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Evaluation of replacing fixed with controllable line reactors in mature power systems overlaid with higher voltage linesNojozi, Hactor Ma-Ande 27 May 2013 (has links)
M.Ing. (Electrical and Electronic Engineering) / Shunt reactors are used in power system amongst other things, to suppress overvoltages in the network during network switching, auto reclosing of transmission lines and under low loading condition of the network. Traditionally, shunt reactors of fixed type have been used and these have been permanently connected to the system. This research work investigated the feasibility of replacing the fixed shunt line reactors with a reactor, whose parameters are automatically varied depending on the system reactive power requirements, in a mature power system overlaid with high voltage lines to improve amongst, other things voltage stability. However, in a mature system overlaid with parallel higher voltage lines, power tend to flow on the matured system rather than higher voltage system as predetermined by various impedances of the power system. It is therefore desirable that loading of higher voltage lines be increased because of their higher power transfer capability and fact that higher voltage networks generate capacitive power which is substantially more than for each line at the original voltage. However, replacing a large number of fixed line reactors, at low loadings of higher voltage lines, even when system collapse is averted by increasing the number of reactors inserted into the system, overvoltage problems may still be an issue, until a certain number of must-run reactors, operating at full reactance, are put into service. If too much inductive reactance is removed from the system when the loading levels are extremely low, the power system will collapse. Therefore, there was no economic benefit in replacing all the fixed shunt line reactors with controllable type when the loading was still relatively low. Thus, the majority of the converted reactors were operating in their full rating as there was still more reactive power to be absorbed. However, when the power was diverted to flow on the higher voltage system through the use of series compensation of the higher voltage system, there was a possibility of making some fixed shunt line reactors on the higher voltage network controllable. This also allowed more power to be transferred in the higher voltage system thus improving its utilisation. Also, a positive impact on active system losses was realised.
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Application of catastrophe theory to transient stability analysis of multimachine power systemsParsi-Feraidoonian, Raiomand January 1990 (has links)
Transient stability analysis is an important part of power planning and operation. For large power systems, such analysis is very time consuming and expensive. Therefore, an online
transient stability assessment will be required as these large power systems are operated close to their maximum limits. In this thesis swallowtail catastrophe is used to determine the transient stability regions. The bifurcation set represents the transient stability region in terms of power system transient parameters bounded by the transient stability limits. The system modelling is generalized in such, that the analysis could handle either one or any number of critical machines. This generalized model is then tested on a three-machine as well as a seven-machine system. The results of the stability analysis done with the generalized method is compared with the time solution and the results were satisfactory. The transient stability regions determined are valid for any changes in loading conditions and fault location. This method is a good candidate for on-line assessment of transient stability of power systems. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
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Calcul des courants de courts-circiuts tenant compte des éléments shunts et des rapports hors-normaux des transformateursProulx, Robert January 1981 (has links)
No description available.
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Analysis and characterization of general security regions in power networksBanakar, M. Hadi January 1980 (has links)
No description available.
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Secure operation and planning of electric power systems by pattern recognition by Danny Sik-Kwan Fok.Fok, Danny Sik-Kwan January 1986 (has links)
No description available.
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Electricity theft detection on a low voltage reticulation environmentDoorduin, Riaan 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Electricity theft in South Africa has become a major problem. This led to several developments
from both industries and research institutes to counter these actions. Since equipment is already
installed and major capital has been invested to provide electricity for a broad spectrum
of consumers, the challenge is to find a low cost solution harnessing current investments and
technology to detect electricity theft more accurately.
This thesis investigates into the electricity theft topic. Two different methods, Time Domain
Pulse Reflectometry and a data driven platform based on the Theory of Constraints philosophy,
were investigated to provide means to detect and determine the impact of illegal electricity
usage. Both methods required detailed designs to conduct preliminary proof of concept tests in
a laboratory environment.
These methods are evaluated against their economical viability, possible practical implications
and applications. This thesis presents a practical approach to electricity theft detection
and provides the basic tools for management of this ever-increasing problem. / AFRIKAANSE OPSOMMING: Suid Afrika se elektrisiteit diefstal statistiek het die afgelope jare skrikwekkend gegroei. Dit het
die industrie genoop om baie meer navorsing in die area te doen. Met reeds gevestigde toerusting
en tegnologie om di´e energie medium so effektief moontlik te versprei, is die uitdaging juis
om ’n ekonomiese oplossing te vind om reeds beskikbare tegnologie¨e meer doeltreffend aan te
wend.
