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.

The use of power-electronics-based devices in distribution generation seeks to improve energy quality and reduce costs. The inverter-based distributed generator, that works in different operation modes, has emerged as a promising technology. In a high distributed generation penetration scenario it is important to know the voltage profile and fault information due to the uncertainty in the generator operation and the impact that have on the network. This study aims to use two proposed methods of analysis: for power flow, based on backward/forward sweep method, and short-circuit, based on hybrid impedance matrix, that considers the inverter operation modes and represents each generator as a voltage-controlled current source. The chosen network is the IEEE 34-Node Test Feeder with a generator on each load per phase. The voltage profiles obtained will be validated with a Simulink/Matlab phasorial model. The results show an average error of 2.39% and a gain in voltage profile processing time of 2185.24%, making its use consistent for larger systems.