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Distribution of 60 HZ ground fault currents along transmission lines : (an improved algorithm) /Gooi, Hoay Beng January 1983 (has links)
No description available.
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Simulation and study of harmonic interference in power line communicationsRoongsita, Somsak January 1985 (has links)
Power line carrier (PLC) is one of the communication and load control (C&LC) techniques employed in direct load control. A PLC is, within itself, a communication system. It utilizes power transmission line as a medium of transmitting control functions, and relaying. High frequencies, in the order of 30 to 300 kHz, are used. Power line carrier systems are, at present, the most attractive C&LC systems.
Recently, dispersed generation - photovoltaics, wind energy, small scale hydro - is introduced to power systems. The introduction of small scale dispersed generation sources degrades the performance of PLC systems by injecting dc-ac inverter related harmonics into the distribution lines. These harmonics interfere with PLC signals. Thus load control functions assigned to PLC systems are affected.
It is the purpose of this research to study how a PLC signal propagates through the transmission line and how it is affected by the harmonic interference. An experiment is conducted using a distribution network provided by the Jet Propulsion Laboratory discussions, and conclusions are presented. / M.S.
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An evaluation of the utility of four in-situ test methods for transmission line foundation designMullen, W. G. 11 July 2007 (has links)
A major powerline is typically supported by many widely spaced structures. Each structure is, in turn, supported by a foundation or foundations. The prevailing philosophy behind transmission structure design to date has been based on the notion that information for geotechnical conditions is sparse and relatively simple in nature. Within this context, it is useful to note that one mile of construction for a routine lattice tower line, can involve twenty five to thirty separate foundations. More accurate soils data can allow for more efficient (smaller) foundation designs with consequent reductions in construction and material costs for the construction.
This research examines four existing in-situ soil strength testing methods; standard penetration test (SPT), the cone penetrometer (CPT), the flat plate dilatometer (DMT), and the pressuremeter (PMT). Soils data were collected at eight separate sites using each of the devices. The test sites were chosen to mirror soil conditions encountered within the service territory of Virginia Power, the project sponsor. A total of 19 standard soil borings, 30 cone penetrometer soundings, 26 dilatometer soundings, and 33 pressuremeter tests were undertaken in residual, alluvial and marine clay soil conditions.
The testing program was conducted with five areas of concern: (1) comparison of the penetration/ stiffness data from the four tests, (2) comparison of values of undrained shear strength and angle of internal friction developed from each of the test methods, (3) determination if pressuremeter data can be correlated to and thereby developed from one of the more rapid tests, (4) comparison of indirect soil type identifications from the cone and dilatometer with laboratory identifications from the standard borings, (5) development of information on the relative effort required for each test.
Comparison of the penetration resistance stiffness data produced useful correlations among the CPT and DMT, with the SPT data yielding more erratic results. Shear strength data was most consistent for the marine clay sites, while the CPT and DMT returned useful friction angle data in the alluvial sands. PMT data correlated well to both the CPT and DMT test results. Correlation of PMT results to the SPT was more erratic. Indirect soil identification from the CPT and DMT was fully adequate for transmission line foundation design purposes, and finally, useful comparative data on the relative testing time required for the four insitu tests was developed. / Ph. D.
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Mimic circuit simulation in real timeCenteno, Virgilio A. 15 July 2010 (has links)
An algorithm is derived for the removal of the DC offset from a faulted current signal using a microprocessor sampling on real-time. The algorithm is to be used instead of the analog Mimic circuit in distance computer relaying. Four variations of the algorithm were derived and tested to determine the best compromise between time response and noise sensitivity. The relay hardware is taken into consideration for the derivations to avoid adding any hardware to the relay. The graphical results of the test run in an analog simulator at the Virginia Tech Power Systems Laboratory are presented. Faults at different voltage angles were performed to determine the algorithm's performance at different levels of DC offset. From the graphical response obtained from the test and taking into consideration hardware and software limitations, a preferred algorithm is selected with a good compromise between time response and noise sensitivity. / Master of Science
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Transmission line simulation for transient network analyser at Virginia TechDellinger, Robert January 1983 (has links)
M.S.
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The relation of soil characteristics and chemical constituents of soil solutions to the self corrosion of underground lead cableTraylor, Edward Lowry January 1925 (has links)
The experiments made in this study covered the investigation of the “self corrosion” of antimony and tin alloy lead cable sheath that was effected by various soil characteristics and by various classes of soil solutions. The study was made entirely with laboratory specimens and solutions and while it was difficult to attain the desired results, yet results of sufficiently distinctive character were secured in most cases to permit of an intelligent comparison and interpretation.
