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Smart enhancement of the reliability of the “NordBalt” power link between Lithuania and Sweden

Smart enhancement of the reliability of the “NordBalt” power link between Lithuania and SwedenKey information about the project:

  • Challenge. “NordBalt” power link between Lithuania and Sweden is an alternative electricity import and export interconnection that has enabled the participants of the Baltic market to purchase electricity from the northern European countries, which are rich in water resources. Reliable and uninterrupted operation of the interconnection is extremely important to market participants, thus it is crucial to eliminate any possible disruption as quickly as possible. At the moment, the preliminary location of the “NordBalt” cable malfunction is calculated mathematically, using the existing data from the converter management system. Sadly, such calculation is imprecise. Traditional methods used to determine the location of a malfunction in the event of a disruption in the operation of the interconnection are extremely expensive and comparatively slow.
  • Aim. We are seeking to ensure greater reliability of the operation of the “NordBalt” marine interconnection by reducing the time needed to resolve a possible malfunction with the help of introduction and testing of effective equipment for automatic detection of the location of a malfunction in the marine cable.
  • Solution. Real-time detection of the location of a malfunction is carried out with the help of the transient recorder “HiRES Locator”. The manufacturer states that the location of a cable malfunction is determined when the equipment is mounted on one end of the interconnection only. However, at this time, detection is effective when the length of the cable amounts to no more than 200 km. Over the course of the experimental project, the effectiveness of the equipment will be tested in the “NordBalt” interconnection cable, which is twice as long (400 km).
  • Period of implementation. 2019-2020.

Mindaugas Kripas, head of High-Voltage Direct Current Interconnection Department at “Litgrid”, provides more information about the innovation:

During the project’s implementation, the 450-km-long “NordBalt” interconnection between Lithuania and Sweden was the longest marine electricity transmission cable in the world. However, high-voltage direct current (HVDC) technologies are developing at a fast pace. At the moment, the longest HVDC cable stretches between Great Britain and Denmark – it is the “Viking Link” interconnection (740 km). In spite of this, the diagnostics of possible malfunctions in cables of such length still pose a serious challenge to the specialists of today.

According to Mindaugas Kripas, head of High-Voltage Direct Current Interconnection Department at “Litgrid”, without automatic malfunction detection equipment, the preliminary location of a cable malfunction is calculated mathematically, using the existing data from the converter management system. Sadly, such calculation is imprecise.

In such a case, exact detection and resolution of a marine malfunction can take as long as two weeks. The rent of a ship needed for this purpose would cost 200 thousand euros per day. Detection and resolution of an onshore cable malfunction would take up to one week, while one day of inaction of “NordBalt” can cost as many as 85 thousand euros.

“Equipment that would enable us to find out at once not only that there has been a malfunction, but also where exactly it has occurred, would be an effective investment, allowing for a shorter duration of the resolution of a possible malfunction, as well as smaller operational costs and possible losses,” says the representative of “Litgrid”.

Malfunction diagnosticsMalfunction diagnostics is a pressing issue

In order for such high-voltage direct current interconnections as “NordBalt” to be as reliable and accessible as possible, ENTSO-E, the association of European transmission operators, recommends installing equipment for automatic detection of the location of a cable malfunction.

This is particularly relevant to “Litgrid”, who is preparing to lay the second marine cable – the “Harmony Link” interconnection with Poland, which will stretch from Darbėnai to Žarnowiec and whose length will amount to 330 km.

According to M. Kripas, as the number of underground and submarine cable lines in the world grows, methods used for the detection of the location of a cable malfunction are developing as well. An innovative approach can help us to determine the strategy best fitted for cables as long as “NordBalt”.

Following the analysis of the solutions proposed by various manufacturers at the moment – submarine structure protection system and acoustic sensing system – it was decided that these systems are more useful when seeking to avoid malfunctions caused by third parties. Also, although one of the alternatives was designed to detect malfunctions of various nature in real time, it is comprised of two devices that would have to be installed at both ends of the interconnection.

„Highvolt“ recorder „HiRES Locator“

The recorder “HiRES Locator” manufactured by the German company “Highvolt” was determined to be the best choice. “It is a universal device that can be used for the diagnostics of both underground and marine cables, for the purposes of both recording and analysing malfunctions.

However, the manufacturer recommends using this device for cables that are no longer than 200 km, thus, in order to make sure that we can use it for the “NordBalt” cable, we have decided to perform an experiment. We will simulate a malfunction at the other end of the interconnection, in Sweden, and this will allow us to find out if the equipment can be used to recognise a malfunction and determine its location.  If the experiment is a success, we will consider buying the equipment and using it.”