Exploring the effects of geometric parameters is indispensable when designing an air filter, as they are the main parameters capable of influencing both collection efficiency and pressure drop. This paper aims to experimentally investigate the impact of these parameters on the pressure drop and the collection efficiency of Electric Metal Mesh Filter (EMMF), and then evaluate the quality factor to identify the most suitable combination of parameters for optimal filtration performance. The studied parameters include mesh size and fiber diameter of a metallic grid, as well as the number of the grids and the spacing between them. The results indicate that, for a three-layer configuration and an applied voltage of 4.9 kV, the finest grid considered, with a fiber diameter of 25 μm, achieves the best collection efficiency (85%). On the other hand, the grid with the largest mesh opening studied (250 μm) leads to the best quality factor, with a value of 4 Pa⁻¹. Furthermore, an inter-grid distance of 20 mm improves collection efficiency by 7% compared to a distance of 5 mm, under an average electric field of 0.6 kV/mm. These results indicate that optimal filtration performance can be achieved by combining a minimal fiber diameter, a maximal mesh size, a large inter-mesh spacing, and the highest possible applied voltage. However, such a configuration may affect the structural robustness of the filter media. This investigation highlights the complex relationship between geometric parameters and the filtration performance, offering key insights essential for optimizing filter's effectiveness and durability.

The insertion of a dielectric barrier between the conductors in gas insulation can improve effectively the insulation performance in high voltage equipment such as MV gas insulated switchgear. The dielectric barrier increases the breakdown voltage because of two main reasons: increasing the shortest path, and allowing surface charge deposition to reduce the total electric field. The electric field measurement in such systems is a very important to understand the physical involved phenomena, however, it is so challenging. In this work, the electric field at the vicinity of the HV electrode is investigated experimentally and numerically in a needle-barrier-plane configuration under positive lightning impulse. The electric field is measured using a very compact and fully dielectric electrooptic probe. The results of the experimental measurements show a good agreement with the numerical simulations for both Ez and Er field components. The surface charge density having the same polarity as the applied voltage impacts mainly the vertical component of the electric field, while the space charge density generated by the PD activity impacts mainly the radial component of the electric field.

This work investigates the viability of natural and synthetic ester liquids as potential alternatives to mineral oil in MVDC and HVDC transformer insulation systems. Finite Element Method simulations (FEM) were performed using the measured dielectric properties of the oils and their impregnated pressboards as input parameters to evaluate their influence on steady state electric field distribution. A comparison on the field distribution under AC and DC condition is performed for the different materials, identifying regions of maximum stress around the corona head and high voltage electrode. The temperature dependence of electrical conductivity values of the materials and their effect on the steady state DC electric field distribution is explored. The higher conductivity of ester liquids when compared to mineral oil provides a more uniform field redistribution between the oil and pressboard, also facilitating the shift of maximum electrical stress from the oil to pressboard. The results support the technical merits of using ester-based insulation material for field stress equalization in HVDC networks.

The aim of this paper is to use Pockels effect-based electro-optic (EO) sensor to characterize corona and dielectric barrier discharges (DBD). In the realm of electrical engineering, partial discharges (PD) pose significant risks due to their potential to accelerate insulation aging in high-voltage systems, necessitating ongoing advancements in detection and monitoring techniques. This study hones in on the distinctive attributes of EO sensors, including their wide bandwidth, minimal perturbation, high spatial resolution, and fully dielectric properties, which enable accurate electric field measurements in close proximity to discharge locations. The paper highlights the advantages of EO sensors over traditional methods, such as high-frequency current transformers (HFCTs), by comparing their performance in various discharge configurations and types. The EO sensors' capability to capture vectorial electric field variations and perform continuous wavelet transform (CWT) analysis is also explored, offering a more nuanced understanding of discharge properties. The findings reveal that the EO sensors can be used efficiently for PD characterization. The characteristics of the recorded signals are discharge-type dependent, making EO sensors particularly valuable for fault detection and diagnosis in insulation systems. Moreover, this research underscores the potential for EO sensors to enhance the accuracy and efficiency of PD detection, contributing to improved maintenance strategies and the overall reliability of high-voltage power equipment.

The use of high voltage direct current (HVDC) transmission technology has increased significantly in recent years due to its numerous advantages over traditional alternating current (AC) transmission. The aim of the present work is to investigate the efficiency of different non-intrusive sensors for partial discharge measurement in medium or high voltage direct current equipment such as air or gas insulated switchgear. HV equipment are susceptible to partial discharges such as corona and surface discharges, which can lead to the premature aging of the insulation and its breakdown. The partial discharges appear because of the enhancement of the electric field around sharp edges, triple points, floating metallic particles or in cracks or cavities inside solid insulation. In HVAC systems, partial discharge detection and quantification are well understood. However, under HVDC, there is a necessity to evaluate the efficiency of classic techniques and commercial non-intrusive sensors. This work presents a study of three different sensors for partial discharge measurement under HVDC: high frequency current transformer (HFCT), ultra-high frequency antenna (UHF), and transient earth voltage (TEV). The signals of the different sensors partial discharge detection are presented and compared in both temporal and frequency domains.

