Amir Hesam Khavari

A Review of Recent Studies on Positive Lightning

Lightning is a natural phenomenon that has much impact on man and man-made systems. Lightning can be generally characterized as either negative return stroke (NRS) or positive return stroke (PRS). PRS have high peak currents and long continuing current that are responsible for more intense damage than negative return strokes. However, PRS are considerably less studied compared to NRS due the complexity and paucity of PRS. This study attempts to provide an overview of the positive lightning characteristic research in recent years. The review is classified into four groups, which are: preliminary breakdown pulse of positive lightning, compact intracloud discharge, positive leader and positive lightning return stroke. In spite of recent progress made in this area, our knowledge on the physics of positive lightning remains considerably poorer than negative lightning. Many questions regarding the characteristic of positive lightning and their properties cannot be answered without further research. It would be of great interest to examine the positive lightning parameters under different meteorological conditions as well.

Techno-Economic Analysis of Stand-Alone Hybrid Energy System for the Electrification of Iran Drilling Oil Rigs

This paper explores the potential of use of stand-alone hybrid wind/solar energy system in electrification of calibrating equipment of drilling oil rig in Iran. To achieve this, different hybrid energy system configurations based on calibration equipment demand are proposed. This study puts emphasis on the energy production and cost of energy from both wind turbine and photovoltaic (PV) in the hybrid system. In addition, to make conditions more realistic, the real meteorological data is used for HOMER software to perform the technical and economic analysis of the hybrid system. Results indicate that the PV array shares more electricity production than the wind turbine generator if both wind turbine and PV array are utilized in the wind/solar hybrid system. Moreover, results show that the operational cost will be reduced by the suggested hybrid system.

An Economic Assessment of Hybrid Renewable Energy for a Remote Area Electrification in Iran

The utilization of renewable resources is growing, in part due to the environmental impacts caused by fossil fuels. The largest sources of renewable energy are wind and solar and many predict that these energy sources will be increasingly used for distributed generation. In this paper, the feasibility is examined of a grid-independent system applied for a remote area electrification in Binalood, Iran. Traditional power systems for remote or rural areas are based on fossil fuels. After addition of renewable energy resources, solar energy applications have become popular in remote energy systems. The recent study and research works show that adding other possible renewable energy resources such as wind, hydro and biomass could make a hybrid system more cost-effective and environmentally friendly. Hence, in the present study, an overview of applied hybrid renewable energy system (HRES) for worldwide villages with special attention on Iran has been proposed to help present and future works for better achievement in this field. Furthermore sensitivity analyses are performed to determine the impact on performance of several key parameters: wind speed and fuel costs. HOMER was used to evaluate the feasibility of various hybrid systems. The results of a comprehensive feasibility data analysis along with its economic evaluation indicate that the wind-diesel hybrid system with battery storage is most efficient energy system for supplying this remote areas electrical energy demands.

Assessment of Series Compensator for Ferroresonance Damping in Power System

Nowadays power quality is a critical issue in power system. Moreover the connection of three-phase transformers through underground cables is growing fast in residential, commercial, industrial and rural applications. Due to this increasing situation, the possibilities of having a series connected capacitance and a non-linear inductance, and hence ferroresonance, become more probable. Ferroresonance can also occur in power transformers or reactors by capacitive coupling from neighbouring phases or lines. It is necessary to have a general idea about what would be the best preventive decisions to take in order to avoid unexpected surprises. It is necessary to have an accurate ferroresonance model so that a device that can smoothen the sharp effects of ferroresonance can be found. In this paper, the FACTS device, namely the static synchronous series compensator (SSSC) had been used to mitigate ferroresonance. Results show that using SSSC dramatically decreases and mitigates the ferroresonance shock as well as the instabilities of the network.

Nonlinear Resonance Suppression as Distorting and Saturating Source in Voltage and Current of Power Transformer: UPFC and STATCOM Performance Evaluation

Non linear resonance usually resonates in network which is consisting of ferromagneticcore. When distributed capacitance calculated form circuit breaker; mainly circuit breaker and cablecapacitance; after switching and opening the network feed apparatus, magnetization current on ferromagnetic core jump to saturation. Duration of ferroresonance is deeply relying on capacitance, and itwill be decaying by disembarking total store energy. Although, ferroresonance commence by switching circuit breaker off; protecting relay and other protecting schemes have no reaction, because thelast protection step for saving a device is a circuit breaker. There is no reported method to mitigatedisruptive phenomenon; which elder publication focus on the explosion of capacitive transformer,melting of power transformer core lamination and arresters problem. This work is tried to dampingferroresonance and reducing devastation effect on the apparatus. While, protecting devices is useless,fault point topology mutating by FACTS to control and decrease this phenomenon. FACTS deviceis settled at the upstream of apparatus to improve power quality, is switched on at initiating momentresonating. Modeling and simulating of ferroresonance are done by the actual value of transformerand other power system related devices extracted by UTM-TNB.

