Igor Ivankovic

• PhD
• Managing Director at Croatian Transmission System Operator

The consequences of climate change are felt everywhere, especially on power systems assets, whereby overhead lines as one of its most exposed elements. It is expected that impact of climate changes, especially effects of evident global warming will be even more expressed in the coming decades, with increased frequency and severity of extreme weathe...

To smoothly integrate Renewable Energy Sources (RES) into the transmission power system, the Croatian Transmission System Operator (HOPS) must address potential congestions in the power system promptly, in the day ahead and intraday planning phase as well as in the real-time operation. Therefore, implementing a real-time congestion management syste...

The consequences of climate change are felt everywhere, especially in power systems and overhead lines as one of its most exposed elements. It is expected that impact of climate changes will be even more expressed in the coming decades, with an increasing possibility of occurrence of extreme conditions in the form of storms, winds, snow, ice, high...

Increasing the production of renewable energy sources has become an important goal in the power energy sector in European Union. At the same time, volatile nature of wind, solar, and unplanned outages causes congestion and imbalances in power system operation. To compensate for these deviations from the normal state, transmission system operators h...

This paper analyzes the impact of the two dominant business processes of the last several years on transmission system operators' short-term and long-term sustainability. The two processes are the green transition and the disturbance in energy markets that began in 2021. We will examine the case of the Republic of Croatia, but we will provide more...

A study of transients in a high voltage substation 400/110 kV is presented in the paper. An analysis was carried out after a fault on the 110 kV busbar, which caused severe damage in the substation. Investigation was focused on a time frame of several sequential circuit breaker trippings. A first step of the study was collection of data from the pr...

Angle stability appears in many forms in transmission network. There are small active power oscillations which do not endanger the normal operations whereas medium and large oscillations have implications on normal operations. These latter kinds of oscillations in some cases develop in out of step condition, which is dangerous disturbance with seri...

Classic approach to preventive maintenance of equipment in power system substations was based on periodical maintenance according to regulations and best practices recommended by vendors. SCADA system in HOPS is used primary for real-time monitoring and control of the equipment in substations. Real time data available in SCADA databases contain use...

The increased integration of the new generation technologies into the electric power system (EPS) which are mainly inverter-based changes its characteristics. The main issue that arises is the appearance of faster frequency dynamics that are caused by production connected through inverters. This leads to the need for changing conventional under-fre...

An experiences related to implementation of line surge arresters on overhead transmission lines in Croatian power system, which are used due to transmission line lightning performance improvement, reduction of overhead lines outages and increasing reliability of the entire transmission system are presented. The first part of this paper describes th...

This paper presents an advanced model for monitoring losses on a 400 kV over-head transmission line (OHL) that can be used for measured data verification and loss assessment. Technical losses are unavoidable physical effects of energy transmission and can be reduced to acceptable levels, with a major share of technical losses on transmission lines...

Operating personnel in control room act on SCADA alarm generated on data from station computer. Using new technologies and advanced technical solutions assistance tool can be designed. This tool provides quick help in busy situations for operator. For this new tool with three types of case studies insight will be given in this paper. Introduction p...

An experiences related to implementation of line surge arresters on overhead transmission lines in Croatian power system, which are used due to transmission line lightning performance improvement, reduction of overhead lines outages and increasing reliability of the entire transmission system are presented. The first part of this paper describes th...

Highvoltage circuit breakers in transmission network play crucial role for reliability and secure operation of transmission network, thus they must have extraordinary and meticulous maintenance. Today technology allows continuous collection of huge amount of data for circuit breakers, which applications process into valuable and worthy information...

Priključivanjem novih tehnologija u elektroenergetski sustav (EES) koje su uglavnom temeljene na izmjenjivačima, značajno se mijenjanju karakteristike konvencionalnog EES-a. Dolazi do smanjenja sinkrone inercije što uzrokuje bržu dinamiku promjene frekvencije. Sinkrona inercija izravno utječe na najveću vrijednost parametra brzine promjene frekvenc...

