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BETA
Thottappillil, RajeevORCID iD iconorcid.org/0000-0002-1607-2493
Alternative names
Publications (10 of 138) Show all publications
Becerra Garcia, M., Long, M., Schulz, W. & Thottappillil, R. (2018). On the estimation of the lightning incidence to offshore wind farms. Electric power systems research, 157, 211-226
Open this publication in new window or tab >>On the estimation of the lightning incidence to offshore wind farms
2018 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 157, p. 211-226Article in journal (Refereed) Published
Abstract [en]

Field observations have shown that the frequency of dangerous lightning events to wind turbines, calculated according to the IEC standard 61400-24:2010, is grossly underestimated. This paper intends to critically revisit the evaluation of the incidence of downward lightning as well as self-initiated and other-triggered upward flashes to offshore wind power plants. Three different farms are used as case studies. The conditions for interception of stepped leaders in downward lightning and the initiation of upward lightning is evaluated with the Self-consistent Leader Inception and Propagation Model (SLIM). The analysis shows that only a small fraction of damages observed in the analysed farms can be attributed to downward lightning. It is also estimated that only a small fraction (less than 19%) of all active thunderstorms in the area of the analysed farms can generate sufficiently high thundercloud fields to self-initiate upward lightning. Furthermore, it is shown that upward flashes can be triggered even under low thundercloud fields once a sufficiently high electric field change is generated by a nearby lightning event. Despite of the uncertainties in the incidence evaluation, it is shown that upward flashes triggered by nearby positive cloud-to-ground flashes produce most of the dangerous lightning events to the case studies.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Lightning, Lightning damage, Risk assessment, Upward lightning, Wind power farms, Clouds, Damage detection, Electric fields, Standards, Wind power, Wind turbines, Downward lightnings, Field observations, High electric fields, Offshore wind power plants, Positive cloud-to-ground flashes, Propagation modeling, Offshore wind farms
National Category
Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-223115 (URN)10.1016/j.epsr.2017.12.008 (DOI)000425203500021 ()2-s2.0-85039859714 (Scopus ID)
Note

Export Date: 13 February 2018; Article; CODEN: EPSRD; Correspondence Address: Becerra, M.; KTH Royal Institute of Technology, Department of Electromagnetic EngineeringSweden; email: marley@kth.se. QC 20180327

Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2018-03-27Bibliographically approved
Long, M., Becerra, M. & Thottappillil, R. (2017). Modeling the Attachment of Lightning Dart and Dart-Stepped Leaders to Grounded Objects. IEEE transactions on electromagnetic compatibility (Print), 59(1), 128-136
Open this publication in new window or tab >>Modeling the Attachment of Lightning Dart and Dart-Stepped Leaders to Grounded Objects
2017 (English)In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 59, no 1, p. 128-136Article in journal (Refereed) Published
Abstract [en]

Attachment of downward subsequent dart leaders has been recently proposed as a possible mechanism of lightning damage of wind turbine blades. Since subsequent dart and dart-stepped leaders propagating after the first lightning discharge are one-to-two orders of magnitude faster than downward stepped leaders, the direct evaluation of the dart leader interception by upward connecting leaders from the turbine has not been attempted before. In this paper, the self-consistent leader inception and propagation model SLIM is used to evaluate the lightning attachment process of subsequent dart leaders by accounting the rapid changing electric fields produced by their fast descent toward the ground. For this, an improved evaluation of the charge per unit length required to thermalize the upward connecting leader is derived. The analysis considers upward connecting leaders propagating along the preheated channel of a prior discharge. Three study cases of lightning attachment of dart leaders and dart-stepped leader reported in rocket-triggered lightning experiments are evaluated. It is shown that reasonable predictions of the length, duration, and velocity of positive upward connecting leaders can be obtained with SLIM in agreement with the experimental results. Further research on upward leader discharges necessary to improve the modeling of attachment of dart lightning leaders is discussed.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2017
Keywords
Lightning attachment, lightning dart and dart-stepped leaders, rocket-triggered lightning
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-198944 (URN)10.1109/TEMC.2016.2594703 (DOI)000387359700015 ()2-s2.0-84982204112 (Scopus ID)
Funder
StandUp
Note

