounted for 0.5 percent of all cable faults. The most recent analysis — from 2007 to 2014 — recorded no cable faults attributable to sharks.

The reduction in faults is consistent with improved design, protective sheathings and other measures to protect subsea technology. Faults to be more concerned about relate to natural phenomena like subsea landslides and ocean currents (less than 10 percent) and component failure (5 percent).

http://www.smartgridnews.com/story/swimming-sharks-fate-subsea-hvdc/2015-07-07

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