This paper proposes a practical approach to estimate the symmetrical short-circuit current (SCC) levels in overcurrent protection devices (OCPDs) installed on radial feeders for any penetration level of inverter-based distributed energy resources (DERs). The proposed method restores the lost phase protection coordination by estimating SCC values and changing the TMS of OCPDs accordingly. The method is validated by comparing the results with simulations on the IEEE 34-Node Test Feeder using MATLAB/Simulink, which shows an average error of 1.5% and a maximum error of 3.0%. For a 100% penetration level, the SCC variation through OCPDs installed on the main fault trunk (MFT) exceeds ± 10%, leading to compromised phase protection coordination. The SCC flowing reversely through OCPDs on lateral branches and the fault on the MFT could cause improper tripping. Higher SCC levels are estimated and measured for fault impedances equal to zero. The phase protection is restored by changing the TMS of OCPDs using the estimated values. The study proposes two phase protection schemes to accommodate inverter-based DERs injecting 1.2 pu and 2.0 pu of SCC for a 100% penetration level. This study contributes to improving the protection coordination of distribution networks with high penetration levels of DERs. The findings have practical implications for distribution system operators and planners to maintain safe and reliable operation of distribution feeders.

With the worldwide growth of distributed generation (DG), specially photovoltaic (PV), several studies discussed about the impacts on voltage profile of distribution feeders. However, they do not apply the actual Brazilian electricity regulation for DG and PV systems, and the results are presented in a common way. This paper aims to study the voltage profile of IEEE 13-Node Radial Test Feeder with high PV penetration level under electricity regulation from Brazilian Electricity Regulatory Agency (ANEEL) and Brazilian National Electrical System Operator (ONS). The results are presented in a three-dimensional graphic, making the interpretation easier. The study is conducted simulating a residential region at noon where the PV generation is maximum and the consumer units consumption is on a medium level, making a scenario of 200% of PV penetration level. The PV generators, attending ANEEL and ONS requirements, has the ability to operate in fixed inductive or capacitive power factor (pf). A capacitive pf operation raises the node voltages by 4.0%, in average, with maximum of 12.7%. On other hand, inductive pf operation drops the node voltages by 0.5%, in average, with maximum voltage raise of 1.3% and maximum voltage drop of 2.0%. These results shows that PV generators operating with fixed pf may cause voltage issues impacting directly on electricity quality levels. A central control or PV inverters with smart control can mitigate these problems.

Due to its easy installation, easy operation and plenty solar light, the photovoltaic (PV) generators were the ones that emerged as favourites among the other types. However, the high integration of PV generators in distribution networks may cause impacts on power system protection, mainly on overcurrent protection (OCP). This work aims to assess the variation of fault currents magnitude through the OCP relays of a distribution network with integration of small scale PV generators. The distribution feeder and the PV generator were implemented in Simulink ^® /MATLAB ^® and the faults were applied at two different points. As the fault moves away from substation, the positive variation of the fault current through OCP relay increases and the negative variation decreases. Moreover, the current variability for line-to-ground (LG) faults are, in average, 130.94% greater than three line-to-ground (3LG) faults. In the case where the fault is upstream from OCP relay, the average current variation was −1,443.22% for 3LG faults and −842.28% for LG faults. This can lead to miscoordination and tripping issues of OCP devices, making it necessary to evaluate the impacts on protection system reliability.

This paper investigates the impacts of small-scale distributed energy resources (DERs) on fault currents and overcurrent protection (OCP) coordination in distribution feeders, considering the Brazilian regulatory framework. Changes in fault current levels and OCP coordination are analyzed by focusing on the relationships between DER location, output power, and OCP positioning. Simulations were conducted in Simulink/MATLAB using the IEEE 13-Node Distribution Test Feeder as a case study, considering various DER integration scenarios. The DER model adheres to the Brazilian standard NBR 16149:2013, which governs fault current injection and voltage ride-through behavior. The results indicate that DER integration can disrupt OCP coordination and significantly affect fault current levels, despite their relatively small current contributions during faults. In one scenario, OCP coordination was lost, while in others, coordination time intervals decreased. The findings show that DER location has a minimal influence on fault current changes, whereas output power plays a more critical role. Faults occurring farther from the substation cause greater current variation in installed relays, with deviations nearing ±10%. Additionally, reverse fault currents through relays are identified as a key concern for protection engineers.