140 results on '"Theethayi, Nelson"'
Search Results
2. Performance of underground cables that use OFDM systems for broadband power-line communications
- Author
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Anatory, Justinian, Theethayi, Nelson, and Thottappillil, Rajeev
- Subjects
Power lines -- Design and construction ,Broadband transmission -- Research ,Electrical cables -- Design and construction ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Published
- 2009
3. Channel characterization for indoor power-line networks
- Author
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Anatory, Justinian, Theethayi, Nelson, and Thottappillil, Rajeev
- Subjects
Computer network protocols -- Usage ,Communications circuits -- Design and construction ,Communications circuits -- Models ,Power lines -- Design and construction ,Protocol ,Business ,Computers ,Electronics ,Electronics and electrical industries - Published
- 2009
4. A method for interfacing lumped-circuit models and transmission-line system models with application to railways
- Author
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Mazloom, Ziya, Theethayi, Nelson, and Thottappillil, Rajeev
- Subjects
Crosstalk -- Observations ,Business ,Computers ,Electronics ,Electronics and electrical industries - Published
- 2009
5. Effects of multipath on OFDM systems for indoor broadband power-line communication networks
- Author
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Anatory, Justinian, Theethayi, Nelson, and Thottappillil, Rajeev
- Subjects
Broadband transmission -- Research ,Communications circuits -- Design and construction ,Power lines -- Properties ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
Power-line networks are an excellent infrastructure for broadband data transmission. However, various multipaths within a broadband power-line communication (BPLC) system exist due to stochastic changes in the network load impedances, branches, etc. This further affects network performance. This paper attempts to investigate the performance of indoor channels of a BPLC system that uses orthogonal frequency-division multiplexing (OFDM) techniques. It is observed that when a branch is added in the link between the sending and receiving end of an indoor channel, an average of 4-dB power loss is found. Additionally, when the terminal impedances of the branch change from the line characteristic impedance to impedance of lower values, the power loss (signal-to-noise ratio) is about 0.67 dB/[ohm] On the contrary, for every increase in the terminal impedances by 100 [ohm], above the line characteristic impedance, the power loss is 0.1 dB/[ohm]. When the line terminal impedances are close to short or open circuits, OFDM techniques show degraded performance. This situation is also observed when the number of branches increases. In this paper, it is shown that to overcome such performance degradation, the concatenated Reed-Solomon codes/interleaved Viterbi methods can be used. The observations presented in the paper could be useful for an efficient design of a BPLC system that uses OFDM techniques. Index Terms--Branched network, broadband power-line communication (BPLC), communication channel model, concatenated coding, convolutional codes, impulsive noise, interleaving, orthogonal frequency-division multiplexing (OFDM), Reed--Solomon codes.
- Published
- 2009
6. A broadband power-line communication system design scheme for typical Tanzanian low-voltage network
- Author
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Anatory, Justinian, Theethayi, Nelson, Thottappillil, Rajeev, and Mvungi, Nerey H.
- Subjects
Telecommunication lines -- Properties ,Communications circuits -- Design and construction ,Broadband transmission -- Research ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
Information and communications technologies (ICTs) are gaining importance in developing countries. Power-line network is a potential infrastructure for ICT services provision. Power-fines are highly interconnected network with stochastic variation in number of branches. Under such distributed network conditions the design of a broadband power-line communication (BPLC) system is a challenge. In this paper a case study of an actual power-line network, representative of a low-voltage BPLC channel in Dares Salaam, Tanzania is considered. We shall investigate the performance of such a low-voltage channel that uses orthogonal frequency division multiplexing (OFDM) technique with binary phase shift keying (BPSK) modulation scheme for communication. For sensitivity analysis, three different transmitter locations were chosen and receiver points were varied to identify the possible degraded performance scenarios. Analysis show that in the frequency bands of 100 MHz, the channel delay spread for such networks is about 4 [micro]s, giving a maximum number of subchannels 4096 with 512 cyclic prefix. To improve the degraded performance scenarios, the concatenated Reed Solomon outer code with punctured convolution inner code was applied to the network. It was found that when the branches were terminated by its corresponding characteristic impedances the performance is improved by 10-20 dB compared to a corresponding uncoded system. On the contrary for a coded system when the branches were terminated either in low or higher impedances compared to branch characteristic impedances the improvement was greater than 2-15 dB. This study demonstrates that the specification proposed by IEEE-802.16 Broadband wireless access working groups can be used for performance improvement of distributed low-voltage systems. Index Terms--Broadband power-line communication, channel model, concatenated coding, impulsive noise, interleaving, multipath channel, punctured convolutional codes, Reed Solomon codes, transfer function.
- Published
- 2009
7. The effects of load impedance, line length, and branches in typical low-voltage channels of the BPLC systems of developing countries: transmission-line analyses
- Author
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Anatory, Justinian, Theethayi, Nelson, Thottappillil, Rajeev, Kissaka, Mussa, and Mvungi, Nerey
- Subjects
Power lines -- Usage ,Transfer functions -- Evaluation ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper presents the influence of line length, number of branches (distributed and concentrated), and terminal impedances on the performance of a low-voltage broadband power-line communication channel. For analyses, the systems chosen are typical low-voltage power-line networks found in Tanzania. The parameters varied were the network's load impedances, direct line length (from transmitter to receiver), branched line lengths, and number of branches. From the frequency responses of the transfer functions (ratio of the received and transmitted signal), it is seen that the position of notches and peaks in the amplitude responses are affected by the aforementioned network parameters and topology. As a result, the time-domain responses are attenuated and distorted. Time-domain responses of power-line channels under various conditions are also investigated for a given pulse input at the transmitter. The observations presented in this paper could be useful for suitable power-line communication system design. Index Terms--Branched network, broadband power line, impulse response, interconnections, load impedance, low-voltage channel, multipath, transfer function.
- Published
- 2009
8. Power-line communication channel model for interconnected networks--Part II: multiconductor system
- Author
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Anatory, Justinian, Theethayi, Nelson, and Thottappillil, Rajeev
- Subjects
Powerline networks -- Methods ,Broadband transmission -- Methods ,Time-domain analysis -- Usage ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
In this paper, we present an approach to determine the transfer function for multiconductor power-line networks with distributed branches and load terminations for broadband powerline communication (BPLC) applications. The applicability of the proposed channel model is verified numerically in rime domain using the finite-difference-time domain (FDTD) method for the solution of transmission lines. The channel model simulation results are in excellent agreement with the corresponding FDTD results. The model therefore could be useful in the analysis and design of BPLC systems involving multiconductor power-line topology. Index Terms--Broadband power-line communication (BPLC), communication channel model, multiconductor, multipath branched network, transfer function.
