Integration of Frequency Dependent Soil Electrical Properties in Grounding Electrode Circuit Model

The effect of frequency dependent soil properties on the impedance and transient response of the grounding electrode was investigated. The frequency dependent soil models as proposed by Scott, Smith-Longmire, and Visacro-Alipio were critically reviewed. A novel method was proposed to integrate the frequency dependent soil electrical properties in the circuit model of grounding electrode. To validate the application of the method in circuit model, the voltage responses of the grounding electrode obtained by the circuit and electromagnetic models were compared. The voltage responses obtained by the circuit and electromagnetic models were in excellent agreement in terms of voltage peaks and wave shapes. The differences between voltage peaks obtained by the circuit and electromagnetic models were found less than 1%

Lightning generated electric field over land and sea at Northern Region of Peninsular Malaysia: Measuring Setup

Lightning is the transfer of significant charge between two charged object, it can appear between cloud-to-cloud, cloud-to-air and cloud-to-ground. All lightning activities are correlated with charge movement and therefore, it can be studied using measurement of electrostatic field (slow field changes), radiation field (fast field changes) and magnetic field affiliated with charge movement. The measuring equipment was a parallel flat plate and vertical whip antenna with an analog filter buffer circuit, connected to a digital high speed oscilloscope. In principle, both antenna have a similar measuring operation, with the exclusion of the antennas dimension, mode of transient recoder and the association of circuitry characteristic (decay time constant). This measurement setup are commonly used to perform electric field characterization related to various lightning events such as as preliminary breakdown, stepped leader, return stroke, subsequent return stroke, dart leader, dart-stepped leader, narrow bipolar pulses and cloud activity between strokes, such as regular pulse trains, K and M changes and chaotic pulse trains. The measurement systems are located very close to the sea, with respect in obtaining a perspicuous explaination of lightning propagation effects on sea instead on land. Noise-distorted effects in data captured usually introduce in a noisy environment or when the lightning strike far from the measurement station, thus the data gathered from the measurement need to be filter using MATLAB computer simulation before conducting further analysis. A promising wavelet 1-D technique, then, were used in signal denoising process rather using conventional filtration. In this works, the state of art in measuring vertical component of electric field focalized sea area during the thunderstorm days been demonstrate and explained

Review on Feasibility of Gravity Power Generation Mechanism in Malaysia's Sustainable Energy Program

Malaysia being an oil-producing country has a vast amount of other natural resources that has not been used efficiently. In regard to focusing more in producing oil and gas, natural resources such as sunlight, water, wind, geothermal and gravity have not received a huge recognition by the government. Although hydroelectric power has been up and coming in the energy policies to promote power production in a sustainable way, other means of gravity power generation mechanism were not reviewed for this country, due to the lack of knowledge in this particular field. Gravity power generation mechanism can be of small scale which can actually fit in properly in areas that are off-the-grid. Hence, literature must be reviewed to discover the different type of gravity power generation mechanisms and run viability studies to implement the right system that offers sustainable energy production in rural parts of Malaysia. This review paper will analyze the feasibility of two systems in Malaysia, by assessing the viability of these system through the Malaysian economic, social, environmental, and sustainable standards. &nbsp

Power transmission lines electromagnetic pollution with consideration of soil resistivity

The alternating current (AC) total interference of power lines may pose a threat to personnel and equipment in its vicinity. The main objective of this work is to determine the electromagnetic distribution and induced voltages on human body, equipment, and houses due to the AC total interference for different soil resistivities. The electromagnetic field and induced voltages may cause health problems to the human body and put it at risk. Two main approaches were used to compute the electromagnetic and induced voltages, namely the field approach, which is based on electromagnetic field distribution, and the circuit approach, which uses the circuit grounding analysis to compute the conductive interference and then uses the circuit based models to compute the inductive interference. Human body, steel houses and 10-km-long transmission line were modelled. The soil resistivity was varied, and the induced voltages obtained from both approaches were compared. Soil resistivity and soil structure are important parameters that affect the AC interference level. The results show that the touch voltage increases when the distance between electromagnetic source and human body increases. For high soil resistivity, the danger of the touch voltage becomes more prominent compared to that for low soil resistivity. Power system voltage level and soil resistivity are two key factors influencing the induced voltage level

Comparison of lightning return stroke channel-base current models with measured lightning current

