- Department of Electrical & Electronic Engineering, University of Agriculture and Environmental Sciences, Umuagwo, P.M.B 1038, Owerri, Imo State, Nigeria
Power designer has sought several means to reduce the discharges in form of ozone gases called corona effect that diminishes conductor on high voltage overhead transmission lines. Various factors affect the corona loss in transmission... more
Power designer has sought several means to reduce the discharges in form of ozone gases called corona effect that diminishes conductor on high voltage overhead transmission lines. Various factors affect the corona loss in transmission lines, some of which are natural and some are equipment-related. While we cannot control the natural causes, we can take certain measures to prevent corona. This paper considers a corona mitigation model for a single-conductor single-phase line, but the model can be extended to multi-conductor and multi-phase cases. The model employed Peek's mathematical equations which was modeled using matlab application tool. From the results obtained, the corona loss decreases with a decrease in applied voltage and also by the implementation of the maximum length ℎ leading to the correction of the irregularity factor mo with high voltage values of 300 and 400 kV. Consequently, corona loss decreased as conductor radius is increased. At maximum voltage of 400 kV, the corona loss due to the mitigation models was completely dropped to 0 kW/km. This paper helped in determining the capacitive effect of a line under corona surge using dynamic capacitance theories. Although corona power can be acceptable to a certain level, it should always be considered when designing transmission systems, along with resistive power loss calculations.
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Distance relays and protection schemes are used in the protection of transmission and distribution lines. The speed of isolating faulty circuits from the network is relatively low and this operation speed was improved in this paper by... more
Distance relays and protection schemes are used in the protection of transmission and distribution lines. The speed of isolating faulty circuits from the network is relatively low and this operation speed was improved in this paper by using a microprocessor to make fast tripping decision for the relay. The microprocessor was programmed by using results obtained from fault studies carried out on the network. Using simulations in Power System Computer Aided Design (PSCAD) software, for a line-to-line (LLG) fault between lines A and B to ground (AB-G) occurring at 35 km on the tested line having a fault impedance of 5 Ω, the operating time of the developed system was 5.4 ms whereas it was 15 ms with the old system without the microprocessor (the conventional distance relay system). The new protection system working with the microprocessor was found to have improved the average operating speed of the distance protection scheme from 6.144 ms to 4.390 ms resulting to an improvement of the operating speed or speed of isolating faulty circuit by approximately 29%.
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This paper investigates the comparative effects of static series synchronous compensator (SSSC) and static synchronous compensator (STATCOM) on Nigeria's 48-bus, 330 kV transmission system. The SSSC is connected in series with a... more
This paper investigates the comparative effects of static series synchronous compensator (SSSC) and static synchronous compensator (STATCOM) on Nigeria's 48-bus, 330 kV transmission system. The SSSC is connected in series with a transmission line, while the STATCOM is shunt-connected for reactive compensation. The study aims to determine which of the two FACTS devices provides greater improvement to the voltage profile of Nigeria's 48-bus, 330 kV transmission system. The network was modeled using the power system analytical tool (PSAT) and analyzed using MATLAB. Simulation results demonstrate significant improvement across all 48 buses when both SSSC and STATCOM devices are integrated into the network. Specifically, the placement of STATCOM led to a 1.5% increase in voltage profile at the highest bus (Bus 18), from 314.8 kV to 319.5 kV. Conversely, SSSC resulted in a 3.3% increase in bus voltage profile compared to the base case, and a 1.8% increase compared to STATCOM, with Bus 18 reaching 325.3 kV. These findings suggest that for voltage profile improvement in power network design, SSSC FACTS should be prioritized over the shunt counterpart due to its greater impact.
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This study involves modeling of the transformer core for flux pattern analysis of variant core materials which include metglass, ferrite, soft iron, silicon steel and solid iron under different frequencies and time intervals. The analysis... more
This study involves modeling of the transformer core for flux pattern analysis of variant core materials which include metglass, ferrite, soft iron, silicon steel and solid iron under different frequencies and time intervals. The analysis techniques deployed were 2D Finite Element Method (FEM) using Comsol Multiphysics software. FEM was used to determine the various flux pattern of the candidate transformer core materials, while MATLAB was used to simulate the distances between the lines of flux for the respective candidate core materials. The result from the flux pattern mapping shows that the lines of flux in metglass core material are more compact than in the rest candidate materials followed by silicon steel, ferrite core, soft iron and solid iron respectively. The flux pattern mapping was successfully deployed in the selection of a better core material with stronger magnetic field and lower losses. Among the samples considered, metglass gave the least core loss of 0
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The requirement to create a safer, non-flammable, and ecologically friendly transformer coolant to replace the petroleum-based oil currently used as transformer oil is the aim of this study. To identify a viable and sustainable vegetable... more
The requirement to create a safer, non-flammable, and ecologically friendly transformer coolant to replace the petroleum-based oil currently used as transformer oil is the aim of this study. To identify a viable and sustainable vegetable oil substitute for transformer oil, electrical and chemical experiments were conducted on samples of melon, jatropha, coconut, and palm kernel oil (PKO) with the aid of mechanical and solvent method. The insulation breakdown voltage test results of the vegetable oil samples without nanoparticle addition were Jatropha oil 21 kV, Coconut oil 18 kV, Melon seed oil 15 kV and PKO 25 kV, while with the introduction of nanoparticles, the results became 25 kV, 19 kV, 15 kV and 35 kV respectively. Results obtained from the research show that PKO can suitably serve as coolant in a distribution transformer rated 11 kV/415 V which can serve as a good substitute for mineral oil. The following technical data from the research will help transformer designers make important decisions about the use of biodegradable transformer coolant.
