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Thottappillil, Rajeev
Publications (10 of 100) Show all publications
Midya, S., Bormann, D., Schütte, T. & Thottappillil, R. (2011). DC Component From Pantograph Arcing in AC Traction System: Influencing Parameters, Impact, and Mitigation Techniques. IEEE transactions on electromagnetic compatibility (Print), 53(1), 18-27
Open this publication in new window or tab >>DC Component From Pantograph Arcing in AC Traction System: Influencing Parameters, Impact, and Mitigation Techniques
2011 (English)In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 53, no 1, p. 18-27Article in journal (Refereed) Published
Abstract [en]

Pantograph arcing in ac traction system generates transients, and causes asymmetries and distortion in supply voltage and current waveforms. These asymmetric voltage and current lead to a net dc component and harmonics that propagate within the traction power and signalling system and cause electromagnetic interference. This problem is enhanced during winter because of the layer of ice/snow on the overhead contact wire. The sliding contact becomes poor and a visible arc moves along with the pantograph. In this paper, it is shown how different parameters like traction current, line speed, power factor, and supply voltage influence the arcing, its characteristics, and the dc components. It is shown that the dc current component increases with increasing train speed and traction current, and reduces at a lower power factor. It is also discussed how the presence of an ice layer influences the arcing and the dc components. It is found that running the trains below the normal operating power factors is an effective choice to mitigate this problem. The findings presented in this paper could be beneficial to estimate the probable limit of the dc component at the planning stage so that proper precautions can be taken at the design stage itself.

Keywords
arcs (electric), electromagnetic interference, interference suppression, pantographs, power factor, power overhead lines, railway electrification, signalling, traction power supplies, AC traction system, DC component, current waveforms, overhead contact wire, pantograph arcing, power factors, signalling system, supply voltage
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-164214 (URN)10.1109/TEMC.2010.2045159 (DOI)
Available from: 2011-12-16 Created: 2011-12-16 Last updated: 2017-12-08Bibliographically approved
Raysaha, R., Kumar, U., Cooray, V. & Thottappillil, R. (2010). Special case of lightning strike to tall objects on ground. In: 30TH International Conference on Lightning Protection, ICLP: . Paper presented at 30TH International Conference on Lightning Protection, ICLP. Cagliary, Italy
Open this publication in new window or tab >>Special case of lightning strike to tall objects on ground
2010 (English)In: 30TH International Conference on Lightning Protection, ICLP, Cagliary, Italy, 2010Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Cagliary, Italy: , 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-142458 (URN)
Conference
30TH International Conference on Lightning Protection, ICLP
Available from: 2011-01-14 Created: 2011-01-14 Last updated: 2016-04-19Bibliographically approved
Anatory, J., Theethayi, N., Thottappillil, R. & Mvungi, N. H. (2009). A broadband power-line communication system design scheme for typical Tanzanian low-voltage network. IEEE Transactions on Power Delivery, 24(3), 1218-1224
Open this publication in new window or tab >>A broadband power-line communication system design scheme for typical Tanzanian low-voltage network
2009 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 3, p. 1218-1224Article in journal (Refereed) Published
Abstract [en]

Information and communications technologies (ICTs) are gaining importance in developing countries. Power-line network is a potential infrastructure for ICT services provision. Power-lines 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 Dar es 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 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.

Place, publisher, year, edition, pages
USA: IEEE, 2009
Keywords
broadband networks, carrier transmission on power lines, channel coding, concatenated codes, convolutional codes, modulation coding, OFDM modulation, phase shift keying, radio access networks, Reed-Solomon codes, wireless channels
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113132 (URN)10.1109/TPWRD.2009.2014478 (DOI)000267765100029 ()0885-8977 (ISBN)
Note

10731611 broadband power-line communication system design Tanzanian low-voltage network orthogonal frequency division multiplexing OFDM technique binary phase shift keying BPSK modulation scheme sensitivity analysis channel delay spread concatenated Reed Solomon outer code punctured convolution inner code characteristic impedance IEEE-802.16 broadband wireless access network

Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
Anatory, J., Theethayi, N. & Thottappillil, R. (2009). Channel characterization for indoor power-line networks. IEEE Transactions on Power Delivery, 24(4), 1883-1888
Open this publication in new window or tab >>Channel characterization for indoor power-line networks
2009 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 4, p. 1883-1888Article in journal (Refereed) Published
Abstract [en]

Power-line networks are promising mediums by which broadband services can be offered, such as Internet services, voice over Internet protocol, digital entertainment, etc. In this paper, an analysis of delay spread, coherence bandwidth, channel capacity, and averaged delay in the frequency bands up to 100 MHz for typical indoor power-line networks are studied. Earlier studies for indoor power-line networks considered frequencies up to 30 MHz only and earlier works have shown that at these frequency bands, the data rates are generally low and are inefficient for digital entertainment in comparison with wireless local-area networks standards, such as IEEE 802.11 n. In this paper, it is shown that at 100 MHz, the average channel capacity for typical indoor power-line networks can be up to 2 Gb/s and it is found that by increasing the number of branches in the link between transmitting and receiving ends, the average channel capacity decreases from 2 Gb/s to 1 Gb/s (when the number of branches was increased by four times for a power spectral density of -60 dBm/Hz). At the same time, the coherence bandwidth decreased from 209.45 kHz to 137.41 kHz, which is much better than the coherence bandwidths corresponding to 30-MHz systems. It is therefore recommended to operate the indoor power-line networks at 100-MHz bandwidths for a wide variety of broadband services.

