July 2026, Issue 7 (865)
TABLE OF CONTENTS
Jacek Dziura, Mateusz Skowron, Rafał Wojciechowski
Specific case of photovoltaic transformer failure
Artur Polak, Tadeusz Glinka
Diagnostic testing of hermetic and dry-type transformers – examples
Tomasz Bednarczyk, Dennis Albert, Bernhard Engstler, Aleksander Pirker
Diagnostic measurements of phase shifting transformers
for the purpose of evaluating their technical condition and the protection system
Kacper Blus, Piotr Dargiel, Grzegorz Drygała, Bartłomiej Pasternak
DC component of current in power transformer windings
Stanisław Pokora, Marek Figura, Tomasz Mnich
Development of the national power syste in the aspect of PSE’s strategy until 2040
– the role of technical standards for autotransformers and compensation reactors
Karolina Kucal
Selected design solutions and the arrangement of equipment in medium-power transformers
that are important for operation and maintenance
Magda Wymysło, Klaudia Sokół
The role of laboratory testing in quality assurance of newly manufactured power transformers
Teresa Buchacz
Current possibilities for assessing the condition of transformer paper insulation based on oil analysis
Karolina Kaletka
The importance of accreditation for the development of the ENERGOPOMIAR-ELEKTRYKA Sp. z o.o.
Electrical Insulation Materials Laboratory
Grzegorz Grzegorzyca
Total Transformer Protection – a system-level approach to the protection of power transformers in critical infrastructure
13th Scientific and Technical Conference
“Managing the safety of transformer operation in the era of energy transformation” – summary
POLISH POWER ENGINEERS
Waldemar Olech (14.06.1938 – 23.12.2025)
SUMMARIES
Jacek Dziura, Mateusz Skowron, Rafał Wojciechowski
Specific case of photovoltaic transformer failure
The paper deals with one of the cases concerning photovoltaic transformer breakdown. The advanced „post mortem” analysis not only allowed to detect the root cause of the failure but also indicated the potential risks the transformer was exposed to. In details paper describes the aspects of proper protection and its selectivity, quality of energy supply also from the perspective of currents phase shift from the inwerter side and generally minimizing risks and reducing time of exposure emergency and failure conditions.
Artur Polak, Tadeusz Glinka
Diagnostic testing of hermetic and dry-type transformers – examples
This article presents a method for diagnosing the main insulation of transformer windings: hermetic and dry-type oil-immersed, using a direct voltage U0, and the turn-to-turn insulation using a direct current I0. The main insulation resistances Rg15 and Rg60 are identified using a direct voltage U0, and a polarization test is performed: charging the insulation system to voltage U0, short-circuiting it at time and partially discharging it, then opening it and recording the voltage recovery curve. The turn-to-turn insulation parameters: capacitance Cz and resistance Rz are measured using a direct current I0. Using the energy balance equation 0,5LI02 = 0,5CzUmax2, at the instant of a step-like interruption of the current I0, the parameters Cz and Rz are calculated. The measurement procedure is illustrated with an example. The test object was a 160 kVA dry-type transformer.
Tomasz Bednarczyk, Dennis Albert, Bernhard Engstler, Aleksander Pirker
Diagnostic measurements of phase shifting transformers for the purpose of evaluating their technical condition and the protection system
Phase Shifting Transformers (PSTs) are used in both transmission and distribution networks to control power flow in the power system. Their use significantly improves the control and stability of the power system. Their strategic importance requires the use of advanced in-service condition diagnostics that go beyond factory acceptance tests. This paper presents a methodology for field testing PSTs, combining transformer topology, core configuration, and tap changer (OLTC) arrangement with feasible measurement methods, test sequences, and data interpretation. It has been demonstrated that key PST design variants – single- or dual-core, direct or indirect phase-shift control, and symmetric or asymmetric configurations – significantly affect test feasibility, short-circuit impedance behavior, magnetization characteristics, and tap changer diagnostics. An optimized test sequence was proposed to reduce downtime while ensuring comprehensive coverage, ranging from basic insulation and dissipation factor measurements to advanced diagnostics such as frequency-dependent dielectric response, SFRA, FRSL, zero-impedance, and specialized OLTC evaluation using dynamic current measurement or vibroacoustic methods. In addition to fault detection, the study highlights the role of field test data in establishing reliable data to support trend analysis and the validation of computer-based electromagnetic models [1]. Such data are essential for protection studies, short-circuit simulations, and the verification of complex protection schemes, ultimately improving the reliability of the entire system.
