Lightning Interaction with Tall Towers
• Nelson Theethayi (past member)
Sponsors: Swedish Research Council (VR) [2006-2008], Swedish National Rail Administration (Banverket), and European COST Action P-18 ‘Physics of Lightning Flash and its Effects’.
It has been observed that very tall towers, usually in excess of 100 m, is capable of initiating lightning from thunderclouds under certain conditions by launching an upward leader from the tower top all the way to the overhead cloud. Height of the tower, topography of the place where the tower is situated, the background electric field just before launching of the leader from tower top, and meteorological conditions (height of charged cloud) are some of the factors that are known to influence the lightning initiation from towers. The research is an extension of the work that was carried out by the group previously in a VR project during the period 2005-2008. Emphasis in this project will be 1) to create validated models that can quantify a given tower’s influence on the incidence of lightning in that area, 2) to estimate the influence of the struck object on the statistics of the lightning current parameters to the tower and retrieve the undisturbed statistics of parameters if lightning were to ground, 3) to estimate the possible enhancement of the lightning electromagnetic pulse far from the tower, both at ground level and at high altitudes, due to lightning strike to towers as opposed to level ground, 4) to validate concepts of lightning protection of associated electrical network and equipment connected to communication tower.
The 100-m tall radio communication tower locates at the mountain Gaisberg, near Salzburg in Austria will continued to be used as the experimental facility (see http://www.aldis.at/research/projects.html) in collaboration with ALDIS (Austrian Lightning Detection & Information System), Austrian Electrotechnical Association (OVE). This tower is situated on a mountain 1287 meters above sea level. At present, the tower is instrumented for measuring lightning currents simultaneous with wide-band electric fields at close and far ranges. A high-speed video system, which can take up to 1000 frames per second provides sufficient optical information of the total lightning strike to the Gaisberg tower.
Lightning, Tall towers, Electromagnetic compatibility.
Helin Zhou, G. Diendorfer, Rajeev Thottappillil, H. Pichler, and M. Mair, Characteristics of upward bipolar lightning flashes observed at the Gaisberg Tower, Journal of Geophysical Research, doi:10.1029/2011JD015634, in press, 2011.
Helin. Zhou, N. Theethayi, G. Diendorfer, Rajeev Thottappillil, and V.A. Rakov, On estimation of the effective height of towers on mountaintops in lightning incidence studies, Journal of Electrostatics, 68(5), 415-418, 2010.
Zhou H., G. Diendorfer, R. Thottappillil, H. Pichler, and M. Mair, A Preliminary Analysis of Bipolar Lightning Observed to the Gaisberg Tower from 2000 to 2008, 4th International Symposium on Lightning Physics and Effects, Vienna, Austria, May 25-27, 2009.
Zhou H., N. Theethayi, G. Diendorfer, R. Thottappillil, and V.A. Rakov, Effective Height of Towers on Mountain Tops in Lightning Incidence Studies: Sensitivity Analysis, 4th International Symposium on Lightning Physics and Effects, Vienna, Austria, May 25-27, 2009.
Theethayi, N., R. Thottappillil, G. Diendorfer, M. Mair, H. Pichler, Currents in Buried Grounding Strips Connected to Communication Tower Legs during Lightning Strikes, IEEE Transactions on Dielectrics and Electrical Insulation Vol. 15, No. 4; pp. 1153-1161, August 2008.
Nelson Theethayi, Vladimir A. Rakov and Rajeev Thottappillil, Responses of Airport Runway Lighting System to Direct Lightning Strikes: Comparisons of TLM Predictions With Experimental Data, IEEE Transactions On Electromagnetic Compatibility, Vol. 50, No. 3, pp. 660-668, August 2008.
D. Flache, V. A. Rakov, F. Heidler, W. Zischank, and R. Thottappillil, Initial-stage pulses in upward lightning: Leader/return stroke versus M-component mode of charge transfer to ground, Geophysical Research Letters, Vol. 35, L13812, doi:10.1029/2008GL034148, 2008.
Nelson Theethayi, Yoshihiro Baba, Farhad Rachidi and Rajeev Thottappillil, On the Choice Between Transmission Line Equations and Full-Wave Maxwell's Equations for Transient Analysis of Buried Wires, IEEE Trans. on Electromagnetic Compatibility, Vol. 50, No. 2, 2008, pp. 347-357.
Nelson Theethayi and Rajeev Thottappillil, On Reducing the Lightning Transients in Buried Shielded Cables Using Follow-On Earth Wire, IEEE Trans. on Electromagnetic Compatibility, Vol. 49, No. 4, November. 2007, pp. 924-927.
Thottappillil, R., V. A. Rakov, and N. Theethayi, Expressions for far electric fields produced at an arbitrary altitude by lightning return strokes, J. Geophys. Res., 112, D16102, doi:101029/2007JD008559.
Nelson Theethayi, Rajeev Thottappillil, Mario Paolone, Carlo Alberto Nucci and Farhad Rachidi, External Impdeance and Admittance of Buried Horizontal Wires for Transient Studies Using Transmission Line Analysis, IEEE Trans. on Dielectrics and Electrical Insulation, Vol. 14, No. 3, pp. 751-761, June 2007.
Thottappillil, R., V. A. Rakov, Review of Three Equivalent Approaches for Computing Electromagnetic Fields from an Extending Lightning Discharge, Journal of Lightning Research, Vol. 1, pages 90-110, 2007. Online access www.jolr.org
Nelson Theethayi and Rajeev Thottappillil, Some Issues Concerning Lightning Strikes to Communication towers, Journal of Electrostatics, Vol. 65, Issues 10-11, October 2007, pp. 689-703.
Thottappillil, R. and N. Theethayi, Realistic sources for modeling lightning attachment to towers, Proceedings of International Conference of Grounding and Earthing Ground' 2006 and International Conference on Lightning Physics and Effects 2nd LPE, Nov. 26-29, 2006, Maceio, Brazil, paper no. 4, 2006.