QC 20170113

Available from: 2017-01-13 Created: 2016-12-22 Last updated: 2017-11-29Bibliographically approved
Long, M., Becerra Garcia, M. & Thottappillil, R. (2017). On the attachment of dart lightning leaders to wind turbines. Electric power systems research, 151, 432-439
Open this publication in new window or tab >>On the attachment of dart lightning leaders to wind turbines
2017 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 151, p. 432-439Article in journal (Refereed) Published
Abstract [en]

Wind turbines are prone to damages due to lightning strikes and the blades are one of the most vulnerable components. Even though the blade tip is usually protected in standard designs, lightning damages several meters away from it have also been observed in some field studies. However, these damages inboard from the tip cannot be explained by the attachment of downward stepped leaders or the initiation of upward lightning alone. In this paper, the attachment of dart leaders in an upward lightning flash is investigated as a mechanism of strikes to inboard sections of the blade and the nacelle of large wind turbines. Dart leaders in an upward lightning flash use the channel previously ionized by the preceding stroke or the continuous current. The analysis is performed with the self-consistent leader inception and propagation model (SLIM). A commercial large wind turbine with 45 m long blades and hub height of 80 m is analysed as a case study. The impact of the prospective return stroke peak current, the rotation angle of the blade and the wind on the location of lightning strikes on this mechanism is analysed. The probability of lightning attachment of dart leaders along the blade for the case study is also calculated. It is shown that this damage mechanism could create a new strike point only when the blade of a wind turbine rotates sufficiently from its initial position (at the inception of the initial upward leader) until the start of the dart leader approach. Thus, dart leader attachment is a mechanism that can explain lightning strikes to the nacelle and to the inboard region several meters away from the blade tip in large wind turbines. However, dart leader attachment cannot explain the lightning strikes observed in the close vicinity of the blade tip (in the region between 1.5 and 6 m from it).

Place, publisher, year, edition, pages
Elsevier Ltd, 2017
Keywords
Dart lightning leaders, Lightning attachment, Lightning damages, Wind turbines, Lightning, Lightning protection, Turbomachine blades, Damage mechanism, Large wind turbines, Leader inception, Lightning leader, Lightning strikes, Propagation modeling, Upward lightning, Turbine components
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-218880 (URN)10.1016/j.epsr.2017.06.011 (DOI)000406984700039 ()2-s2.0-85021219468 (Scopus ID)
Note

QC 20180115

Available from: 2018-01-15 Created: 2018-01-15 Last updated: 2018-01-15Bibliographically approved
Kande, M., Isaksson, A. J., Thottappillil, R. & Taylor, N. (2017). Rotating Electrical Machine Condition Monitoring Automation-A Review. MACHINES, 5(4), Article ID 24.
Open this publication in new window or tab >>Rotating Electrical Machine Condition Monitoring Automation-A Review
2017 (English)In: MACHINES, ISSN 2075-1702, Vol. 5, no 4, article id 24Article, review/survey (Refereed) Published
Abstract [en]

We review existing machine condition monitoring techniques and industrial automation for plant-wide condition monitoring of rotating electrical machines. Cost and complexity of a condition monitoring system increase with the number of measurements, so extensive condition monitoring is currently mainly restricted to the situations where the consequences of poor availability, yield or quality are so severe that they clearly justify the investment in monitoring. There are challenges to obtaining plant-wide monitoring that includes even small machines and non-critical applications. One of the major inhibiting factors is the ratio of condition monitoring cost to equipment cost, which is crucial to the acceptance of using monitoring to guide maintenance for a large fleet of electrical machinery. Ongoing developments in sensing, communication and computation for industrial automation may greatly extend the set of machines for which extensive monitoring is viable.

Place, publisher, year, edition, pages
MDPI AG, 2017
Keywords
condition monitoring, rotating electrical machine, motor fleet, plant-wide
National Category
Reliability and Maintenance
Identifiers
urn:nbn:se:kth:diva-219328 (URN)10.3390/machines5040024 (DOI)000415730400004 ()2-s2.0-85034232859 (Scopus ID)
Note

QC 20171204

Available from: 2017-12-04 Created: 2017-12-04 Last updated: 2017-12-04Bibliographically approved
Long, M., Becerra, M. & Thottappillil, R. (2016). On the lightning incidence to wind Farms. In: : . Paper presented at 33rd International Conference on Lightning Protection - Estoril, Portugal, 25-30 September, 2016. IEEE
Open this publication in new window or tab >>On the lightning incidence to wind Farms
2016 (English)Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
IEEE, 2016
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-197280 (URN)10.1109/ICLP.2016.7791459 (DOI)000392212500124 ()2-s2.0-85011079198 (Scopus ID)
Conference
33rd International Conference on Lightning Protection - Estoril, Portugal, 25-30 September, 2016
Note

