In human civilization, Water Pumping Systems (WPS) are fundamental for industrial, drinking, and agricultural applications. One of the best practical solutions for reducing grid load demand and supplying electricity in various regions is a locally installed standalone Solar Photovoltaic (SPV) - powered WPS. Generally, WPS is drawn to Brushless DC Motors (BLDCMs) among other motors because of their many benefits. However, adding battery banks to WPS can raise the maintenance needs and cost, which farmers cannot afford. This study thus explores and applies a sensorless speed control method of a BLDCM powered by SPV energy, eliminating the need for a battery. Partial Shading Conditions (PSCs) typically impair the power generated by SPV systems, and the conventional P&O mechanism fails, preventing the systems from producing maximum availability of electricity. This work integrates the Botox Optimization Algorithm (BOA) with the traditional P&O technique to address this issue. The Hybrid Botox Optimization-P&O (BOPO) method can efficiently harvest the most power from SPV under both normal and partial shade circumstances. For MPPT under PSC, the outcomes are contrasted with those of Modified Grey Wolf Optimization (MGWO), Particle Swarm Optimization (PSO), and Modified Invasive Weed Optimization (MIWO) algorithms. By integrating the BOPO technique with the inverter’s control method, the inverter also functions as a MPPT converter of the SPV unit, lowering system costs. Therefore, an additional DC-DC converter won’t be needed for the operation of MPPT. In order to validate the suggested system in both transient and steady state scenarios, extensive results are shown using OPAL-RT. Furthermore, this work presents hardware results based on dSPACE to validate the proposed method.

The degradation behaviour of SnO2-based varistors (SCNCr) due to current pulses (8/20 µs) is reported here for the first time in comparison with the ZnO-based commercial varistors (ZnO). Puncturing and/or cracking failures were observed in ZnO-based varistors possessing inferior thermo-mechanical properties in comparison with that found in a SCNCr system free of failures. Both systems presented electric degradation related to the increase in the leakage current and decrease in the electric breakdown field, non-linear coefficient and average value of the potential barrier height. However, it was found that a more severe degradation occurred in the ZnO-based varistors concerning their non-ohmic behaviour, while in the SCNCr system, a strong non-ohmic behaviour remained after the degradation. These results indicate that the degradation in the metal oxide varistors is controlled by a defect diffusion process whose rate depends on the mobility, the concentration of meta-stable defects and the amount of electrically active interfaces. The improved behaviour of the SCNCr system is then inferred to be associated with the higher amount of electrically active interfaces (85%) and to a higher energy necessary to activate the diffusion of the specific defects. (Some figures in this article are in colour only in the electronic version)

Metal oxide varistors based on ceramic technology are extensively used nowadays as limiting voltage devices, covering an amazing range of systems from microelectronics equipment up to very large power system networks. These varistors are formed through the sintering of a mixture of ZnO or SnO<;sub>2<;/sub> metal oxides with several other metal oxide dopants containing the elements of O<;sub<;2<;/sub>, Bi, Sb, and Cr [1], [2]. The electrical behavior is governed by the microstructure in which the conductive zinc oxide grains are surrounded by a resistive intergranular boundary of other oxides, forming “microcomponents” and acting like diodes with relatively low voltage turn-on [3]. This results in a highly nonlinear voltage-dependent conduction mechanism, or the I-V characteristic. This article presents an extension of earlier works [9], [10] utilizing lightning impulses to cause catastrophic failures of the surge arresters and applying diagnostic tests covering the transition from the new state to failure.

Over the last few decades, and more prominently currently, many countries have launched and reinforced campaigns to reduce CO₂ emissions from all human activities and, in the area of energy, promote energy generating technologies from low carbon, renewable sources, especially wind and solar. In recent years, this promotion of renewables can be seen in statistics as well as an extraordinary increase in plants using renewable sources. There is more activity surrounding the use of small devices installed close to consumers, such as small wind turbines (SWT). In cities, the best places to install SWT are tall buildings. The Institute of Energy and Environment (IEE-USP) has installed a 1.8 kW SWT on the University of São Paulo campus in São Paulo, Brazil. Even with low-magnitude winds at the site, the SWT installation was carried out to serve as a didactic apparatus and demonstration initiative of wind energy generation connected directly to the University’s electric grid, which already has other embedded renewable sources installed, namely photovoltaic and biogas plants. The turbine was placed on the roof of the existing High Voltage Laboratory building, leading to an operating height of 35 m. This paper presents previous local wind data measurements using a Lidar system, annual energy yield estimation calculations, and measurements, also bringing all implementation details. It reports and analyzes the operation and energy production data from three full operational years, from 2018 to 2020, discussing and concluding with further improvements of SWT from technical and economic aspects.