ЗМЕНШЕННЯ ВТРАТ НА КОРОНУ НА ПОВІТРЯНИХ ЛІНІЯХ ЕЛЕКТРОПЕРЕДАВАННЯ ЗА РАХУНОК ВИКОРИСТАННЯ СУЧАСНИХ КОНСТРУКЦІЙ ПРОВОДІВ

The total cavopulmonary connection (TCPC), a palliative correction for congenital defects of the right heart, is based on the corrective technique developed by Fontan and Baudet. Research into the TCPC has primarily focused on reducing power loss through the connection as a means to improve patient longevity and quality of life. The goal of our study is to investigate the efficacy of including a caval offset on the hemodynamics and, ultimately, power loss of a connection. As well, we will quantify the effect of vessel wall compliance on these factors and, in addition, the distribution of hepatic blood to the lungs. We employed a computational fluid dynamic model of blood flow in the TCPC that includes both the non-Newtonian shear thinning characteristics of blood and the nonlinear compliance of vessel tissue. Power loss in the rigid-walled simulations decayed exponentially as caval offset increased. The compliant-walled results, however, showed that after an initial substantial decrease in power loss for offsets up to half the caval diameter, power loss increased slightly again. We also found only minimal mixing in both simulations of all offset models. The increase in power loss beyond an offset of half the caval diameter was due to an increase in the kinetic contribution. Reduced caval flow mixing, on the other hand, was due to the formation of a pressure head in the offset region which acts as a barrier to flow.

The aim was to develop a methodology for selecting an optimal wire grade and cross-section for overhead power lines with a voltage of above 1 kV under intensive development of power grid systems. This aim was solved using the authors’ previously developed methods: selection of an optimal wire grade based on hierarchy analysis and selection of an optimal wire cross-section by optimizing the specific discounted costs during the entire period of construction and operation of overhead power lines. In the present study, these methods are integrated into a single methodology. It is proposed to implement wire inspections prior to the stage of technical and economic calculations, since the necessary data has already been taken into account during the selection of a wire grade and its cross-section. The proposed methodology was tested on a typical example of reconstruction of the Zapadnaya– Davydovka 110 kV overhead line, which creates limitations in the power supply of Primorsky Krai due to insufficient wire capacity and its operation beyond the normative period. SENILEK AT3/C 150/24 wire was selected as a solution for the example under consideration. The application of this wire grade allows not only the overhead line capacity to be increased by 151% without replacing the existing supports, but also active and reactive power losses in the electric network to be reduced by 18.9 and 2.5%, respectively. The proposed methodology enables selection of an optimal grade and cross-section of any wire design, taking the dynamically changing operational conditions of power grid systems into account. The solutions found by the proposed methodology may contribute to a more efficient operation of power lines due to increasing their transmission capacity, reducing the number of used supports, replacing the line wire without replacing supports, decreasing ice formation on wires, and reducing power losses.

High-performance turbomachinery relies on tilting pad journal bearings (TPJBs) for high-speed operation while maintaining acceptable stability margins. However, TPJBs can produce large drag power losses that increase with machine size and surface speed. In a conventional configuration, the unloaded pads will drag on the surface of the shaft while, presumably, having a minimum impact on the bearing dynamic performance. The effects of removing unloaded pads from a TPJB have been studied before, but research has yet to describe the force coefficients of this bearing type. The present work aims to evaluate the effect on dynamic forced performance and power loss of a 4-pad TPJB configured as load on pad (LOP) and having the unloaded pad, opposite to the loaded pad, replaced by a fixed insert with a large clearance. The replacement insert has a significantly larger clearance (∼14.4 × nominal clearance), effectively making this a 3-pad bearing. The original 4-pad bearing was previously tested, hence allowing for an accurate comparison before and after the pad exchange. The experiments include operation at both 6 and 12 krpm (shaft surface speeds of 32 m/s and 64 m/s, respectively) with unit loads equaling 345 kPa, 862 kPa, and 1379 kPa. The bearing is supplied with ISO VG 46 oil (inlet T = 50 °C) and flow equaling 50%, 100%, and 150% of a nominal flow set for the original 4-pad bearing. For the lowest flow (50%) and a unit load of 345 kPa, the modified bearing shows a substantial decrease in drag power loss, ∼24% at 6 krpm and ∼19% at 12 krpm. For the largest supplied flow, however, the drag power loss increases, 15% at most. Higher churning losses within the 3-pad bearing internal cavities produce the power loss increase. On the other hand, the power reduction is always positive and with higher margins when comparing power losses derived from oil temperature rise measurements. The 3-pad bearing shows signs of lubricant starvation due to the large volume created by replacing the unloaded pad with the large clearance fixed pad. Incipient subsynchronous vibrations (SSVs) appeared at 100% nominal flow, at both 6 and 12 krpm and a unit load of 1379 kPa. SSV hash is a common occurrence in bearings supplied with a low flow rate and low loads. During tests with the lowest flow rate, the modified bearing produced very small stiffness (∼75% reduction) and damping (∼57% reduction) coefficients along the unloaded direction, most likely due to lubricant starvation.