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To shift from the overdependence on petroleum/mineral oil for the insulation of transformer core, this work sought to suggest vegetable oil as an alternative. To validate the authenticity of the vegetable oil, tests were done to determine... more
To shift from the overdependence on petroleum/mineral oil for the insulation of transformer core, this work sought to suggest vegetable oil as an alternative. To validate the authenticity of the vegetable oil, tests were done to determine the Free Fatty Acid (FFA), acid value and the interfacial tension, which were used to compare the standard value and suggest the best performing vegetable oil suitable for transformer cores. The results obtained for Jatropha, coconut oil, Melon seed and Palm Kerner Oil (PKO) were 3.983 MgKOH, 0.2805 MgKOH, 1.5145 MgKOH and 9.8735MgKOH for FFA respectively, 7.966, 0.561, 3.029 and 19.747 for acid values respectively, and 40dynes/cm, 48dynes/cm, 43dynes/cm, and 45dynes/cm for an interfacial tension respectively. Though the values deviate slightly from the standard values (Nil for FFA, 0.597 for acid value and 48dynes/cm i.e. 2dynes/cm less than the standard value for Interfacial tension), it can be clearly seen that coconut oil possesses properties close to the accepted standard value, and can be recommended for transformer oil alternative.
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This paper involves analysis and simulations on the 48-bus 330 kV Nigeria’s power network system under line failure contingency. The study used NEPLAN software for the simulation and MATLAB m-file for plotting of the charts in various... more
This paper involves analysis and simulations on the 48-bus 330 kV Nigeria’s power network system under line failure contingency. The study used NEPLAN software for the simulation and MATLAB m-file for plotting of the charts in various cases. It is aimed to examine the voltage profile, load flow and available transfer capability of transmission grid system under base case conditions and transmission line contingency situation using the method of repeated power flow based on Newton Raphson. The unified power flow controller, UPFC is placed in the network for the enhancement of voltage profile, power flow and ATC. From the results obtained, integration of UPFC in the ATC least five locations had increased the values of the elements. When the network is operating without UPFC controller, the system had voltage profile of 293.12 kV with real and reactive of 742.93 MW and 1127.80 MVar respectively. However, when the network is operating with UPFC FACTS, the network had voltage profile of 309.23 kV with real and reactive of 783.76 MW and 1189.80 MVar respectively. From the deduced results, as UPFC FACTS increased power transfer during line failure, these FACTS should be installed in the specified locations of the Nigeria 330 kV network for the improvement of voltage profile, real and reactive power and ATC of the power system network.
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Nigeria is faced with endemic electricity generation problem which has remained a big obstacle to her becoming one of the developed nations of the world despite her being endowed with vast natural resources. There exist many power... more
Nigeria is faced with endemic electricity generation problem which has remained a big obstacle to her becoming one of the developed nations of the world despite her being endowed with vast natural resources. There exist many power generating stations in Nigeria that are not operating at full capacity. Many methodologies of optimizing the cost of fuel in running generating stations are in existence but this study focuses on optimizing the cost of fuel in power generation using maximum output approach (Lagrange Multipliers method of solution) with the MATLAB/SIMULINK and MINITAB software packages as tools for the analysis. The study presents an effort to help in solving high cost of power generation in Nigeria. The aim of this study is to minimize the cost of power generation in Nigeria using Omoku Power Station as a case study. The expected overall outcome is to solve the cost function equations under the given constraints for improved performance. The cost function equations or cost models and constraints for obtaining minimized cost values are formulated for the Omoku generating station turbines as non-linear equations. The two (2) different test cases of the six (6) turbines at the Omoku power generating station were considered by keeping the generated power constant within 24 hours of operation daily for a month and varying the number of hours of operation of the station yielded only 3% fuel cost saving while varying the generated power between 18 MW and 25 MW under fixed operating hours a month yielded 32% fuel cost saving. The results so obtained from the varied exercises showed huge savings in fuel consumption better when the operating hours are kept constant. These results showed that the fuel cost of power generation can be minimized with maximum output. The system will assist operators in power generation stations or the Generating Companies of Nigeria (GENCOS) to minimize their costs of power generation so as to plan for generation in the most economic and efficient manner.
