Electrical Circuit Research Articles

ПУТИ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ ЭКСПЛУАТАЦИИ ТРАДИЦИОН-НЫХ И ГИБРИДНЫХ РАСПРЕДЕЛИТЕЛЬНЫХ СЕТЕЙ

The main goals, development methodology and existing problems in distribution networks are con-sidered. It has been established that a promising direction for the development of electrical networks is the introduction of hybrid DC-AC networks, which combine the advantages of AC and DC net-works. Hybrid networks are promising, and already at the design stage, “smart” networks can be cre-ated on their basis, which can facilitate the work of the power system dispatcher, reduce personnel and maintenance costs

Dynamic phasor model of HVDC links for linear analysis of dynamic performance

This paper presents a linearized HVDC link model, which was implemented in PacDyn software and is applicable to dynamic performance studies of power electronic equipment considering electrical network electromagnetic transients, differently from electromechanical studies where the network dynamics is usually neglected. The proposed HVDC model was developed employing equivalent switching functions concepts and dynamic phasors. Simulations and results for small and large-scale test systems are presented. Model validation is performed through comparisons between results obtained by PacDyn and PSCAD. In sequence, there are practical examples of controller tunning considering adverse dynamic interaction mitigation between HVDC Link and electrical grid. The final results on a large-scale model of the Brazilian power system demonstrate that the proposed HVDC model can be used in actual engineering studies.

Использование прогностических регуляторов для улучшения качества процессов управления асинхронизированными гидрогенераторами

The introduction of distributed generation (DG) plants into electric power systems (EPS) requires solving problems related to the development of control systems in normal, emergency and post-emergency modes in order to increase their reliability and stability. Asynchronous generators (ASG), which have advantages over synchronous machines can be used in DG plants. However, their application requires the development of modern automatic control systems (ACS). The article discusses a distribution electric network with DG plants based on ASG. At the same time, special attention is paid to the development of ACS ASG models. The aim of the research was to determine the effects of the use of predictive regulators (PR) for ASG management. For this purpose, modeling of the normal, emergency and post-emergency modes of the electric network was performed, which included two ASGs driven by hydraulic turbines. The third and fifth harmonics were generated in the connection node of the power plant. A three-phase short circuit in a 35 kV network with a duration of one second was considered as a disturbance. The results obtained allowed us to draw the following conclusions: the use of PR improves the quality of electricity. The harmonic coefficients of the voltage are reduced by 7.35 %, and the voltage asymmetry coefficients in the reverse sequence are reduced by 50 %. Predictive frequency regulators of ASG with a fixed forecast time calculated according to the proposed methodology improve the control processes. For example, the duration of the transition process for the first ASG is reduced by a third, and the maximum frequency deviation is reduced by 20 %. The degree of its attenuation increases by 33 %.

Different Demand Response Programs with its Implementation in Various Countries and the Role of TOU DR in the Context of Nepal

With the increasing trend of electricity consumption worldwide, it creates a cumbersome, reliable power system and necessitates the construction of new generator companies, transmission lines, and other infrastructures. Despite investing in new infrastructures to manage occasional peaks, utilities can use the demand response concept to effectively handle demand during such peak time intervals, and in doing so, it enhance the grid stability. This assists in balancing the supply and demand for electricity, making the grid more resilient to fluctuations, and reducing the risk of blackouts. This paper delves into the diverse DR programs across different countries and comparative analysis for finding the suitable DR method to make a more reliable electric power network in Nepal.

Wind energy cost evaluation based on a techno-economic assessment in the Algerian highlands

Wind energy is an important and growing source of renewable energy. It is becoming increasingly integrated into electricity markets around the world. In Algeria in particular, the integration of wind power into the electricity grid is being developed based on a government project to achieve a high penetration rate. In this context, this study is elaborated to analyse the techno-economic assessment of the electrical energy production from four selected wind turbines: Vestas V-80; Suzlon S-82; Enercon E-58 and Gamesa G-114, installed at three sites in the Algerian highlands, namely El Beidh, Sétif and Djelfa. The three highland sites are chosen due to their good wind potential. On the other hand, the Algerian transmission electrical network DZ-114 bus presents some technical problems in the highlands related to low voltage profiles. Therefore, wind farm integration in these three sites can be beneficial as voltage magnitude support. Besides, it can be an important tool to reduce fossil fuel consumption and pollutant gases from conventional plants. Wind potential assessment and economic analysis were carried out for the three selected sites using wind speed data measured 10 m above ground level over 10 years. The results obtained confirm that the Gamesa G114 wind turbine is the most suitable for all the sites and in particular for El Bayadh, as it offers both the highest annual energy production (AEP) and capacity factor (CF) values in all the selected sites and guarantees the lowest unit energy cost (UEC) compared to other types of wind turbines.