Gas Insulated Switchgears (GIS) are essential equipment in medium (MV) and high voltage (HV) power distribution networks. These systems are filled with pressurized gas to provide effective insulation and ensure operational reliability. This work aims to investigate the application of design of experiments to estimate the positive lightning impulse breakdown voltage of pressurized dry air under non-uniform field conditions. A response surface methodology was conducted using a composite face-centered design of experiments. Experimental investigations have been carried out to assess the breakdown as function of the electric field non-uniformity and dry air pressures. The results show that the accuracy of the design of experiments model depends on the utilization factors that is considered. The use of two separate design of experiment strategies for strongly nonuniform and weakly non-uniform field utilization factors ranges respectively leads to more accurate breakdown voltage values.

Medium- and high-voltage gas-insulated switchgear (GIS) play a vital role in the infrastructure of electrical power transmission and distribution systems. The equipment within these substations is primarily insulated with pressurized gas to ensure optimal operational performance. Solid insulation is also used in switchgears in the form of shafts, spacers or dielectric barriers. The aim of this work is to investigate the influence of dielectric barriers on the breakdown voltage in pressurized air insulated rod-plane gaps. A design of experiments is used to optimize the number of experiments and create a model for the estimation of the breakdown. A Box-Behnken Design (BBD) was used to produce an empirical formula of the breakdown voltage as a function of multiple parameters. The investigated parameters considered in the BBD are the barrier location in the gap space, the barrier dimensions, the absolute pressure and the electric field non-uniformity factor. The obtained results indicated that the barrier effect was most significant in the arrangement with strongly non-uniform field for $\mathbf{1. 5}$ bar and led to an increase of breakdown voltages.

The potential of solar energy as a sustainable power source remains hindered by various efficiency limitations. One of the major challenges is the accumulation of dust on photovoltaic (PV) panels, leading to the decrease of the efficiency and the need for regular cleaning. To address this issue, this work aims to explore the use of ionic wind, generated by corona discharge, as an innovative method for dust removal from PV panels. In line with this objective, this paper presents a numerical analysis of electro-hydrodynamic (EHD) air blowers with wire-to-rectangle configurations to harness the potential of ionic wind for cleaning PV panels. The study utilizes 2D models that have undergone experimental validation. The results highlight a parametric analysis, shedding light on how different geometrical parameters influence the performance of the ionic wind air blower and its energetic efficiency.

This study presents a novel actuator design for photovoltaic (PV) panel cleaning using ionic wind generation. The compact design features two electrodes: a high-voltage sawtooth electrode and a grounded electrode with parallel tubes, housed in a 60 cm frame that matches the width of the solar panel. The actuator moves on the panel surface and generates ionic wind through an opening at its base, effectively removing sand dust. We experimentally analysed wind speed and power consumption, investigating the influence of electrode configuration, electrode spacing, inter-tube distance and applied voltage. First, “one factor at a time” experiments identified preliminary ranges for voltage, electrode spacing, and inter-tube distance. Subsequently, a Design of Experiments (DOE) using a central composite design was implemented to develop wind speed and power consumption models. It was found that all three factors had a significant effect on the wind speed, with an optimal configuration achieving nearly 3 m/s at minimal power consumption.

Medium and high voltage gas insulated switchgear (GIS) are key installations in the electrical power transmission and distribution network. The equipment in these substations are insulated with pressurized gas in order to guarantee their proper functioning. This work aims to investigate the performance, in DC, of dry air under non-uniform electric field conditions for medium voltage switchgear applications. Experimental investigations have been carried out to assess the breakdown and the partial discharge inception voltages as function of the electric field non-uniformity and dry air pressures. The experimental work has been compared with numerical study of the breakdown electric field based on streamer criterion using COMSOL Multiphysics numerical software. The results show that the breakdown maximum field decreases as a function of the utilization factor till 0.3, then it stabilizes for weakly non-uniform electric field. The breakdown maximum field is not dependent on the polarity of the DC voltage for utilization factors higher than 0.2. Otherwise, the breakdown maximum field seems to be lower under positive DC voltage for utilization factors under 0.2. Simulation results of the maximum field obtained using the streamer criterion are in good agreement with the experimental partial discharge results.