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This study examined electricity generation and Sulphur (iv) oxide (S02) emission abatement of a known fertilizer industry in Nigeria. The specific objectives of the study are to: determine the trend analysis of trend analysis aggregate... more
This study examined electricity generation and Sulphur (iv) oxide (S02) emission abatement of a known fertilizer industry in Nigeria. The specific objectives of the study are to: determine the trend analysis of trend analysis aggregate Green House Gas emissions in Nigeria, evaluate the effect of S02 gas emissions on energy performance in Nigeria, examine the effect of S02 gas emissions on electricity generation in Nigeria and analyse the trend of S02 gas emissions against Gross Domestic Product emission index in Nigeria. The data used for the study was extracted from National Green House Gases Inventory Report over a period of 18 years. The greenhouse gases and other parameters that were extracted from the statistical bulletin include; S02 Emission, CH4 emission, N02 Emission (Gg) C02 emission, (Gg), Energy consumed, Gross Domestic Product emissions index and Electricity generation in Nigeria. The E-view version 12 software was used to analyse the data. The result of the study and analysis revealed that a unit increase in S02 emission will lead to 0.000853unit increase in C02 emission. Unit increase in S02 emission led to 1.19E-05unit increase in CH4. Similarly, the result revealed that a unit increase in S02 emission will lead to 0.005395unit increase in N02 emission. Energy consumed had a significant positive relationship with S02 emission. The result of the study showed that a unit increase in S02 emission will lead to 0.001426unit increase in Energy consumed. Also, the Gross Domestic Product Emission index recorded a negative relationship with S02 emissions in the country.
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Distance protection schemes are used in the protection of transmission and distribution lines and they use distance relay in their operations. The protection scheme is always partitioned into two or more zones and each zone is a certain... more
Distance protection schemes are used in the protection of transmission and distribution lines and they use distance relay in their operations. The protection scheme is always partitioned into two or more zones and each zone is a certain percentage of the entire length of the line (which may also include the next line). With all things being equal, the tripping of the relays is solely a function of the zones where the fault occurred, that is, the location of the occurrence of the fault. However, it has been shown in this paper through simulations in Power System Computer-Aided Design (PSCAD) that for a LLG fault on the line (in Zone 1), the distance relay/protection system tripped inaccurately in Zone 2 for a fault impedance of 0.1Ω, 0.5Ω and 5Ω and trips accurately in Zone 1 for fault impedance of 1Ω, and 10Ω for the same type of fault and same location. Also, for a fault impedance of 0.1Ω, the system tripped at Zone 1 for LL and 3 phase faults and tripped in Zone 2 for LG and LLG faults for the same fault impedance and at the same location. This indicates that tripping zone in distance protection schemes are not solely dependent on fault locations but also slightly dependent on the fault impedance and type of fault.
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This paper presents the study of motor sensitivity to parameters variation on the dynamic behaviour of exterior permanent magnet synchronous motor with the aid of matlab m-file for simulation. This study is carried out due to factors that... more
This paper presents the study of motor sensitivity to parameters variation on the dynamic behaviour of exterior permanent magnet synchronous motor with the aid of matlab m-file for simulation. This study is carried out due to factors that hinder the motor performance like limited speed range and high stator core loss. The motor differential models are indicated in reference frame of the rotor with rotor angular position, mechanical rotor speed, q-and d-axes stator currents as state variables. The motor parameters used in this research is a 3-phase, 2 KW, 50 Hz, 4 poles, 220 V. The results showed that increase in frequency leads to increase in motor synchronous speed (1500 rpm to 2250 rpm to 3000 rpm for 50 Hz, 75 Hz and 100 Hz respectively) due to its direct relation, and slightly increased electromagnetic torque and output power. The frequency variation helps in determining the motor speed range. The effect of increase in resistance of the stator winding shows that it reduces the magnitude of ripple of the output characteristics (torque, power and speed) but maintains the same steady state value, while the effect of increase in coefficient of viscous friction decreases the magnitude of ripple and increase the value of the steady state. Similarly, variation on the inertia moment of the motor has little or no effect on the motor output characteristics. Effect of load variation only affects the output power and air-gap torque of the motor as increase or decrease in load leads to increase or decrease in output power and airgap torque respectively. The loading of the motor is not to exceed the 15 Nm otherwise, the motor will operate in reverse condition. The results gotten in this research as compared to other literatures gives a clear understanding and knowledge of the parameters required of a particular motor for improve operating performance with respect to the design requirement.