Advancing anti-corrosion performance of composite coating: Self-aligned fluorinated graphene for multifunctional electronic packaging

Fluorinated graphene (FG) is considered an ideal filler for polymer nanocomposites to enhance anti-corrosion performance due to its hydrophobicity and electrical insulation properties. A key objective in advanced anti-corrosion design is to create a structure where FG sheets are stacked and aligned, forming an ultra-long, circuitous path to impede the diffusion of active corrosion species. Additionally, integrating aligned FG sheets with polymers prevents the formation of electrical percolation paths, making the coating suitable for electronic passivation. However, achieving a high degree of alignment of FG within the polymer matrix has been a challenge. In this study, we employ a straightforward electrophoretic deposition method to align FG sheets in a polyurethane (PU) matrix for anti-corrosion coatings on copper. The optimized coating exhibits outstanding corrosion resistance for copper, with a stable corrosion rate of 4.0 × 10−3 μm/year in a 3.5 wt% NaCl solution. Moreover, the FG composite coating significantly enhances thermal conductivity, increasing it by 97 % compared to pristine PU, while also providing high electrical resistance. This results in a high breakdown electric field of 28 kV/cm and an extremely low current density of 1.32 × 10−8 A/cm2, which is advantageous for electronic packaging. This multifunctional coating meets industrial standards for large-scale production, uniformity, and controllable thickness, offering a promising approach to improving anti-corrosion protective coatings.

Memristor Effect in Layered Film Structures

Equivalent electrical circuits of multilayer film structures with memristor switching of resistance at interlayer boundaries and at the boundaries of crystal grains in each layer are proposed. Numerical modeling of the current-voltage characteristics of such structures has shown that their loop-shaped form, typical of memristors, is transformed into a linear ohmic dependence of the total current on the magnitude of the applied external voltage as both the number of layers and the number of grains in each layer increase. A certain combination of the number of layers and grains in a layer has been established, at which the maximum total current flowing through the structure and the ratio of resistances in the “off” and “on” states reach the highest values.

Exploring temperature effects on raw polysaccharide in semi-diluted solution using complex conductivity: Correlation analysis of activation energies

The evolution of the complex conductivity of raw polysaccharides extracted from Cystoseira myriophyloides algae exhibited significant temperature dependence in an aqueous solution. An analysis of the complex conductivity versus frequency was conducted using an appropriate electrical circuit based on our theoretical approach. This facilitated the generation of analytical functions representing the relaxation processes occurring at different temperatures. Subsequently, extrapolation and deconvolution procedures were employed to further investigate and identify all relaxation processes and their origins. These approaches revealed the presence of three relaxation processes. The first relaxation, observed at low frequency, is attributed to interfacial polarization between the electrode and the solution. The second and third relaxations, observed at medium and high frequencies, are attributed to bulk relaxation processes. Then, subtracting the low-frequency process clarified the bulk relaxation processes. Both relaxations are described by the Cole-Cole relaxation, which effectively models the well-known Maxwell-Wagner-Sillars (MWS) phenomenon typically observed in polyelectrolyte solutions. This relaxation is typically caused by interfacial polarization between molecular chains and counterions in the sample. Both relaxations were found to be thermally activated. The temperature dependence of useful parameters extracted from each relaxation, such as relaxation time (τσ) and conductivity (σdc) and (σ∞), followed Arrhenius law behavior. Furthermore, activation energy values for each relaxation process were determined, establishing a linear correlation between activation energy values related to relaxation time (τσ) and both conductivities (σdc) and (σ∞). These results confirm the origin of bulk relaxations and demonstrate a strong link between relaxation and conduction mechanisms.

