Submarine cable checks for the North Sea

The North Sea is set to become Europe’s green power plant. But before we get that far, we first need to install hundreds of kilometers of submarine cables. This demands efficient cable monitoring systems. Thanks to a new module for the measurement and monitoring system HiMON^® we can now monitor neutral conductors, which was previously not possible.

Submarine cable checks for the North Sea

The North Sea is set to become Europe’s green power plant. But before we get that far, we first need to install hundreds of kilometers of submarine cables. This demands efficient cable monitoring systems. Thanks to a new module for the measurement and monitoring system HiMON^® we can now monitor neutral conductors, which was previously not possible.

On average it takes more than 80 days to repair a submarine cable that has been damaged due to disruptive discharge. This is a very long time – and time for which the entire infrastructure is out of action. However, the situation can be improved by installing the intelligent monitoring system HiMON^®. And this is set to become even more efficient in the near future thanks to a new module, which features active monitoring that feeds signals into the cable and then checks where a fault is located – something that can even be done in neutral conductors. This will provide operating companies with even greater control over their system and help them to save huge amounts of time during troubleshooting.

Major expansion plans on the high seas

Things are set to get busy in the North Sea over the next few years, with plans to expand offshore wind power production capacities to around 300 gigawatts in order to supply electricity to surrounding countries. At present, only around 30 gigawatts is supplied from the North Sea. To ensure that this expansion is a success, the plans include the construction of a large international electricity system in the North Sea featuring artificial energy islands and platforms acting as collection and distribution hubs for the clean electricity. Read more in ONLOAD the Reinhausen magazine

This is how an artificial energy island could look like.

This mammoth project will require the installation of hundreds of kilometers of new submarine power cables. To ensure that these new cables operate reliably, an extensive monitoring and maintenance system will be required in turn. Around half of all outages in offshore wind power plants are attributed to cable damage. But as Dan Keller, Head of Monitoring Solutions at HIGHVOLT, explains, repairing these cables is not an easy task: “The entire process from registering the disruptive discharge to completing the repairs takes around 80 to 90 days. Of this time, it takes around two weeks just to localize the fault site.” In a normal case.

300 gigawatts

(and more) of wind power is to be additionally installed in the North Sea over the next decade.

Passive monitoring for fast localization

But things are different with the HiMON^® monitoring system. With sensor technology from the HiMAG^® range and intelligent components from the HiRES^® family, this setup maintains a full overview of the entire cable system. The passive monitoring registers when a signal reaches the sensors and immediately triggers an alarm to warn that a disruptive discharge is occurring – and then localizes the affected site of the malfunction within a matter of seconds to save the operating company up to two weeks of time. At this point the preparations for repairs begin, which can take nearly another month themselves.

Active Monitoring now also for Neutral Conductors

Submarine cables use energy transmission systems with and without an additional neutral conductor. In the event of a fault, energy transmission systems with a neutral conductor can still deliver half the energy, which is why they should generally be preferred over systems without a neutral conductor. There are two variants of neutral conductors: firstly as a DMR cable, which extends together with the positive and negative pole along the entire length of the cable; and secondly as an electrode line, where a submarine cable with a length of around 10 to 30 kilometers terminates in a uninsulated electrode implemented under the sea, from where the energy can be still be transmitted with a pole cable in the event of a fault. Since no voltage is applied to these neutral conductors, passive monitoring systems are unable to detect the site of a malfunction due to the lack of arriving signals. This is a dilemma for operating companies – but it can also be solved with the new HiMON^® module. “Because we use it to actively feed in signals, it is also capable of investigating neutral conductors for faults.”

„With active monitoring of the neutral conductor it is possible to locate faults even though the system is not under a live voltage. This increases reliability for the operating company.“

Dan Keller, Head of Monitoring Solutions

Complex cable connections

The vast energy expansion plans for the North Sea also mean that the complexity of the corresponding cable network is also set to grow dramatically. When wind farms and energy islands are interconnected, transmission path redundancies are created so that electricity can continue to flow after an outage. For normal monitoring systems, this makes it very difficult to locate the fault site. “Our system is also multi-terminal-capable. As long as the cable topology is known and the data from all the sensors is brought together in our cloud, we can still deal with complex systems – in fact, this is precisely what our algorithms have been developed for”, explains Keller.

53 percent

of malfunctions and outages in offshore systems are attributed to cable damage.

80 days

(or longer) is how long it takes to locate and repair faults in submarine cables.

500 kilometers

(and more) of cable can be monitored with the HiMON® system.

And, as Dan Keller explains, the new module is also designed to offer a third capability. At the start and end points of the neutral conductor there are buildings measuring around 20 by 20 meters, the so-called “neutral areas” from which the neutral conductors start. If faults occur here that go unnoticed, this can paralyze the entire power electronics. “What this means is that, with the new module, we want to provide continuous monitoring not only of the neutral conductor, but also of the ‘neutral areas’ – which is something nobody else can offer apart from us yet.” HIGHVOLT is currently working in close collaboration with Siemens to establish what exactly will be required for this.

Intelligent Algorithms, Secure Cloud Storage

Three functions – one component. HIGHVOLT manages this via the corresponding algorithms and by linking the data in the cloud. The solution is based on Microsoft Azure and satisfies all the necessary standards for data security and data backup. “We can also use it as a way to connect one of our experts to help with the data analysis. But, in fact, we have designed it primarily so that our customers’ own in-house engineers can operate and maintain our systems by themselves, i.e. without help from us.” A streamlined system with major benefits and great time savings – leaving no obstacles in the way of developing the North Sea into a green power plant.

Passive and active monitoring

Sensor technology from the HiMAG^® family, which can also be installed retrospectively on all joints
Intelligent components from the HiRES^® family bring together data, act as event recorders and perform data analysis
HIMON^® intelligence clusters as a cloud solution enable operating companies to get fast expert assistance from HIGHVOLT

erfahren Sie mehr über HiMON

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Submarine cable checks for the North Sea