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This study evaluated the impact of energy consumption on economic growth in Nigeria covering the period of 1981 to 2018. The objectives of the study were to investigate the impact of energy consumption on economic growth in Nigeria and to... more
This study evaluated the impact of energy consumption on economic growth in Nigeria covering the period of 1981 to 2018. The objectives of the study were to investigate the impact of energy consumption on economic growth in Nigeria and to ascertain the long-term relationship between energy consumption and economic growth in Nigeria. The study adopted ex-post facto method of research design, Ordinary Least Square (OLS) regression technique and Johansen co-integration test in arriving at a decision. Gross fixed capital formation, electricity consumption, and crude oil consumption have a positive and significant impact on economic growth in Nigeria while coal consumption has a positive but insignificant impact on economic growth in Nigeria also there exist a long-term relationship between energy consumption and economic growth in Nigeria. based on the result of the findings the following recommendations were made; government should undertake cogent approach towards improving the electricity supply in such a way that it will lead to increased industrial production and economic growth respectively. Government privatization policy of the electricity sub-sector should be highly monitored to provide enough electricity generation and consumption to encourage mass employment of skilled and unskilled labour in the economy. More attention should be given to the crude oil and coal economy in the country in order to galvanize the manufacturing sector. This will not only spur the manufacturing sector but create employments and reduce poverty. Thus, leading to economic growth and development in Nigeria.
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In this study, three models of induction motor (IM) were used to examine the effect of different air-gaps (0.3 mm, 0.5 mm, and 1.0 mm) which have the same electrical features. One of these is the standard 3phase, 1.5 kW, wye connected... more
In this study, three models of induction motor (IM) were used to examine the effect of different air-gaps (0.3 mm, 0.5 mm, and 1.0 mm) which have the same electrical features. One of these is the standard 3phase, 1.5 kW, wye connected motor and the others are modified motors which have different diameters. The torque, efficiency and ripple values of each model were calculated using Finite Element. It was observed that the model with 1.0 mm has lower efficiency of 88.4% compared with the other efficiencies of 94% and 92%. Also, lower power factor values of 0.92 and 0.95 were obtained at 0.7 mm and 1.0 mm gaps respectively while highest power factor of 0.97 were obtained at 0.3 mm gap at the same speed of 1360 rpm. Furthermore, it was observed that increase in the gap increases the magnetizing current produced in the gap from 3 A to 4.36 A at rated conditions. Besides, losses were increased from 73.7 W to 91.4 W while the torque ripples increased from 4.15% to 4.74%. Considering the reliability and efficiency of the motor, the prime value of the air-gap thickness should be between 0.3-0.5 mm for the studied motor. Hence, there is need for the designer of induction motor to maintain the minimum air-gap length in order to improve the power factor and to reduce the no-load losses in the motor.
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Faults occur in substations and the effects of these faults range from damage of electrical equipment connected to the substation to electrocution of personnel operating the substations. When protective devices fail in their operations... more
Faults occur in substations and the effects of these faults range from damage of electrical equipment connected to the substation to electrocution of personnel operating the substations. When protective devices fail in their operations after fault occur, mitigating the fault effects can be the only option of saving the lives of the personnel and equipment around the fault location in the substation. A balanced three phase fault, line-to-ground (LG) fault, line-to-line (LL) fault and double line to ground (LLG) fault at the primary and secondary of the respective transformers in the 80 MVA 132/33 kV Ohia Transmission substation were simulated in Electrical Transient Analyzer Program (ETAP). Ranges of fault current flow into the bus of the primary of the respective transformer causing corresponding arc flash energy in calories/cm2, arc flash boundary in centimeters and arc flash distance in centimeters, appropriate recommendations of respective levels of radiating personnel protective equipment (PPE) amongst levels A, B, and D based on the results were made in accordance with National Fire Protection Association (NPFA) 70E2009/2012. The results recorded show the highest fault current flow of 451.01 kA in the primary of the second transformer as a result a three-phase fault and LG fault causing 8.962 cal/cm2 energy to radiate within an arc flash boundary of 76.50 cm (2.51 ft.) given an arc flash distance of 9.75 cm (3.840 inches) and a corresponding choice level D PPE. Further mitigation of the faults effects can be done with a well-designed earth grid with touch potential of 797.7 volts, step potential of 938.5 volts and earth resistance of 2.9 ohms all being within the IEEE tolerable range. Mitigating faults effects can also be achieved using a well-designed fault current limiter (FCL) with normal operating condition of negligible impedance and maximum impedance during fault as 70 ohms and 1200 ohms respectively for the secondary sides of superconducting fault current limiter (SFCL).