Enhanced Wettability and Adhesive Property of PTFE through Surface Modification with Fluorinated Compounds.

Polytetrafluoroethylene (PTFE) is prized for its unique properties in electrical applications, but its natural hydrophobicity poses challenges as it repels water and can cause electrical short circuits, shortening equipment lifespan. In this work, the mentioned issue has been tackled by using two different fluorinated compounds, such as perfluorooctanoic acid (PFOA)/perfluorooctanol (PFOL), along with plasma processing to enhance the surface hydrophilicity (water attraction) of PTFE. This method, demonstrated on Teflon membrane, quickly transformed their surfaces from hydrophobic to hydrophilic in less than 30 s. The treated films achieved a water contact angle saturation of around 80°, indicating a significant increase in water affinity. High-resolution C 1s X-ray photoelectron spectroscopy (XPS) confirmed the formation of new bonds, such as -COOH and -OH, on the surface, responsible for enhanced hydrophilicity. Extended plasma treatment led to further structural changes, evidenced by increased intensity in infrared (IR) and Raman spectra, particularly sensitive to vibrations associated with the C-F bond. Moreover, Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR) showed the formation of surface-linked functional groups, which contributed to the improved water attraction. These findings decisively show that treatment with fluoro-compound along with plasma processing can be considered as a highly effective and rapid method for converting PTFE surfaces from hydrophobic to hydrophilic, facilitating its broader use in various electrical applications.

Enhancement of the underground cable current capacity by using nano‐dielectrics

AbstractIn most underground power cables, cross‐linked polyethylene (XLPE) is utilized as the main insulating material, while polyvinyl chloride (PVC) is usually used as a nonmetallic sheath or jacketing for the cable. Accordingly, improving the electrical and thermal characteristics of these materials leads to an increase in cable dielectric strength, besides a rise in the current capacity of the underground power cables. Thus, enhancing the thermal characteristics of cable insulation is the goal of many research studies. In this regard, increasing the current capacity of underground power cables is an essential topic for electrical distribution and transmission networks. This usually occurs by increasing the cross‐sectional area of the cable conductor, which means raising the cost of transmitting electrical energy. Another proposed alternative may be to improve the thermal properties of the dielectric material using nanotechnology to allow better dissipation of heat resulting from the cable losses. This article proposes the use of nano‐composite dielectrics to increase the current capacities of underground power cables. Nano‐fillers are used to enhance the thermal and electrical characteristics of XLPE and PVC, which represent cable dielectric materials. Accordingly, in this paper, many experiments are conducted on various nano‐dielectric materials to choose the most appropriate nano‐dielectrics for improving both the thermal and electrical properties. Hence, measurements are performed on the thermal and electrical properties of dielectric nano‐materials manufactured in the laboratory. Further, calculations of the cable's current capacities by the use of the measured properties of nano‐dielectrics are done considering several backfill soils. From the obtained measurements and calculations carried out on cable capacities, it is concluded that the use of XLPE/ZnO 5 wt.% as the insulation and PVC/ZnO 5 wt.% as the jacket material increased the cable current capacity by 6.2% for a cable of 33 kV rating, 9.2% for 66 kV cable, and 15.7% for 220 kV cable when wet clay is used as backfill soil. From the calculations carried out it is found that the use of nano‐composite dielectrics reduces the temperature of the cable components by significant values. For example, the core temperature of the 33 kV cable is reduced by 15.6°C, while for the 66 kV cable, the cable core temperature is decreased by 12.6°C, and for 220 kV the conductor temperature is reduced from 71.3°C to 58.3°C when each cable is loaded by its rating.