- Published
- 2009
9. Power-line communication channel model for interconnected networks--Part I: two-conductor system
- Author
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Anatory, Justinian, Theethayi, Nelson, and Thottappillil, Rajeev
- Subjects
Powerline networks -- Models ,Computer-generated environments -- Methods ,Computer simulation -- Methods ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper presents a generalized transmission-line approach to determine the transfer function of a power-line network of a two-conductor system (two parallel conductors) with distributed branches. The channel frequency responses are derived considering different terminal loads and branches. The model's time-domain behavior is validated using commercial power system simulation software called Alternative Transients Program-Electromagnetic Transients Program (ATP-EMTP). The simulation results from the model for three different topologies considered have excellent agreement with corresponding ATP-EMTP results. Hence, the model can be considered as a tool to characterize any given power-line channel topology that involves the two-conductor system. In the companion paper (Part II), the proposed method is extended for a multiconductor power-line system. Index Terms--Branched network, communication channel model, multipath, power-line communication (PLC), transfer function.
- Published
- 2009
10. An efficient implementation of the Agrawal et al. model for lightning-induced voltage calculations using circuit simulation software
- Author
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Montano, Raul, Theethayi, Nelson, and Cooray, Vernon
- Subjects
Impedance (Electricity) -- Evaluation ,Electromagnetic interference -- Control ,Power lines -- Design and construction ,Electric power systems -- United States ,Electric power systems -- Research ,Electrical engineering software ,Business ,Computers and office automation industries ,Electronics ,Electronics and electrical industries - Abstract
One of the popular, simple, and accurate field-to-wire coupling models for studying transmission-line lightning interaction is the Agrawal et al. model [1]. In this model, the coupling mechanisms are represented by distributed sources along the line, wherein each distributed source is due to the horizontal component of the illuminating electric field at that point on the line. These sources give rise to the propagating scattered voltage along the line, while the total voltage at any instant at a given point along the line is the sum of scattered voltage and the voltage at that point due to the illuminating vertical component of the electric field. There is a difficulty in applying the Agrawal et al. model with the built-in transmission-line models of various circuit simulation software such as the Alternate Transients Program-Electromagnetic Transients Program [2]-[5], PSpice [6], Simpow [7], PSS/E [7], etc., as the voltage source due to the horizontal component of the electric field in the Agrawal et al. model is in series with the line impedance [1], [8] and not in between two transmission-line segments. In this paper, a simple circuit approach for efficient implementation of the Agrawal et al. model using any circuit simulation software that has built-in transmission-line models is proposed. Index Terms--Electric impedance, interference, lossy circuits, power systems, transient response, transmission line.
- Published
- 2008
11. Responses of airport runway lighting system to direct lightning strikes: comparisons of TLM predictions with experimental data
- Author
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Theethayi, Nelson, Rakov, Vladimir A., and Thottappillil, Rajeev
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Electric lighting -- Safety and security measures ,Lighting -- Safety and security measures ,Airports -- Buildings and facilities ,Lightning -- Influence ,Airports -- Runways ,Electric power systems -- Protection and preservation ,Electric power systems -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
A test airport runway lighting system, including a buried cable protected by a counterpoise and vertical ground rods, was subjected to direct lightning strikes, and currents and voltages measured in different parts of the system were reported earlier by Bejleri et al. In this paper, we attempt to model the lightning interaction with this system using the transmission line theory. Lumped devices along the cable such as current regulator and transformers are ignored; possible nonlinear phenomena (arcing) in the system are neglected; the soil is assumed to be homogeneous. The model-predicted currents in the counterpoise, ground rod, and the cable are compared with the measurements, and a reasonable agreement was found for the currents along the counterpoise. It is found that current in the counterpoise is not much influenced by the presence of the cable. Further, vertical ground rods connected to the counterpoise do not have significant influence on the current distribution along the counterpoise. It appears that the model is unable to predict cable currents and voltages in the test system, presumably due to neglecting nonlinear phenomena in the soil and in cable's insulation and electromagnetic coupling with the lightning channel. Index Terms--Buried cables, counterpoise, lightning, lighting system, transient analysis, transmission line modeling (TLM).
- Published
- 2008
12. Currents in buried grounding strips connected to communication tower legs during lightning strikes
- Author
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Theethayi, Nelson, Thottappillil, Rajeev, Diendorfer, Gerhard, Mair, Martin, and Pichler, Hannes
- Subjects
Towers -- Design and construction ,Towers -- Maintenance and repair ,Power lines -- Design and construction ,Lightning -- Properties ,Impedance (Electricity) -- Control ,Business ,Electronics ,Electronics and electrical industries - Abstract
During a lightning strike to communication tower stroke currents are shared by the tower and by the shields of the cables along the tower. The currents in the tower proceed towards the grounding system (possibly a combination of counterpoises or ring conductors or ground rods or grounding grids) connected to tower legs' foundation. In this paper, lightning strike to communication tower on mount Gaisberg in Austria is considered and measured currents at the tower top and those shared by an instrumented grounding strip connected to one of the tower leg's are presented. The measured currents at different locations on the 70-m long ground strip are compared with the predictions of a frequency dependant lossy transmission line (TL) model and reasonably good agreement was found. From this validation it is claimed that the TL models are appropriate for lightning transient analysis of grounding systems. Index Terms--Transmission line theory, lightning, impedance, admittance, counterpoise.
- Published
- 2008
13. Pulse propagation along transmission lines in the presence of corona and their implication to lightning return strokes
- Author
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Cooray, Vernon and Theethayi, Nelson
- Subjects
Power lines -- Design and construction ,Electric waves -- Observations ,Electromagnetic radiation -- Observations ,Electromagnetic waves -- Observations ,Wave propagation -- Research ,Lightning -- Properties ,Corona (Electricity) -- Properties ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
Transmission line equations in air in the presence of corona are derived. The analysis shows that the corona caused by a voltage or a current pulse propagating along a transmission line can be represented by a series of corona current sources distributed along the line. Corona has two effects on the voltage or current pulses propagating along a transmission line. First, it will clamp down the pulse amplitude at the front of the pulse to the corona threshold. Second, it will cause the portion of the pulse whose amplitude is larger than the corona threshold to travel with a speed less than the speed of light. The effects of corona on the voltage or current pulses propagating along a transmission line can also be evaluated by introducing a time varying capacitance and a conductance into the transmission line. If the time varying capacitance is assumed to be proportional to the ratio between the corona charge and the applied voltage then one requires both this and the time varying conductance to represent the corona effects more accurately. Analysis of the return stroke as a current pulse propagating along a transmission line undergoing corona shows that the corona effects may explain the reason why the measured return stroke speeds are considerably less than the speed of light. Moreover, based on the effects of corona, a physical justification for the concepts used in the current generation type return stroke models is provided. Index Terms--Admittance, corona, electromagnetic transient propagation, impedance, lightning, transmission lines.
