This article, besides offering data of great value for any designer of high-power short-circuits of special three-winding design, illustrates the correlation with the corresponding FRA measurements, validating this type of measurement. The frequency response measurements can provide data about the transformer’s status after it is put into service, its vulnerability in incipient states, and, particularly for this type of transformer, its insulation, which is the subject of high dielectric stress due to its invertor working regime. This article presents the behavior of a three-phase 8400 kVA medium-voltage step-up transformer (corrugated hermetic tank) specially designed for photovoltaic applications during short-circuit tests. This transformer, fed by two inverters, has two secondaries with elliptical windings (non-circular aluminum foil for LV windings and an aluminum conductor for HV windings). Various experiments were performed, including measurements of winding resistance, measurements of voltage ratio, measurements of short-circuit impedance and load loss on three tappings, measurements of no-load loss and current, a frequency response analysis, and short-circuiting. These experiments were performed to study the behavior of the transformer, which, in real life, is powered by photovoltaic inverters on the LV side that feed into the MV grid on the HV side, making it the interface between the photovoltaic inverter and the MV grid. An auxiliary supply transformer may be connected to the LV side. Given these elements, concerning both the importance and the particularities of the problem studied, we can say that this article represents a niche study on the guarantee of good functioning and safety in operation given the passing of the test to withstand the dynamic effects of short-circuiting.

High-voltage fuses are found in most electrical installations, where they are used for overcurrent protection and are the pieces of equipment providing the highest degree of protection for the lowest initial cost. This article focuses on the behavior of high-voltage fuses containing a fuse element entirely made of aluminum. We made high-power linear electrical circuits for experiments on these fuses under the most severe operating conditions. The article presents the construction details of the fuse element and its features, as well as various arc extinguishing media. The heating behavior and time–current characteristics were studied in comparison with fuses made of copper. We obtained the maximum instantaneous value of the current reached during interruption for a 24 kV, 50 kA, 50 A fuse, as well as the value of the minimum breaking current.

If an R.M.U. (Ring Main Unit) cubicle is installed, operated and maintained in accordance with current standards and the manufacturer’s instructions, the likelihood of internal arcing is reduced, but should not be completely ignored. This article outlines the experimental situations in which arcing can occur and the catastrophic effects seen if R.M.U. is not properly designed for this type of damage. This type of failure can be caused by a fault, abnormal operating conditions or a malfunction and represents a danger during its installation and to persons present. The situations in which this type of failure can occur are presented and experimentally analysed: bi-phase internal arcing in the connections compartment, three-phase internal arcing in the switching compartment, internal arcing in the fuse compartment and single-phase arcing between a phase and the switchgear enclosure.

An important part of the design of power transformers is based on short circuit behaviour. This paper presents an experimental study of a transformer with circular concentric coils, using metal foil as a conductor in the low voltage winding, with a rated power of 2000 kVA.

The design of power transformers is heavily influenced by their performance during short circuit. This paper explores the experimental analysis of a power transformer with circular concentric coils, utilizing metal foil conductor in the low-voltage winding, and a rated power of 2000 kVA. To validate its behavior, the study employs Frequency Response Analysis (FRA), a widely recommended diagnostic method for identifying internal faults in power transformers. Furthermore, the paper provides insights into the design specifics of power transformers used in renewable energy power plants. By highlighting the unique aspects and criticalities examined, this study establishes itself as a niche contribution to understanding safety in transformer operation. The research also delves into experiments conducted in a high-power laboratory to investigate how transformers respond to the dynamic effects of short circuit. Particular attention is given to the thermal and mechanical impacts of short circuit currents, with an emphasis on their negative consequences. Additionally, the paper discusses a system configuration where direct current (DC) produced by photovoltaic cells is converted into alternating current (AC) using one or more inverters connected to the low-voltage windings of a step-up transformer. Finally, the study underscores the importance of assessing the short circuit behavior of power transformer, focusing on the irreversible deformations caused by axial and radial forces during short circuit events.