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This paper presents a study of high impedance fault (HIF) arc analysis on 6 km 11 kV distribution network from New Haven to New NNPC, Enugu State. These HIF currents have low fault current ratings and are not readily detected by the... more
This paper presents a study of high impedance fault (HIF) arc analysis on 6 km 11 kV distribution network from New Haven to New NNPC, Enugu State. These HIF currents have low fault current ratings and are not readily detected by the distribution sub-station relays and protective equipment. This was realized with the aid of MATLAB. Firstly, the HIF was modelled based on the electric arc theory method for single line-to-ground and double line-toground faults, when the 11 kV New-haven to New NNPC Enugu distribution line interfaces with a dry asphalt ground surface. The HIF was incident on the midpoint of the distribution line between the switching times of the circuit breaker from 0.02 to 0.05 seconds. The results showed that for single line-to-ground and double line-to-ground faults, a peak current magnitude of 12.4 A and 2280 A were seen respectively and initial spikes due to arcing in the system voltages at the initial switching times of 0.02 seconds. The corresponding residual currents Ib and Ic are very small with a peak spike of 0.3 A and 1.9 A for double line-to-ground fault (BC-G). These spikes are because of the impact of the initial transients caused by the arc flames as its quenches and re-ignites.
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This work presents a cogent framework to inspect the performance of a network call handoff based on Nigerian Communications Commission (NCC) key performance indicators for 4G. To quantify the performance of a network handoff, the call... more
This work presents a cogent framework to inspect the performance of a network call handoff based on Nigerian Communications Commission (NCC) key performance indicators for 4G. To quantify the performance of a network handoff, the call setup success rate and handover success rate were used to analyze the network performance. The ever-increasing demand for handoff decisions on mobile communication network especially as the volume of the network users increase leads to this work. The traditional means where the handoff is performed on the basis of the evaluation of signal strength are not enough. They do not take into consideration various mobile users attachment options such as the current context or the attachment of the user option. The mathematical model for the mean Call Setup Success Rate (CSSR) and mean Handover Success Rate (HOSR) were adopted to evaluate the network handoff performance. The probability threshold interval medium is assigned to characterize the defect in vertical handoff decisions that is made under uncertain information conditions. The accuracy of vertical handoff decisions which is based totally on the CSSR and HOSR were evaluated. These was done by benchmarking with NCC key performance indicators for 4G network and the evaluation was carried out using Microsoft Excel. These analytical results are applied to examine the performance of the vertical handoff model between any two base transceiver stations. Finally, we recommend an improved performance of the HOSR and CSSR in order to enhance the call handoff of a network.
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The efficient and reliable operation of a protection system cannot be overemphasized as any shortfall in such system has both huge financial implications and makes the station dangerous and unsafe. The data for the overcurrent relay... more
The efficient and reliable operation of a protection system cannot be overemphasized as any shortfall in such system has both huge financial implications and makes the station dangerous and unsafe. The data for the overcurrent relay coordination analysis used in this study was obtained from the Ohiya Umuahia 132/33 kV substation of the Transmission Company of Nigeria (TCN) while the electric transient analyzer program (ETAP) software was used for the analysis. Firstly, a three-phase (3-phase) short circuit test was conducted on the network at the 33 kV busbar. Then, a detailed sequence of operation of the station’s overcurrent relays was done for standard inverse relay setting, very inverse relay setting and extremely inverse relay setting characteristics. Results showed that at t = 0 seconds a 3-phase fault of initial symmetrical current root mean square (RMS) of 3.049 kA, peak value of 7.746 kA and a steady state value of 2.615 kA was induced on the 33 kV busbar, which lasted till t = 0.2 seconds upon action of the circuit breaker. Also, results showed that the individual time current curve (TCC) for the three relays indicated a fault current of 7.746 kA which lasted for 3.57, 3.57 and 3.28 seconds on the network respectively. Effective device coordination of the 132/33 kV transmission station is an appropriate sequence of operation of its protective devices.
