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Connecting international grids for increased distribution flexibility

Flexible interconnections can help deliver less expensive grid connection faster. Grid upgrades can be deferred or avoided and enhanced flexibility can introduce new value streams in capacity trading and local.

Through enhanced interconnection, national power supplies can become more flexible with regard to distribution. Interconnection also enhances grid stability, helps make electrification a reality, and reduces outages, shortages and price fluctuations. Broadly speaking, flexible international grid connections bring three key advantages.

 

  • Greater stability of supply

In the event of disasters, outages and blackouts, emergency interchange can ensure power systems remain up and running. Deployment of smart meters and smart grids will also make sure peak demand times do not too adversely affect grid stability. An enhanced grid will allow electricity to be transported to central demand and storage facilities.

  • Support for deployment and utilization of renewables

Grid interconnection is key to harnessing the potential of renewable sources. European grid operators have been trading electricity generated by a variety of renewable energy sources, which tend to have fluctuating yield levels, for some time. Renewable energy potential tends to be concentrated in locations nowhere near power grids or where grid transfer capacity is minimal. The areas where power is needed are not necessarily close to where it is produced at a certain time. A country where solar yields drop off in winter might want to but energy from a country where wind yields are highest in winter – and vice versa. By setting up submarine and land interconnections transmission system operators can accommodate this.

"Annual marginal cost differences between neighbouring countries (ENTSO-E Powerfacts, 2019)"
"Annual marginal cost differences between neighbouring countries (ENTSO-E Powerfacts, 2019)"
  • Lower electricity costs

Electricity from sources with low generation costs such as hydro, wind, and solar can be made more freely accessible across regions and markets. According to an EC study, more renewables in the power system would make fossil fuels less significant in setting wholesale market prices: “Enhanced interconnection between Member States will lead to greater price convergence and lower prices. Improved efforts to achieve greater energy efficiency will lower demand requirements for the grid and also contribute to lower prices. A well-functioning and well-integrated EU energy market, continued investment in renewable technology and improvements in energy efficiency are key to keep prices in check for all consumers.”

 

"European Curtailed Renewable Energy Range (ENTSO-E Powerfacts, 2019)"
"European Curtailed Renewable Energy Range (ENTSO-E Powerfacts, 2019)"

“Enhanced grid flexibility decreases curtailment of renewable energy sources because you can meet the demand from the large energy centres, which are typically located far from consumption centres’” explains Davide Pietribiasi, Head of DC Electrical Engineering for Submarine Cables, Prysmian. “Increased grid flexibility will definitely help increase the amount of renewable energy that can be shipped to these consumption centres. This will also help level the price of energy among countries that participate in an interconnection. What’s more security of supply is supported. In the event of production issues in one country, the others can support.”

Davide Pietribiasi

Head of DC Electrical Engineering for Submarine Cables, Prysmian

The international, cross-border character of these interconnected grids has far-reaching legal ramifications, involving national governments and ministries, national and private utilities, financiers, and other stakeholders. As the UN points out, legal agreements are required on a country-to-country basis.

 

“There are two main challenges that need to be considered. The first is obtaining permits for corridors to be used. Sharing infrastructure can help alleviate this. We’ve worked on projects where transmission lines for interconnecting countries have been built in existing infrastructure such as road or railway tunnels. Secondly, we’re seeing a need in the market to connect renewable sources and countries. It no longer makes sense to build point-to-point connections for this purpose. Instead, multi-purpose infrastructure is increasingly being used. For instance, if you have a wind farm located between the UK and Germany in the North Sea, it would previously be connected to one country. But in the future, it is more likely that the wind farm will be connected to both countries. In this way, the wind power can be provided to both countries, but when there’s no wind, the link can be used to exchange energy between the two countries. Instead of using an export cable and an interconnector, you use a single cable continuously, making the best use of your power transmission capacity.”

Traditional methods of operating a network across generation, transmission and distribution portions are being replaced by more integrated approaches. This deregulation requires is not only driving the need for more interconnections, but also for better monitoring and management of the network. Corrective control methods and fail-to-safe mechanisms are also essential. 

Historically, interconnections revolved around capacity agreements between power providers and utilities. The grid was expected to absorb the total output under any circumstances. However, spikes in decentralized renewable yields may exceed hosting capacity, potentially leading to poor power quality, thermal overloads, or voltage fluctuations. “You need to ensure that if an offshore plant is offline, for instance, the effect on the grid is mitigated. In recent years, we’ve seen a chain effect cause a grid to fail when a wind plant suddenly went down. The more interconnections you have with other countries, the more resilient your network is” Davide Pietribiasi says.

Increasing interconnection between systems introduces a large number of new interfaces and vast amounts of data that needs to be processed in smart electrical grids. In order to realise cost-effective integration between systems, technical standards, data models and communication protocols should be standardised and interoperable. “Building international interconnections requires a lot of cable manufacturing capacity and large cable sizes,” Davide adds. “Prysmian can support this as we can provide cables of all sizes have the largest manufacturing capacity in the market. Our R&D is working to improve cable power and transmission capacity. Large cable sizes help decrease transmission loss, which means reduced loss of revenue and renewable power. By increasing the cable operating temperature range for example, you can use the same interconnection asset to deliver more power, or you can handle emergencies better, for example when you need a short overload. We are also focused on monitoring – if you are able to predict the health of your interconnection, you can anticipate issues and plan downtime and maintenance in advance. Whatever the operator’s strategy, we can come up with an optimised solution.”