- Published
- 2008
14. An experimental validation for broadband power-line communication (BPLC) model
- Author
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Anatory, Justinian, Theethayi, Nelson, Thottappillil, Rajeev, Kissaka, Mussa M., and Mvungi, Nerey H.
- Subjects
Broadband transmission -- Equipment and supplies ,Power lines -- Design and construction ,Communications circuits -- Design and construction ,Voltage -- Measurement ,Frequency response (Electrical engineering) -- Evaluation ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
Recently, different models have been proposed for analyzing the broadband power-line communication (BPLC) systems based on transmission-line (TL) theory. In this paper, we make an attempt to validate one such BPLC model with laboratory experiments by comparing the channel transfer functions. A good agreement between the BPLC model based on TL theory and experiments are found for channel frequencies up to about 100 MHz. This work with controlled experiments for appropriate validation could motivate the application and extension of TL theory-based BPLC models for the analysis of either indoor or low-voltage or medium-voltage channels. Index Terms--Branched network, broadband power line, frequency response, indoor channel, low-voltage channel, medium-voltage channel, multipath, power-line channel, transfer function.
- Published
- 2008
15. On the choice between transmission line equations and full-wave Maxwell's equations for transient analysis of buried wires
- Author
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Theethayi, Nelson, Baba, Yoshihiro, Rachidi, Farhad, and Thottappillil, Rajeev
- Subjects
Power lines -- Design and construction ,Maxwell equations -- Analysis ,Lightning -- Properties ,Electric currents -- Grounding ,Electric currents -- Methods ,Electric power systems -- Protection and preservation ,Electric power systems -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
In this paper, we evaluate the validity of transmission line (TL) solutions in the study of interaction of lightning transients with buried wires. The considered transients have frequencies between a few kilohertz to a few megahertz with risetimes 0.1-10 [micro]s. Comparative simulations using TL equations and full-wave Maxwell's equations are carried out in the paper, and the solutions to both the equations are based on the finite-difference time-domain method. It is found that TL solutions are sufficiently accurate for lightning transient analysis of buried wires. It is also claimed that the TL approach remains valid for all transients having frequencies lower than those of lightning. TL solutions are computationally efficient, particularly when dealing with distributed power and railway systems. The TL approach is valid as long as the transverse electromagnetic mode (TEM) is dominant. However, other modes of propagation, classified as antenna modes, might be present depending upon the type of excitation source, its location, frequency, and the associated media. A possible approximate formula for the frequency above which the validity of TL solutions for buried systems is questionable is proposed based on the concept of penetration depth of fields into the soil. Discussions presented in the paper could motivate the application of TL solutions for electromagnetic transient analyses of the buried conductors of power, railway, and telecommunication systems. Index Terms--Grounding, lightning, power system lightning effects, transmission line (TL) theory, transient analysis.
- Published
- 2008
16. Expressions for current/voltage distribution in broadband power-line communication networks involving branches
- Author
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Anatory, Justinian, Theethayi, Nelson, Thottappillil, Rajeev, Kissaka, Mussa M., and Mvungi, Nerey H.
- Subjects
Power lines -- Design and construction ,Electromagnetic compatibility -- Evaluation ,Impedance (Electricity) -- Control ,Broadband transmission -- Equipment and supplies ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
Estimation of electromagnetic (EM)-field emissions from broadband power-line communication systems (BPLC) is necessary, because at its operating frequencies, the radiated emissions from BPLC systems act as sources of interference/crosstalk to other radio-communication systems. Currently, the transmission-line (TL) system used for BPLC is complex, involving arbitrarily/irregularly distributed branched networks, arbitrary termination loads, varying line lengths, and line characteristic impedance. In order to study the electromagnetic-compatibility (EMC) issues associated with the radiated emissions of such complex BPLC networks, knowledge of current and voltage distributions along the length of the power-line channels is needed. This paper attempts to derive and present generalized expressions for either the current or voltage distribution along the line (whose TL parameters are known) between the transmitting and receiving ends for any line boundary condition and configuration based on the TL theory. The expressions presented in this paper could be beneficial for direct calculation of EM emissions from BPLC systems. Index Terms--Broadband power line, communication channels, electromagnetic compatibility (EMC), load impedance, transmission lines (TLs).
- Published
- 2008
17. The influence of load impedance, line length, and branches on underground cable power-line communications (PLC) systems
- Author
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Anatory, Justinian, Theethayi, Nelson, Thottappillil, Rajeev, Kissaka, M.M., and Mvungi, N.H.
- Subjects
Impedance (Electricity) -- Influence ,Broadband transmission -- Equipment and supplies ,Power electronics -- Research ,Power lines -- Underground ,Power lines -- Design and construction ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
An underground cable power transmission system is widely used in urban low-voltage power distribution systems. In order to assess the performance of such distribution systems as a low-voltage broadband power-line communication (BPLC) channel, this paper investigates the effects of load impedance, line length, and branches on such systems, with special emphasis on power-line networks found in Tanzania. From the frequency response of the transfer function (ratio of the received and transmitted signals), it is seen that the position of notches and peaks in the magnitude are largely affected (observed in time-domain responses too) by the aforementioned network configuration and parameters. Additionally, channel capacity for such PLC channels for various conditions is investigated. The observations presented in this paper could be helpful as a suitable design of the PLC systems for better data transfer and system performance. Index Terms--Branched network, broadband power line, channel capacity, interconnections, load impedance, low-voltage channel, multipath, transfer function, underground cable.
- Published
- 2008
18. On the efficacy of using ground return in the broadband power-line communications--a transmission-line analysis
- Author
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Anatory, Justinian and Theethayi, Nelson
- Subjects
Power lines -- Design and construction ,Impedance (Electricity) -- Control ,Voltage -- Measurement ,Broadband transmission -- Equipment and supplies ,Electric currents -- Grounding ,Electric currents -- Research ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
The power-line infrastructure has been identified as an efficient system suitable for broadband power-line communication (BPLC) to connect and control various end users. However, the network is affected by stochastic attenuations due to the number of interconnected branches, their line lengths, associated terminal loads, etc. There is yet another parameter that could influence the above stated attenuations or distortions depending on the way the signals are allowed to return to the transmitting end. In this paper, we investigate whether a finitely conducting ground return could be used for BPLC and to investigate its performance over the conventional methods where one of the adjacent power-line conductors is used as signal return. This study could be helpful to those who are proposing the use of ground as a return conductor in BPLC systems. It will be shown that the use of ground return for the BPLC system is effective or better only when the ground conductivity is high (>50 mS/m). When ground conditions are poorer, attenuations increase with frequency, making them unsuitable for BPLC. There are situations where poor ground conditions can still be used but only the transmission-fine lengths are shorter. The analysis presented here is based on transmission-line solutions both under lossless (without ground return) and lossy (with ground return) conditions and are applied to typical low-voltage and medium-voltage channels. Comparisons are also made based on the power spectral densities and channel capacities. Index Terms--Branched network, broadband power line, channel capacity, frequency response, ground impedance, low-voltage (LV) channel, medium-voltage (MV) channel, multi-path, power-line channel, transfer function.