Electromagnetic pulse radiation produced around the lightning stroke channel has caused the disturbance to the microelectronic industry, especially to disturbance of high frequency to electronic systems. Lightning channel-base current function (CBC) characteristics and parameters determine lightning electromagnetic field (LEMF) results obtained on the basis of the used models. This paper evaluated and compared the measured lightning current and six lightning current-based channels models namely Bruce and Golde, Heidler, Diendorfer and Uman, Nucci, Pierce and Cianos and new current-based current (NCBC) models. In terms of the waveshape, among all the six lightning channel-based current models discussed, the models developed by Javor, Nucci and Diendorfer and Uman have showed a good agreement compared to the measured lightning current. In terms of 10-90% risetime and full width half maximum time (FWHM) comparison, NCBC and Nucci models have showed compatible comparison. However, Nucci model is not easily adjustable to different desired pulse-current waveshapes. On the other hand, NCBC model can be simplified, the values of lightning peak current and risetime can be chosen arbitrarily and independently from other parameters, and there is no need for the peak-correction factor, so that reduces the number of parameters. Therefore, the NCBC model was suggested to be used in the future in order to simulate much accurate return stroke model. This knowledge will contribute to the development of a new accurate and efficient return stroke model

Techno‐economic analysis of direct combustion and gasification systems for off‐grid energy supply: A case for organic rankine cycle and dual fluidized‐bed

Biomass is one of the most versatile sustainable energy sources. This versatility allows utilization of different biomass feedstock using a verity of conversion techniques. Often, a biomass-to-bioenergy conversion method is selected depending on the application, end-use product, and the type of feedstock. In many applications such as residential energy supply, it is possible to select amongst various technologies. Although, there exist several challenges such as cost-effectiveness and sustainability that constrains bioenergy development. To this end, this research elaborates on the impacts of different conversion methods on techno-economic performance of bioenergy systems for residential energy supply. In this context, Organic Rankine Cycle based on direct combustion, and Dual Fluidized-Bed technology based on gasification were selected for that purpose. A techno-economic comparative analysis illustrates that the primary product of the system and fuel cost are the two most important factors in feasibility assessment. The negative impact of feedstock price was more severe on the Organic Rankine Cycle. For wood chips prices below 55$/t, Organic Rankine Cycle could be the better option due to lower capital and maintenance costs. In contrast, Dual Fluidized-Bed could better tolerate the variation of feedstock price; offering 8$/t wood chips

Effect Of Lightning Impulse Current On The Grounding System Model

The main purpose of the grounding system is to protect human, electrical appliance and building from electrical shock due to lightning or another form of electricity that hazardous. Therefore, to achieve this goal, the fundamental part must be taken into account. In this paper, a different 3-D orientation of concrete has been designed using Comsol software to analyze the performance of the electric potential of the injected impulse in different cases and position of grounding system modelled. In this study, few grounding systems was modelled, which consist of Full concrete, Three-quarter concrete, Half concrete and A quarter concrete to analyse the electric potential of the injected lightning impulse current to the performance of the grounding system modelled. From the result obtained, full concrete was chosen as the best orientation of concrete to be employed at the grounding site. This is because, full concrete has the lowest electric potential value compared to the other cases and position of concrete

Effect of ambient temperature on leakage current of gapless metal oxide surge arrester

Zinc oxide (ZnO) gapless surge arresters are used for lightning and overvoltage protection in electrical power system. The leakage current monitoring is one of the well known method for the ZnO surge arrester ageing level determination. However, the ZnO leakage current is known to be dependent on the ambient temperature. This paper aims to study the effects of temperature variation due to ambient conditions on the leakage current of ZnO surge arrester. The effect of a significant increment of leakage current with an increase in temperature may result in a wrong assesment of the ageing level of the arrester. The leakage current of three 120kV rated polymeric housed ZnO surge arresters were measured in a custom made thermally insulated enclosures at varying temperatures. Up to 20% increase in the leakage current was observed with a 20°C increment above the ambient temperature. For a typical variation of ambient temperature in Malaysia in the range of between 30°C and 40°C, the corresponding changes in the leakage current can be up to 11%. The temperature does significantly affect the leakage current measurements used for monitoring of zinc oxide surge arresters. This significant change in the leakage current due to ambient temperature variation can affect the decision in assessing the condition of surge arresters during routine monitorin

Perinatale mortaliteit : twee vir 'n stuiwer?

11 A4 pages in pdf format. Includes bibliographical references.Inaugural address delivered by Prof DW Steyn on 19 September 2006