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This paper presents the comparative analysis of technical losses on its financial assessment associated with the distribution of power in the South Eastern part of Nigeria. This analysis is performed with the aid of electrical transient... more
This paper presents the comparative analysis of technical losses on its financial assessment associated with the distribution of power in the South Eastern part of Nigeria. This analysis is performed with the aid of electrical transient and analysis program (ETAP), wherein the South Eastern Nigeria distribution network was first modeled and its load flow generated using Newton Raphson iterative load flow method for all two hundred and three (203) load buses in the network. The system technical losses are evaluated for four cases: system alone, on-load tap changes (OLTC), fixed tap and on-load tap changes (FTOLTC), and optimal capacitor placement. The results showed that when the network is operating at 100 percent (%) load demand, the system active and reactive power losses recorded were 44.33 MW and 165.3511 MVAR respectively, while they were 11.973 MW and 0.68 MVAR when capacitor banks are used in the loss reduction. The results also showed improvements of the average power factor of 74.9% lagging. The average percentage bus loading improves to 30.1% from 42.69%, while the percentage voltage drop across transmission is 5.75%. The financial assessment of these losses show the accumulative profit over a four year period in billions of naira as the system yields profit of three hundred and eighty-seven billion, four hundred and forty-three million six hundred and sixty eight thousand naira only (N387,443,668,000) in its first year of operation and gradually increases to one trillion, five hundred and sixty-two billion, eighty-seven million, three hundred and ninety thousand naira only (N1,562,087,390,000) even after the installation and operation capitals are removed from the net annual loss reduction savings in naira. It is therefore recommended for the proposed rated capacitor banks to be installed at the recommended sub-stations to yield profit which could be then injected back into the generation to improve system supply in the South Eastern Nigeria electricity distribution system.
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This paper presents an Improved Under-Voltage Load Shedding Scheme in Power System for South Eastern Nigeria distribution network. The south eastern Nigeria distribution network was first modeled and its load flow regenerated using Newton... more
This paper presents an Improved Under-Voltage Load Shedding Scheme in Power System for South Eastern Nigeria distribution network. The south eastern Nigeria distribution network was first modeled and its load flow regenerated using Newton Raphson iterative load flow method for all 203 load buses in the network. The aim is to improve the existing network’s bus voltage profile with the use of various under-voltage load shedding schemes for improved power and its effect of the system voltage profile was analyzed and recorded for 100%, 60% and 50% load shedding case studies. Results showed an improvement in the entire network bus voltage level after the load shedding scheme between 10.34 kV to 11.22 kV for 11 kV buses and between 31.02 kV to 33.66 kV for 33 kV buses indicating the nominal voltage level. It showed an increment in the total number of nominal voltage buses of each case study, from 22 buses at 100% load demand to 105 buses when 40% of the load has been shed to finally, 126 buses when 50% of the load has been shed in the 50% load demand scenario A and B. Finally, the number of under-voltage buses decreases to 3 and 7 buses in Scenario A and B respectively when 50% of the total load demand has been shed by Enugu Electric Distribution Company (EEDC).
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This paper presents the dynamic analysis and computer simulation of interior permanent magnet synchronous motor (IPMSM) with intermittent loading. This objective was realized with the aid of MATLAB m.file function program, which is based... more
This paper presents the dynamic analysis and computer simulation of interior permanent magnet synchronous motor (IPMSM) with intermittent loading. This objective was realized with the aid of MATLAB m.file function program, which is based on an explicit Runge-Kutta fourth order numerical method to solve a set of first order differential system of equations describing electrical and mechanical models of IPMSM. The IPMSM used in this research is of specifications 3-phase, 2 KW, 50 Hz, 4 poles, 240 V. The IPMSM differential equations are expressed in rotor reference frame with q-and d-axes stator currents, mechanical rotor speed, and rotor angular position as state variables. The analysis and simulation of the motor is initially done with no-load and with the parameters as given in Table 1. Subsequently, the motor was loaded and parameter variations were carried out. The result of a typical responses of the motor were obtained which showed that IPMSM has more ripples, overshoot, slower response but can carry load of up to 90 Nm. The effect of higher stator resistance shows that it minimizes the magnitude of ripple of the output characteristics (torque and power) but takes more time to attain the same steady state value. In the same vein, variation of moment of inertia has little or no effect on the output characteristics of the motor. The findings obtained in this research work as compared to other literatures showed that with the parameters recommended, an improved design and operation of IPMSM will be obtained for best performance and without unsynchronous operation due to overloading.
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This paper presents a review on the applications of various types of circuit breakers (CB) used in electric power transmission and distribution. Circuit breakers are majorly classified under direct current (DC) or alternating current (AC)... more
This paper presents a review on the applications of various types of circuit breakers (CB) used in electric power transmission and distribution. Circuit breakers are majorly classified under direct current (DC) or alternating current (AC) system. It shows that the most suitable way of classifying circuit breakers is on the level of voltage rating which is broadly grouped under direct current (DC) or alternating current (AC) circuit breakers. However, reviewed literatures did not clearly distinguish the respective applications of the different types of circuit breakers as applied to DC and AC power network. The DC circuit breakers which comprises of mechanical, solid-state and hybrid breakers are mostly applied in domestic and industrial applications that employ the use of direct current (DC) especially in high voltage direct current (HVDC) network system for the protection of electrical devices. AC circuit breakers are grouped in high voltage and low voltage forms. The low voltage CB comprises of miniature and molded case circuit breakers used majorly in domestic and commercial installations. The high voltage circuit breakers are further subdivided into oil and oil-less forms. The oil-less CB is made up air, vacuum and sulphur hexafluoride (SF6 ) circuit breakers. These high voltage circuit breakers are majorly applied in high voltage and extra high voltage transmission systems for protection of power system equipment and electrical machines.
