Time-domain modeling of high-frequency electromagnetic wave propagation, overhead wires, and earth

Prediction of radiated fields from transmission lines has not previously been studied from a panoptical power system perspective. The application of BPL technologies to overhead transmission lines would benefit greatly from an ability to simulate real power system environments, not limited to the transmission lines themselves. Presently circuitbased transmission line models used by EMTP-type programs utilize Carson’s formula for a waveguide parallel to an interface. This formula is not valid for calculations at high frequencies, considering effects of earth return currents. This thesis explains the challenges of developing such improved models, explores an approach to combining circuit-based and electromagnetics modeling to predict radiated fields from transmission lines, exposes inadequacies of simulation tools, and suggests methods of extending the validity of transmission line models into very high frequency ranges. Electromagnetics programs are commonly used to study radiated fields from transmission lines. However, an approach is proposed here which is also able to incorporate the components of a power system through the combined use of EMTP-type models. Carson’s formulas address the series impedance of electrical conductors above and parallel to the earth. These equations have been analyzed to show their inherent assumptions and what the implications are. Additionally, the lack of validity into higher frequencies has been demonstrated, showing the need to replace Carson’s formulas for these types of studies. This body of work leads to several conclusions about the relatively new study of BPL. Foremost, there is a gap in modeling capabilities which has been bridged through integration of circuit-based and electromagnetics modeling, allowing more realistic prediction of BPL performance and radiated fields. The proposed approach is limited in its scope of validity due to the formulas used by EMTP-type software. To extend the range of validity, a new set of equations must be identified and implemented in the approach. Several potential methods of implementation have been explored. Though an appropriate set of equations has not yet been identified, further research in this area will benefit from a clear depiction of the next important steps and how they can be accomplished. Prediction of radiated fields from transmission lines has not previously been studied from a panoptical power system perspective. The application of BPL technologies to overhead transmission lines would benefit greatly from an ability to simulate real power system environments, not limited to the transmission lines themselves. Presently circuitbased transmission line models used by EMTP-type programs utilize Carson’s formula for a waveguide parallel to an interface. This formula is not valid for calculations at high frequencies, considering effects of earth return currents. This thesis explains the challenges of developing such improved models, explores an approach to combining circuit-based and electromagnetics modeling to predict radiated fields from transmission lines, exposes inadequacies of simulation tools, and suggests methods of extending the validity of transmission line models into very high frequency ranges. Electromagnetics programs are commonly used to study radiated fields from transmission lines. However, an approach is proposed here which is also able to incorporate the components of a power system through the combined use of EMTP-type models. Carson’s formulas address the series impedance of electrical conductors above and parallel to the earth. These equations have been analyzed to show their inherent assumptions and what the implications are. Additionally, the lack of validity into higher frequencies has been demonstrated, showing the need to replace Carson’s formulas for these types of studies. This body of work leads to several conclusions about the relatively new study of BPL. Foremost, there is a gap in modeling capabilities which has been bridged through integration of circuit-based and electromagnetics modeling, allowing more realistic prediction of BPL performance and radiated fields. The proposed approach is limited in its scope of validity due to the formulas used by EMTP-type software. To extend the range of validity, a new set of equations must be identified and implemented in the approach. Several potential methods of implementation have been explored. Though an appropriate set of equations has not yet been identified, further research in this area will benefit from a clear depiction of the next important steps and how they can be accomplished

A new methodology for network scale simulation of emerging power line communication standards

This paper presents the development of a new methodology for the simulation of Power Line Communication (PLC) within the popular Electromagnetic Transients Programme-Alternative Transients Programme (EMTP-ATP). As a first application, the comparative performance of the emerging Orthogonal Frequency Division Multiplexing (OFDM) based Prime and G3-PLC narrowband standards is investigated. Models of both standards have been created within the EMTP-ATP and simulations performed using frequency dependent line models and realistic transformer models as terminations. It is observed that both standards are severely affected by the highly frequency selective nature of the MV power line channel and a more considered choice of OFDM parameters may be necessary for optimal performance on MV networks

Comparative study of 220 kV overhead transmission lines models subjected to lightning strike simulation by using electromagnetic and alternative transients program