By integrating the new production technologies into the electric power system (EPS) which are mainly inverter-based, the characteristics of the conventional bulk EPS are significantly changed leading to a reduction of synchronous inertia which causes faster frequency dynamics. Synchronous inertia directly affects the maximum value of the rate of ch...

The power system is an example of a nonlinear syste m with many different oscillation sources and accordingly many oscillation types, including e lectromechanical oscillations, oscillations caused by control e le ments, or sub-synchronous oscillations. The estimation of oscillation types in the power system gives a direct insight into the state of...

Wide are a monitoring system (WAMS) installed in Croatian Transmission system operator (HO PS) control ce nte r collects and proce ss synchrophasor data in re al time. There are ongoing activities on continuous, incremental and gradual upgrading of existing WAMS with new protection functions and control algorithms towards WAMPAC system. This pape r...

Three phase power system in some circumstances suffers from imbalances in the operation. This condition might lead to more serious contingencies, operational security risks and can leads to higher losses and insulation degradation. One phase breakage, high resistance fault or two phase operation in the power system (short circuit or earth fault) is...

Operating personnel in control room act on SCADA alarm generated on data from station computer. Using new technologies and advanced technical solutions assistance tool can be designed. This tool provides quick help in busy situations for operator. For this new tool with three types of case studies insight will be given in this paper. Introduction p...

Croatian TSO has finalized a Proof of Concept (PoC) for monitoring generators with purpose of primary frequency regulation mode within Wide Area Monitoring System (WAMS) using synchrophasors in control room. The main goal of PoC was testing well proven synchrophasor technology for purposes of advanced monitoring of generator units connected to tran...

Transmission system operator has many applications on its disposal for collecting data from network and substations. Majority of that data are collected with SCADA system but new applications in control room also provide significant and specific data for daily business processes. Interoperability and data exchange has to be increased in order to im...

Transmission system operator has many applications on its disposal for collecting data from network and substations. Majority of that data are collected with SCADA system but new applications in control room also provide significant and specific data for daily business processes. Interoperability and data exchange has to be increased in order to im...

This paper deals with the volatility of wind power production and load observed in Croatian power system during four full consecutive years (2012-2015), based on the measured one-hour data of total load, and total wind electricity production [1]. The research goal was to investigate and establish relations, if any, between temporal variability of l...

Energy Management System Calculations for transmission system control and analysis give many useful results that are usually only used in EMS real-time system and later archived. Tool presented in this paper uses these results and perform analysis in time domain and sliced according to various categories to find useful information that cannot be fo...

The objective of the Volt Var Control (VVC) function is maintaining system voltage within predefined limits and minimizing system active power losses by controlling reactive power flow. The main focus of this paper is to review and evaluate the technical requirements to implement a centralized VVC function within an existing SCADA/EMS system in a t...

Transmission system operators encounter new dimensions in their business operations in recent years. Huge sets of data are collected in control room and new functionalities are created for both real time and off line operations. Data from lighting detection system in control room will be used in a new way in next to real time manner. Transmission l...

The standard of living is in a direct connection to the availability and quality of the energy delivered, and therefore the electric power system presents the backbone for the development of a modern human society. While balancing between the economical and environmental issues, the transmission system operators are coping to maintain the power sys...

An electrical power transmission networks are one of the most complex modern artificial networks which provides the vital link from generation sources to the distribution networks and presents crucial factor for the security of electricity supply. Harmonic resonance is a phenomenon that occurs when a frequency of external oscillations corresponds w...

Establishing a complex function in real time operation such as the Volt Var control (VVC) function requires addressing some of the challenges related to quality of input data (measurements and estimated values). The paper deals with the topic of real time calculation in SCADA/EMS system for automatic regulation of voltage and reactive power in the...

Active power losses occur during transfer of electricity through transmission grid from power plants to end users. This is a well-known consequence of the current flow through power system elements. The value of the losses on the transmission grid is a few percentages at each voltage level and the value increases with proximity to the grid users. L...

