Vladimír Kohan
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Vladimír Kohan has a total of 11 co-authors. Here are the top co-authors by number of shared publications:
- Peter Havran
Department of Electric Power Engineering, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice, Slovakia
2 shared publications - Ľuboš Šárpataky
Department of Electric Power Engineering, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice, Slovakia
2 shared publications - Bystrík Dolník
Technical University of Košice
1 shared publication - Dusan Medved
Department of Electric Power Engineering, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 042 00 Košice, Slovakia
1 shared publication - Iraida Kolcunová
Department of Electric Power Engineering, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice, Slovakia
1 shared publication - Jozef Király
Department of Electric Power Engineering, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Mäsiarska 74, 040 01 Kosice, Slovakia
1 shared publication
Latest Publications
- Open Access
- 1 September 2022
- Published by Walter de Gruyter GmbH in Acta Electrotechnica et Informatica
- Vol. 22 (3) , 9-17
Modeling of Protection Relays and Renewable Energy Sources for Microgrid Systems
Further research and development in the field of microgrids and related modelling and testing will be necessary for successful application in practice, which will require various model elements. It will be possible to create near-real test microgrids to help better understand the behaviour of such grids. For this reason, it is necessary to develop elements of independent parts that appear in distribution networks that will experience conversion to microgrids in the future. Therefore, this article will describe and propose models of basic protection relays, whose potential for application in microgrids is high. The article will additionally provide models of some power supplies that will be found in such reconstructed new grids.
- 1 September 2022
- Published by Walter de Gruyter GmbH in Acta Electrotechnica et Informatica
- Vol. 22 (3) , 9-17
Open AccessModeling of Protection Relays and Renewable Energy Sources for Microgrid Systems
Further research and development in the field of microgrids and related modelling and testing will be necessary for successful application in practice, which will require various model elements. It will be possible to create near-real test microgrids to help better understand the behaviour of such grids. For this reason, it is necessary to develop elements of independent parts that appear in distribution networks that will experience conversion to microgrids in the future. Therefore, this article will describe and propose models of basic protection relays, whose potential for application in microgrids is high. The article will additionally provide models of some power supplies that will be found in such reconstructed new grids.
- Open Access
Dielectric Properties of Electrical Insulating Liquids for High Voltage Electric Devices in a Time-Varying Electric Field
The motivation to improve components in electric power equipment brings new proposals from world-renowned scientists to strengthen them in operation. An essential part of every electric power equipment is its insulation system, which must have the best possible parameters. The current problem with mineral oil replacement is investigating and testing other alternative electrical insulating liquids. In this paper, we present a comparison of mineral and hydrocarbon oil (liquefied gas) in terms of conductivity and relaxation mechanisms in the complex plane of the Cole-Cole diagram and dielectric losses. We perform the comparison using the method of dielectric relaxation spectroscopy in the frequency domain at different intensities of the time-varying electric field 0.5 kV/m, 5 kV/m, and 50 kV/m. With the increasing intensity of the time-varying electric field, there is a better approximation of the Debye behavior in all captured polarization processes of the investigated oils. By comparing the distribution of relaxation times, mineral oil shows closer characteristics to Debye relaxation. From the point of view of dielectric losses at the main frequency, hydrocarbon oil achieves better dielectric properties at all applied intensities of the time-varying electric field, which is very important for practical use.
Open AccessDielectric Properties of Electrical Insulating Liquids for High Voltage Electric Devices in a Time-Varying Electric Field
The motivation to improve components in electric power equipment brings new proposals from world-renowned scientists to strengthen them in operation. An essential part of every electric power equipment is its insulation system, which must have the best possible parameters. The current problem with mineral oil replacement is investigating and testing other alternative electrical insulating liquids. In this paper, we present a comparison of mineral and hydrocarbon oil (liquefied gas) in terms of conductivity and relaxation mechanisms in the complex plane of the Cole-Cole diagram and dielectric losses. We perform the comparison using the method of dielectric relaxation spectroscopy in the frequency domain at different intensities of the time-varying electric field 0.5 kV/m, 5 kV/m, and 50 kV/m. With the increasing intensity of the time-varying electric field, there is a better approximation of the Debye behavior in all captured polarization processes of the investigated oils. By comparing the distribution of relaxation times, mineral oil shows closer characteristics to Debye relaxation. From the point of view of dielectric losses at the main frequency, hydrocarbon oil achieves better dielectric properties at all applied intensities of the time-varying electric field, which is very important for practical use.