QC 20161220

Available from: 2016-11-30 Created: 2016-11-30 Last updated: 2017-02-27Bibliographically approved
Zhou, H., Rakov, V. A., Diendorfer, G., Thottappillil, R., Pichler, H. & Mair, M. (2015). A study of different modes of charge transfer to ground in upward lightning. Journal of Atmospheric and Solar-Terrestrial Physics, 125, 38-49
Open this publication in new window or tab >>A study of different modes of charge transfer to ground in upward lightning
Show others...
2015 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 125, p. 38-49Article in journal (Refereed) Published
Abstract [en]

We examined simultaneous measurements of currents and close electric field changes, as well as highspeed video images, associated with pulses superimposed on the initial continuous current (ICC pulses) and M-components following return strokes in upward flashes initiated from the Gaisberg Tower in Austria. For tower-initiated lightning, upward leaders often create multiple branches below the cloud base that can facilitate initiation of transients at relatively low heights along the grounded channel carrying ICC of some tens to hundreds of amperes. In this situation, a conducting channel is present, which is necessary for the M-component mode of charge transfer to ground, but the excitation wave (leader), after entering the channel, cannot form a long-front downward M-wave, because of the relatively short distance between the entry (junction) point and the strike-object top. Clearly, two parallel channels, one previously existing and the other newly formed (or rejuvenated) are involved in the charge transfer, and there is a common channel section between the junction point and the strike object. We use the term "mixed mode of charge transfer to ground", to indicate that in the case of low junction point the "classical" M-component mode is not possible, even though a conducting channel to ground (an attribute of the M-component mode) is present. The mixed mode scenario is also applicable to impulsive processes during continuing currents following return strokes in upward lightning.

National Category
Geochemistry
Identifiers
urn:nbn:se:kth:diva-164433 (URN)10.1016/j.jastp.2015.02.008 (DOI)000351648300005 ()2-s2.0-84924557006 (Scopus ID)
Note

QC 20150427

Available from: 2015-04-27 Created: 2015-04-17 Last updated: 2017-12-04Bibliographically approved
Long, M., Becerra, M. & Thottappillil, R. (2015). On the Simulation of the Interception of Lightning Dart Leaders. In: Lightning Protection (XIII SIPDA), 2015 International Symposium on: . Paper presented at 2015 International Symposium on Lightning Protection (XIII SIPDA), Balneário Camboriú, Brazil, 28th Sept. – 2nd Oct. 2015 (pp. 288-292). IEEE conference proceedings
Open this publication in new window or tab >>On the Simulation of the Interception of Lightning Dart Leaders
2015 (English)In: Lightning Protection (XIII SIPDA), 2015 International Symposium on, IEEE conference proceedings, 2015, p. 288-292Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the numerical evaluation of the propagation of positive upward connecting leaders under the influence of lightning dart leaders. The simulation is performed with the self-consistent leader inception and propagation model - SLIM-. An analytical expression is derived for calculating the charge per unit length required to thermalize a new upward leader segment. The simulation is validated with two dart leader attachment events in a lightning triggering experiment reported in the literature. Good agreement between the estimations and the measurements of dart leader interception in length, duration and velocity of upward leader propagation has been found. Further analysis is carried out on dart lightning leader interception.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2015
Keywords
dart leader, upward connecting leader, rocket triggered lightning
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-178002 (URN)000382966700051 ()2-s2.0-84962292059 (Scopus ID)978-1-4799-8753-5 (ISBN)
Conference
2015 International Symposium on Lightning Protection (XIII SIPDA), Balneário Camboriú, Brazil, 28th Sept. – 2nd Oct. 2015
Note

QC 20160216

Available from: 2015-12-01 Created: 2015-12-01 Last updated: 2016-12-01Bibliographically approved
Zhou, H., Thottappillil, R. & Diendorfer, G. (2014). A new approach to calculate electric fields and charge density distribution when lightning strikes a tall object. Electric power systems research, 113(SI), 15-24
Open this publication in new window or tab >>A new approach to calculate electric fields and charge density distribution when lightning strikes a tall object
2014 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 113, no SI, p. 15-24Article in journal (Refereed) Published
Abstract [en]

We derive electric field expressions, associated with lightning strikes to a tall object, using the monopole (Continuity Equation) technique which is distinctly different from the traditional dipole (Lorentz Condition) technique. Expressions to calculate the charge density along the tall object and lightning channel based on the assumptions of the transmission line model of the lightning strikes to a tall object and a series point current source placed at the object top, are also derived. These expressions are used to calculate the very close-range electric fields in the monopole (Continuity Equation) technique in terms of the retarded current and charge density along the tower and lightning channel and their results are compared with those calculated from the traditional dipole (Lorentz Condition) technique in terms of the retarded current along the tower and lightning channel. Alternative explanations are provided to the inversion of polarity of the vertical electric field at very close range based on distribution of charge density along the tower and lightning channel.