Introduction. In high voltage networks intended for the transport of electrical energy, lightning can strike an electric line striking either a phase conductor, a pylon or a ground wire, causing significant overvoltage on the transmission lines classified as stresses the most dangerous for transformer stations and electro-energy systems in general. Modeling transmission lines becomes more complicated, if the frequency dependence of resistance and serial inductance due to the effect of lightning strike in the conductors and in the earth is considered. The difficulty increases the fact that the parameters of the line can be defined and calculated only in the frequency domain, while the simulation of transients is wanted to be in the time domain. Problem. Several models (J.R. Marti, Bergeron, nominal PI, Semlyen and Noda) exist for the modeling of transmission lines, the Electromagnetic Transients Program/Alternative Transient Program software (EMTP/ATPDraw) gives the possibility to choose between these models which is delicate due to the fact that we do not have experimental results to validate and justify the choice among the models available in the software. In this context, practical value: the overhead transport line OAT-El Hassi (220 kV) of the city of Sétif located in the north east of Algeria is used for the modeling of lightning strike by using the EMTP/ATPDraw software. Originality. A comparative study of the investigation of a lightning strike on an existing high voltage transmission line by different models of existing lines in the EMTP/ATPDraw software library of this software. Results. It was concluded that the choice of the model of the line is very important given the accuracy and quality of the curves of the voltage presented at the different calculation points. Вступ. У високовольтних мережах, призначених для передачі електроенергії, блискавка може вдарити по лінії електропередач, уразивши або фазний провід, опору, або заземлюючий провід, викликаючи значні перенапруги на лініях електропередач, визначені як загрози, найбільш небезпечні для трансформаторних підстанцій та електроенергетичних систем загалом. Моделювання ліній електропередач ускладнюється, якщо враховувати частотну залежність опору та послідовної індуктивності внаслідок дії удару блискавки у провідниках та землі. Складність підвищується тим, що параметри лінії можуть бути визначені і розраховані тільки в частотній області, в той час як моделювання перехідних процесів бажано проводити в часовій області. Проблема. Існує кілька моделей (J.R. Marti, Bergeron, номінальна П-подібна схема заміщення, Semlyen і Noda) для моделювання ліній електропередач, комп‘ютерна  програма електромагнітних перехідних процесів/альтернативна програма перехідних процесів EMTP/ATPDraw дає можливість вибирати між цими моделями, що є «тонким питанням» через те, що ми не маємо експериментальних результатів для перевірки та обґрунтування вибору серед моделей, доступних у програмному забезпеченні. У цьому контексті, практична цінність: для моделювання удару блискавки за допомогою програмного забезпечення EMTP/ATPDraw використана повітряна лінія електропередачі ОАТ-Ель-Хассі (220 кВ) міста Сетіф, розташованого на північному сході Алжиру. Оригінальність. Порівняльне дослідження вивчення удару блискавки на існуючій високовольтній лінії електропередач за різними моделями існуючих ліній у бібліотеці програм  EMTP/ATPDraw цього програмного забезпечення. Результати. Зроблено висновок, що вибір моделі лінії дуже важливий з урахуванням точності та якості кривих напруг, представлених у різних розрахункових точках.

Power system fault analysis based on intelligent techniques and intelligent electronic device data

This dissertation has focused on automated power system fault analysis. New contributions to fault section estimation, protection system performance evaluation and power system/protection system interactive simulation have been achieved. Intelligent techniques including expert systems, fuzzy logic and Petri-nets, as well as data from remote terminal units (RTUs) of supervisory control and data acquisition (SCADA) systems, and digital protective relays have been explored and utilized to fufill the objectives. The task of fault section estimation is difficult when multiple faults, failures of protection devices, and false data are involved. A Fuzzy Reasoning Petri-nets approach has been proposed to tackle the complexities. In this approach, the fuzzy reasoning starting from protection system status data and ending with estimation of faulted power system section is formulated by Petri-nets. The reasoning process is implemented by matrix operations. Data from RTUs of SCADA systems and digital protective relays are used as inputs. Experiential tests have shown that the proposed approach is able to perform accurate fault section estimation under complex scenarios. The evaluation of protection system performance involves issues of data acquisition, prediction of expected operations, identification of unexpected operations and diagnosis of the reasons for unexpected operations. An automated protection system performance evaluation application has been developed to accomplish all the tasks. The application automatically retrieves relay files, processes relay file data, and performs rule-based analysis. Forward chaining reasoning is used for prediction of expected protection operation while backward chaining reasoning is used for diagnosis of unexpected protection operations. Lab tests have shown that the developed application has successfully performed relay performance analysis. The challenge of power system/protection system interactive simulation lies in modeling of sophisticated protection systems and interfacing the protection system model and power system network model seamlessly. An approach which utilizes the "compiled foreign model" mechanism of ATP MODELS language is proposed to model multifunctional digital protective relays in C++ language and seamlessly interface them to the power system network model. The developed simulation environment has been successfully used for the studies of fault section estimation and protection system performance evaluation