- Published
- 2008
19. Broadband power-line communications: the channel capacity analysis
- Author
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Anatory, Justinian, Theethayi, Nelson, Thottappillil, Rajeev, Kissaka, Mussa M., and Mvungi, Nerey H.
- Subjects
Broadband transmission -- Equipment and supplies ,Power lines -- Design and construction ,Voltage -- Measurement ,Broadband Internet ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
The power line has been proposed as a solution to deliver broadband services to end users. Various studies in the recent past have reported a decrease in channel capacity with an increase in the number of branches for a given channel type whether it is an indoor or low-voltage (LV) or medium-voltage (MV) channel. Those studies, however, did not provide a clear insight as to how the channel capacity is related to the number of distributed branches along the line. This paper attempts to quantify and characterize the effects of channel capacity in relation to the number of branches and with different terminal loads for a given type of channel. It is shown that for a power spectral density (PSD) between -90 dBm/Hz to--30 dBm/Hz, the channel capacity decreases by a 20-30 Mb/s/branch, 14-24 Mb/s/branch, and a 20-25 Mb/s/branch for an MV channel, LV channel, and indoor channel, respectively. It is also shown that the channel capacity is minimum when the load impedance is terminated in characteristic impedances for any type of channel treated here. It is shown that there could be a significant loss in channel capacity if a ground return was used instead of a conventional adjacent conductor return. The analysis presented in this paper would help in designing appropriate power-line communication equipment for better and efficient data transfer. Index Terms--Branched network, broadband power line, channel capacity, frequency response, indoor channel, low-voltage (LV) channel, medium-voltage (MV) channel, multipath, power-line channel, transfer function.
- Published
- 2008
20. On reducing the lightning transients in buried shielded cables using follow-on earth wire
- Author
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Theethayi, Nelson and Thottappillil, Rajeev
- Subjects
Transients (Dynamics) -- Control ,Power lines -- Design and construction ,Electric currents -- Grounding ,Electric currents -- Methods ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper investigates the importance of a follow-on buried bare earth wire for the lightning protection of buried shielded cables. The use of follow-on bare wires for lightning protection of communication towers was suggested as a recommendation in certain standards, without being complemented either by theory or experiments. When lightning transients couple to the cable shields, it induces large currents (depending on the type of coupling) causing transient overvoltages between the inner conductors and the shield. It is shown by simulations based on multiconductor transmission line theory that if the follow-on bare earth conductor is placed in parallel with the shielded cable with the bare earth wire connected to the shield at the current injection end, then the shield current, and thereby, the internal transient voltages of the cable are reduced considerably. Index Terms--Cable insulation, cable shielding, grounding, lightning, transfer impedance, transmission lines.
- Published
- 2007
21. The effects of load impedance, line length, and branches in the BPLC--transmission-lines analysis for medium-voltage channel
- Author
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Anatory, Justinian, Theethayi, Nelson, Kissaka, Mussa M., Mvungi, Nerey H., and Thottappillil, Rajeev
- Subjects
Electric power transmission -- Research ,Impedance (Electricity) -- Control ,Transfer functions -- Measurement ,Voltage -- Measurement ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper presents the effects of load impedance, line length and branches on the performance of medium-voltage power-line communication (PLC) network. The power-line network topology adopted here is similar to that of the system in Tanzania. Different investigation with regard to network load impedances, direct line length (from transmitter to receiver), branched line length and number of branches has been investigated. From the frequency response of the transfer function (ratio of the received and transmitted signal), it is seen that position of notches and peaks in the magnitude and phase responses are largely affected in terms of attenuation and dispersion by the above said network parameters/configuration. These are observed in the time domain responses too. The observations presented in the paper could be helpful in suitable design of the PLC systems for a better data transfer and system performance. Index Terms--Broadband power line, channel model, communication channels, load impedance, transfer function, transmission lines.
- Published
- 2007
22. The effects of load impedance, line length, and branches in the BPLC--transmission-line analysis for indoor voltage channel
- Author
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Anatory, Justinian, Theethayi, Nelson, Thottappillil, Rajeev, Kissaka, Mussa M., and Mvungi, Nerey H.
- Subjects
Voltage -- Measurement ,Impedance (Electricity) -- Control ,Transfer functions -- Measurement ,Electric power transmission -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper presents the effects of load impedance, line length and branches on the performance of an indoor voltage broadband power line communications (BPLC) network. The power line network topology adopted here is similar to that of the system found in Tanzania. Different investigations with regard to network load impedances, direct line length from transmitter to receiver, branched line length, and number of branches has been carried out. From the frequency response of the transfer function (ratio of the received and transmitted signal), it is seen that position of notches and peaks in the magnitude and phase responses are largely affected by the above said network parameters/configuration, mainly in terms of attenuation and dispersion. These effects are observed in the time domain responses also. The observations presented in the paper could be helpful in the suitable design of the BPLC systems for a better data transfer and system performance. Index Terms--Branched network, communication channel model, multipath, power-line communication, transfer function.
- Published
- 2007
23. External impedance and admittance of buried horizontal wires for transient studies using transmission line analysis
- Author
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Theethayi, Nelson, Thottappillil, Rajeev, Paolone, Mario, Nucci, Carlo Alberto, and Rachidi, Farhad
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Electrical wire -- Properties ,Power lines -- Properties ,Business ,Electronics ,Electronics and electrical industries - Abstract
The paper investigates the applicability of some closed form expressions for the ground impedance and ground admittance of buried horizontal wires (bare and insulated) for lightning or switching transient analyses based on transmission line (TL) theory. In view of the frequency contents that typically characterize such transients, the behavior of the ground impedance and admittance is studied for a wide frequency range up to 10 MHz. Low frequency approximation of the ground impedance is not always appropriate for transient analysis. Sensitivity analyses show that, unlike overhead wires, the ground impedance for buried wires is little sensitive to the ground conductivity. On the other hand, the ground admittance varies strongly with the ground conductivity. The paper also discusses the results of transient analysis of buried cables performed by means of electromagnetic transient programs (EMTP) that neglect the ground admittance. The limits of such an approximation are discussed in order to evaluate the applicability of EMTP-like programs to the transient analysis of buried conductors. Transient pulse propagation in time domain based on finite difference time domain (FDTD) method of solution of TL equations is also discussed for a future inclusion of non-linear phenomena, like soil ionization and arcing/breakdown mechanisms, in the soil. The analysis presented could be useful in estimating surge propagation characteristics of buried wires for appropriate insulation coordination and transient protection. Index Terms--Transmission line theory, lightning, power system transients, impedance, admittance, cables.