Place, publisher, year, edition, pages
USA: IEEE, 2009
Keywords
Branched network, communication channel model, multipath, power-line communication, transfer function
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113129 (URN)10.1109/TPWRD.2009.2021044 (DOI)000270139900017 ()0885-8977 (ISBN)
Note

10880672 channel characterization indoor power-line networks channel capacity averaged delay frequency bands wireless local-area networks transfer function power-line communication

Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
Midya, S., Bormann, D., Mazloom, Z., Schütte, T. & Thottappillil, R. (2009). Conducted and Radiated Emission from Pantograph Arcing in AC Traction System. In: : . Paper presented at IEEE PES General Meeting. Calgary, Canada.
Open this publication in new window or tab >>Conducted and Radiated Emission from Pantograph Arcing in AC Traction System
Show others...
2009 (English)Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Calgary, Canada.: , 2009
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113289 (URN)
Conference
IEEE PES General Meeting
Available from: 2010-01-26 Created: 2010-01-26 Last updated: 2018-06-08Bibliographically approved
Anatory, J., Theethayi, N. & Thottappillil, R. (2009). Effects of multipath on OFDM systems for indoor broadband power-line communication networks. IEEE Transactions on Power Delivery, 24(3), 1190-1197
Open this publication in new window or tab >>Effects of multipath on OFDM systems for indoor broadband power-line communication networks
2009 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 3, p. 1190-1197Article in journal (Refereed) Published
Abstract [en]

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/. On the contrary, for every increase in the terminal impedances by 100 , above the line characteristic impedance, the power loss is 0.1 dB/. 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.

Place, publisher, year, edition, pages
USA: IEEE, 2009
Keywords
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
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113130 (URN)10.1109/TPWRD.2009.2014281 (DOI)000267765100026 ()0885-8977 (ISBN)
Note

10731635 OFDM systems indoor broadband power line communication networks broadband data transmission indoor channels orthogonal frequency division multiplexing techniques signal-to-noise ratio power loss concatenated Reed-Solomon codes interleaved Viterbi methods

Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
Månsson, D., Thottappillil, R. & Bäckström, M. (2009). Methodology for Classifying Facilities with respect to Intentional EMI. IEEE transactions on electromagnetic compatibility (Print), 51(1), 46-52
Open this publication in new window or tab >>Methodology for Classifying Facilities with respect to Intentional EMI
2009 (English)In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 51, no 1, p. 46-52Article in journal (Refereed) Published
Abstract [en]

It is argued that it is the intent behind the electromagnetic interference in intentional electromagnetic interference (IEMI) that causes problems to large distributed systems and facilities even if   they are designed by traditional zoning concept rules. Hardening such   facilities against IEMI requires a correspondence between the electromagnetic zone boundary and the physical access control boundary. The three characteristics of a facility, the accessibility, susceptibility, and consequence, are discussed in the context of vulnerability to IEMI. A methodology for classification of facilities

Keywords
Classification, electromagnetic (EM) topology, facilities, intentional electromagnetic interference (IEMI)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-97503 (URN)10.1109/TEMC.2008.2010327 (DOI)000263641000006 ()
Available from: 2008-09-10 Created: 2008-09-10 Last updated: 2017-12-14Bibliographically approved
Midya, S., Bormann, D., Schutte, T. & Thottappillil, R. (2009). Pantograph Arcing in Electrified Railways—Mechanism and Influence of Various Parameters—Part I: With DC Traction Power Supply. IEEE Transactions on Power Delivery, 24(Copyright 2009, The Institution of Engineering and Technology), 1931-9
Open this publication in new window or tab >>Pantograph Arcing in Electrified Railways—Mechanism and Influence of Various Parameters—Part I: With DC Traction Power Supply
2009 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no Copyright 2009, The Institution of Engineering and Technology, p. 1931-9Article in journal (Refereed) Published
Abstract [en]

Pantograph arcing is a common phenomenon in electrified railway systems. This is also a source of broadband-conducted and radiated electromagnetic interference (EMI) for vehicle as well as traction power and signaling systems. In this paper and the companion paper, experimental analyses of pantograph arcing phenomena are presented for dc and ac feeding systems, respectively. Influences of different parameters on dc traction system, such as supply-voltage polarity, relative motion between pantograph and overhead contact wire, namely, forward motion along the track (longitudinal), and lateral sliding motion of the pantograph (zigzag) are presented here. From the voltage and current waveforms of the test runs, it is shown that pantograph arcing is a polarity-dependent phenomenon. For the positive-fed overhead traction system, where pantograph is cathode, the supply interruptions due to zigzag motion are comparatively less compared to negatively fed traction systems. As a result, the transients, due to pantograph arcing, are more frequent in negatively fed traction systems. It is found that the arc root movement along the electrode surfaces (pantograph-contact wire) is governed by the relative motion and polarity of the electrodes. The analyses presented in this paper also form a foundation to understand the pantograph arcing process and the corresponding influential parameters with the ac supply presented in the companion paper. The findings presented in this paper could be beneficial for coming up with appropriate mitigation techniques from the EMI due to pantograph arcing in dc-fed traction systems.