Kacper Blus, Piotr Dargiel, Grzegorz Drygała, Bartłomiej Pasternak
DC component of current in power transformer windings
The negative impact of directcurrent (DC) components flowing through a transformer has been known for decades, and one of the most frequently analyzed phenomena in this area has been geomagnetically induced currents (GIC), which lead to halfcycle core saturation, an increase in noload losses and additional losses in the core structure, as well as a significant rise in transformer noise levels. Although GIC have remained the main source of DC current discussed in the literature, an equally hazardous and increasingly common phenomenon is the forced and continuous DC component generated by modern reactivepower compensation systems such as SVC (Static Var Compensator) and STATCOM (Static Synchronous Compensator). In these solutions, the generated DC component is not accidental, it results from asymmetries in power electronics operation, measurement errors in control loops, and limitations of regulation algorithms, causing the transformer to be subjected to continuous unidirectional core magnetization and a shift of its operating point into the saturation region. This phenomenon must be considered and analyzed at an early stage of activepart transformer design to ensure reliable operation. The article presents a practical approach to designing transformers intended to work with FACTS (Flexible AC Transmission Systems), including criteria for evaluating resultant induction, methods for minimizing saturation risk, and fundamental design solutions enabling safe and stable operation in the presence of a DC current component.
Stanisław Pokora, Marek Figura, Tomasz Mnich
Development of the national power syste in the aspect of PSE’s strategy until 2040 – the role of technical standards
for autotransformers and compensation reactors
The National Power Grid is expected to undergo a significant transformation over the next decade. According to the International Energy Agency (IEA), by 2035 the demand for electricity will grow six times faster than the demand for all other forms of energy combined. Distributed energy resources already play a major role in determining the operating conditions of the power system. Ensuring system stability and security requires transmission system operators to have full visibility of all connected assets and, whenever necessary, the ability to monitor and control them. As part of ongoing investments in new and modernized high-voltage substations, the technical specifications for autotransformers and shunt reactors have been updated. This paper presents the key technical requirements applied by Polskie Sieci Elektroenergetyczne (PSE) when procuring these devices for operation within the National Power Grid.
Karolina Kucal
Selected design solutions and the arrangement of equipment in medium-power transformers that are important for operation and maintenance
This article presents selected design solutions and device layout methods in medium-power transformers, which significantly impact their operation. Issues related to operational safety, technical diagnostics, service accessibility, and transport and installation logistics are discussed. Particular attention is paid to online monitoring systems, transformer protection systems, and design solutions that increase reliability and facilitate maintenance and operation of the equipment.
Magda Wymysło, Klaudia Sokół
The role of laboratory testing in quality assurance of newly manufactured power transformers
Transformer oil performs cooling and insulating functions and serves as a valuable source of diagnostic information regarding the technical condition of the equipment. Dissolved Gas Analysis (DGA) enables the early detection of developing internal faults, including partial discharges, thermal faults over a wide temperature range, and low- and high-energy electrical discharges. Water content determination using the Karl Fischer method provides an assessment of the moisture condition of the transformer insulation system and enables verification of the effectiveness of manufacturing processes. Physicochemical analyses, including the determination of solid contaminants and Fourier Transform Infrared Spectroscopy (FTIR), provide additional information on the condition of the insulating oil, supporting the reliable and safe long-term operation of transformers. The laboratory investigations presented in this study were conducted to verify the quality of newly manufactured transformer units before their release from the production plant.
Teresa Buchacz
Current possibilities for assessing the condition of transformer paper insulation based on oil analysis
This article discusses oil analysis for detecting products indicating degradation of paper insulation in transformers. Particular attention is paid to the analysis of furan derivatives and the evaluation of results obtained after oil regeneration and the addition of an inhibitor. New indicators of cellulose aging – light alcohols: methanol and ethanol – are also presented, as well as the applicability of existing research methods to thermally stabilized paper (TPP) insulation systems. The advantages and limitations of each research method are discussed.
Karolina Kaletka
The importance of accreditation for the development of the ENERGOPOMIAR-ELEKTRYKA Sp. z o.o.
Electrical Insulation Materials Laboratory
The article presents the Insulating Materials Laboratory of ENERGOPOMIAR-ELEKTRYKA Sp. z o.o., which complies with the accreditation requirements of PN-EN ISO/IEC 17025:2018-02. The implemented system is based on personnel competence, impartiality, confidentiality, and supervision of testing processes, resulting in high-quality measurement results with minimal uncertainty. The paper presents the scope of the laboratory’s accreditation, which includes: the determination of free and dissolved gases in insulating liquids using the gas chromatography method, as well as the determination of water content using the Karl Fischer method. The presented article highlights the importance of the quality of performed tests in the context of the safety of energy sector infrastructure.
Grzegorz Grzegorzyca
Total Transformer Protection – a system-level approach to the protection of power transformers in critical infrastructure
This paper presents the concept of Total Transformer Protection (TTP) as a systemic approach to the protection of power transformers operating in critical infrastructure. TTP integrates protection, diagnostic and operational systems into a closed-loop decision framework including measurement, interpretation, correlation, prediction and operational actions. Particular attention is paid to the impact of dynamic phenomena occurring in power systems, the role of the on-load tap changer (OLTC), the significance of SFRA diagnostics and the application of algorithmic data correlation. The proposed approach enables a transition from reactive maintenance to active transformer risk management. Furthermore, the paper highlights the cumulative effects of dynamic system interactions and the importance of correlating operational disturbances with diagnostic results to better understand long-term degradation mechanisms.
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