Rare events and disturbances in transmission network can occur in some time frames or with some electrical values which are not fully covered with relay protection and SCADA systems. This gap can be fixed with Wide area monitoring system in control room. WAM system collects synchrophasor data from all 400 and 220 kV transmission lines. Inside WAM s...

When working with SCADA systems transmission system operator faces with challenges which arose from several issues that appeared over the last 10 years. SCADA system is crucial application for power system control. Refurbishment of those systems are planned usually once in a decade or even rarer. This strategy is now compromised because of intertwi...

The standard of living is in a direct connection to the availability and quality of the energy delivered, and therefore the electric power system presents the backbone for the development of a modern human society. While balancing between the economical and environmental issues, the transmission system operators are coping to maintain the power sys...

Angle stability appears in many forms in transmission network. There are small active power oscillations which do not endanger the normal operations whereas medium and large oscillations have implications on normal operations. These latter kinds of oscillations in some cases develop in out of step condition, which is dangerous disturbance with seri...

Classic approach to preventive maintenance of equipment in power system substations was based on periodical maintenance according to regulations and best practices recommended by vendors. SCADA system in HOPS is used primary for real-time monitoring and control of the equipment in substations. Real time data available in SCADA databases contain use...

Design process of the Wide area monitoring, protection and control system (WAMPAC) in control rooms consists of many project phases. Crucial part is to determine parameters for alarms triggering and setting parameters for control and protection modules. Integral segment is to define key performance indices (KPIs) through verified simulation models....

For the developed dynamic angle instability simulation framework a reference IEEE 9 bus model was adapted and created in Matlab simulation environment. Model was validated and verified with available real operation historical data and fine tuning process was conducted. With the reference model, flexible platform for study work in the field of trans...

Transmission system operators utilize phasor measurement unit devices from different vendors. Those devices are basic parts of Wide Area Monitoring Protection and Control system installed in control center. Detail study work needs to be obtained in order to have deep analyses of data generated from those devices. Data gathered in WAMPAC system is u...

In wide area monitoring, protection, and control (WAMPAC) systems, angle stability of transmission network is monitored using data from phasor measurement units (PMU) placed on transmission lines. Based on this PMU data stream advanced algorithm for out-of-step condition detection and early warning issuing is developed. The algorithm based on theor...

Modern Supervisory Control and Data Acquisition (SCADA) systems collect any available data from the systems they monitor and control. Some of the data available in modern SCADA systems include types of the data that can be used for centralized monitoring of transformers. Paper presents possible advanced analysis and reports for monitored transforme...

Smart microgrids are small modern centralized power systems which contain all constituents as large power systems (production – usually Renewable energy sources (RES); power storage systems; transfer – from the source to the consumer; consumers). The basic characteristic is that the microgrid may be controlled just like a large power system and it...

Complete lightning data were collected using lightning locating system (LLS) in Croatia by the Croatian transmission system operator (TSO). The LLS correlation system runs as a part of the National control center’s utility function, collecting lightning data and correlating with network data in real-time. The real-time lightning correlator function...

Power transformers and shunt reactors may be subjected to various dielectric stresses such as lightning and switching overvoltages. Since the exposure of equipment to overvoltages during operation and the overvoltage amplitudes are usually unknow, an on-line overvoltage transient recorder is used with the ability to sample, analyze and store transi...

Power transformers and shunt reactors may be subjected to various dielectric stresses such as lightning and switching overvoltages. Since the exposure of equipment to overvoltages during operation and the overvoltage amplitudes are usually unknow, an on-line overvoltage transient recorder is used with the ability to sample, analyze and store transi...

A wide area monitoring system (WAMS) with reliable telecommunication infrastructure can be expanded and enhanced with additional protection and control functionalities using synchronized phasor data measurements. With that aim, we have developed a multifunctional line protection (MFLP) model with both system and back-up protection functions. Theore...