The paper investigates the power losses for real distribution networks in harmonic polluted state. Actually, the low voltage (LV) distribution networks supply a significant number of nonlinear consumers which causes a distorted and unbalanced state. A negative effect of these states is represented by the increase of power losses in distribution network elements. Even if the symmetrical sinusoidal state is initially considered for the power losses, in reality this often leads to power lines overloading, especially for the neutral. The method for power losses estimation in LV distribution network in harmonic polluted environment is very difficult to use. The aim of this paper is to present a reasonably accurate approach to evaluate the effects of harmonic currents on power losses for LV distribution networks using fuzzy techniques. Moreover, to highlight the proposed methodology, a study case for a real low voltage distribution network in order to compute the additional power losses due to the distorted state is provided.

The power grid has significant power losses, unstable voltage, and large voltage drops during high demand due to its high resistance. One way to reduce power loss is by strategically placing and sizing Distributed Generation (DG) within the distribution network. However, improper installation of DG can increase power loss. To address this issue, various optimization techniques have been used, but finding the best solution and dealing with complex issues has been challenging. It is important to make efforts to optimally place and size DG in the distribution network to minimize power loss. To this end, a research study aimed to minimize power loss and improve the voltage profile on the DG network using the Whale Optimization Algorithm (WOA) was done. Objective functions were formulated and integrated into WOA, and power flow analysis on the standard IEEE 33-bus and 33-bus Ilorin industrial distribution feeder with and without DG was conducted using the forward and backward sweep distribution load flow algorithm. The optimal size and location of DG for power network loss reduction using sensitivity analysis (SA) and the whale optimization algorithm were determined. The results of the power flow analysis indicated that the total active losses and reactive power losses were reduced to varying extents with the integration of DG using both SA and WOA. The validation results showed that WOA is more efficient and provides high-quality solutions in terms of system loss reduction and best placement for DG in power systems compared to the application of SA. Additionally, WOA was found to offer accurate and high-quality solutions for power loss reduction compared to other existing techniques such as Loss Sensitivity Analysis (LSA), Grey Wolf Optimizer (GWO), Adaptive Shuffled Frogs Leaping Algorithm (ASFLA), and One Rank Cuckoo Search Algorithm (ORCSA). Keywords: Optimization, Distributed Generation (DG), Whale Optimization Algorithm (WOA), Sensitivity Analysis (SA)

This work presents a sensibility analysis for the journal bearings of combustion engines mass balancing systems. Applying it, it’s possible to improve the journal bearings and avoid possible failures. This analysis consists on studying the effects of the variation of the journal bearings main parameters (radial clearance, journal bearing diameter and journal bearing length) on the journal bearings operating conditions (minimum film thickness, maximum pressure and power loss). The analysis also includes the comparison and selection of the different metallic materials that can be used in these journal bearings, as well as the selection of the lubrication system groove suitable for the journal bearings used in this kind of application. This sensibility analysis shows that: increasing the radial clearance the minimum film thickness increases, the maximum pressure remains approximately the same and the power loss decreases; increasing the journal bearing length, the minimum film thickness and power loss increase and the maximum pressure decreases; increasing the journal bearing diameter, the minimum film thickness and power loss increase and the maximum pressure decreases. At last, it’s found that the white metals (Babbitts) are considered the most advantageous and indicated materials for these journal bearings, and that the lubrication system grooves should be circumferential.