A STUDY OF PROTECTION SYSTEM TO IMPROVE POWER SYSTEM RELIABILITY USING ATP (ALTERNATIVE TRANSIENT PROGRAM)

Electric power systems are one of the largest and more complex systems man has ever built. Faults represent a threat to the operation and security of power systems if the faults are not promptly corrected. Therefore protection of the power system is very important. Protective relays are electronic or electromechanical devices that are designed to protect equipment and limit injury caused by electrical failures. Protective relays cannot prevent faults; they can only limit the damage caused by faults. This thesis investigates the importance of power systems protection and also introduces the widely used power system software, ATP ( Alternative Transient Program ). Using this software, power system are modeled and disturbance scenarios such as lightning overvoltages and short circuit are generated. The simulation of this scenarios provides the graphical charateristics of the power system through the use of PLOTXY function. Another major work in this project is the modeling of relays that were embeded in the system to enable classed loop simulation whereby the relay will provide a 'feedback' to the system. The 'feedback' is a trip signal which will be sent to the circuit breaker to open or reclose. The algorithm of the relay are designed by writing specific code using the MODELS language. The relays succesfully fuctioned according to the algorithm when simulated under different disturbance scenarios and the results obtained were same as the predicted output

Fault location on the high voltage series compensated power transmission networks

Nowadays power transmission networks are capable of delivering contracted power from any supplier to any consumer over a large geographic area under market control, and thus transmission lines are incorporated with FACTs series compensated devices to increase the power transfer capability with improvement to system integrity. Conventional fault location methods developed in the past many years are not suitable for FACTs transmission networks. The obvious reason is that FACTs devices in transmission networks introduce non-linearity in the system and hence linear fault detection methods are no longer valid. Therefore, it is still a matter of research to investigate developing new fault detection techniques to cater for modern transmission network configurations and solve implementation issues maintaining required accuracy. This PhD research work is based on developing an accurate and robust new fault location algorithm for series compensated high voltage transmission lines, considering many issues such as transmission line models, configurations with series compensation features. Building on the existing knowledge, a new algorithm has been developed for the estimation of fault location using the time domain approach. In this algorithm, instantaneous fault signals from the transmission line ends are measured and applied to the algorithm to calculate the distance to fault. The new algorithm was tested on two port transmission line model developed using EMTP/ATP software and measured fault data from the simulations are exported to the MATLAB space to run the algorithm. Broad range of faults has been simulated considering various fault cases to test the algorithm and statistical results obtained. It was observed that the accuracy of location of fault on series compensated transmission line using this algorithm is in the range from 99.7 % to 99.9% in 90% of fault cases. In addition, this algorithm was further improved considering many practical issues related to modern series compensated transmission lines (with TCSC var compensators) achieving similar accuracies in the estimation of fault location

Solid state transformer technologies and applications: a bibliographical survey

This paper presents a bibliographical survey of the work carried out to date on the solid state transformer (SST). The paper provides a list of references that cover most work related to this device and a short discussion about several aspects. The sections of the paper are respectively dedicated to summarize configurations and control strategies for each SST stage, the work carried out for optimizing the design of high-frequency transformers that could adequately work in the isolation stage of a SST, the efficiency of this device, the various modelling approaches and simulation tools used to analyze the performance of a SST (working a component of a microgrid, a distribution system or just in a standalone scenario), and the potential applications that this device is offering as a component of a power grid, a smart house, or a traction system.Peer ReviewedPostprint (published version