The performance of outdoor insulators directly affects the reliability of power supply. However, their insulation performance is highly dependent on the environmental factors such as pollution. Evaluating the extent of pollution on insulators is essential for maintaining high power quality standards. This study explores a novel approach to assess the severity of pollution and its impact on insulation integrity of composite insulators, utilizing Electro-Optic (EO) sensor technology for electric field mapping. Given the challenges associated with collecting and analyzing such data during power line inspections, this research seeks to evaluate the feasibility of EO sensor-based diagnostics for preventive maintenance. The objective is to identify and map variations in electric field associated with pollution-induced insulation degradation. Furthermore, this study investigates the distribution of two components of the electric field under different contamination scenarios, taking into account the position of the sensor and the applied voltage. The results demonstrate a significant influence of the pollution deposition on the measured electric field values, highlighting the efficiency of the EO sensor in accurately assessing insulation condition. These findings provide valuable insights for implementing targeted maintenance strategies, ultimately enhancing the longevity and reliability of high-voltage equipment and fortifying resilience within the energy sector.

This paper aims to explore experimentally the effects of geometric parameters on the collection efficiency of submicron particles using a developed filter assembly. The studied parameters include mesh size and fiber diameter of a metallic grid, as well as the number of the grids and the spacing between them. Results indicate that filtration efficiency can be significantly enhanced by reducing mesh size, fiber diameter, and grid spacing. Furthermore, adding more layers of grids can also improve the filter's performance. This investigation highlights the complex relationship between geometric parameters and the filtration efficiency, offering key insights essential for optimizing filter's design and effectiveness.

This paper presents an investigation of superimposed harmonics effects on partial discharge (PD) activity under high voltage direct current (HVDC). Experiments were performed on a positive needle-plane corona and triple point surface discharge configurations, which can be considered as representative of commonly encountered faults in HVDC insulation systems. First, typical PD characteristics like apparent charge and time interval between consecutive discharge events are extracted using Python environment for different cases with and without harmonic content. Three cases for different level of applied voltage are studied: pure DC and DC with superimposed harmonic at two different frequencies. Statistical distribution is also studied to better understand the behaviors of the discharge. Then, Pulse Sequence Analysis (PSA) representations are given to highlight PD patterns that can serve as sensitive markers for different types of defects, regardless of harmonic activity. Results of this study can help understanding the effect of these harmonics on partial discharge activity and offers an opportunity to develop a fault diagnosis method robust to the frequency content of DC voltage.

The aim of the present work is to investigate the efficiency of electro-optic electric field sensor to characterize and detect the partial discharges in medium or high voltage equipment such as air or gas insulated switchgear. Partial discharges (PD) are frequently caused by an increase in the electric field surrounding conductors (metal particles, spikes, etc.) or at the level of cavities and cracks in solid insulators (cables, insulators, etc.). These phenomena cause gas ionization, heating, material physicochemical degradation, electromagnetic disturbances, and, as a result, premature aging of the insulation. Traditional measurement methods based on purely electrical techniques such as HFCT and UHF antennas allow a global measurement of partial discharges in the whole system. This work presents a study of Pockels effect based electro-optical sensors for partial discharge measurement under AC and DC voltage waveforms and compare their signals to those of traditional methods. Having no metallic parts, these sensors offer a local characterization of the discharge based on the induced local electric field variations.

Off-grid electrical energy systems based on renewable energy sources (RESs) have become increasingly popular for their ability to generate low-carbon electricity in remote areas without access to traditional power grids. These systems rely on the effective management of RESs and storage solutions. Designing and sizing these systems can be a complex task, requiring careful consideration of various parameters such as energy demand, solar irradiance, storage capacity of batteries and State of Charge, power management of fuel cells, and hydrogen production and storage. This study presents an adaptive power management tool that facilitates the sizing of energy equipment for standalone low-carbon microgrids. The proposed simulation tool, implemented in Matlab/Simulink, is based on mathematical models for each energy unit and incorporates a specific power management strategy to determine the optimal size of each component in the system. The effectiveness of the tool is illustrated through a case study involving a PV-battery-hydrogen energy system designed to supply electricity to a standalone district. Results show that the developed tool can be a valuable aid for system designers and planners for creating sustainable and reliable off-grid electrical energy systems, as well as for educational and learning activities.