Transmission network control and protection system can be enhanced using synchrophasor measurement data. Wide Area Monitoring, Protection and Control (WAMPAC) systems incorporate three levels of protection functions. The first layer is the basic relay protection, the second layer is the central system protection with wide area protection functions...

In this paper, a new method of hybrid non-linear state estimation with PMU and SCADA measurements will be proposed. PMU measurements, the voltage and current phasors, are used for real time transmission line parameters (impedance and admittance) calculation. Transmission line parameters are input data for the conventional state estimator. Calculate...

New technologies have a major impact on the improvement of transmission grids, and this impact will be even greater in the near future. The introduction of intelligence in the network, by wide application of information and communication technology, has led to the so-called "smart" grid. Power systems have indeed always been smart, (especially at t...

Transmission network control and protection can be enhanced using phasor data. In a first step multifunctional line protection with system protection function set and back up protection function set can be created. The Matlab model was developed using the experience from the operation of existing wide area system and expended with new function sets...

This paper analyzes the transmission system voltage angle footprint obtained from both the real-time synchrophasor data and the simulations. The simulations are performed on the 400 kV Croatian transmission system. The paper further elaborates the possibilities how to use this type of angle footprint information for both the planning and the real-t...

Power swing and out of step conditions are two power system phenomena which are elaborated in this paper from the power system protection point of view. For that purpose a Matlab model of a part of a 400 kV transmission grid with system protection was modelled. Transmission system disturbance analysis represents a background for different types of...

The monitoring and control of smart power transmission grid represents active infrastructure capable of obtaining increased transfer and distribution of electrical energy, with considerable rate of generation from renewable energy sources without compromising the stability, security and reliability of power grid in different operating conditions. T...

The paper presents a Special Protection Scheme solution for the central Zagreb transmission system. The Central Zagreb transmission system is characterized by a highly meshed network with combined overhead and cable sections and a special operation of the 110 kV cable link between two power plants important for the city's heat and electricity suppl...

Specificity of residential area transmission system is a highly meshed network with combined overhead and cable sections. In center of Zagreb town, control of transmission system is additionally complicated by a special operation of the 110 kV cable link between two power plants important for town's heat and electricity supply. Cable link has to be...

Modernization of a power system involves development and deployment of an Intelligent System or a System Integrity Protection Scheme for a Power Transmission System. As the observed urban Power Transmission System has a ring topology, including overhead lines and underground cables, various scenarios of a closed loop and island operation are consid...

The power grid of the future will be more internet-like grid, with multidirectional flows of data and energy from central and distributed generation plants. Concept of smart grid is a "super" network connecting to the national power grid, the market, consumers and generation with intention to optimize the overall process. The basic concept of smart...

Recent deregulation of electric industry markets within the UCTE (Union for the Coordination of Transmission of Electricity) in Europe is creating new opportunities for reliable, market-based transmission of electric power among participating countries. Croatia, which is strategically located in the southeastern part of the UCTE system, is seeing i...

The paper describes the custom developed phasor data concentrator model for data acquisition, processing and visualization in the wide area monitoring system (WAM) for the Croatian transmission system operator(TSO) HEP. The Croatian power system makes part of a very well meshed interconnected UCTE (Union for the Coordination of Transmission of Elec...

Transient recovery voltage (TRV) is calculated according to the IEC standards and using the EMTP-ATP software. Modelling of electric arc for the SF 6 circuit breaker is presented. Influence of grading capacitors and line bay disposition on the TRV waveform on the side of the line in a 400 kV substation is analyzed for the short-line fault (SLF) con...

The paper presents the results of a study for the reduction of the number of flashovers on a 220 kV double-circuit line. With known geometry of the tower and ground-flash density it is possible to calculate the number of flashovers. The procedure for the calculation of flashovers includes three steps: application of an electro-geometric model, simu...