- Published
- 2007
24. Technique for reducing transient voltages in multiconductor-shielded cables
- Author
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Theethayi, Nelson, Mazloom, Ziya, and Thottappillil, Rajeev
- Subjects
Strip transmission lines -- Usage ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
It is a common practice that the unused pairs (inactive conductors) in shielded cables are left open (open circuited at the terminal block) in telecommunication systems. In this paper, it is shown by both theory (based on transmission line analysis) and experiments that if those inactive conductors are shorted to the cable shield, then the transient voltages on the other active conductors (conductors in service) can be reduced when external transients/faults due to lightning or switching couple to the shield. This could be a good EMC practice for transient voltage reduction in telecommunication systems. Index Terms--Cable shielding, lightning and transmission line theory, transfer impedance, transient analysis.
- Published
- 2007
25. Experimental investigation of lightning transients entering a Swedish railway facility
- Author
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Theethayi, Nelson, Thottappillil, Rajeev, Yirdaw, Tegegne, Liu, Yaqing, Gotschl, Thomas, and Montano, Raul
- Subjects
Lightning -- Electric properties ,Lightning -- Research ,Electric power systems -- Research ,Railroads -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
Transients caused by lightning in railway facilities have not received much attention. In this paper, we describe the measurements of lightning transients entering a Swedish railway facility during the summer of 2003. The measurements of the transients were made in a technical house that provides an uninterrupted power supply for telecommunication systems and the signal systems. An analysis of the data has shown that transients in excess of 7 kV (peak to peak) can appear across the line-to-neutral supply system due to an indirect lightning strike. Some typical characteristics of the line-to-neutral transient voltages in terms of stroke locations and stroke amplitudes are presented. Further, from the experimental data, an empirical relation for predicting the line-to-neutral transient voltage in terms of stroke location and stroke current amplitude is obtained. Simple induced voltage calculations are presented to identify the levels of induced voltages appearing at the input of the technical house. The influence of ground conductivity on those induced voltages is also presented. The information presented in the paper is an important electromagnetic-compatibility issue associated with the lightning protection for railway systems. Index Terms--Lightning, rail transportation power systems, rail transportation reliability, transients.
- Published
- 2007
26. Some issues concerning lightning strikes to communication towers
- Author
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Theethayi, Nelson and Thottappillil, Rajeev
- Published
- 2007
- Full Text
- View/download PDF
27. The lightning striking distance—Revisited
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Cooray, Vernon, Rakov, Vladimir, and Theethayi, Nelson
- Published
- 2007
- Full Text
- View/download PDF
28. Investigating the validity of existing definitions and empirical equations of effective length/area of grounding wire/grid for transient studies
- Author
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Liu, Yaqing, Theethayi, Nelson, and Thottappillil, Rajeev
- Published
- 2007
- Full Text
- View/download PDF
29. The striking distance of lightning flashes and the early streamer emission (ESE) hypothesis
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Cooray, Vernon and Theethayi, Nelson
- Published
- 2007
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30. On the representation of the lightning return stroke process as a current pulse propagating along a transmission line
- Author
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Theethayi, Nelson and Cooray, Vernon
- Subjects
Electric power transmission -- Research ,Power lines -- Research ,Lightning -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
Assuming that the representation of the lightning return stroke as a current pulse propagating along a transmission line is valid, the effects of different transmission line parameters both on the channel current and the electromagnetic fields are investigated. The transmission line parameters that are incorporated into the study are the spatial variation of the inductance and the capacitance, the channel resistance and its temporal variation and the finite conductance of the line. The results show that the introduction of the time varying channel resistance and the finite conductance will change the predictions of the model in such a direction that they will come closer to the experimental observations. Index Terms--Lightning, modeling, transmission line.
- Published
- 2005
31. An engineering model for transient analysis of grounding system under lightning strikes: nonuniform transmission-line approach
- Author
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Liu, Yaqing, Theethayi, Nelson, and Thottappillil, Rajeev
- Subjects
Lightning -- Research ,Power lines -- Research ,Electric power transmission -- Research ,Electromagnetism -- Research ,Electric currents -- Grounding ,Electric currents -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
A nonuniform transmission line approach is adopted in this paper for modeling the transient behavior of different types of grounding systems under lightning strikes in time domain by solving Telegrapher's equations based on finite-difference time-domain (FDTD) technique. Electromagnetic couplings between different parts of the grounding wires are included using effective per-unit length parameters (l, c, and g), which are space and time dependent. The present model can predict both the effective length and the transient voltage of grounding electrodes accurately, while, an uniform transmission line approach with electrode length dependent per-unit length parameters [19]-[22] fails to predict the same. Unlike the circuit theory approach [1]-[4], the present model is capable of predicting accurately the surge propagation delay in the large grounding system. The simulation results for buried horizontal wires and grounding grids based on the present model are in good agreement with that of the circuit and electromagnetic field approaches [3], [9]. From an engineering point of view, the model presented in this paper is sufficiently accurate, time efficient, and easy to apply. Index Terms--Grounding, lightning, transient analysis, transmission line and finite-difference time-domain (FDTD) methods.
