# Vereinfachte Kurzschlussstromberechnung für Mittel- und Niederspannungsgleichstromnetze

• Simplified short-circuit current calculation for medium and low-voltage direct current networks

1. Auflage. - Aachen : printproduction M. Wolff GmbH (2020, 2021)
Book, Dissertation / PhD Thesis

In: Aachener Beiträge zur Energieversorgung 203
Page(s)/Article-Nr.: 1 Online-Ressource (ix, 256 Seiten) : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2020

Abstract

Medium- and low-voltage direct current (DC) distribution networks are focus of current research. As in today's three-phase alternating current (AC) networks, currents in DC distribution networks generally cause the greatest stresses for current-carrying equipment in terms of their thermal and mechanical load in case of short circuits. Therefore, the knowledge of possible short-circuit currents in DC distribution systems is absolutely essential for the safe and yet economically appropriate design of current-carrying equipment. For AC systems, simplified approximation approaches for short-circuit current calculation are available today. In practice, such simplified approximation approaches for the calculation of possible short-circuit currents are desired, since the data requirements and the computation time can be significantly reduced compared to transient calculations. For this reason, a simplified short-circuit current calculation based on an approximation approach is also desirable for DC distribution networks. The aim of this research project is therefore to derive a method for simplified short-circuit current calculation for DC distribution networks. For the simplified short-circuit current calculation, we focus on the calculation approach of superposition of approximated current courses. In this calculation approach, the current courses of all feeding short-circuit current sources are approximated in the first step without taking into account the feedback effects from other short-circuit current sources. Then, the current courses of the individual short-circuit current sources are superposed, taking the DC system into account. Finally, short-circuit current characteristics of the current-carrying equipment are determined. To evaluate the simplified short-circuit current calculation method, a comparison of the calculated short-circuit currents with comparative data is required. Due to the lack of realized DC distribution networks in practice, realistic comparison data is generated by transient calculations in the form of numerical simulations and compared with the results of the simplified calculation. In the course of the investigations, the simplified calculation method is evaluated for a large number of different DC distribution networks. The network structure, the supply task, the equipment and the operating voltage of the DC distribution networks are varied. According to the evaluation, the calculation of short-circuit current characteristics of partial short-circuit currents is not valid. However, the calculation of the design-relevant short-circuit current characteristics of current-carrying equipment appears to be possible with restrictions.