Engineering
Ebadollah Amouzad Mahdiraji
Abstract
Corona electric discharge phenomenon occurs when the electric field intensity exceeds the corona threshold. In the analysis of this paper, three types of hypotheses of partial charge (electrons, positive ions, negative ions) generated in the air due to corona electrical discharge are considered. The ...
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Corona electric discharge phenomenon occurs when the electric field intensity exceeds the corona threshold. In the analysis of this paper, three types of hypotheses of partial charge (electrons, positive ions, negative ions) generated in the air due to corona electrical discharge are considered. The physical process is produced along with the changes and dynamics of the electric charge applied to the field by the charge movement which has velocity due to electric fields and motion due to slope (diffusion) and we will also see losses in electric charge. In this paper, electric load evaluation on a polymer surface by a positive impact corona in the air was performed. Output (circuit current) and input (electric fields and electric charge space density) are considered in computer simulation analysis. Different models have been used to identify the corona, depending on the intensity and extent of the voltage surges. The dynamics and distribution of electric charges and electric fields are analyzed and compared by two models of corona charging (glow and burst impulse).
Engineering
Reza Kolbadinezhad; Ebadollah Amouzad Mahdiraji
Abstract
Due to the accelerated trend of transferring most of the activities to contracting companies, the rate of indicators related to occupational accidents has grown alarmingly and has led to the discussion of evaluating and selecting construction contractors in terms of health. Safety and the environment ...
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Due to the accelerated trend of transferring most of the activities to contracting companies, the rate of indicators related to occupational accidents has grown alarmingly and has led to the discussion of evaluating and selecting construction contractors in terms of health. Safety and the environment are of paramount importance. The presented model was performed by analyzing quantitative studies as well as completing a specific questionnaire and field surveys, and the sample size was determined to be 252 with a 95% confidence level and a 5% error probability. The test method was performed using Cameo and Bartlett test and confirmatory factor analysis. The results of the present study indicate that the highest intensity of impact is related to the human resources criterion and the lowest intensity is related to the planning criterion. The proposed model can meet the growing need of organizations for a comprehensive model of evaluation and selection of contractors.
Engineering
Ebadollah Amouzad Mahdiraji; Reza Kolbadinezhad
Abstract
This study aimed to investigate the status of the establishment of occupational safety and health management system and environmental management system on environmental factors and employee satisfaction. This paper was a quasi-experimental study of before and after type that was conducted in 2012 in ...
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This study aimed to investigate the status of the establishment of occupational safety and health management system and environmental management system on environmental factors and employee satisfaction. This paper was a quasi-experimental study of before and after type that was conducted in 2012 in Milad Industrial Complex based on the results of measuring occupational and environmental pollutants. Data collection was structured through a form and a questionnaire. The validity of the questionnaire was confirmed by content validity and reliability by Cronbach's alpha (r = 81%). The statistical population of the study using Cochran's formula (α = 95%) consisted of 100 employees by random sampling method. After the installation of the systems, the average sound intensity decreased from 54.79 dB to 72.51 dB, the percentage of stations with the allowable light intensity increased from 8.30% to 4.70% and the number of gases and vapors Decreased from 14.2 to 11.4 mg/m3. In the evaluation of the number of suspended particles, carbon monoxide was reduced from 0.143 to 0.062, and carbon dioxide from 0.28 to 7.49 and was within the standard range. Employees' satisfaction analysis of the environmental conditions showed that the majority of employees in the statistical community (88.7%) are satisfied. The simulation results show that with the establishment of occupational safety and health management systems, environmental factors in the organization are controlled and with the improvement of environmental conditions, employee satisfaction increases and individual and organizational performance improves.
Engineering
Reza Kolbadinezhad; Ebadollah Amouzad Mahdiraji
Abstract
Exposure to dust in the air is one of the most common environmental hazards in workshops that can have devastating effects on health. In this study, workers' exposure to particles in inhaled air by conventional methods as well as GIS has been investigated. The research was performed cross-sectionally-analytically ...