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- 2005
32. Surge propagation and crosstalk in multiconductor transmission lines above ground
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Theethayi, Nelson, primary and Thottappillil, Rajeev, additional
- Published
- 2008
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33. Surge propagation in multiconductor transmission lines below ground
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Theethayi, Nelson, primary and Thottappillil, Rajeev, additional
- Published
- 2008
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34. Electric and magnetic fields from a semi-infinite antenna above a conducting plane
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Thottappillil, Rajeev, Uman, Martin A., and Theethayi, Nelson
- Published
- 2004
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- View/download PDF
35. An improved model for soil ionization around grounding system and its application to stratified soil
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Liu, Yaqing, Theethayi, Nelson, Thottappillil, Rajeev, M. Gonzalez, Raul, and Zitnik, Mihael
- Published
- 2004
- Full Text
- View/download PDF
36. Comparison of different Channel Modeling Techniques used in the BPLC Systems
- Author
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Anatory, Justinian and Theethayi, Nelson
- Subjects
Broadband Power line Channel Models ,loadimpedance ,Branched network - Abstract
The paper compares different channel models used for modeling Broadband Power-Line Communication (BPLC) system. The models compared are Zimmermann and Dostert, Philipps, Anatory et al and Anatory et al generalized Transmission Line (TL) model. The validity of each model was compared in time domain with ATP-EMTP software which uses transmission line approach. It is found that for a power-line network with minimum number of branches all the models give similar signal/pulse time responses compared with ATP-EMTP software; however, Zimmermann and Dostert model indicates the same amplitude but different time delay. It is observed that when the numbers of branches are increased only generalized TL theory approach results are comparable with ATPEMTP results. Also the Multi-Carrier Spread Spectrum (MC-SS) system was applied to check the implication of such behavior on the modulation schemes. It is observed that using Philipps on the underground cable can predict the performance up to 25dB better than other channel models which can misread the actual performance of the system. Also modified Zimmermann and Dostert under multipath can predict a better performance of about 5dB better than the actual predicted by Generalized TL theory. It is therefore suggested for a realistic BPLC system design and analyses the model based on generalized TL theory be used., {"references":["Justinian Anatory, N. Theethayi, and R. Thottappillil \"Power-Line\nCommunication Channel Model for Interconnected Networks - Part I:\nTwo Conductor System\", IEEE Transactions on Power Delivery, Vol.\n24, No. 1, January 2009.","T. Banwell and S. Galli, \"A Novel Approach to the Modeling of the\nIndoor Powerline Channel -Part I: Circuit Analysis and Companion\nModel\", IEEE Trans. On Power Delivery, vol. 20, no.2, April 2005. pp.\n655-663.","M. Zimmermann and K. Dostert; \"A Multipath Model for the Powerline\nChannel\", IEEE Trans. On Communications, vol. 50, No. 4, April 2002.\npp. 553-559","C. Hensen and W. Schulz, \"Time dependence of the channel\ncharacteristics of low voltage power-lines and its effects on hardware\nimplementation,\"AEU Int. J. Electron. Commun., vol. 54, no. 1, pp. 23-\n32, Feb. 2000.","H. Philipps, \"Modeling of power line communication channels,\" in\nProc. 3rd Int. Symp. Power-Line Communications Applications,\nLancaster, U.K., 1999, pp. 14-21.","F. J. Canete, L. Diez, J. A. Cortes, J. T. Entrambasaguas, \"Modelling and\nEvaluation of the Indoor Powerline Transmission Medium\", IEEE\nCommunications Magazine, April 2003.","F. J. Canete, L. Diez, J. A. Cortes, J. T. Entrambasaguas, \"Broadband\nModeling of Indoor Power-Line Channels\", IEEE Trans. On Consumer\nElectronics, Vol. 48, No. 1, Feb. 2002.","X. Ding and J. Meng, \"Channel Estimation and Simulation of an Indoor\nPower-Line Network via a Recursive Time-Domain Solution\", IEEE\nTrans Power Del., vol. 24, no. 1, Jan. 2009.","J. Anatory, M.M. Kissaka and N.H. Mvungi, \"Channel Model for\nBroadband Powerline Communication\", IEEE Trans. On Power\nDelivery, Vol. 22, no. 1, January 2007, pp. 135-141.\n[10] H. W. Dommel, Electromagnetic Transients Program (EMTP Theory\nBook). Portland, OR: Bonneville Power Administration, 1988\n[11] Justinian Anatory and Nelson Theethayi, Broadband Power-Line\nCommunication Systems: Theory and Applications, WIT Press, UK,\nMay, 2010, ISBN 978-1-84564-416-1\n[12] J. Anatory, N. Theethayi, and R. Thottappillil and N.H. Mvungi \"A\nBroadband Power-Line Communication System Design Scheme for\nTypical Tanzanian Low Voltage Network\", IEEE Transactions on Power\nDelivery, Vol. 24, No. 3, pp. 1218-1224, July, 2009"]}
- Published
- 2011
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37. Broadband PowerLine Communications: Performance Analysis
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Anatory, Justinian, Theethayi, Nelson, M. M. Kissaka, and N. H. Mvungi
- Subjects
modulation ,channel performance ,Powerline Communications ,branched network ,channel model ,Data_CODINGANDINFORMATIONTHEORY ,OFDM ,Computer Science::Information Theory - Abstract
Power line channel is proposed as an alternative for broadband data transmission especially in developing countries like Tanzania [1]. However the channel is affected by stochastic attenuation and deep notches which can lead to the limitation of channel capacity and achievable data rate. Various studies have characterized the channel without giving exactly the maximum performance and limitation in data transfer rate may be this is due to complexity of channel modeling being used. In this paper the channel performance of medium voltage, low voltage and indoor power line channel is presented. In the investigations orthogonal frequency division multiplexing (OFDM) with phase shift keying (PSK) as carrier modulation schemes is considered, for indoor, medium and low voltage channels with typical ten branches and also Golay coding is applied for medium voltage channel. From channels, frequency response deep notches are observed in various frequencies which can lead to reduce the achievable data rate. However, is observed that data rate up to 240Mbps is realized for a signal to noise ratio of about 50dB for indoor and low voltage channels, however for medium voltage a typical link with ten branches is affected by strong multipath and coding is required for feasible broadband data transfer., {"references":["J. Anatory, M.M. Kissaka and N.H. Mvungi., \"Trends in\nTelecommunication Services Provision: Power line Network can provide\nalternative for Access in Developing countries\", in the proc. of IEEE\nAfricon, Gaborone, BOTSWANA, 2004, 601-606.","Y.H.Ma, P.L. So, E. Gunawan, \"Performance Analysis of OFDM\nSystems for Broadband Powerline Communications under Impulsive\nNoise and Multipath Effects.\" IEEE Trans. On Power Delivery, Vol. 20,\nNo. 2. April, 2004.","Kim, Y.-H., Kim, S.-C., OFDM Receiver Performance Analysis With\nMeasured Power Line Channel Model For Coded OFDM System,\nProceedings of the 9th IEEE International Symposium on Power-Line\nCommunications, Vancouver, Canada, April 2005, pp. 201 - 205.","Ma, Y.H., So, P.L., Gunawan, E., Guan Y.L., Analysis of Impulsive\nNoise and Multipath Effects on Broadband Power Line\nCommunications, Proceedings of the International Conference on Power\nSystem Technology, Singapore, November. 2004, pp. 1404 - 1409.","Justinian Anatory, M.M. Kissaka and N.H. Mvungi, \"Powerline\nCommunications: The effects of Branches in the network performance\",\nto appear IEEE-ISPLC 2006, Florida, USA, March, 2006.","Ezio Biglieri and Politecnico di Torino, \"Coding and Modulation for a\nHorrible Channel\", IEEE Communications Magazine, May, 2003. pp.