More electricity crosses the sea every year. Subsea power cables carry supply to islands and offshore installations, and interconnectors link national grids so that power can move between countries. When one of these cables is damaged the result is lost supply and a repair that can run for weeks. Subsea power cable monitoring is the work of keeping vessels away from them, so supply is not interrupted.
UltramapGlobal has protected subsea cables since 2009, and power is one of the five sectors we watch every day. This is how monitoring works for power cables and the interconnectors that carry electricity between nations.
What is at risk around a subsea power cable
A subsea power cable does one job without interruption: it moves electricity. An interconnector does the same across a border, and increasingly it is part of how countries balance supply between grids. The threat to both is the ordinary vessel in the wrong place, dropping an anchor or dragging gear across the cable.
A seabed cable gives almost no warning that it has been struck. The first sign is often a fault and a loss of supply, and by then the cost of the outage and the repair are already mounting. UltramapGlobal has watched routes like these since 2009, and that record is what lets a developing risk stand out early. Watching the traffic is how the problem is caught while there is still time to act.
How subsea power cable and interconnector monitoring works
UltramapGlobal is always on. A power cable or an interconnector is given protection zones, and those zones are policed for compliance without a break. The watch runs on AIS, the Automatic Identification System, which is the position and movement information vessels broadcast about themselves. AssetMonitor®, our specialist cable monitoring software, takes that feed from several sources at once: shore-based receivers, satellites, and receivers aboard guard and patrol vessels. On a long interconnector route the multiple sources earn their place, because a single shore receiver does not reach the whole line.
Across every route it watches, AssetMonitor handles well over 100 million live AIS messages from around the world every single day.
Where it helps, we advise a layered defence, commonly a 1,000 metre early-warning perimeter with a 500 metre action-required perimeter inside it. The outer ring buys time. An analyst can look at a vessel’s course, speed and behaviour and judge whether it is a developing risk or simply passing through. The inner ring is where that judgement has to become a call. Trained analysts are behind the software 24 hours a day and 365 days a year, and on a route feeding a national grid the call gets made early, because the consequence of being late runs well past the cable itself.
The security and commercial case
An interconnector carries the energy security of the countries it links. A strike on one has consequences well beyond the repair bill. Continuous monitoring keeps the supply route protected, and it keeps the people working around the cable out of harm’s way.
There is a commercial dimension too. Many subsea power cables are insured, unlike most telecoms cables. The interruption is the harder part to put right. An interconnector out of service for weeks is a large asset earning nothing, and the electricity it was carrying has to come from somewhere else for as long as the fault lasts. A tailored approach to protecting a cable plays to what UltramapGlobal calls its assurance not insurance credentials, in that the work is aimed at preventing the strike rather than settling up after it.
What the archive since 2009 adds
The value of a monitoring service grows with what it has seen. Behind the live AIS picture sits an archive gathered continuously since 2009, covering cable strikes, shipping routes, fishing patterns and vessel behaviour. That history lets a team recognise a developing risk on a given stretch of seabed, rather than reacting only once a vessel is already too close. The watch itself runs from three teams in the UK, the Philippines and Oman, handing on as each eight-hour shift ends, so cover follows the clock rather than office hours. Caught early, a vessel heading for a cable becomes a phone call and a change of course, rather than an outage and a repair.
If you are responsible for a subsea power cable or an interconnector and want to know it is being watched, UltramapGlobal can be reached on +44 (0)191 233 6351 or at info@ultramapglobal.com. For the wider picture, see our guide to how subsea cables are protected.
Frequently asked questions
What is subsea power cable monitoring?
It is the continuous watching of the subsea cables that carry electricity, including interconnectors between countries, to keep vessels from damaging them. UltramapGlobal uses AIS vessel tracking and trained analysts to monitor the traffic around the cable 24 hours a day, 365 days a year, and acts when a vessel becomes a threat.
How is an interconnector protected from vessel damage?
By defining and policing protection zones around the cable, then monitoring vessel traffic constantly with AIS data. A layered defence, such as a 1,000 metre early-warning perimeter and a 500 metre action-required perimeter, gives the team time to warn a vessel off before contact.
Why does monitoring matter for energy security?
Interconnectors link national grids and help countries balance supply. A strike can interrupt that supply and take weeks to repair, so keeping vessels away from the cable protects both the asset and the wider network that depends on it.
What does a strike on a subsea power cable cost?
More than the repair. A damaged power cable can be out of service for weeks while a repair vessel and crew are mobilised, and replacement supply has to be bought in the meantime. Monitoring is aimed at the strike that starts all of it.
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