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Exposure to dust in the air is one of the most common environmental hazards in workshops that can have devastating effects on health. In this study, workers' exposure to particles in inhaled air by conventional methods as well as GIS has been investigated. The research was performed cross-sectionally-analytically and the sample size was determined through homogeneous exposure groups and environmental and individual exposure was performed based on standard methods and individual and environmental sampling methods. The obtained data were analyzed using GIS software to determine the distribution maps. In this paper, the mean concentration of exposure to dust for each individual in the matched exposure groups was 8.361 mg/m. The highest level of individual exposure was estimated in the powder operator with a value of 21313 mg/m3 and the lowest in the fine wire emperor with a value of 1.97 mg/m3. The minimum environmental concentration in the cutting hall was 0.305 mg/m and the maximum value was 22 mg/m3 in the powder hall. The results of the evaluation with AIHA criteria in all methods showed that weaving, material, and packaging halls have the highest concentration and cutting halls have the lowest dust concentration. Comparison with the GIS method showed that powdering, materializing, and packing halls have the highest concentration and cutting halls have the lowest dust concentration. Comparison with the GIS method showed that in this method, more people are classified in the risk area.
Engineering
Ebadollah Amouzad Mahdiraji; Mojtaba Sedghi Amiri
Abstract
Nowadays, to involve wind turbines in controlling the network frequency, drop and inertia control methods are usually used for variable speed wind turbines. Adjusting the benefits of droop and inertia control loops is very effective on the performance of wind turbines, but due to the variability of wind ...
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Nowadays, to involve wind turbines in controlling the network frequency, drop and inertia control methods are usually used for variable speed wind turbines. Adjusting the benefits of droop and inertia control loops is very effective on the performance of wind turbines, but due to the variability of wind speed and network conditions, adjusting the control coefficients that produce the best response in all conditions is impossible. In this paper, a new method for the comparative regulation of the gain of the droplet control loops and the inertia of the doubly-fed induction generator (DFIG) is presented. Also, due to the relief of problems and shortcomings of wind turbine and network modeling, the use of a data-driven method, which operates only on the input and output of the system, has been proposed. In the new idea presented for faster control and prevention of sharp frequency droop, new equations have been calculated to update the coefficients of the control loops using the second fault derivative, which is used in the comparative adjustment of the gain of the droop and inertia control loops. In the proposed control method, the next instantaneous output is first estimated using KVNN and then the coefficients of the frequency control loops are adjusted adaptively using the Hessian matrix. The simulation results for a DFIG wind farm show the proper performance of an adaptive method based on data-driven control in increasing the minimum frequency and improving the network frequency in a permanent and transient state when a fault occurs.
Engineering
Mojtaba Sedghi Amiri; Ebadollah Amouzad Mahdiraji
Abstract
One of the most commonly used equipment in the power system, which is exposed to various types of faults for various reasons, is high and low voltage pressure cables. Due to the fact that cables, either power or distribution cables are mostly transported from underground, despite their further reliability ...
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One of the most commonly used equipment in the power system, which is exposed to various types of faults for various reasons, is high and low voltage pressure cables. Due to the fact that cables, either power or distribution cables are mostly transported from underground, despite their further reliability in airway, they are more difficult to repair and possibly replace in case of fault, in line with this the correct fault detection and location of them is of utmost important. In this paper, as is clear from the title of the research, the Fourier transform and Modal transform methods are used to find the type and location of faults, so that the efficiency of the selected method for detecting and locating the faults in underground transmission cables is examined and the speed and accuracy of finding a solution to the problem is assessed. In this paper, it is expected that the Fourier transform method, followed by the Modal transform has substantial speed and accuracy in determining the type and location of the faults. Meanwhile, the detection and location indicators are used to determine the type and location of the fault, which as shown in the simulations, will have efficient performance. The sample model is simulated to demonstrate the correctness of these methods. The simulation results from MATLAB and EMTP/ATP software confirm the precise and rapid performance of the proposed method.
Engineering
Ebadollah Amouzad Mahdiraji
Abstract
In general, the stability of the power system can be considered a feature of the system that enables it to remain in equilibrium under normal conditions and regain a different acceptable state if affected by disturbance. Instability in a power system may take many forms, depending on the composition ...
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In general, the stability of the power system can be considered a feature of the system that enables it to remain in equilibrium under normal conditions and regain a different acceptable state if affected by disturbance. Instability in a power system may take many forms, depending on the composition of the system and its operating modes. In order to evaluate the proposed method in damping transient fluctuations and network stability, a study has been carried out on a typical network. Since the topic of the article is in the field of transient stability, in part of the paper, braking resistance modeling in transient stability studies has been investigated. In the section on brake resistor control, brake resistor control is introduced by a switched Thyristor, using the trapezoidal method. Finally, the simulation results of the studied network are presented with the presence of TCBR and its capability of damping in the desired network.