Die doel van die tesis is om die gebied van elektrisiteit diefstal na te vors. Twee verskillende
metodes is ondersoek, naamlik Tydgebied-pulse-reflektometrie en ’n informasie gebaseerde
stelsel wat op die Randvoorwaarde Teorie gebaseer is, om effektief die omvang van elektrisiteit
diefstal in ’n mikro, asook makro omgewing te bepaal. Die twee metodes is in ’n beheerde
omgewing getoets sodat die konsepte wat ontwikkel is bewys kon word.
Die metodes is ge-evalueer in terme van die ekonomiese lewensvatbaarheid daarvan met inagneming
van die praktiese implikasies. Die tesis bied bestuur die nodige kennis om elektrisiteit
diefstal in die praktyk doeltreffend die hok mee te slaan.
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MMI, SCADA and ALARM philosophy for disturbed state operating conditions in an electrical utilityCandy, Richard Brodrick Charles January 1995 (has links)
A project report submitted to the Faculty of Engineering, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 1995. / Advances in digital computing technology make it possible to improve the design
of the Man Machine Interface (MMI), SCADA and ALARM modules used in
electrical utility control centres. to overcome the problem of control staff data
overloading. A possible solution is proposed, based on-an explicit representation
of a disturbed power system state in addition to quiescent conditions.
The structure of modem SCADA, installations is analysed in terms of the
computing power of full graphic workstations, the quantities of element data
delivered to the control room and the capabilities of intelligent remote terminal
units. This analysis indicates that existing designs for the presentation of SCADA
data need to change to solve the data overloading-problem.
The proposed philosophy moves the focus of attention from the element level up
to the device level by grouping and dividing all elements into categories at the
RTU and linking them to their parent device, Control staff are notified graphically
on the one-line displays, next to the device in question, of the existence of
abnormal elements by category. The element state details for the device are only
displayed on demand, resulting in a 95% reduction of alarm text messages.
Suggestions are made as to the software functions needed at tbe RTU and the
workstation to assist with the display of system data. Lastly racommendations are
offered to reduce maintenance by standardising and pre-ordering device element
data. / AC2017
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Power control in CDMA systems.January 2000 (has links)
by Kin Kwong Leung. / Thesis submitted in: November 1999. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 67-[70]). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Code Division Multiple Access (CDMA) --- p.1 / Chapter 1.1.1 --- The Cellular Concept --- p.2 / Chapter 1.2 --- Fading and Power Control --- p.3 / Chapter 1.2.1 --- Large Scale Fading --- p.3 / Chapter 1.2.2 --- Small Scale Fading --- p.4 / Chapter 1.2.3 --- Power Control --- p.5 / Chapter 1.2.4 --- Standard Interference Function --- p.5 / Chapter 1.3 --- Previous Work --- p.6 / Chapter 1.3.1 --- Power Control --- p.6 / Chapter 1.3.2 --- Convergence Analysis --- p.8 / Chapter 1.4 --- Scope of this Thesis --- p.8 / Chapter 1.5 --- Organization of the Thesis --- p.9 / Chapter 2 --- System Model --- p.10 / Chapter 2.1 --- System and Definitions --- p.10 / Chapter 2.2 --- Varying Link Gains Model --- p.11 / Chapter 2.3 --- SIR model in CDMA System --- p.13 / Chapter 2.4 --- Simulation Model --- p.14 / Chapter 3 --- Fade Margin --- p.17 / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.2 --- Fixed-step Power Control Algorithm --- p.18 / Chapter 3.3 --- Definitions and Feasibility of SIR --- p.19 / Chapter 3.3.1 --- Definition --- p.19 / Chapter 3.3.2 --- Feasibility --- p.20 / Chapter 3.4 --- Performance Analysis on Fading Channel --- p.22 / Chapter 3.4.1 --- Single-User --- p.22 / Chapter 3.4.2 --- Multiple-User --- p.24 / Chapter 4 --- Generalized Step Power Control Algorithm --- p.28 / Chapter 4.1 --- Introduction --- p.28 / Chapter 4.2 --- Generalized Fixed Step Power Control Algorithm --- p.29 / Chapter 4.3 --- Existence of the Solution --- p.30 / Chapter 4.4 --- Parameter Optimization --- p.31 / Chapter 4.4.1 --- Single-User --- p.34 / Chapter 4.4.2 --- Multiple-User --- p.37 / Chapter 4.5 --- Performance Analysis --- p.41 / Chapter 4.5.1 --- Single-User --- p.41 / Chapter 4.5.2 --- Multiple-User --- p.42 / Chapter 4.6 --- Hybrid Scheme --- p.47 / Chapter 5 --- Convergence Analysis --- p.49 / Chapter 5.1 --- Introduction --- p.49 / Chapter 5.2 --- Totally Asynchronous Models --- p.50 / Chapter 5.3 --- Normalized Interference Function --- p.52 / Chapter 5.4 --- Existence of Quantized Solution --- p.53 / Chapter 5.5 --- Convergence Theorem --- p.55 / Chapter 6 --- Conclusion and Future Work --- p.64 / Chapter 6.1 --- Conclusion --- p.64 / Chapter 6.2 --- Future Works --- p.65 / Bibliography --- p.67
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Nonlinear neural control with power systems applicationsChen, Dingguo 30 September 1998 (has links)
Extensive studies have been undertaken on the transient stability of large interconnected
power systems with flexible ac transmission systems (FACTS) devices installed.