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This paper presents the study of characteristics of corona effect on AC high voltage transmission line with variation of parameters associated with the transmission line. This objective was achieved with the aid of MATLAB m-file function... more
This paper presents the study of characteristics of corona effect on AC high voltage transmission line with variation of parameters associated with the transmission line. This objective was achieved with the aid of MATLAB m-file function program. The line specifications are 220 kV line-to-line, 50 Hz, 1.2 cm conductor radius, 200 cm distance between conductors, and 0.85 conductor surface condition factor. The responses of the simulation on the effect of corona on transmission line show that as line width from the point of electric field intensity is decreased towards the conductor radius, the potential gradient increases and power loss decreases, and at point when line width is decreased to conductor radius, potential gradient attained its maximum value. Also when the line width is increased towards the value of conductors distance, the potential gradient tends to infinity and power loss tends to zero. When conductor surface condition factor is increased, the critical disruptive voltage increases while the power loss decreases. On the other hand, increase in frequency increases power loss and the variation of line voltage from minimum to maximum value increases the potential gradient and subsequent decrease in corona power loss. However, as the decrement in corona power loss gets to the point of 180 kV line-to-line critical disruptive voltage, the power loss started increasing thereafter. The results obtained from this work in relation to other literatures show that in designing transmission line, these effects need to be considered for the lines to properly manage corona effect during discharges and underground cable can also be employed in some design since it can prevent power loss as it is not affected by change in weather condition.
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This paper presents the effect of circuit breaker arc on transmission line comprising inductive and capacitive circuit with terminal faults and short line faults. This was realized with the aid of MATLAB and PSCAD/EMTDC software. The... more
This paper presents the effect of circuit breaker arc on transmission line comprising inductive and capacitive circuit with terminal faults and short line faults. This was realized with the aid of MATLAB and PSCAD/EMTDC software. The system voltage, current, arc current, arc voltage and transient recovery voltage during fault conditions were analyzed for all for four (4) cases. The analysis shows the respective system voltage and current plots as well as the breaker arc voltage and currents plots. The fault occurs at 0.2 seconds while breaker operation was between 0.3 seconds to 0.5 seconds. The circuit breaker separation was studied at t = 0 secs and t =0.009 seconds and the TRV and current zero-crossing were recorded. A TRV of 1.985 × 10-5 V and a zero crossing at t = 3.24 × 10-3 s were recorded with interruption of small inductive currents and current chopping. The transient recovery voltage was 1.59 × 10 5 V and its breaker zero crossing at t = 2.1 × 10-2 s was recorded during interruption of capacitive currents. Also, the first transient recovery voltage was 2.66 × 10 5 V and its zero crossing occurred at t = 0.0149 s with interruption of terminal faults. Similarly, the TRV was 1.59 × 10 5 V and the breaker zero crossing occurred at t = 2.1 × 10-2 s from contact separation when fault was between a distance for of a few kilometers from the circuit breaker.
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This paper presents the effect of saliency and core losses on the dynamic behavior of permanent magnet synchronous motor. This objective was realized with the aid of Matlab/Simulink. The two motors (Interior and Surface-Mounted Permanent... more
This paper presents the effect of saliency and core losses on the dynamic behavior of permanent magnet synchronous motor. This objective was realized with the aid of Matlab/Simulink. The two motors (Interior and Surface-Mounted Permanent Magnet Synchronous Motor) used in this work are of specifications 3-phase, 2 KW, 50 Hz, 4 poles, 240 V each. The transient and steady state responses of the motors were obtained, which revealed that when core loss is introduced to the motor, it decreases the magnitude of the ripple of electromagnetic torque and output power but affects the speed of the motor as it takes more time to attain steady state. The effect of saliency caused by reluctance torque showed that the load angle during the rated operation increases, and so the pull-out torque is obtained at the power angle greater than 90 0. The maximum fundamental and electromagnetic torque is achieved at saliency ratio of 0.5. The results obtained in this work as compared to other literatures show improved design of Interior and Surface-Mounted Permanent Magnet Synchronous Motor with clear understanding of the parameters required of a particular motor for best operating performance.
