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Techno-Economic Analysis of Harmonic Disturbances in a University Environment - A Case Study at the University of Cape Coast
Joseph Cudjoe Attachie,
Benedict Addo-Yeboa
Issue:
Volume 10, Issue 4, August 2022
Pages:
128-141
Received:
27 June 2022
Accepted:
15 July 2022
Published:
22 July 2022
DOI:
10.11648/j.jeee.20221004.11
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Abstract: This research investigates the adverse impact of harmonic disturbances present in distribution substations on the electrical installations and distribution network of the University of Cape Coast in economic terms. Power quality analyser using the “very-short time” monitoring duration and referenced against the IEEE 519-2014 harmonics standard was employed to obtain both the voltage total harmonic distortion (THDV) and current total harmonic distortion (THDI). The average total harmonic distortions measured on the university was 16.43% with dominant harmonics of the 3rd, 5th, 7th, 11th and 13th orders culminating in a reduced true power factor of 0.944. Further computations and analysis on the network showed a reduction of the THDI level from 16.43% to 8%. Modelling and simulation of the electrical distribution system was also carried out using Electrical Transient and Analysis Program (ETAP) software. The extracted harmonic waveforms and spectrums revealed harmonics of the 3rd, 5th, 7th and 9th orders to be more dominant within the network. Significant improvement of the true power factor with considerable savings of about Gh¢ 1,161,493.71 per annum was realised. The installation of tuned paralleled passive filters to mitigate harmonics gave a net present value of Gh¢ 2,736,028.00 at a discount rate of 8% with a payback period of 6.23 years.
Abstract: This research investigates the adverse impact of harmonic disturbances present in distribution substations on the electrical installations and distribution network of the University of Cape Coast in economic terms. Power quality analyser using the “very-short time” monitoring duration and referenced against the IEEE 519-2014 harmonics standard was ...
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Fiber Fuse Simulation in Dispersion-Shifted Fibers
Issue:
Volume 10, Issue 4, August 2022
Pages:
142-148
Received:
10 July 2022
Accepted:
22 July 2022
Published:
29 July 2022
DOI:
10.11648/j.jeee.20221004.12
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Abstract: Silica-based optical fibers are the most important transmission medium for long-distance and large-capacity optical communication systems. The most distinguished feature of optical fiber is its low loss characteristics. A single-mode optical fiber (SMF) exhibits a very low transmission loss (0.142 dB/km) at 1.55 μm. Together with such low loss characteristics, zero chromatic dispersion near 1.55 μm is required for high capacity signal transmission. The zero-dispersion wavelength of optical fibers can be shifted to the vicinity of 1.55 μm by the mutual cancellation of material dispersion and waveguide dispersion. Such fibers are called dispersion-shifted fibers (DSFs). The unsteady-state thermal conduction process in several DSFs was studied theoretically by the explicit finite-difference method using the thermochemical SiOx production model. The calculated threshold power and velocity of fiber fuse propagation in a step-index SMF were in fair agreement with the experimental values observed at 1.55 μm. It was found that the calculated threshold powers were proportional to the effective cross sectional areas of several DSFs and there is a linear relationship between the threshold powers and the mode-field diameters in the range of up to 2 W. These results were in fair agreement with the experimental results observed at 1.55 μm.
Abstract: Silica-based optical fibers are the most important transmission medium for long-distance and large-capacity optical communication systems. The most distinguished feature of optical fiber is its low loss characteristics. A single-mode optical fiber (SMF) exhibits a very low transmission loss (0.142 dB/km) at 1.55 μm. Together with such low loss char...
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Feedback Modelling in Amplifier Circuits Using Open-Loop Transfer Functions
Issue:
Volume 10, Issue 4, August 2022
Pages:
149-157
Received:
10 July 2022
Accepted:
25 July 2022
Published:
29 July 2022
DOI:
10.11648/j.jeee.20221004.13
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Abstract: Negative feedback is an established technique used to improve the quality of an amplifier. The modelling of the closed-loop circuit is a complex procedure that, if not done properly, may give erroneous results. A new method for modelling amplifiers that use negative feedback over a broad frequency range is presented. The method overcomes the main difficulties of the two-port analysis, namely the identification of the feedback type and the determination of the feedback network loading to the open-loop amplifier. Compared to other methods, it is more suitable for handling frequency-dependent quantities. All topologies are treated as voltage amplifiers. The open-loop amplifier is described by three open-loop transfer functions. The theoretical context of the non-ideal op amp is used to derive the closed-loop quantities, discriminating between the non-inverting and the inverting case. The proposed method provides accurate results over a broad range of frequencies. The poles and the zeros can be readily calculated as well as the loop gain, to examine the stability of the amplifier. It can account for complex loads and frequency-dependent gain-setting resistors. Another advantage is that once the open-loop transfer functions are known, other closed-loop configurations can be computed with no additional effort. Circuit complexity has not been found to be a problem. The proposed modelling technique has been used in the class for a number of years with undergraduate students responding positively to it.
Abstract: Negative feedback is an established technique used to improve the quality of an amplifier. The modelling of the closed-loop circuit is a complex procedure that, if not done properly, may give erroneous results. A new method for modelling amplifiers that use negative feedback over a broad frequency range is presented. The method overcomes the main d...
