Smart Cable Guard

The cable monitor Smart Cable Guard is monitoring the Dutch power grid in more and more locations to safeguard the continuity of our energy supply. The idea for this arose more than twenty years ago alongside a motorway, during an hours-long discussion between a scientist and a grid manager.

Luchtfoto van elektriciteitsnetwerk van stad

Text: Amanda Verdonk, image: Shutterstock en Alliander

The Dutch power grid is bursting at the seams. Capacity is in short supply because people are using an increasing number of devices — such as electric vehicles, heat pumps and induction hobs — which, in turn, consume a great deal of energy. All this energy must be supplied by the existing network. In addition, the increase of renewable energy sources such as sun and wind energy produce significant load fluctuations in the network. It’s called volatility, and it’s increasing. Denny Harmsen, a system operations consultant at grid manager Alliander, explains what is taking place: ‘If a lot of solar energy is generated on a sunny afternoon, a large energy flow goes to the substation. But if the sun is suddenly blocked out by dark clouds and we are charging our car and start cooking as well, the energy flow drops to zero or even lower. These changes in the load influence the temperature and the pressure in the cables. You then run the risk that the sleeves joining the cables together will weaken, resulting in partial discharges.’

Punctures and power failures

Partial discharges are the invisible enemy of grid managers. These discharges eat at the insulation material and can eventually cause a puncture, a power failure or even fire and explosions. Previously, a cable had to be disconnected to locate the discharges, but a new cable monitoring system — the Smart Cable Guard — does that automatically and continuously. These are control units that are the size of a thick book and are placed on both ends of a cable and can send signals to each other. They measure whether there is a weak spot and, if found, pass this information on to a power station, where a decision can be made to temporarily divert the electricity. The units also very precisely indicate the spots where action must be taken immediately and those which can wait. This makes maintenance more predictable.

Partial discharges are the invisible enemy of grid managers

Watchful eye on the network

Harmsen has been working at Alliander on the development and introduction of the system for more than twenty years, and he now sees that his endless “nagging” to convince people has finally paid off. The first prototypes were installed in the Alliander grid in 2007, and the improved version followed at the end of 2014. That version worked well and a more affordable version followed in 2017, which resulted in the grid manager introducing it on a larger scale. By now, some 2,300 systems consisting of 4,600 units have been installed. Harmsen expects this number to double. To date, Alliander has equipped 6,200 kilometres — of the total of 40,000 kilometres of medium-voltage cables it manages — with this system. ‘By doing so, we have been able to keep a watchful eye on the network. By now, we can no longer do without it.’ The Smart Cable Guard is marketed by technical consultancy firm DNV, which has already sold 3,500 systems to 45 customers worldwide. Besides grid managers, these include large industrial companies, railway companies and wind farms.

No digging

According to tradition, the idea for a cable guard started on the side of a motorway in 2000. Fred Steennis, Professor of Electrical Engineering at the Eindhoven University of Technology, and Maarten van Riet, an innovation expert at Alliander (then called Nuon), were driving together in a car when Steennis hit upon an idea: Wouldn’t it be handy if we could create a system that could detect weak spots online, so without having to dig up the cable? The discussion became so intense that they parked the car and talked for more than two hours. They saw potential in this idea and brought various parties together in a consortium. Besides the other energy companies operating at that time, KEMA — which was later acquired by DNV — was also immediately on board with the plan. The NWO Domain Applied and Engineering Sciences (formerly Technology Foundation STW) financed the research. After five years, there was a proof of principle: a first demonstration that the product should work in practice. This was enough reason for Alliander and DNV to continue to work on the product, along with five doctoral candidates (see box).

Stop using gas

Richard Denissen has been involved in the development of the cable guard since 2016, and he has been doing that since 2019 as manager of the Smart Cable Guard product group. His goal is to find even more customers for the smart control units. He expects that more and more Northern European countries will encounter problems with outdated infrastructure. ‘Because we want to stop using gas, our electricity infrastructure is increasingly subject to heavier demands. We can solve that problem by increasing the capacity of the infrastructure and installing new equipment, but that takes a long time and is very expensive. Alternatively, you can take advantage of the possibilities to keep the existing equipment in the ground longer, with the aid of scientific research and domain knowledge. That is what we are doing with the Smart Cable Guard.’

Back-of-the-napkin idea

Looking back on the first research years — which Denissen was not involved in — he wonders why fifteen years elapsed between the “back-of-the-napkin idea” and the first sale. ‘Why couldn’t it be achieved in eight years? You need field experience and a quick market introduction to properly test a product. It is better to find a launching partner at an early stage and construct the product in such a way that you can develop it further. As soon as you have a proof of concept in the field, you must set up a parallel commercial team that elaborates on the strategy and the business plan. Then you know what the potential is, and it becomes easier to convince others.’

Harmsen, involved from Day 1, doesn’t think it could have been done faster. ‘Innovation is quality times acceptance. First, the quality must be good and stable; then you can create a base of support and train people. People underestimate the time it takes to embed something new in the operation.’ According to Harmsen, the role of the doctoral candidates and their fundamental research formed an essential base. ‘Often you see that fundamental research does not translate well into practice. It’s precisely because the grid managers were involved that an interaction developed between science and practice, and the Smart Cable Guard became a success.’