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This paper presents a study of the effects of proportional (P), integral (I) and differential (D) controller in speed regulation of a direct current (DC) motor. Controlling the speed of a DC motor is very important as any small change can... more
This paper presents a study of the effects of proportional (P), integral (I) and differential (D) controller in speed regulation of a direct current (DC) motor. Controlling the speed of a DC motor is very important as any small change can lead to instability of the closed-loop system. The steady-state equation of a motor is given. All simulations were performed in Matlab. Simulations were performed in threefold: The open-loop system response is first analyzed. Then feedback without PID control is studied. Finally, PID control is applied. Results obtained show that a combination of P, I and D can maintain stability and improve the overall system performance.
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This paper presents an analysis of the design of rotational energy harvesting systems. In this background a review of rotational structures is presented. Energy harvesting as a feedback problem is given. The methods of controller and... more
This paper presents an analysis of the design of rotational energy harvesting systems. In this background a review of rotational structures is presented. Energy harvesting as a feedback problem is given. The methods of controller and observer designs are analyzed. Finally, the limitation of portable electrical energy is presented.
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This paper presents the design and construction of a comprehensive digital security system with the aim of providing a 24 hour digital watchdog for institutions such as banks, schools, the church, residential homes or anything that... more
This paper presents the design and construction of a comprehensive digital security system with the aim of providing a 24 hour digital watchdog for institutions such as banks, schools, the church, residential homes or anything that requires monitoring. The infra-red and digital technologies were used in the realization of this objective. The infra-red (I.R.) signal is transmitted by an I.R diode which is intercepted and decoded by the receiver circuitry. Obstructing the line of sight (within 8 meters) produced a digital display of the zone trespassed. This also triggers an alarm, both of which are designed to have duration of 30 seconds. The transmitters and sensors should be raised at least 1 meter above the ground to ensure that only humans trigger the alarm.
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In this paper, we seek to address means of automatically registering students, recording attendance, saving students' data on the personal computer (PC) as well as backing this data via the global system for mobile communication (GSM) and... more
In this paper, we seek to address means of automatically registering students, recording attendance, saving students' data on the personal computer (PC) as well as backing this data via the global system for mobile communication (GSM) and finally making a decision on the eligibility of a student to sit for an examination course. Owing to the challenges of the manual method of taking attendance in Nigerian universities and colleges especially in the Michael Okpara University of Agriculture Umudike, an automated attendance system needs to be adopted. The challenges include difficulty in keeping the attendance list over a long period of time, unnecessary time wastage during writing and signing attendance, improper documentation, students forgetting to write or sign the attendance paper, lecturers forgetting the attendance list in the classroom, students writing or signing illegally for an absentee amongst others. A modular approach was utilized in the design. The design has four major parts: input section (RFID tag and RFID reader), control section, power section and display unit. All simulations were performed using the PROTEUS software. Results obtained show that when a student who enters a classroom swipes the RFID tag near the reader that is connected externally to microcontroller based embedded system, the system grants access to a registered student and stores the attendance information on a PC database. An SMS containing the same details is sent to mobile phone for data backup through the GSM SIM 900 Modem. The design was successfully tested and implemented.
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This paper presents the appropriate energy mix to facilitate rural industrial development and economic growth in Nigeria. The study discusses the national energy policies, plans and programmes, its sustainable energy for all targets and... more
This paper presents the appropriate energy mix to facilitate rural industrial development and economic growth in Nigeria. The study discusses the national energy policies, plans and programmes, its sustainable energy for all targets and its on-grid and off-grid energy mix demographic analysis including its percentage of population with access to energy. The results show that although Nigeria numerous renewable power project/plans still ongoing implementation, fossil fuel and hydropower are the only two sources currently in its energy mix. The results of the study also displayed a poor percentage of rural population with access to energy and rural electrification rate of 25.5 % and 55.6% respectively. The study concluded stating that the suitable energy mix in the rural area that would rapidly increase its development was labelled as the use of off-grid solution and stand-alone solar homes solutions, as this would increase their rural electrification and industrial development which will in turn contribute immensely to Nigeria's economic growth.
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The performance of an electric system is characterized by the stability of the frequency and voltage. To sustain electric performance, a governor is used to maintain the speed (and hence frequency) of the generator at its nominal value.... more
The performance of an electric system is characterized by the stability of the frequency and voltage. To sustain electric performance, a governor is used to maintain the speed (and hence frequency) of the generator at its nominal value. Another important factor in stability is the excitation control. In this paper, a study of the effect of excitation and governor on the stability of electric machines is presented. In particular, a model of a synchronous machine (in generator mode) connected to a hydraulic turbine Proportional-Integral-Derivative (PID) governor with excitation system is analyzed. A three phase fault is used to represent system disturbance. All simulations were performed in simulink. Simulation results obtained shows that excitation and governor control stabilizes the output terminal voltage of the synchronous electrical machine within three seconds in the presence of a fault. This shows that excitation and governor control play a vital role in the dynamic stability of electric machines.