The Independent System Operator in Bosnia and Herzegovina (NOSBiH) oversees and manages the country’s power transmission system. Its competencies and responsibilities are defined by the overarching Law on Transmission, Regulator, and System Operator of Electricity in Bosnia and Herzegovina, as well as by the Law on Establishing the Independent System Operator for the Transmission System.
Bojan Rebić, Head of the Real-Time Power System Operation Department, highlights the challenges the system faces due to the increasing integration of renewable energy sources. He explains how these challenges affect the electricity market, from which countries balancing energy is imported, and what the future holds for the power system.
Q: How does NOSBiH technically and operationally manage major transmission lines and high-voltage substations?
A: The management of the power system in Bosnia and Herzegovina is carried out from the Main Dispatch center of NOSBiH through 24/7 operational activities. In addition to the Main Dispatch center, and in line with obligations defined by the ENTSO-E network codes, NOSBiH operates a Backup Dispatch center, fully equipped with the tools and systems necessary for managing the power system in the event of a loss of the Main Dispatch center.
Operation of the transmission network at 400 kV and 220 kV levels, as well as all interconnected 110 kV transmission lines, is conducted by issuing direct instructions to operational staff at transformer substations and switchyards.
The operation of 110 kV lines that connect generation facilities to the transmission network is conducted indirectly, via the Generation Control Centers (CUP) of power utilities in BiH and the relevant Operational Areas (OP) of Elektroprenos BiH. Meanwhile, the operation of 110 kV line bays owned by users (new generating facilities) is performed remotely via the SCADA/EMS system from the NOSBiH Dispatch center (DC).
Through coordinated operation between the dispatch centers of NOSBiH, Elektroprenos BiH, the power utilities in BiH, and neighboring system operators, reliable and stable functioning of the BiH power system is ensured. In coordination with the Regional Security Coordination Center (SCC) in Belgrade, regular and additional security analyses of the power system are performed on a day-ahead and intra-day basis. These analyses are carried out for every hour using the interconnected model of the Continental European power system. If the N-1 security criterion is not met, available preventive and corrective measures are applied.
Supervision and management of the BiH transmission system are conducted through the SCADA/EMS system installed at the NOSBiH Dispatch center. Every two seconds, the SCADA/EMS system collects and archives data from all substations in BiH as well as from the observability zones of neighboring system operators.
In addition to the SCADA/EMS system, various software applications are used for day-ahead scheduling, balancing services, work approvals, dispatch logs, and information exchange at the ENTSO-E level.
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Q: How challenging is it to balance the electricity market in Bosnia and Herzegovina, and how is it done?
A: Balancing the electricity market is becoming increasingly demanding and complex, making it an equally important task for the operational staff of the NOSBiH Dispatch center. A decade ago, balancing was almost negligible compared to transmission system operation.
With the integration of a large number of variable renewable energy sources, we are facing growing deviations and rapid changes in generation, which result in imbalances within the BiH control area. Often, within a short period of time, balancing services must be activated in opposite directions, leading to higher balancing costs. Deviations are also influenced by electricity prices on regional and European exchanges.
In cases of imbalances, NOSBiH procures and activates balancing energy daily to cover electricity deficits or surpluses. This is done by using automatic and manual frequency restoration reserves (aFRR and mFRR), procured from registered providers. NOSBiH has signed agreements for the procurement of balancing energy from neighboring systems, including the SHB block (Slovenia, Croatia, BiH), as well as cross-border tertiary reserve exchanges with Serbia and Montenegro.
The quality of regulation had been satisfactory in previous years; however, in 2024 and the first quarters of 2025, it has significantly deteriorated, indicating the need to identify new balancing resources. Given the expected increase in renewable integration and current difficulties in the BiH power system, NOSBiH has sought modalities to expand the balancing reserve within the system.
According to the European Commission Regulation (SOGL), transmission system operators are entitled to exchange imbalances across different areas. At present, NOSBiH only has access to the GCC (INOM) platform, used by EMS (Serbia) and CGES (Montenegro). Together with EMS and CGES, NOSBiH has analyzed the possibilities of joining this platform, which would bring both technical and financial benefits. The agreement has been finalized and is pending approval from the relevant institutions. This would serve as a temporary solution until Bosnia and Herzegovina potentially joins the pan-European platform for automatic imbalance netting (IGCC).
Q: What are the biggest challenges for the BiH transmission network in the coming years?
A: The greatest challenge for any transmission system operator in the upcoming period is ensuring secure and stable operation of the transmission grid during the ongoing and future energy transition.
One of the major issues in operating the BiH power system is overvoltage – a problem for which the NOSBiH Dispatch center currently has no mechanism of control. Unfortunately, BiH leads the region in overvoltage problems, partly due to the structure of consumption in the country, and partly because neighboring transmission systems have already implemented voltage regulation measures, such as installing compensation devices. Overvoltages can result in partial or total collapse of the BiH power system, as well as the regional grid. Elektroprenos BiH has included the installation of four compensation devices in its investment plans, which have been approved, and procurement and installation activities are expected to commence.
Another major challenge is posed by large fluctuations in cross-border transit flows, which create significant operational difficulties. The BiH power system is integrated into the Continental European transmission system, which generally contributes to its secure and stable operation. However, during certain periods, due to significant transit flows from east to west and vice versa – directly driven by electricity markets and the integration of large volumes of renewables in Southeast Europe – severe overloads occur on both cross-border transmission lines and internal lines and transformers. These issues were the cause of the last two major disturbances: on January 8, 2021, when the Continental European transmission system split into two parts, and on June 21, 2024, when a major disturbance affected the power systems of BiH, Montenegro, Albania, and parts of Croatia.
In both cases, the BiH power system was neither the cause of the disturbance nor in a position to prevent its occurrence and propagation. Fortunately, all disturbances were resolved in record time. The dispatchers of the NOSBiH Dispatch center and neighboring TSOs successfully restored system stability: on January 8, 2021, Europe was re-synchronized within around 40 minutes, and during the blackout on June 21, 2024, system restoration was completed within approximately two hours.
Interview by Jasna Dragojević
The interview was published in Energy portal Magazine CLIMATE CHANGE
