Search

This article presents an extended algorithm for one of the most important tasks in source–receiver optimal cooperation—minimization of the source's RMS current value while ensuring the required active power is supplied to the receiver. The current state of the art ensures optimal steady-state cooperation. The presented extension introduces an approximated transient state to the optimization equations. By using an extended algorithm, it is possible to provide the optimal current not only in a steady state but also at any time during the transient state. The influence of the assumed transients—finite and permanent—on the EMF and optimal current signals is shown. The obtained results are compared with conventional calculation methods to show the advantage of the presented algorithm. The developed algorithm was also tested on measurement data obtained from a real-world test setup that reflects an actual section of the power system. The article also demonstrates, using a measurement example, how the proposed current optimization process during fault conditions in the power system can contribute to reducing short circuit-related losses. [ABSTRACT FROM AUTHOR]

This article presents the hitherto unknown concept of transient active power in two-terminal networks. This phenomenon occurs when current and voltage signals are not sinusoidal but quasi-sinusoidal—in the case of an approximation of transient state. The modification of Parseval's formula and the power–immittance relations are presented in this paper. To illustrate the phenomenon, a simulation is included for several types of transient states, and their influence on transient active power waveform is shown. The article also contains a comparison of transient active power and classical active power and highlights situations where it is impossible to use classical theory but where transient active power yields measurable results. In the article, an analysis of an idealized case and measurement data obtained from a modeled voltage sag in a laboratory setup is conducted. The impact of disturbance power on the total power in the case of disturbances that may occur in the real power network is demonstrated. [ABSTRACT FROM AUTHOR]

The active power losses are dependent on the flowing electric power value through overhead and cable lines. The current flow through the conductor causes negative phenomena to occur, such as released heat. The source of the current harmonics is the non-linear loads. Hence, the skin effect occurs, and the current carrying capacity of cables is reduced. This results in the increase in and uneven distribution of the temperature inside the conductor. This paper presents a comparison of the temperature distribution inside a power cable for an ideal 50 Hz sine wave and highly distorted current (T H D I = 41 %) . The calculated active power losses for the IEC 60287-1-1:2006+A1:2014 standard and the method described in the literature were used as a basis for further calculations. The obtained results revealed the problem of the uneven distribution of the conductor temperature. Considering the skin effect, increasing the temperature in the outer layers leads to severe damage and faster insulation aging. The abovementioned phenomenon is a decrease in the permissible load capacity of the conductor. The table given in the IEC 60364-5-52 standard summarizes the percentage contribution of the third harmonic to the current waveform. For percentages between 15% and 33%, the current carrying capacity is reduced by up to 86% of the full-load current rating. In addition, consideration of thermal conditions forces the use of cables with larger cross-sections. This leads to their non-optimal use and makes the investment more expensive from an economic point of view. [ABSTRACT FROM AUTHOR]

This article was written to present a new solution for a phase-shifting transformer and to show that, in many aspects, the proposed device is more functional and improved when compared to the other currently available phase-shifting structures. The article shows the construction of the new phase-shifting transformer, with longitudinal and transverse voltage regulation. The proposed device's functionality and available operation states are compared to other existing solutions. Selected steady-state variants of the operation of the proposed transformer were checked based on computer simulations and the laboratory model presented in detail in the article. Convergence between measurements and simulations was achieved. Power flow calculations were also performed in the five-node electrical power system model. In these calculations, two variants of the proposed device's work were considered and compared with the asymmetric phase shifter. The tests confirmed in the proposed structure, both angle and voltage regulation, enabled maintaining a constant active power flow. The authors show that the proposed solution combines the advantages and functionality of various types of phase shifters while, at the same time, being characterized by a much simpler structure, which results in a two-times-lower cost of the device. [ABSTRACT FROM AUTHOR]

Copyright of Technical Transactions / Czasopismo Techniczne is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technical Transactions / Czasopismo Techniczne is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Single-phase short-circuits are most often faults in electrical systems. The analysis of this damage type is taken for backup power supply systems, from small power synchronous generators. For these hybrid installations, there is a need for standard protection devices, such as fuses or miniature circuit breaker (MCB) analysis. Experimental research mentioned that a typical protective apparatus in low-voltage installations, working correctly during supplying from the grid, does not guarantee fast off-switching, while short-circuits occur during supplication from the backup generator set. The analysis of single-phase short-circuits is executed both for current waveform character (including sub-transient and transient states) and the carried energy, to show the problems with the fuses and MCB usage, to protect circuits in installations fed in a hybrid way (from the grid and synchronous generator set). [ABSTRACT FROM AUTHOR]