Performance evaluation of multiple-beam free space optics in tropical rainy weather

Free space optics (FSO) has the potential to replace optical fiber as a solution for the last mile problem. FSO is favored because of its cheap maintenance costs and quick deployment time as compared to other communication system such as fiber optics. Atmospheric attenuation is a problem for FSOs with classic single beam systems, especially when it rains heavily specially in tropical region like Malaysia. As a result, a multibeam FSO transceiver system has become popular as a solution to this problem. The purpose of this study is to compare the standard single beam FSO system with the suggested multibeam FSO system. At a bit error rate (BER) of 10-9, the comparison is made in terms of received optical power, channel distance, and geometrical losses. Rain intensity data is gathered over a six-month period. To evaluate the performance of both systems, the average rain attenuation is calculated from this data and exposed to single beam and multibeam FSO systems. The multibeam FSO approach was found to increase the system's performance. The results show that employing up to four beams improves the quality of received power and increases the channel distance to 1150 m when compared to a single beam FSO system with a channel distance of only 830 m

Investigation of high voltage polymeric insulators performance under wet pollution

In this paper, a unique approach based on electrical characteristics observed from measurements of contaminated polymeric insulators was established to calculate the electric field distribution over their surfaces. A case study using two different 33 kV polymeric insulator geometric profiles was performed to highlight the benefits of the proposed modeling approach. The conductance of the pollution layer was tested to establish a nonlinear field-dependent conductivity for pollution modeling. The leakage current (LC) of the polluted insulator was measured in a laboratory under clean and wet conditions. Then, using the finite element method (FEM), the electric field and current density distributions along the insulator were computed. The results showed that the insulators experienced an increase in the electric field (EF) magnitude ranging from 0.3 kV/cm to 3.6 kV/cm for the insulator with similar sheds (type I) and 2.2–4.5 kV/cm for the insulator with alternating sheds (big and small, type II) under the high rain condition with a flow rate of 9 L/h. Meanwhile, the highest electric field under fog was 1.74 kV/cm for the insulator with similar sheds and 2.32 kV/cm for an insulator with alternating sheds. Due to the larger diameter on the big shed and the longer leakage distance on the insulator with alternating sheds, the EF on the insulator with alternating sheds is higher than the EF on the insulator with similar sheds. The proposed modeling and simulation provided a detailed field condition estimation around the insulators. This is critical for forecasting the emergence of dry bands and the commencement of flashover on the surfaces of the insulators

Pollution flashover characteristics of coated insulators under different profiles of coating damage

Based on experiments and numerical analysis techniques, this paper aims to investigate the influence of the four different coating damage profiles on the performance of coated 33 kV porcelain insulator strings under polluted and clean surface conditions. The performance of the insulators coated with room temperature vulcanizing (RTV) under partial coating damage and undamaged coating was evaluated. The influence of humidity on pollution flashover was taken into consideration. The ring-shaped, fan-shaped, and random-shaped coating was applied following coating damage. The results showed that the flashover characteristic of the RTV-coated insulators had a significant difference as compared to the normal insulators. Electrical characteristics such as the flashover voltage, critical current, and surface resistance were significantly affected by coating damage distribution and humidity level on the insulators’ surface. The electric field and potential difference were analyzed as well using the finite element method (FEM). The initiation of the arc was observed to appear at the area of insulators where the electric field was the highest. It was also observed that different coating distributions of pollution and humidity levels resulted in a change in the surface pollution layer resistance and an uneven distribution of the electric field. This indicates that the coated insulators’ parameters are directly related to the coating damage distribution on the insulator surface, particularly in the presence of humidity

Lighting system for camera barcode detector

Lighting control system for Camera based barcode reader is a system that automatically controls the illumination of the barcode lighting device by sensing the light intensity reflected off the barcode. Automatic light sensing, comparing the intensity level and illumination control have been developed in order to reduce light reflection from the barcodes. In this project, microcontroller is used to implement the light control strategies such as turn on or off the number of LEDs automatically and thus controls the brightness of the light source. The system has been designed in such a way that, it can capture the barcodes and process them perfectly under different lighting conditions. The different lighting conditions are produced by barcodes printed on different objects such as shiny covers, plastic wraps, round shaped bottle etc. The camera lens is used to detect the light intensity and to send the correct signal to microcontroller to perform the suitable actions. Thus, it reduced the use of extra sensor circuit for light sensing. A digital to analog convertor is used to convert the binary codes into analog voltages. This voltage is supplied to the power circuit for controlling the light intensity. The microcontroller is pre-programmed to do this task efficiently. Finally, some laboratory experiments have been conducted to validate the efficiency of the control circuit

Millimeter-wave propagation measurements and models at 28 GHz and 38 GHz in a dining room for 5G wireless networks

To meet 5G requirements, industries are looking forward to a new set of frequency allocation in the millimeter spectrum space, where there is huge amount of bandwidth for wireless gigabit communications. In this paper, the statistics of large-scale path loss and time dispersion parameters are investigated based on ultra-wideband measurements using a steerable directional horn antenna at transmitter (Tx) and omni-directional antenna at the receiver (Rx). The measurement was conducted in a dining room line-of-sight (LOS) scenario, which represents a typical closed-plan for in-building communication. The single-frequency, multi-frequency directional and omni-directional large-scale path loss models are evaluated at 28 GHz and 38 GHz bands based on data acquired from unique Tx and Rx antennas with combination pointing angles. The results show that the large-scale path loss models for indoor propagation developed in this paper is less complex, and yet more physically-based than those used in the third-generation partnership project (3GPP) systems, which involve additional model parameters but yield less accurate results. The time dispersion statistics for mmWave systems using directional antennas and omni-omni antennas configuration at both Tx and Rx are presented for co-polarization scenarios. We show that the multipath root mean square delay spread can be reduced when Tx and Rx antenna are pointed to each other, which results in the strongest received power

