Impacts on electrical protections in radial distribution networks with distributed generation, considering a high penetration of sources based on invertersThis document analyzes the time response of two electrical protection schemes in different scenarios of distributed generation. Its implementation is carried out in the 13-node IEEE system, to which modifications were made in order to simulate a typical 13.2kV electrical network in Colombia. Initially, there is presented a theoretical part in which the characteristics of electrical protections and the main protection schemes implemented for distribution networks are explained, to later analyze the case studies and their considerations.Finally, the results of the simulations obtained for each of the selected protection coordination schemes are presented, taking into consideration the scenarios of minimum and maximum demand of the system. The different fault impedances that can occur and the types of generation connected to the distribution network are also taken into account (synchronous generators and static generators).
In this paper, two factors typical of large photovoltaic (PV) arrays are investigated: one is the current-voltage (I-V ) mismatch consequent to the production tolerance; the other is the impact of reverse currents in different operating conditions. Concerning the manufacturing I-V mismatch, the parameters of the equivalent circuit of the solar cell are computed for several PV modules from flash reports provided by the manufacturers. The corresponding I-V characteristic of every module is used to evaluate the behavior of different strings and the interaction among the strings connected for composing PV arrays. Two real crystalline silicon PV systems of 8 × 250 kW and 20 kW are studied, respectively. The simulation results reveal that the impact of the I-V mismatch is negligible with the usual tolerance, and the insertion of the blocking diodes against reverse currents can be avoided with crystalline silicon technology. On the other hand, the experimental results on I-V characteristics of the aforementioned arrays put into evidence the existence of a remarkable power deviation (3%-4%) with respect to the rated power, linkable to the lack of measurement uncertainty in the manufacturer flash reports.
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