Performance of the systems equipped with PWM inverters can be improved through increasing frequency of switching. However, frequency improvement made some troubles in the system such as electromagnetic interactions or interferences (EMI) and increased power loss. Generally in the inverters working based on PWM method, the losses of switching are so high, where the load is induction. But, in the presented method, it is possible to minimize the switching losses. In this investigation, by adding Snubber circuit in the driver circuit, switching losses significantly reduced. The results obtained from simulation showed that soft switching inverter is more efficient than hard switching inverter in terms of reduction of switching losses.

In recent years, electric vehicles (EVs) have been a countermeasure to the serious carbon emission problem in the transportation sector. However, despite being one of the essential infrastructures in the EV ecosystem, the EV charging load causes voltage instability and increases power losses in the distribution network. Thus, this paper proposed optimizing distribution network reconfiguration (DNR) to solve the problem. The best two metaheuristic methods, Cuckoo Search Algorithm (CSA) and Particle Swarm Optimization (PSO) were compared to get the optimum solution. It was tested on the IEEE 33-bus system in the MATLAB environment with various cases of charging activity. As a result, the CSA showed better consistency with better power loss reduction and voltage stability compared to PSO.

This paper presents performance analysis of high voltage transmission line disc insulators installed on 220 KV and 500 KV transmission line towers in highly contaminated and thus polluted southern coastal areas of Pakistan. This study is based on case studies carried out on three 500 KV transmission lines and two 220 KV transmission lines to investigate the effects of Room-Temperature Vulcanized (RTV) Silicon Coating on disc insulators in mitigating tripping and power outages resulting from pollution flashover. The flashover inhering from atmosphere in high voltage disc insulators on high power transmission lines is a major bottleneck in smooth power evacuation of electrical power. The improving behavior of transmission lines resulting in reduced tripping and reduced maintenance cost in terms of lesser power outages in the aftermath of replacement of faulty and poor condition disc insulators is also studied and results are concluded. Mitigation of frequent tripping and power outages occurring from flashovers due to environmental constraints is possible by either employing Room-Temperature Vulcanized Silicon and Polymer Coating of disc insulators or replacing poor quality disc insulators with good quality disc insulators.

Severe harmonics propagation in power systems may result in increased power losses and equipment damages. In this paper, an elliptic formula is derived to analyse the harmonic spatial distribution not only at the substations but also along the power lines or cables and to give a system‐wide overview of harmonic levels. It is observed that harmonic distortion along power lines can be higher than that at the busbars and the maximum amplitude of harmonic voltage and current denoted as weak positions along power lines depends on the steady‐state harmonic angle difference of voltage and current at busbars, the length of power lines, and the harmonic order. All cases are modelled in detail by analytical geometry and analysed in MATLAB. In this regard, a method to identify the weak positions in terms of maximum harmonic levels in a power system is presented, and its corresponding harmonic orders are determined. The accuracy of the model is tested using time‐domain simulations in PSCAD/EMTDC.

The continuous increase in power demand and huge power losses in modern power systems have been a growing concern to power utilities. Such phenomenon often results in epileptic power supply, power system instability, supply fluctuations and security problems in many parts of the globe. Identification of suitable places for the installation of reactive power compensators to minimize voltage drop and system power losses in a power system becomes imperative. In this paper, the Newton-Raphson iterative method was used for the power flow solution of the 28 bus Nigerian 330KV grid system. The Generalized Unified Power flow Controller (GUPFC) is installed at identified weak load buses of the Nigerian 28-bus power system to reduce the losses and voltage drop of the system. A comparative analysis of the GUPFC with Load Tap Changing Transformers (LTCT) is also performed. Result obtained shows that the GUPFC can largely (effectively) improve the system power stability and selectively balance the power flow of multi-lines power flows when placed at identified weak buses compared with LTCT. Thus, GUPFC can be used to reduce overall power losses along transmission lines as well as improve stability overall reliability of the power grid system.