A survey of Free Space Optics (FSO) communication systems, links, and networks

The next generation (NG) optical technologies will unveil certain unique features, namely ultra-high data rate, broadband multiple services, scalable bandwidth, and flexible communications for manifold end-users. Among the optical technologies, free space optical (FSO) technology is a key element to achieve free space data transmission according to the requirements of the future technologies, which is due to its cost effective, easy deployment, high bandwidth enabler, and high secured. In this article, we give the overview of the recent progress on FSO technology and the factors that will lead the technology towards ubiquitous application. As part of the review, we provided fundamental concepts across all types of FSO system, including system architecture comprising of single beam and multiple beams. The review is further expanded into the investigation of rain and haze effects toward FSO signal propagation. The final objective that we cover is the scalability of an FSO network via the implementations of hybrid multi-beam FSO system with wavelength division multiplexing (WDM) technology

Interactions of implanted dopants and the metal/Si system: fundamental aspects and applications of ion beam mixing and dopant redistribution

SIGLEKULeuven Campusbibliotheek Exacte Wetenschappen / UCL - Université Catholique de LouvainBEBelgiu

Pollution flashover under different contamination profiles on high voltage insulator: Numerical and experiment investigation

This work aimed to study the influence of contamination profiles and humidity on flashover electrical characteristics of polluted insulators. Firstly, the flashover tests on cap and pin glass insulators under four pollution levels represented by salinity were conducted. Eight artificial contamination profiles based on the solid layer method have been modeled for the selected insulators. The numerical analysis has been used to determine the insulator electrical characteristics such as potential, electric field, and power dissipation under proposed contamination profiles using finite element methods (FEM). Next, the power dissipation has been simulated with consideration of thermal stress propagation in locations with high power. Finally, flashover voltage gradient tests have been conducted under various humidity and contamination profiles. The values of the flashover voltage gradient due to pollution were determined as the percentage of the value of the flashover voltage gradient in the clean condition which was identified as the reference point. The numerical model indicated that the initiation of arc generally occurs at area in which the electric field and power dissipation is maximum. It was also observed from experimental results that the flashover voltage gradient under different contamination profiles has different values depends on the location and dimension of the pollution region

Investigating and Modeling Ageing Effects on Polymeric Insulator Electrical Properties

Polymeric insulators, in particular silicone rubber (SIR) are lightweight, have good hydrophobicity characteristics, and are easy to carry and install. They are commonly used for outdoor insulation in power lines. However, pollution, UV radiation, temperature, discharge, wetness, and stress can cause them to degrade over time, losing their electrical properties. Therefore, evaluating the ageing and degradation of polymeric insulators under different conditions becomes crucial. This paper investigates the ageing effects of the polymeric insulators with differences in pollution, applied voltage, hydrophobicity class, and geometrical structures of insulators. The investigation includes the experimental tests of the insulators’ electrical properties such as leakage current and flashover voltage, after assessing the initial characteristics of insulators based on their age and supply voltage. In addition, the aged polymeric insulator model based on an equivalent circuit model was developed to determine the leakage current and breakdown voltage of aged insulators. Moreover, an artificial neural network model is carried out to predict the critical leakage current and flashover voltage of the insulator under the ageing effect. The experiment results were used to validate the accuracy of the proposed models; with an aggregate error of less than 10%, the proposed models appeared to be satisfactory. These models can serve as a scholarly resource for designing, operating, and maintaining insulators, especially in polluted environments

Sensorless microcontroller-based zero-crossing detection system for AC signals using a rounding function

Microcontroller-based methods for zero-crossing detection (ZCD) presented in the literature employ external integrated circuits (ICs) to sense electrical signals, and their algorithms are sophisticated. Therefore, this paper proposes a simple open-loop sensorless microcontroller-based algorithm for determining zero-crossing (ZC) instants of sinusoidal signals that can be used for phase detection (PD) in phase-locked loops (PLLs). The proposed algorithm employs a built-in rounding function in the Arduino software environment. The developed system was simulated using MATLAB Simulink® to demonstrate its prominent features in recognizing zero-crossing points in two cases: a pure sine signal at a grid frequency of 50 Hz, and distorted signals with total harmonic distortions (THDs) of 10 %, 20 %, 30 %, and 40 %. In the simulation, the proposed system exhibited outstanding results in terms of simplicity, accuracy, and robustness. However, in practice, accuracy and robustness are relative terms, because they depend on the specifications of the microcontroller board. In this study, a low-cost microcontroller board, Arduino Uno, was used. The Uno is an 8-bit board with a 16-MHz clock speed. Therefore, an error in terms of the phase shift emerged in the output signal, which was measured to be 0.0314 rad at 50 Hz. Moreover, the proposed system detected the ZC points of distorted signals with a THD of up to 30 % without using filters and failed at a THD of 40 %. Finally, the ZC points were identified in a three-phase system, and the validity of applying the proposed method to polyphase systems was demonstrated