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The increasing importance of Slovenia’s transmission network – interview with ELES’ CEO Aleksander Mervar

While Slovenia’s net electricity production rose by 12 per cent month-on-month in May, the country continues investing in the development of its transmission network.

CEENERGYNEWS spoke with Aleksander Mervar, CEO of ELES, the operator of Slovenia’s electric power transmission network, about the company’s current projects and the importance of increasing connectivity with neighbouring countries.

Mr Mervar mentions several new constructions and reconstructions that are being carried out on the 400 kilovolts (kV), 220 kV and 110 kV transmission lines. The most important projects are the 2×400 kV Overhead line (OHL) Cirkovce-Pince, the 2×400 kV OHL Beričevo-Okroglo and the 110 kV OHL Grosuplje-Ribnica-Kočevje. While, when it comes to the distribution transformation stations, Cirkovce, Beričevo and Divača are considered to be the most important.

“The OHL 2×400 kV Cirkovce–Pince project and the construction of RTP 400/110 kV Cirkovce represent important investments in the transmission network, through which the first connection to the transmission system of the neighbouring country of Hungary will be established.”

Indeed, the most important projects in the field of smart grids are the SINCRO.GRID and the NEDO projects. The first one is an EU Project of Common Interest (PCI), whose purpose is to enable more efficient use of the existing electricity network in both Slovenia and Croatia; while the second one is an international project between the Japanese Agency NEDO and ELES.

“The SINCRO.GRID smart grid project offers an innovative system integration of mature technologies that will synergistically benefit the electricity systems of Slovenia and Croatia as well as the other countries in the region,” explains Mr Mervar. “This project also brings extensive cross-border effects also to maintain and increase the connectivity capabilities with the neighbouring transmission systems.”


In particular, the phase 1 aims to provide for more efficient use of the existing electricity grid in Slovenia and Croatia, which will enable the existing infrastructure to accept larger quantities of electricity from renewable sources and ensure more reliable electricity supply. For this reason, compensation devices for reactive power control, battery electricity storage systems, dynamic thermal rating system (DTR) and virtual cross-border control centre will be used.

“We have already achieved some important milestones,” Mr Mervar underlines. “In November 2019, a variable shunt reactor (VSR) of 100 Mvar (mega volt-amps) went into initial operation in the substation of Mraclin, in Croatia.”

Also, recently ELES made a trial connection of the variable shunt reactor of -150 Mvar to the electricity grid in substation Divača (in Slovenia), where it is now getting ready to begin work on the installation of a +100 Mvar capacitor.

“We have finished with preparatory works at the substations of Pekre and Okroglo (in Slovenia), where two battery electricity storage systems, each with a capacity of 5 megawatts (MW), will be installed,” he continues. “The installation of the battery storage systems is planned to begin in the 3rd quarter of the year and will be finished in the 4th quarter. For better forecasting of the weather conditions, we equipped 27 steel constructed transmission towers with innovative weather stations. Data from these stations will enable a system for real-time and short-term forecast assessment of power grid operating limits (DTR SUMO) to better assess the limited capacities of transmission grid components and therefore enable better utilisation of existing transmission lines and transformers. Activities for the establishment of the virtual cross-border control centre will enable voltage control and loss optimisation in transmission systems, better control and forecasting of electricity generation from RES as well as the implementation of additional ancillary services with the management of consumption and dispersed generation in Slovenia and Croatia.”

Mr Mervar also reminds how the participation of RES in the provision of ancillary services is proceeding according to plan and the implementation of the SINCRO.GRID project will maintain the reliability and security of the power supply in Slovenia and Croatia as well as in other countries in the region, despite the growing share of electricity being generated from RES.

On the other hand, the NEDO project is centrally managed by ELES and Hitachi, which has been authorised by NEDO to carry out the work.

“As part of the project, the Japanese partner contributes modern equipment while ELES develops advanced functionalities,” adds Mr Mervar. “ELES also participates in the international project OSMOSE, which is a four-year international research project involving 33 partners from nine European countries. As part of the OSMOSE project, system operators (RTE, REE, TERNA and ELES) will conduct four demonstrations to increase the technological and economic potential of many solutions and sources of flexibility.”

During the coronavirus pandemic, all key operating processes within ELES were running smoothly and the development policy and investment plans remained unchanged. Earlier in April, the company hosted a visit by the Minister of Infrastructure Jernej Vrtovec and State Secretary Blaž Košorok, who both evaluated ELES’ operations as stable and successful.

“However, we adopted a change in the dynamics (for later periods) and we also set priorities in terms of investment dynamics,” Mr Mervar says. “In regards to projects already under construction, there have been disruptions to the supply of imported equipment and the physical provision of services by companies not established in the Republic of Slovenia.”

At the same time, the pandemic has shown how societies need electricity now more than ever.

“The transmission system of the electricity network and the system of information and communication services and networks work flawlessly,” the CEO of ELES underlines. “We will certainly gain experience from the current crisis how necessary it is to be prepared and to take constant care of the health of the employees and the vitality of the transmission network infrastructure because the operation of key functions in the country, economy and social life depends on uninterrupted electricity supply.”

Nevertheless, the World Economic Forum included Slovenia among the countries which made the most progress on their energy transition. And speaking about the future, both ELES and GEN-I, one of the leading and fastest-growing energy trading and sales groups in Central and South-Eastern Europe, jointly established a consortium with the aim of decarbonising Slovenia by 2050. Soon, other three Distribution System Operators (DSO) also joined the consortium, namely Elektro Celje, Elektro Gorenjska and Elektro Ljubljana.

“Consortium members, together with the Milan Vidmar Electric Power Research Institute, the University of Ljubljana and the Faculty of Electrical Engineering, are designing a locational market and a methodology for advanced grid planning that takes into account flexibility sources as a substitute for the reinforcement of the grid.”

“The plan is to prepare methods and a proof of concept, including regulatory support for efficiency-related investments for Transmission System Operators (TSOSs) and DSOs, by the end of 2020,” ” reveals Mr Mervar. “The consortium joined forces with the British company Piclo as an independent external partner.”

According to ELES’ CEO, the Consortium members, together with 67 other companies, also applied for the co-financing of the project One Network for Europe (OneNet) from the Horizon 2020 EU fund and they are now waiting for the official decision.

“The Green Consortium Members would be the most active in the work package 9 that would be led by ELES,” he concludes. “The Demo Cluster East aims to develop and extend capabilities of existing flexibility market platforms for TSO and DSO grid services using varied flexibility providers, which will be standardised to an appropriate European format. The focus will be on a coordinated activation of flexibility services for congestion management and balancing (TSO, DSO), which will be achieved by establishing a combined and digitalised TSO-DSO flexibility process for balancing, congestion management and other ancillary services commonly procured and activated to deliver services for TSOs and DSOs. The cluster will address these services as standardised products provided in a market-based environment.”

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