In general, the principal cause of soil corrosion of underground lead cable are the presence of organic matter and poor drainage. When organic matter decomposes the resulting organic solids, mainly acetic, attack the cable sheath with resulting corrosion products. Moisture, up to a certain point, is very detrimental, not only in aiding electrolysis, but by causing the formation of hydroxides. However, the presence of a great amount of water seems to retard corrosive action by making the approach of oxygen difficult. The presence of oxidizing agents, such as the nitrates, also enhances corrosion.
The nature of soil corrosion on cable sheath is usually that of a crater-like pitting of the surface. In these pits are found the corrosive products, probably lead salts in the form of carbonate or sulphate. The amount of corrosion varies over different parts of the surface, due to the non-uniform distribution of the agent causing the corrosion.
Just how much of this corrosion is effected by local galvanic action is indeterminable from this study, but the American Committee on Electrolysis holds this as a very important factor.
Alkalis, as well as acids, have detrimental corrosive effects on lead cable. This was shown very decisively in this study, and for these reasons, it is thought a bad policy to place non-protected cable in the vicinity of calcareous substances, such as concrete. In some cases where acids are probably present in drainage waters, limestone placed near the cable may have a neutralizing effect, but to what extent this principle should be practiced is a matter for conjecture.
It is believed that the chief corrosive effect of salts is due to their aid to galvanic action. However, in many cases it is evident that they also effect corrosion products by chemical union with the cable sheath itself.
From this study it is evident that the whole matter of the corrosion of lead in the soil is very complicated. Not only does the popular amphoteric character of this metal enter into the problem, but also the physical character of the metal structure itself. These factors, combined with the complexities of the chemical content of the ground solutions, make the whole question of the soil corrosion of lead a matter for further and more intense study.
In conclusion, the author wishes to express his appreciation to Mr. D. S. Hilborn, Electrolysis Engineer of the Bell Telephone Company of Pennsylvania, and Professor F. O. Anderegg of the Chemistry Department of the Purdue University, for their advice and directions in the conduction of these experiments. / Master of Science
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Calibration of UV-sensitive camera for corona detectionDu Toit, Nicolaas Serdyn 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / Electrical energy is continuously transported across the world by high voltage transmission lines. These
transmission lines are however subject to losses beside the inherent resistive and dielectric losses. This
additional loss phenomenon is described as corona. The CSIR has developed an optical system to detect
the radiation caused by the corona so that preventive measures can be taken to reduce these losses.
The corona mechanism and how it results in measurable radiation is explored and the structure of the optical
system is analyzed. The optical emissions detected by the present optical system offer no indication of the
severity of the corona discharge. This issue is addressed in this thesis as correlations are sought between
the illuminated pixels displayed on the camera’s display and physical quantities. A blackbody is employed
to find a correlation between these illuminated pixels and radiation. Deviations from the correlation drawn
is explored regarding the saturation mechanisms of the optical system and the distance from the blackbody.
A corona cage is next employed to find a correlation between the illuminated pixels and electrical corona
loss, a quantity indicative of the severity of corona losses on a transmission line. Further tests are also
performed at a reduced gain as it was discovered that the optical system’s response is more linear at reduced
gain than at full gain. It is also indicated that this usage of reduced gain does not have a detrimental effect on
the sensitivity of the optical system. The corona cage measurement employs a small spheric source which
is taken as a base measurement against which all other measurements can be compared. The deviation
of this base analogy is explored against deviations in the corona discharge geometry used, the prevalent
weather condition, and the saturation of the optical system itself.
Both the corona cage and blackbodies used are quite bulky pieces of laboratory equipment. The use of a
smaller, more portable calibration source is therefore also explored. A literature study is made of lasers,
lamp sources, and laser diodes that can be employed as a more portable calibration source. The final choice
of calibration source is shown to be a lamp source. Tungsten calibration lamps are explored in depth and a
circuit is designed to keep the radiation from a lamp source constant in order to improve on its ability as a
calibration source.