Cloud-to-Ground Lightning in Malaysia: A Review Study

Lightning has been the major cause of power interruptions in Malaysia. Malaysia is located near the equator having approximately 200 thunder days per year. It is known to be among the highest lightning activity country worldwide. TNB as the main power supply utility in Malaysia has made an effort to reduce the power interruptions via installation of Lightning Detection Network (LDN) in 1994. This paper presents the history leading to modern LDN that capture lightning radiation fields at multiple remote sensors. The network has undergone a series of improvement between 2004 and 2009 in response to evolving detection technologies and requirements. Recent analyses on actual performance of the current LDN are also summarized. The paper includes short and long term requirements for improving the lightning measurements needed to address some open scientific questions and fill the needs of emerging applications.

Control of compensation devices by synchronous reference frame and fourier control methods to improve the power quality in a microgrid

The present study used passive filters (PF) and designed Active Power Filters (APFs) with two control methods: synchronous reference frame control and Fourier methods. Studies in the domain of microgrids include distributed generation sources and non-linear loads. Distributed Generation Sources (DGs) include Micro-Turbine (MT) and Fuel Cell (FC), which act as a source of harmonic currents with non-linear loads. To achieve this goal, passive filters are applied to cancel the main harmonics and to provide reactive power, whereas SAPFs are applied to adjust system imbalances and remove the remaining harmonics in the system. The results show that the method can reduce the harmonic disturbances of the system from 24.27% to less than 5%. In addition, this study analyzes how the various control methods operate on active filters. The proposed method has been validated experimentally, and the results are in agreement with the simulation results.

A review of modeling ageing behavior and condition monitoring of zinc Oxide Surge Arrester

The gapless Metal Oxide Surge Arresters (MOSA) have been available in the market for many years. Its primary function is to protect the equipment in the system against various electrical over stresses. A reliable condition monitoring of zinc oxide surge arrester is vital to its performance to ensure the continuity and reliability of power supply. It is known that voltage-current characteristics of zinc oxide varistors become degraded due to a series of stresses. Leakage current of the surge arrester can be increased by any increase of ageing level. This paper presents a review and comparison of various techniques for condition monitoring of MOSA. A comparative analysis is carried out in which the advantages and disadvantages for each technique are assessed. Previous review demonstrates some techniques which are simple in setup and measurement but its accuracy depends on the sensitivity and accuracy of the measuring instruments. Furthermore, moreover, some methods are used to simultaneously record the voltage and leakage current waveforms, but these techniques are usually hard to apply in practice.

Effect of Ambient Temperature Zinc Oxide Surge Arrester Condition Monitoring

Various methods have been developed to monitor surge arrester condition and predict the probable interruption which can be caused by the failure of surge arresters. This paper aims to carry out experimental and simulation work to find the relationship between the aging level, arrester surface temperature and ambient temperature. COMSOL simulation software was used for the modeling of 120kV rated gapless ZnO surge arresters. It is observed from both the simulation analysis and experimental data that the leakage current and temperature increase as a consequence of an increase in the applied voltage across the arrester. The thermal profile of the ZnO surge arrester changes depending on the aging level and the ambient temperature. The surface temperature simulation results compare well with the experimental results, for the case of varying aging levels.

Surge Arrester Leakage Current Analysis by Using Particle Swarm Optimization Technique

Surge arresters, as protective equipment, are used to limit any overvoltage in a power system resulting from various sources. The surge arrester affects from degradation due to the continuous operating voltage system as well as due to repeated lightning current discharge. Therefore, condition monitoring and health diagnostics of surge arresters are a necessary issue. Hence, as a feasible solution, a condition monitoring based on leakage current measurement techniques was selected to tackle the problem of age diagnostics of surge arresters. The Particle Swarm Search Algorithm was introduced as a method for extracting the third harmonic resistive component, Ir3rd, from the total leakage current. To employ this method for extracting Ir3rd, codes were developed in Matlab. The setting of Particle Swarm Search Algorithm was configured for extracting Ir3rd and accuracy of 94% was obtained.