Evaluasi Kinerja Sistem Proteksi Penyulang Trawas PT. PLN (PERSERO) ULP Pandaan

The primary objective of this research was to minimize disruptions in the feeder at ULP Pandaan by analyzing the coordination between recloser outgoing and incoming feeders. This study addressed the frequent issue of recloser trips, which caused instability in power supply. The purpose of this research was to provide conclusions and solutions to mitigate these disruptions. The methodology involved a detailed analysis of OCR (Over Current Relay) settings for protective devices on Trawas feeder. This included measurements of primary current settings and TMS (Time Multiplier Setting) values using both standard inverse and normal inverse configurations. Specific settings, such as 25518 A for the Trawas Recloser primary current and a TMS of 0.07, were determined to yield optimal performance. Additional settings for the Outgoing CB (Circuit Breaker) (357061 A, TMS 0.04) and the Incoming CB (181865 A, TMS 1.0) were also established. The important findings revealed that these settings significantly enhanced the reliability of the protective devices, ensuring better coordination between the recloser and CB systems. The implications of this research were substantial, as the optimized settings were expected to reduce the frequency and impact of feeder disruptions. This improvement in system reliability directly benefited both the electricity provider, PT. PLN (Persert), and the consumers by providing a more stable and efficient power supply. In conclusion, this study offered a comprehensive analysis and practical solutions for enhancing the protection system's performance on the Trawas feeder, which could be applied to similar electrical distribution networks to achieve better stability and reliability.

Influence of Ambient Temperature on the Reliability of Overhead LV Power Lines with Bare Conductors

The article presents a study on the influence of weather factors (ambient temperature) on the operational reliability of overhead low-voltage power lines with bare conductors. A method for determining the average failure intensity, average failure duration, average renewal intensity, and failure rate of overhead low-voltage power lines with bare conductors as a function of ambient temperature is presented. Based on many years of observations of power lines operated in electric power distribution networks in Poland, the empirical values of the above-mentioned reliability indicators were determined. An analysis of empirical distribution compliance with the assumed theoretical model was also carried out. The reliability studies conducted showed that the highest failure intensity of the considered power lines occurred at temperatures commonly found in Poland.

Investigation on piezoresistivity of self-sensing cementitious composites containing nano carbon fillers under water content variations

Self-sensing cementitious composites containing nano carbon fillers have extensive application prospects in structural health monitoring (SHM) due to their excellent intrinsic piezoresistivity, good mechanical performances, high compatibility and durability. However, the piezoresistivity is prone to be affected by environmental factors, such as water content. Therefore, it is urgent to study the influence of water content on piezoresistivity to avoid unwanted effect. In the present study, piezoresistivity of self-sensing cementitious composites containing nano carbon fillers under cyclic compression with different water contents is investigated. Moreover, mechanisms are also explored comprehensively. The results indicate that the sensitivity, repeatability and stability of the piezoresistivity deteriorate with decreasing of water content. The maximum FCR and stress/strain sensitivity are decreased from 14.3 % to 4.5 % and 0.72 %·MPa−1/124–0.23 %·MPa−1/39, respectively, when water content decreases from 3.53 % to nearly 0 %. Variation of electrical conductivity pathways and networks caused by enclosed water film on surface of electrical conductive fillers take responsible for the changeable of piezoresistivity with different water content. The outcomes offered validity of self-sensing cementitious composites implementation in SHM withstand variation of water content.

Evaluasi Ketidakseimbangan Beban Pada Penyulang Unicora

Load imbalance in electrical distribution transformers can lead to significant power losses and decreased efficiency in electrical distribution systems. This study focuses on the load imbalance problem at the Unicora feeder of PT PLN (Persero) ULP Singosari, which hinders optimal operational efficiency. The purpose of this research is to evaluate the extent of load imbalance, its impact on power losses, and the effectiveness of load balancing interventions in mitigating these losses. The methodology includes phase load measurements from February to September 2021, analysis of load imbalance, and power loss simulations using ETAP 12.6.0 software. The study's important findings indicate that the average load imbalance decreased from 34% to 21% after implementing load balancing interventions. Concurrently, power losses in the neutral conductor were reduced from 106.3 kW to 78.0 kW. ETAP simulations revealed a total power loss of 773.5 kW in the Unicora feeder, underscoring the significant impact of load imbalance on system efficiency. The implications of this research are crucial for operational practices at PT PLN (Persero) ULP Singosari. The findings demonstrate that effective load balancing can significantly enhance distribution efficiency, reduce operational costs, and improve the reliability of electricity provision. This study advocates for continuous monitoring and adaptive management of load distribution in electrical networks to maintain optimal performance and sustainability.