Fast and very fast transient overvoltages generally appear during switching operations within electrical substations. The oscillatory nature of such phenomena with frequencies that can reach several tens of megahertz tends to degrade the lifetime of high voltage equipment such as bushings and transformers, inducing partial discharges activity or breakdown of the insulation system. According to several case studies, bushings are one of the most sensitive parts to such overvoltages, indeed, a failure in a bushing will in most cases lead to a failure of the transformer, often catastrophically. Generating such overvoltages with a very high frequency character and considerable amplitude can be very difficult, moreover, studying the effect of such overvoltages on the insulated bushings is not easy, even experimentally. Therefore, a simulation of the fast transients in the system can be very useful to understand the consequences of such phenomena. In this context, this document aims to propose a model of high voltage capacitive graded oil impregnated paper (OIP) bushing based on a distributed electrical circuit. The equivalent circuit is constructed based on the geometric design and electrical properties of the materials. The model was developed and implemented using Matlab/SimulinkⓇ software, and was validated with experimental measurements based on impedance sweep frequency analysis. The modeling results are in a good agreement with the experimental ones.

High-voltage direct current (HVDC) links are starting to become widely implemented thanks to their interesting advantages such as reduced operation losses, the absence of reactive power, which allows energy transport via underground cables over long distances, and improved power control. The latter advantage is very essential for renewable energy resource integration into power grids. However, a thorough understanding of the behavior of insulation systems for HVDC components is critical so as to ensure a more reliable service. Indeed, the existence of the direct current (DC) voltage in HVDC components may induce surface and space charge accumulation that can stress insulation further or even promote discharge inception and propagation. As such, this work focuses on showcasing the effect of surface charge on streamers that develop on the interface of liquid–solid insulation due to the advent of lightning impulse (LI) voltage in the HVDC link. This study was performed using finite-element-based numerical simulations that include a quasi-electrostatic model for surface charge accumulation and an electrohydrodynamic fluid model for streamer initiation and propagation. The geometry used was point–plane configuration where the high voltage is applied to the needle electrode located above the liquid–solid interface. The obtained results suggest that streamer initiation is affected by both the accumulated surface charge density and polarity. For a positive streamer, an accumulation of positive surface charge increases the discharge inception voltage as a result of a weakening in the electric field, while an accumulation of negative surface charge decreases the discharge inception voltage due to an intensification in the electric field. Moreover, streamer travel distance and velocity are also both shown to be affected by surface charge accumulation.

This paper aims to study a new solar panels cleaning device based on the ionic wind produced by corona discharge plasma. The device comprises a high-voltage electrode composed of a series of parallel sharp needles and a grounded frame electrode. The system is moved using two driven wheels fixed at its extremities, and is placed at a few millimetres above the solar panel surface at. The cleaning operation is done by moving the dust particles from the surface using the ionic wind coming out through a 5 mm-width opening located at the bottom of the device. The study was carried out by measuring the wind velocity and the cleaning efficiency as a function of the device movement speed and the applied voltage level. The results obtained using Algerian Sahara sand dust allowed to obtain an ionic wind velocity of about 2 m/s and a cleaning efficiency that reaches 95% with a consumed power of about 20 W.

High Voltage Direct Current (HVDC) links make it possible to transmit energy for long distances with lower losses. The development of more reliable insulation systems for HVDC components cannot be achieved without understanding the mechanisms of discharge inception and propagation, not only under HVDC constraints, but also under particular conditions such as HVDC superimposed lightning impulse. In this work, the behavior of liquid-solid insulation system under HVDC superimposed lightning impulse is investigated using finite elements based numerical simulation. The simulation combines the quasi-electrostatic model for interface charge accumulation during the DC phase, and the electrohydrodynamic drift-diffusion model for surface discharge propagation during the lightning impulse phase. The results show that the positive charges accumulated on the interface under positive HVDC voltage reduce the electric field intensity in the liquid. As a consequence, it affects the discharge inception and propagation.

Thunder initiated from lightnings can be heard up to tens of kilometers, with an acoustic pressure up to several pascals. In real atmospheric conditions, the generation of acoustic waves is conditioned by the electric energy, which is not measurable. The geometry of the strikes, for example their length and curvature, also has a great influence on the acoustic waveforms. Furthermore, the real atmospheric conditions (temperature, wind direction or intensity), cannot be controlled nor measured extensively. In this communication, a laboratory-scale acoustical characterisation of thunder is performed on a 75 centimeters long lightning strike. Every strike is characterised using a microphone array, and a synchronised optical visualisation to obtain the shape of the discharge channel. A synchronised measurement of electrical parameters (discharge current and instantaneous voltage) is also performed to obtain the energy of the discharge. The waveforms are similar to those measured on smaller sparks, with an N-wave structure. However the electric parameters are well controlled and stable, a large waveform variability is observed 6 meters away from the source, with acoustic peak pressure between 200 and 600 pascals, and arrival times between 16.5 and 17 microseconds. This variability is linked to the observed variability of the discharge channel geometry.