Varieties of control methodologies have been proposed to stabilize the postfault system
which would otherwise eventually lose stability without a proper control. Generally speaking,
regular transient stability is well understood, but the mechanism of load-driven voltage
instability or voltage collapse has not been well understood. The interaction of generator
dynamics and load dynamics makes synthesis of stabilizing controllers even more challenging.
There is currently increasing interest in the research of neural networks as identifiers
and controllers for dealing with dynamic time-varying nonlinear systems. This study
focuses on the development of novel artificial neural network architectures for identification
and control with application to dynamic electric power systems so that the stability of the
interconnected power systems, following large disturbances, and/or with the inclusion of
uncertain loads, can be largely enhanced, and stable operations are guaranteed.
The latitudinal neural network architecture is proposed for the purpose of system
identification. It may be used for identification of nonlinear static/dynamic loads, which
can be further used for static/dynamic voltage stability analysis. The properties associated
with this architecture are investigated.
A neural network methodology is proposed for dealing with load modeling and
voltage stability analysis. Based on the neural network models of loads, voltage stability
analysis evolves, and modal analysis is performed. Simulation results are also provided.
The transient stability problem is studied with consideration of load effects. The
hierarchical neural control scheme is developed. Trajectory-following policy is used so that
the hierarchical neural controller performs as almost well for non-nominal cases as they do
for the nominal cases. The adaptive hierarchical neural control scheme is also proposed
to deal with the time-varying nature of loads. Further, adaptive neural control, which is
based on the on-line updating of the weights and biases of the neural networks, is studied.
Simulations provided on the faulted power systems with unknown loads suggest that the
proposed adaptive hierarchical neural control schemes should be useful for practical power
applications. / Graduation date: 1999
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Planning for controllable network devices in power transmission systemsKosterev, Dmitry N. 28 February 1996 (has links)
The full capacity of the existing transmission lines is often underutilized
due to the system stability requirements. Controllable network devices represent
the effective means of improving the system stability, and their deployment allows
better use of the existing transmission facilities and can help to avoid construction of
new lines. This dissertation addresses system analysis and modeling of controllable
network devices.
Transient angle stability is one of the major requirements limiting transfer
capability of the power transmission systems. The theoretical concepts of transient
angle controllability using controllable network devices are considered in this dissertation.
The main results are derived for a general transmission network structure
and applied to series and shunt compensators as well as braking resistors. The
proposed approach allows to quantify controllability and to relate it to the control
device size, type and location in the transmission network.
Transient stability controllers are needed to maximize the device effect on the
transient angle stability enhancement. The transient stability controller functional
structure is discussed and the design requirements for each component are specified.
The examples of controller designs are presented.
Emerging technologies such as Thyristor-Controlled Series Compensators and
Synchronous Voltage Sources offer superior control capabilities and performance
characteristics as compared to conventional compensators. Unlike conventional compensators,
the new controllable network devices are very complex dynamical systems
and require more comprehensive modeling for time-domain studies and controller
designs. Detailed models of a Thyristor-Controlled Series Compensator and a Synchronous
Voltage Source for powerflow, transient stability, and electro-magnetic
transient studies are presented.
Finally, a detailed planning study for increasing transfer capability of the
Montana transmission system using controlled series compensation is presented. A
variety of design and performance requirements is considered in this study, which
makes it a useful reference for similar planning projects. / Graduation date: 1996
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