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The characteristics of Hong Kong soils in relation to power supply problemsHalfter, N. A. January 1969 (has links)
published_or_final_version / Electrical Engineering / Master / Master of Science in Engineering
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Electrical transient interaction between transformers and the power system: case study of an onshore wind farmBanda, Cedric Amittai January 2016 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment,
University of the Witwatersrand, in fulfilment of the requirements of the degree of
Master of Science in Electrical Engineering
June 2016 / Through the Renewable Energy Independent Power Producer Procurement Program
(REIPPPP) the South African government has awarded opportunities for growth
of renewable energy through bidding rounds. Round 1 saw a total capacity of
397 MW being awarded to independent power producers (IPP). Subsequently
Rounds 2, 3 and 4 each had a total capacity of 333 MW auctioned. The advent
of renewables on the market has brought upon its own associated problems with
regards to power quality issues and failure of HV equipment. This thesis will
address transformer failures that occurred at an onshore wind farm. The nature
of the transformer failures suggest transient overvoltages are mainly to blame.
A comparison between transformer failures in South African and Brazil suggest
a common failure mechanism. The failure starts with an inter-turn insulation
failure which propagates to an inter-layer insulation. In worst cases the failure
mode results in a puncture through the LV-HV barrier and punctures through the
LV winding. An extensive literature review was performed to find appropriate
methods to predict and explain the failure mode in wind turbine LV-MV step-up
transformers. Of the different models which were reviewed the most notable
was the Multi-conductor Transmission Line (MTL) model which was chosen as
the preferred model due to its ability to predict the inter-turn/inter-layer voltage
stresses. Verification of the developed MTL model by the author was then compared
to published results of an MTL model of a disc winding transformer. The results
of the comparison revealed a relatively good agreement between the developed
model and the published model. The application of the MTL model to represent
the voltage stresses in transformer windings was then extended to two specially
constructed wind turbine step-up transformer prototypes. The prototypes differed
in the winding arrangement of the MV coil. The other used two separate MV coils
separated by an oil gap whereas the other had a single MV coil. To validate the
model accuracy, a comparison of measured results versus those obtained analytically
was done for the two prototypes. The analytical and measured results also had a
relatively good agreement for the two prototypes considered. Measurement of
switching surges was done on-site at the wind farm to understand the nature of the
transients. Using analysis tools such as FFT and frequency domain severity factor
it was possible to understand the impact the nature of these transients would pose
on the transformer insulation. Different mitigation techniques which can be used
to alleviate the transient overvoltages to within safe levels were investigated. The
most notable protection device considered was the RL choke device which offered
a significant reduction of the pre-strikes and is virtually transparent under power
frequency operation. / MT2017
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Classification and modeling of power line noise using machine learning techniquesFamilua, Ayokunle Damilola January 2017 (has links)
A thesis submitted in ful lment of the requirements
for the degree of Doctor of Philosophy
in the
School of Electrical and Information Engineering
Faculty of Engineering and Built Environment
June 2017 / The realization of robust, reliable and e cient data transmission have been the theme of
recent research, most importantly in real channel such as the noisy, fading prone power
line communication (PLC) channel. The focus is to exploit old techniques or create new
techniques capable of improving the transmission reliability and also increasing the transmission
capacity of the real communication channels. Multi-carrier modulation scheme such
as Orthogonal Frequency Division Multiplexing (OFDM) utilizing conventional single-carrier
modulation is developed to facilitate a robust data transmission, increasing transmission capacity
(e cient bandwidth usage) and further reducing design complexity in PLC systems.
On the contrary, the reliability of data transmission is subjected to several inhibiting factors
as a result of the varying nature of the PLC channel. These inhibiting factors include noise,
perturbation and disturbances. Contrary to the Additive White Gaussian noise (AWGN)
model often assumed in several communication systems, this noise model fails to capture
the attributes of noise encountered on the PLC channel. This is because periodic noise or
random noise pulses injected by power electronic appliances on the network is a deviation
from the AWGN. The nature of the noise is categorized as non-white non-Gaussian and
unstable due to its impulsive attributes, thus, it is labeled as Non-additive White Gaussian
Noise (NAWGN). These noise and disturbances results into long burst errors that corrupts
signals being transmitted, thus, the PLC is labeled as a horrible or burst error channel.
The e cient and optimal performance of a conventional linear receiver in the white Gaussian
noise environment can therefore be made to drastically degrade in this NAWGN environment.
Therefore, transmission reliability in such environment can be greatly enhanced if we
know and exploit the knowledge of the channel's statistical attributes, thus, the need for
developing statistical channel model based on empirical data. In this thesis, attention is
focused on developing a recon gurable software de ned un-coded single-carrier and multicarrier
PLC transceiver as a tool for realizing an optimized channel model for the narrowband
PLC (NB-PLC) channel.