Optimization for position and rating of distributed generating units using bacteria foraging algorithm to reduce power losses

The current research has evaluated the effects of cylinder injection signal override technology in internal combustion engines on cylinder liner conditions, friction forces, power losses, and fuel economy. For the development of the research, a mathematical model has been built to describe the tribological behavior between the cylinder liner and the compression ring. The results have showed that the cylinder injection signal override technology leads to a 14.3% increase in the maximum pressure in the cylinder chamber, a 9.2% increase in the cylinder liner temperature, and a 13.6% reduction in the lubrication thickness for the cylinders that remain active. Additionally, a 23.2% and 34.4% increase in power losses associated with friction force and exhaust leakage is evident. Despite the above, cylinder injection signal override allows a 16.9% decrease in engine fuel consumption, which reduces engine operating costs. In general, cylinder injection signal override technology presents a benefit for decreasing engine fuel consumption. However, it is necessary to consider the loss of power and additional wear caused by the engine components.

Energy storage system (ESS) can solve the problems of nodal voltage fluctuation and increase power loss in distribution network caused by high penetration of renewable energy. This paper takes the nodal voltage fluctuation and comprehensive multi-cost of ESS as the composite optimization objective, and combines multiple constraints to establish an energy storage configuration optimization model of the wind-solar-energy storage hybrid distribution network. Based on the optimization model, an improved multi-objective particle swarm optimizer (IMOPSO) is introduced to solve the problem. IMOPSO avoids the particle swarm from falling into the local optimal solution while considering the convergence speed and accuracy. Finally, through analysis of the IEEE-33 node distribution network system, the rationality of the proposed ESS configuration optimization model and the IMOPSO are verified, which can effectively reduce the nodal voltage fluctuation and power loss of the distribution network, and improve the system economy at the same time.

Patients with interrupted inferior vena cava (I-IVC) and azygos continuation who undergo Fontan completion via hepatoazygos shunting exhibit unique hemodynamic challenges. This study evaluates age-related shifts in systemic venous return dominance, hepatic flow distribution (HFD), power loss (PL), and flow disturbances using patient-specific computational fluid dynamics (CFD). Data analysis from 95 patients with I-IVC showed a nonlinear shift in upper-to-lower body systemic flow dominance with ratios of 2, 1, and 0.5 (correlating to ages ∼3, ∼10, and ∼20, respectively). CFD simulations for 17 selected patients revealed a trend of increasing HFD toward the right pulmonary artery, with median splits of 45%-49%, 48%-52%, and 40%-60% for the respective flow ratios. Power loss increased significantly with lower-body flow dominance. Median values for absolute PL were 4.75 mW (ratio 2), 16.5 mW (ratio 1), and 33.7 mW (ratio 0.5). Indexed PL showed a similar trend, rising from 0.04 mW/m2 to 0.11 mW/m2 across the flow ratios. Vorticity and viscous dissipation rates, key metrics of flow disturbances, also increased with lower-body flow dominance, showing strong correlations with PL (R = 0.58-0.76). Kruskal-Wallis-based statistical analysis identified significant statistical differences in absolute PL (P = 0.0045) and flow disturbances (P < 0.001), emphasizing the impact of age-related flow dynamics on Fontan efficiency. Our findings emphasize the need for targeted interventions in patients with I-IVC with azygos continuation to mitigate evolving hemodynamic inefficiencies and optimize Fontan outcomes during critical growth periods.NEW & NOTEWORTHY Evaluate how age-driven changes in patients with interrupted inferior vena cava impact Fontan efficiency. Using patient-specific computational fluid dynamics, our study reveals nonlinear flow dynamics, increasing power loss, and evolving hepatic flow distribution, emphasizing the need for tailored interventions to optimize outcomes.