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Compact Feeding Circuit for an Antenna That Achieves Three-Way Switchable Beam Directions Using Lumped Parameter Elements
Masatoshi Tsuji,
Kota Motozuka
Issue:
Volume 10, Issue 4, August 2022
Pages:
158-161
Received:
8 August 2021
Accepted:
24 August 2021
Published:
17 August 2022
DOI:
10.11648/j.jeee.20221004.14
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Abstract: There have been a number of studies on phased array antennas and adaptive antennas as directional antennas that can be scanned electronically. However, these antenna systems require expensive phase shifters and power controllers, and their construction is complex. Small and relatively inexpensive antenna system, in which the beam is scanned or the beam direction is switched electronically, are expected for consumer applications. This research presents a compact feeding circuit for an antenna which enables its beam to be switched in three directions using lumped parameter elements. The circuit was designed and constructed in such a way that the transmission lines of two conventional rat-race circuits were replaced with phase shifters which utilize lumped elements. The proposed circuit has a single input port and four output ports for connection to the antennas, and can obtain phase differences of ±90° and 0° between antennas. The prototype was fabricated and evaluated at 1 GHz. The measured values were very consistent with the theory. The phase difference and magnitude errors between the antennas were -2.5 ~ +2.6°, -0.4.8 ~ +0.45dB with the SW1-setting, and -1.8 ~ +7.1°, -0.54 ~ +0.45dB with the SW3-setting. The area of the prototype fabricated this time was 8 × 7 mm, and reduced to 1/216 in comparison with the conventional circuit.
Abstract: There have been a number of studies on phased array antennas and adaptive antennas as directional antennas that can be scanned electronically. However, these antenna systems require expensive phase shifters and power controllers, and their construction is complex. Small and relatively inexpensive antenna system, in which the beam is scanned or the ...
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Fiber Fuse Simulation in Multi-Core Fibers for Space Division Multiplexed Transmission
Issue:
Volume 10, Issue 4, August 2022
Pages:
162-169
Received:
7 August 2022
Accepted:
23 August 2022
Published:
31 August 2022
DOI:
10.11648/j.jeee.20221004.15
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Abstract: Owing to the progress of dense wavelength-division multiplexing (WDM) technology using an optical-fiber amplifier, we can exchange large amounts of data at a rate of 100 Tbit/s class over several hundred kilometers. However, it is widely recognized that the maximum transmission capacity of a single strand of fiber is rapidly approaching its limit of ~100 Tbit/s owing to the optical power limitations imposed by the fiber fuse phenomenon and the finite transmission bandwidth determined by optical-fiber amplifiers. To overcome these limitations, space-division multiplexing (SDM) technologies using a multi-core fiber (MCF) were proposed. The fiber fuse experiments of MCFs at 1.55 μm were conducted using two types of MCFs: homogeneous 7-core MCF and heterogeneous 6-core MCF. The fiber fuse effect in these MCFs was studied theoretically by the explicit finite-difference method using the thermochemical SiOx production model. In the calculation, we assumed that two types of MCFs have a simple refractive-index profile, which is similar to that of doubly clad single-mode fibers. The calculated threshold power Pth of the homogeneous MCF was 1.19-1.25 W, which was close to the experimental Pth value of SMF. On the other hand, the Pth of small core fiber in heterogeneous MCF was 0.89 W. It was found that the Pth values of two types of MCFs were proportional to their cross sectional area Aeff values. Next, the cross sectional area A of the vaporized core was estimated using the proportionality constant Vf / P0 of MCFs and SMF at P0 ³ 5 W. The A values of homogeneous MCF and SMF were close to their Aeff values. On the other hand, the A value of small core fiber in heterogeneous MCF was larger than its Aeff value. From these results, it was concluded that the plasma, which occurred in the vaporized core, tends to expand in the small-Aeff fiber. Furthermore, it was found that in the neighboring core layers the generation and propagation of fiber fuse was hindered during fiber fuse propagation in the heated core of homogeneous and/or heterogeneous MCF.
Abstract: Owing to the progress of dense wavelength-division multiplexing (WDM) technology using an optical-fiber amplifier, we can exchange large amounts of data at a rate of 100 Tbit/s class over several hundred kilometers. However, it is widely recognized that the maximum transmission capacity of a single strand of fiber is rapidly approaching its limit o...
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Design and Analysis a 36-Pulse Rectifier to Improve the High-Voltage Harmonic Distortion Rate Under 5% in MRT Systems
Chien Hsu Chen,
Sheng Chieh Huang
Issue:
Volume 10, Issue 4, August 2022
Pages:
170-179
Received:
9 August 2022
Accepted:
25 August 2022
Published:
31 August 2022
DOI:
10.11648/j.jeee.20221004.16
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Abstract: I have served the Taipei MRT Bureau over than 25 years, and the inductive current harmonics affect the MRT power system, causing the train to malfunction and shorten its service life. Therefore, I am interested in solving this problem. The traditional solution is to use RLC high-pass filter. Its disadvantage is that it will reduce the power of the power supply system and need to do power compensation. This study analyzed the conversion designs of the traditional transformer wiring △-△-△-△ and 36-pulse rectifier transformers. This type of transformer is used mainly in the industrial sector and features a system stability function. It involves parallel connection of two 18-pulse transformers to rectify 36-pulse DC power sources. The transformers were wire connected using the Δ pattern, which can convert 22 kV AC into 750 V DC. Regarding the two transformers in parallel connection, the primary side was 22 kV three-phase AC and the second, third, and fourth sides were in parallel connection. In addition, 72 diode rectifiers were used to rectify AC into single-phase 750 V DC. The 36-pulse and 24-pulse simulation results were compared and revealed that the power output of the 36-pulse system was greater than that of the 24-pulse system and presented a relatively straight waveform. This indicated that AC harmonics and DC ripples were reduced, verifying that the 36-pulse design is superior to the 24-pulse design.
Abstract: I have served the Taipei MRT Bureau over than 25 years, and the inductive current harmonics affect the MRT power system, causing the train to malfunction and shorten its service life. Therefore, I am interested in solving this problem. The traditional solution is to use RLC high-pass filter. Its disadvantage is that it will reduce the power of the ...
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