Keywords
Charge density distribution, Monopole technique, Electric field, Polarity reversal, Tall object, Lightning
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-148345 (URN)10.1016/j.epsr.2014.03.011 (DOI)000337554200005 ()2-s2.0-84901603261 (Scopus ID)
Note

QC 20140805

Available from: 2014-08-05 Created: 2014-08-05 Last updated: 2017-12-05Bibliographically approved
Thottappillil, R. (2014). Computation of electromagnetic fields from lightning discharge (2ed.). In: Vernon Cooray (Ed.), The Lightning Flash: (pp. 351-403). London: Institution of Engineering and Technology
Open this publication in new window or tab >>Computation of electromagnetic fields from lightning discharge
2014 (English)In: The Lightning Flash / [ed] Vernon Cooray, London: Institution of Engineering and Technology, 2014, 2, p. 351-403Chapter in book (Other academic)
Abstract [en]

Electromagnetic fields from lightning can couple to electrical systems and produce transient overvoltages, which can cause power and telecommunication outages and destruction of electronics. Knowledge of electromagnetic fields at high altitudes produced by return strokes in cloud-to-ground (CG) lightning are required in the study of transient luminous events in the mesosphere. Electric and magnetic field pulses from various electrical breakdown events in the lightning are used in detecting and locating lightning flashes. Therefore, calculation of the electric and magnetic fields from different lightning processes has several practical applications. In this chapter, expressions for electric and magnetic fields are derived for charge and current configurations applicable to lightning. In general lightning currents and charges vary with time. First, simple expressions for non-time varying cases are presented. Then, electric and magnetic field expressions from time-varying lightning sources are presented.

Place, publisher, year, edition, pages
London: Institution of Engineering and Technology, 2014 Edition: 2
Series
Power and Energy Series ; 69
Keywords
Lightning, Electromagnetic theory, Electromagnetic Compatibility
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-182386 (URN)978-1-84919-691-8 (ISBN)978-1-84919-692-5 (ISBN)
Note

QC 20160225

Available from: 2016-02-18 Created: 2016-02-18 Last updated: 2016-02-25Bibliographically approved
Long, M., Becerra Garcia, M. & Thottappillil, R. (2014). On the interception of dart lightning leaders from wind turbine blades. In: Lightning Protection (ICLP), 2014 International Conference on: . Paper presented at 2014 International Conference on Lightning Protection (ICLP), Shanghai, China (pp. 1376-1381). IEEE conference proceedings
Open this publication in new window or tab >>On the interception of dart lightning leaders from wind turbine blades
2014 (English)In: Lightning Protection (ICLP), 2014 International Conference on, IEEE conference proceedings, 2014, p. 1376-1381Conference paper, Published paper (Refereed)
Abstract [en]

Wind farms are an important part of renewable energy system but they are frequently damaged by lightning strikes, especially to the blades of the turbine. Recent field observations have shown lightning damages several meters inboard away from the blade tip, which cannot be explained fully by the interception of stepped leaders or swept strokes. This paper proposes a possible additional mechanism to explain the lightning attachment points in inboard area of blade due to dart lightning leaders. This mechanism is verified through the Self-consistent Leader Inception and Propagation Model -SLIM-which is used here to dynamically evaluate the upward connecting leader propagation under the influence of both stepped and dart leaders.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2014
Keywords
Dart Lightning Leaders, Lightning attachment points, Turbine blade rotation, SLIM
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-166296 (URN)10.1109/ICLP.2014.6973345 (DOI)000358572100261 ()2-s2.0-84919793515 (Scopus ID)
Conference
2014 International Conference on Lightning Protection (ICLP), Shanghai, China
Note

QC 20150522

Available from: 2015-05-07 Created: 2015-05-07 Last updated: 2016-12-01Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-1607-2493

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