\n92-98.","C. Hensen and W. Schulz, \"Time Dependence of the Channel\nCharacteristics of Low Voltage Power-Lines and its Effects on\nHardware Implimentation, \"AEU Int`l. J. Electronics and\nCommunication, vol. 54, no. 1, Feb. 2000, pp. 23-32.","H. Philipps, \"Modelling of Powerline Communication Channels,\" Proc.\n3rd Int-l. Symp. Power-Line Communications and its Applications,\nLancaster, UK, 1999, pp. 14-21.","Zimmermann M. and Dostert K.; \"A Multipath Model for the Powerline\nChannel\", IEEE Trans. On Communications, vol. 50, No. 4, pp. 553-\n559, April 2002.\n[10] Stefano Gali and Thomas Banwell, \"A Novel Approach to the Modeling\nof the Indoor Powerline Channel -Part II: Transfer Function and Its\nProperties\", IEEE Trans. On Power Delivery, vol. 20, no.2, April 2005.\n[11] Justinian Anatory, N. Theethayi, R. Thottappillil, M.M. Kissaka, N.H.\nMvungi, \"The Effects of Interconnections and Branched Network In The\nBroadband Powerline Communications\", Paper E06.2(01188), in Proc.\nof the XXVIIIth General Assembly of International Union of Radio\nSciences, New Delhi, India, Oct. 23-29, 2005.\n[12] Justinian Anatory, M.M. Kissaka and N.H. Mvungi, \"Channel Model for\nBroadband Powerline Communication, to appear IEEE Trans. On Power\nDelivery.\n[13] Dommel H. W., \"Electromagnetic transients program (EMTP theory\nbook)\", Bonneville Power Administration, 1986.\n[14] Richard Van Nee, Ramjee Prasad, \"OFDM for wireless multimedia\ncommunications,\" Boston, Artech House, 2000.\n[15] P. Amirshahi, S. M. Navidpour, M. Kavehrad, \"Performance Analysis of\nUncoded and Coded OFDM Broadband Transmission Over Low\nVoltage Powerline Channels with Impulsive Noise,\" to appear in IEEE\nTransactions on power delivery 2006\n[16] Despina Anastasiadou and Theodore Antonakopoulos, \"Multipath\nCharacterization of Indoor Powerline Networks\", IEEE Trans. On Power\nDelivery, vol. 20, no.1, pp. 90-99, January, 2005.\n[17] Halid Hrasnica, Abdelfatteh Haidine and Ralf Lehnert, \"Broadband\nPowerline Communications Networks-Network Design\", John Wiley &\nSons, Ltd, 2004."]}
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- 2008
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38. Review of Research on Lightning Interaction with the Swedish Railway Network
- Author
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Theethayi, Nelson, Mazloom, Ziya, Thottappillil, Rajeev, Lindeberg, Per-Anders, and Shütte, Thorsten
- Abstract
In the early electrified railway systems, the design of signal and control networks were not always made in accordance with the strict rules of Electromagnetic Compatibility (EMC). This created problems due to Electromagnetic Interference (EMI) when old electro-mechanical signalling, control and communication systems were replaced by modern sensitive electronic circuits. Modern developments in the railway systems have made the system more vulnerable to lightning transients, a natural source of EMI, because the overall network is not designed to reduce the lightning surges to the low levels tolerable to the electronic systems widely being introduced in the railway system. Railway networks are extensive and modernization of signal/control/communication systems are carried out in stages at different times, it is not unusual to find transient related problems in a section of the network on account of inadequate lightning protection design or EMC design of the existing network in which a new module (equipment or system) is introduced. These problems may act as a brake on the upgrading plans of the railways. Also the new railway systems which incorporate advanced signal/control/communication systems sometimes suffers from the effects of lightning transients because many of the standards and guidelines used in the design dates back to the age of electromechanical devices and hence do not include robust transient protection design. There have been many attempts to address EMC issues in railways, but usually these attempts were confined to solving immediate problems of EMI due to introduction of new locomotive drives and EMI due to sparks at the pantograph. A comprehensive review of railway system from the angle of lightning protection and EMC is not yet fully carried out. The Swedish National Rail Administration (Banverket) reported a delay of about 900-1000 hours in the years 2001-02. Lightning transients were found to damage important devices that control train movements, causing traffic stoppage and delays. This work therefore discusses the EMC problems of large distributed systems, with particular reference to lightning interaction with Swedish rail networks [1]. Lightning induces transient overvoltages in railway conductor systems such as tracks, overhead wires, and underground cables, either due to direct lightning strike to the system or due to the coupling of electromagnetic fields from remote strikes. Models based on multiconductor transmission line theory were developed for calculating the induced voltages and currents [1-3]. Some experiments have also been carried out to better understand the way in which the lighting transients’ couple into the systems and also to verify the models used for analysis [4]. From experiments high frequency behavior of different types of transformers used within the railway systems were also derived [1, 6]. Besides, experimental studies on lightning induced transients entering railway systems, failure modes of relay and rectifier units used in the train position/signaling applications for lightning transients are performed. The simulation models are being converted to user friendly software for the practicing engineers of the railway industry [1]. Presented at the EuroEM Conference 2008, Lausanne, Switzerland
- Published
- 2008
39. Lightning interaction with the swedish railway network
- Author
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Theethayi, Nelson, Mazloom, Ziya, Thottappillil, Rajeev, Lindeberg, Per-Anders, and Schütte, Thorsten
- Subjects
Transmission line ,lightning attachment ,transients ,crosstalk - Abstract
In the beginning, the design of signal and control network of railways in early times was not always done in accordance with the strict rules of Electromagnetic Compatibility (EMC). This created problems due to Electromagnetic Interference (EMI) when old electro-mechanical signalling, control and communication systems were replaced by modern sensitive electronic circuits. Modern developments in the railway systems have made the system more vulnerable to lightning transients, a natural source of EMI, because the overall network is not designed to reduce the lightning surges to the low levels tolerable to the electronic systems widely being introduced in the railway system. Railway networks are extensive and modernization of signal/control/communication systems is carried out only in stages at different times, it is not unusual to find transient related problems in a section of the network on account of inadequate lightning protection design or EMC design of the existing network in which a new module (equipment or system) is introduced. One wonders if these problems act as a brake on the upgrading plans of the railways. Also the new railway systems which incorporate advanced signal/control/communication systems sometimes suffers from the effects of lightning transients because many of the standards and guidelines used in the design dates back to the age of electromechanical devices and hence do not include robust transient protection design. There were many attempts to address EMC issues in railways, but usually these attempts were confined to solving immediate problems of EMI due to introduction of new locomotive drives and EMI due to sparks at the pantograph. A comprehensive review of railway system from the angle of lightning protection and EMC is not yet carried out. This work discusses the EMC problems of large distributed systems, with particular reference to lightning interaction with Swedish rail network. Presented at the Railway Engineering Conference 2007 London