Place, publisher, year, edition, pages
USA: IEEE, 2009
Keywords
arcs (electric), electromagnetic interference, pantographs, railway electrification, traction power supplies
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-139770 (URN)10.1109/TPWRD.2009.2021035 (DOI)
Note

10880716 electrified railway system dc traction power supply broadband-conducted interference electromagnetic interference pantograph arcing phenomena ac feeding system dc feeding system dc traction system supply-voltage polarity pantograph lateral sliding motion polarity-dependent phenomenon positive-fed overhead traction system supply interruption negatively fed overhead traction system arc root movement electrode

Available from: 2010-12-29 Created: 2010-12-29 Last updated: 2017-12-11
Midya, S., Bormann, D., Schutte, T. & Thottappillil, R. (2009). Pantograph arcing in electrified railways-mechanism and influence of various parameters-Part II: with AC traction power supply. IEEE Transactions on Power Delivery, 24(4), 1940-50
Open this publication in new window or tab >>Pantograph arcing in electrified railways-mechanism and influence of various parameters-Part II: with AC traction power supply
2009 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, Vol. 24, no 4, p. 1940-50Article in journal (Refereed) Published
Abstract [en]

Pantograph arcing with AC supply generates transients, cause asymmetries and distortion in supply voltage and current waveforms and can damage the pantograph and the overhead contact line. The asymmetry generates a net dc component and harmonics, which propagate within the traction power and signalling system and causes electromagnetic interference. Unlike DC-fed systems (Part I), the arcing in ac supply is complex because of the zero crossing of currents and voltages. In this paper, we discuss the mechanisms of sliding contact and arcing between pantograph-contact wire using the experimental setup described in Part I. Influences of various parameters and test conditions on arcing phenomenon and their signature patterns on the supply voltage and current waveforms are presented. It is shown how the arcing mechanism and corresponding asymmetry in the voltage and current waveforms are governed by line speed, current, supply voltage, inductive load, and pantograph material. The asymmetry in the current waveform is mainly due to the difference in the duration of successive zero-current regions and uneven distortion of the waveshapes. This, in turn, creates the asymmetry in the voltage waveform. The findings presented in this paper could be beneficial for coming up with appropriate mitigation techniques from the electromagnetic interference due to pantograph arcing in AC traction systems.

Place, publisher, year, edition, pages
USA: IEEE, 2009
Keywords
arcs (electric), pantographs, railway electrification, traction power supplies
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113152 (URN)10.1109/TPWRD.2009.2021036 (DOI)0885-8977 (ISBN)
Note

10880717 electrified railway AC traction power supply pantograph arcing electromagnetic interference mitigation sliding contact mechanism signalling system DC-fed system signature pattern voltage-current waveform

Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2016-04-14Bibliographically approved
Anatory, J., Theethayi, N. & Thottappillil, R. (2009). Performance of underground cables that use OFDM systems for broadband power-line communications. IEEE Transactions on Power Delivery, 24(4), 1889-1897
Open this publication in new window or tab >>Performance of underground cables that use OFDM systems for broadband power-line communications
2009 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 4, p. 1889-1897Article in journal (Refereed) Published
Abstract [en]

Power-line networks are proposed for broadband data transmission. The presence of multipaths within the broadband power-line communication (BPLC) system, due to stochastic changes in the network load impedances, branches, etc. pose a real challenge as it affects network performance. This paper attempts to investigate the performance of an orthogonal frequency-division multiplexing (OFDM)-based BPLC system that uses underground cables. It is found that when a branch is added in the link between the sending and receiving end, there is an average of 4-dB power loss. In addition, when the terminal impedances of the branches that are connected to the link between the transmitting and receiving end vary from line characteristic impedance to low-impedance values, the power loss (signal-to-noise ratio) is about 0.35 dB/ . On the contrary, for an increase in the terminal impedances by 100 above line characteristic impedance, the power loss is 0.23 dB//. When the branch 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. It is shown that to overcome degraded network performance, the concatenated Reed-Solomon codes/interleaved Viterbi methods can be used, which could be used for an efficient design of the BPLC system that uses OFDM techniques.

Place, publisher, year, edition, pages
USA: IEEE, 2009
Keywords
Branched network, broadband communication, concatenated coding, convolution codes, impulse noise, interleaved coding, multipath channels, orthogonal frequency-division multiplexing (OFDM), power-line communication, Reed-Solomon codes
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113126 (URN)10.1109/TPWRD.2009.2031674 (DOI)000270139900018 ()0885-8977 (ISBN)
Note

10880673 OFDM broadband power-line communications broadband data transmission network load impedances orthogonal frequency-division multiplexing concatenated coding convolution codes impulse noise interleaved coding multipath channels Reed-Solomon codes

Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
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