Transmission line arresters (TLA) are commonly used to address lightning- or switching- related phenomena with the intent to improve the overall reliability of transmission lines. Line arresters can improve system reliability by reducing the multi-phase and multi-circuit line outage rates, or be used to help to limit switching overvoltages on EHV t...

High-voltage (HV) electrical equipment (generators, transformers and circuit breakers) in power system has been monitored lately in certain extent. Monitoring systems (MSs) are different, depending on the type of HV equipment witch they supervise and depending on the producer. In plants and substations, besides MSs, are often installed different pr...

Wide Area Monitoring Systems (WAMS) as a valuable tool for improving power system observability, controllability and security has been duly recognized and WAMS are now being increasingly installed in power systems worldwide. In the present state, the basic WAMS function is providing simultaneous and time synchronised system-wide measurements of vol...

Over the twenty years, electric power industry in many countries has been undergoing fundamental changes due to the process of deregulation. In addition, the power system network is growing larger and more complex, shared by more providers after the deregulation. In this situation, the function of state estimation is becoming more important, becaus...

In the project of new 400 kV substations in Croatia and in the preparation phase for reconnection first and second synchronous zone in the UCTE system it was realized first Wide Area System in the Croatian power system. After detail analysis, first WAM system was put in the operation on the 400 kV line in the Croatian grid. Direction of significant...

Traditional security assessment approach - based on SCADA data and off-line studies conducted long in advance of real time operations - are becoming increasingly unreliable for real time operations. New technologies, which rely on accurate, high-resolution, real-time monitoring of actual system conditions using phasor measurement technologies, are...

400MVA, 400/220kV Phase Shifting Transformer is in full commercial operation in Zerjavinec Substation since July 2004. Since then, a few external faults happened which has been used to check proper behavior of existing transformer differential protection relays. At the same time the disturbance records from these faults has been used to successfull...

A study of transients in a high voltage substation 400/110 kV is presented in the paper. An analysis was carried out after a fault on the 110 kV busbar, which caused severe damage in the substation. Investigation was focused on a time frame of several sequential circuit breaker trippings. A first step of the study was collection of data from the pr...

A study of switching surges in a 400/110 kV substation was carried out in order to detect the causes of severe damage to the power transformer, which happened after a busbar fault. The busbar protection generated tripping signals for several circuit breakers and after their sequential tripping, the surge arresters installed on the 10.5 kV stabilizi...

Direction of significant energy transit through Croatian power system takes path form northeast to southwest. Significance can be explained with simple fact that power flows varies from 25% to 50% of overall national load (national load is ~2500 MW). Due to the large energy transit disturbances in Croatian power system can occur and the result can...

Major disturbances in power system might cause big electromechanical oscillations that can influence unwanted operation of different protection functions and lead to a loss of synchronism between generator groups located in two different parts of a power system. In such situations disconnection of subsystems in points closest to the electrical cent...

Three most typical weaknesses of the analogue power transformer differential relays have been: 1.Long operating time in case of heavy internal faults followed by main CT saturation 2.Unwanted operations for external faults and transformer inrush 3.Bad sensitivity for low-level internal faults, such as winding turn-to-turn faults With the introducti...

In the Zerjavinec substation, a Croatian power company is going to install a special type of power transformer, which has two different modes of operation. The power transformer can be used either as a conventional 400 MVA, 400/220kV autotransformer with on-load tapchanger or as phase shifting transformer, interconnecting 400 kV and 220 kV networks...

The paper describes problems with electromag-netic compatibility (EMC) of the secondary equipment in the 123 kV gas insulated switchgear (GIS). The causes for malfunctioning of the busbar protection during disconnector switching have been studied. Thorough measurements and computer simulations were conducted in order to determine magnitudes and fre...

The paper describes problems with electromagnetic compatibility (EMC) of the secondary equipment in 121 kV gas-insulated switchgear (GIS). The causes for the malfunctioning of the busbar protection during disconnector switching have been studied. Thorough measurements and computer simulations were conducted in order to determine magnitudes and freq...