- Published
- 2007
40. Blitzeinwirkungen auf Oberleitungs- und Signalanlagen in Schweden
- Author
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Lindeberg, Per-Anders, Mazloom, Ziya, Theethayi, Nelson, Thottappillil, Rajeev, and Schütte, Thorsten
- Subjects
Other Electrical Engineering, Electronic Engineering, Information Engineering ,Annan elektroteknik och elektronik - Abstract
Für ältere elektrotechnische Bahnanlagen waren die Aspekte der elektromagnetischen Verträglichkeit von geringerer Bedeutung als für heutige Anlagen. Vor allem für neuere Signal- und Zugerkennungsanlagen mit kleineren Abmessungen sanken die erlaubten Höchstwerte für Ströme und Spannungen. Dies hat die Störungsempfindlichkeit erhöht. Eine wichtige, wenn nicht die wichtigste Störungsquelle sind atmosphärische Entladungen, also Blitze. Ihre Einwirkung auf elektrifizierte Bahnstrecken in Schweden wurde theoretisch durch Simulationen untersucht. Die Empfindlichkeit der Komponenten wurde experimentell geprüft. Bei Bahnanlagen reicht die Ableitung von Blitzen nicht aus, um Schäden durch Blitzentladungen zu vermeiden. Gefährdete Komponenten sollten durch angemessene Maßnahmen gegenüber elektromagnetischen Störungen besser geschützt werden. QCR 20161209
- Published
- 2007
41. Electromagnetic Interference in Distributed Outdoor Electrical Systems, with an Emphasis on Lightning Interaction with Electrified Railway Network
- Author
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Theethayi, Nelson
- Subjects
Underground Cables ,Railway Systems ,Transmission Lines ,Electrical engineering, electronics and photonics ,Elektroteknik ,Lightning ,Lightning Protection ,elektronik och fotonik ,Electromagnetic Wave Propagation ,Electrical engineering ,Shielding Effectiveness ,Electromagnetic Transients ,Elektroteknik, elektronik och fotonik ,Electromagnetic Interference ,Electromagnetic Compatibility (EMC) ,Grounding - Abstract
This thesis deals with the electromagnetic compatibility (EMC) problems of distributed electrical networks, especially that caused by lightning to electrified railway. Lightning transients were found to damage important devices that control train movements, causing traffic stoppage and delays. This thesis attempts to develop computational models for identification of parameters influencing the coupling phenomena between those devices and lightning. Some supporting experimental investigations are also carried out. This thesis forms the groundwork on the subject of lightning interaction with the electrified railway networks. Lightning induces transient overvoltages in railway conductor systems such as tracks, overhead wires, and underground cables, either due to direct lightning strike to the system or due to the coupling of electromagnetic fields from remote strikes. Models based on multiconductor transmission line theory were developed for calculating the induced voltages and currents. A transmission line return stroke model, that can predict the remote electromagnetic fields comparable to experimental observations, is also developed. Earlier works on modeling earth return impedances for transient studies in power distribution systems are not readily applicable for railways for lightning transients, in cases of low earth conductivities found in Sweden and for large variation in conductor heights. For the wires above ground, the ground impedance models were modified for wide range of frequencies, soil conductivities and wide spread of conductor heights. Influences of pole insulator flashovers, pole-footing soil ionizations and interconnections between the conductors on the lightning surge propagation are studied. Wave propagation in buried shielded and unshielded cables with ground return is studied. Simplified, valid and computationally efficient ground impedance expressions for buried and on-ground wires are proposed. A model for the coupling phenomena (transfer impedance) through multiple cable shields with multiconductor core is also proposed. Besides, experimental studies on lightning induced transients entering a railway technical house, failure modes of relay and rectifier units used in the train position/signaling applications for lightning transients are performed. A high frequency circuit model for the booster transformer for lightning interaction studies is developed. The simulation models are being converted to user-friendly software for the practicing engineers of the railway industry.
- Published
- 2005
42. Indirect Lightning-Induced Voltages Along a Railway Catenary-Track Multiconductor Transmission-Line System With Lumped Components
- Author
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Mazloom, Ziya, primary, Theethayi, Nelson, additional, and Thottappillil, Rajeev, additional
- Published
- 2011
- Full Text
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43. Method to include lumped devices in multi-conductor transmission line system models
- Author
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Mazloom, Ziya, primary, Theethayi, Nelson, additional, and Thottappillil, Rajeev, additional
- Published
- 2009
- Full Text
- View/download PDF
44. First versus subsequent return‐stroke current and field peaks in negative cloud‐to‐ground lightning discharges
- Author
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Nag, Amitabh, primary, Rakov, Vladimir A., additional, Schulz, Wolfgang, additional, Saba, Marcelo M. F., additional, Thottappillil, Rajeev, additional, Biagi, Christopher J., additional, Oliveira Filho, Alcides, additional, Kafri, Ahmad, additional, Theethayi, Nelson, additional, and Gotschl, Thomas, additional
- Published
- 2008
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- View/download PDF
45. A comparison of different approaches to simulate a nonlinear channel resistance in lightning return stroke models
- Author
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De Conti, Alberto, primary, Visacro, Silvério, additional, Theethayi, Nelson, additional, and Cooray, Vernon, additional
- Published
- 2008
- Full Text
- View/download PDF
46. Broadband power-line communication channel model: Comparison between theory and experiments
- Author
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Anatory, Justinian, primary, Theethayi, Nelson, additional, Thottappillil, Rajeev, additional, Kissaka, Mussa M., additional, and Mvungi, Nerey H., additional
- Published
- 2008
- Full Text
- View/download PDF
47. Investigations of factors influencing the channel capacity of power line network for BPLC systems
- Author
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Anatory, Justinian, primary, Theethayi, Nelson, additional, Thottapilli, Rajeev, additional, Mvungi, N.H., additional, and Kissaka, M.M., additional
- Published
- 2007
- Full Text
- View/download PDF
48. Expressions for far electric fields produced at an arbitrary altitude by lightning return strokes
- Author
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Thottappillil, Rajeev, primary, Rakov, Vladimir A., additional, and Theethayi, Nelson, additional
- Published
- 2007
- Full Text
- View/download PDF
49. Important parameters that influence crosstalk in multiconductor transmission lines
- Author
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Theethayi, Nelson, primary, Thottappillil, Rajeev, additional, Liu, Yaqing, additional, and Montano, Raul, additional
- Published
- 2007
- Full Text
- View/download PDF
50. Broadband Power Line Communications: The factors Influencing Wave Propagations in the Medium Voltage Lines
- Author
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Anatory, Justinian, primary, Theethayi, Nelson, additional, Kissaka, Mussa, additional, and Mvungi, Nerey, additional
- Published
- 2007
- Full Text
- View/download PDF
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