Evaluation of injection current frequency on molten NaCl solidification images reconstructed by high-temperature electrical resistance tomography

Abstract The injection current frequency has been evaluated on molten NaCl solidification images reconstructed by high-temperature electrical resistance tomography (htERT). The evaluation was performed using an electrical equivalent circuit consisting of an electrical double layer (EDL), bulk solution and current–voltage path (CV path). The EDL and bulk solution are the elements that indicate electrochemical noise and bulk noise due to random thermally excited vibrations of Na+ and Cl–. The CV path compensates for measurement device errors due to the low resistivity of molten NaCl. The molten NaCl solidification images were reconstructed by htERT in an alumina crucible with platinum-wire electrodes under an initial temperature air T 0 = 820 °C and temperature drop rate γ = 6.67 °C min−1. As a result, the solid volume fraction φ of molten NaCl was properly obtained at the appropriate injection current frequency of L f < f < H f , which is determined by the electrical equivalent circuit (EEC) with an EDL, bulk solution and CV path. The EEC was validated by comparing the signal to noise ratio and Nyquist plot obtained experimentally with a resistance error. The best frequency range implemented in htERT for molten NaCl solidification images was determined as L f = 1.4 kHz and H f = 41 kHz.

Backward–forward sweep inverse power flow for distribution line parameters estimation with metering data

AbstractThe transition towards the smart grid requires better information on the electrical networks at the distribution system level. Information about electrical line parameters is a critical part of such information. An algorithm for estimating electric line parameters of medium‐voltage distribution networks is proposed. The algorithm relies upon active/reactive power and nodal voltage magnitude data from advanced metering infrastructure and combines an Ordinary Least Squares estimator with the classical Backward–Forward Sweep load‐flow method to iteratively estimate the admittance parameters of the electrical network components. The algorithm is proposed to be applied to balanced loading situations of networks where zero‐injection non‐monitored nodes may exist. Simulations using the IEEE 33‐bus system are used to demonstrate the effectiveness of the method under different loading situations and measurement noise levels.

Electrochemical Impedance Spectroscopy Analysis of Organic Epoxy Coatings Reinforced with Nano Clay.

Electrochemical impedance spectroscopy (EIS) is a modern and efficient method for the evaluation of the protective abilities of coatings. However, the interpretation of the experimental data is a difficult task. This paper aims to investigate the effect of the addition of a nano clay, Cloesite 30B®, on the barrier properties of an epoxy-based system through electrochemical impedance spectroscopy in an aerated sodium chloride solution. The EIS spectra of the samples analysed showed different evolutions over time. The subsequent processing of spectra using equivalent electrical circuits is an excellent analytical tool and allows the protective capacity of coatings to be assessed. By using this analysis, it was possible to define and comprehend the impact of adding nano clay in different concentrations to the epoxy resin coating. The work has shown the effectiveness of increasing the barrier effect of the coating with this type of nano clay. However, the improvement is linked to obtaining a correct dispersion of nanoparticles. Otherwise, there is the formation of macro-clusters of particles inside the coating. Their appearance can cause a deterioration in coating performance.

Research on Teaching Reform of Fundamental Electric Circuit Experiment in Colleges and Universities

Research on Teaching Reform of Fundamental Electric Circuit Experiment in Colleges and Universities

Complex-valued sensitivity analysis tool aimed to power flow optimization

Abstract In this paper, the use of complex differentiation is presented as a robust and concise tool for modeling and sensitivity analysis of large-scale electrical networks. A complex power flow model was employed to determine the network’s operating point, from which the sensitivity analysis of the electrical system is conducted. The proposed methodology, utilizing complex differentiation, was applied to two systems with data extracted from the MATPOWER software. The obtained results are depicted in a network topology graph, highlighting the identified sensitivities.

Review on Coordination of Time Overcurrent Relays in Electrical Distribution Network

Integration of distributed generators in micro grid causes bidirectional current flow as a result of the need for readjustment of the setting of the overcurrent protective relays in the electrical network. Adaptive coordination is one of the solutions that adjust the setting of protective relays according to the dynamics of the distribution network. Various algorithms had been reported on the adaptive coordination of time overcurrent relays. This paper reports a survey about the coordination of time overcurrent relays in micro grid electrical distribution network. The review found that there is limited research on distributed control rules of the multi agent coordination of protection relays. Furthermore, it was found that the trend of coordination algorithms focused on the nature inspired algorithms.