First, a novel recon gurable software de ned un-coded single-carrier and multi-carrier PLC
transceiver is developed for real-time NB-PLC transmission. The transceivers can be adapted
to implement di erent waveforms for several real-time scenarios and performance evaluation.
Due to the varying noise parameters obtained from country to country as a result of
the dependence of noise impairment on mains voltages, topology of power line, place and
time, the developed transceivers is capable of facilitating constant measurement campaigns
to capture these varying noise parameters before statistical and mathematically inclined
channel models are derived.
Furthermore, the single-carrier (Binary Phase Shift Keying (BPSK), Di erential BPSK
(DBPSK), Quadrature Phase Shift Keying (QPSK) and Di erential QPSK (DQPSK)) PLC
transceiver system developed is used to facilitate a First-Order semi-hidden Fritchman
Markov modeling (SHFMM) of the NB-PLC channel utilizing the e cient iterative Baum-
Welch algorithm (BWA) for parameter estimation. The performance of each modulation
scheme is evaluated in a mildly and heavily disturbed scenarios for both residential and
laboratory site considered. The First-Order estimated error statistics of the realized First-
Order SHFMM have been analytically validated in terms of performance metrics such as:
log-likelihood ratio (LLR), error-free run distribution (EFRD), error probabilities, mean
square error (MSE) and Chi-square ( 2) test. The reliability of the model results is also
con rmed by an excellent match between the empirically obtained error sequence and the
SHFMM regenerated error sequence as shown by the error-free run distribution plot.
This thesis also reports a novel development of a low cost, low complexity Frequency-shift
keying (FSK) - On-o keying (OOK) in-house hybrid PLC and VLC system. The functionality
of this hybrid PLC-VLC transceiver system was ascertained at both residential and
laboratory site at three di erent times of the day: morning, afternoon and evening. A First
and Second-Order SHFMM of the hybrid system is realized. The error statistics of the realized
First and Second-Order SHFMMs have been analytically validated in terms of LLR,
EFRD, error probabilities, MSE and Chi-square ( 2). The Second-Order SHFMMs have
also been analytically validated to be superior to the First-Order SHFMMs although at the
expense of added computational complexity. The reliability of both First and Second-Order
SHFMM results is con rmed by an excellent match between the empirical error sequences
and SHFMM re-generated error sequences as shown by the EFRD plot.
In addition, the multi-carrier (QPSK-OFDM, Di erential QPSK (DQPSK)-OFDM) and
Di erential 8-PSK (D8PSK)-OFDM) PLC transceiver system developed is used to facilitate
a First and Second-Order modeling of the NB-PLC system using the SHFMM and BWA
for parameter estimation. The performance of each OFDM modulation scheme in evaluated
and compared taking into consideration the mildly and heavily disturbed noise scenarios
for the two measurement sites considered. The estimated error statistics of the realized
SHFMMs have been analytically validated in terms of LLR, EFRD, error probabilities, MSE
and Chi-square ( 2) test. The estimated Second-Order SHFMMs have been analytically
validated to be outperform the First-Order SHFMMs although with added computational
complexity. The reliability of the models is con rmed by an excellent match between the
empirical data and SHFMM generated data as shown by the EFRD plot.
The statistical models obtained using Baum-Welch to adjust the parameters of the adopted
SHFMM are often locally maximized. To solve this problem, a novel Metropolis-Hastings
algorithm, a Bayesian inference approach based on Markov Chain Monte Carlo (MCMC)
is developed to optimize the parameters of the adopted SHFMM. The algorithm is used to
optimize the model results obtained from the single-carrier and multi-carrier PLC systems
as well as that of the hybrid PLC-VLC system. Consequently, as deduced from the results,
the models obtained utilizing the novel Metropolis-Hastings algorithm are more precise, near
optimal model with parameter sets that are closer to the global maxima.
Generally, the model results obtained in this thesis are relevant in enhancing transmission
reliability on the PLC channel through the use of the models to improve the adopted modulation
schemes, create adaptive modulation techniques, develop and evaluate forward error
correction (FEC) codes such as a concatenation of Reed-Solomon and Permutation codes and
other robust codes suitable for exploiting and mitigating noise impairments encountered on
the low voltage NB-PLC channel. Furthermore, the recon gurable software de ned NB-PLC
transceiver test-bed developed can be utilized for future measurement campaign as well as
adapted for multiple-input and multiple-output (MIMO) PLC applications. / MT2018
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