Modeling and experimental investigation of lightning arcs and overvoltages for medium voltage distribution lines

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Sähkötekniikan korkeakoulu | Doctoral thesis (article-based)
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Aalto University publication series. Doctoral dissertations, 70/2011
In this dissertation, lightning overvoltages in Medium Voltage (MV) lines are thoroughly investigated. The other goal is to propose new protection schemes for the designs. The lines consist of overhead lines, underground cables and covered conductors. These overvoltage problems range from direct and indirect strokes to lightning arcs. All the models and simulations are developed using the Electromagnetic Transient Program (EMTP) and Finite Element Method (FEM), while MATLAB is used for post-processing the results and identification of the model parameters. Improvement in the surge protection of MV overhead lines is demonstrated with a combination of surge arresters and a shield wire. Using the IEEE 34-node feeder injected with multiple lightning strokes, the feeder is simulated using EMTP. The response of the line is modeled both with and without the surge protection devices. The simulation study extends to the performance of a MV underground cable due to a nearby lightning discharge using FEM. The use of shield wire for limiting the overvoltage stress in the cables is proposed. A numerical analysis and simulations are performed to determine the outage rate of MV covered conductors due to lightning strokes of different characteristics. The optimum distance for surge protective devices on the conductors is also assessed. An enhancement in the surge analysis of distribution lines with the shielding effect of trees is proposed. An experimental study shows that a tree can intercept a lightning stroke in the vicinity of a distribution line. This study also analyzes experimental results of the shielding effectiveness of a tree and the induced voltages existing between the tree and the distribution line. The study is extended to evaluate the induced voltage on a distribution line for larger clearances using a Rusck model. This work investigates the lightning arc between an overhead line and a nearby tree under artificial rainfall. A full-scale laboratory experiment confirms that a direct stroke to a tree can cause severe damage to nearby power lines by initiating an arc channel through air to the conductors. A complete model of this phenomenon is developed by combining the existing static and dynamic arc equations. The model is accomplished by the bilateral interaction between the EMTP and Transient Analysis Control System (TACS) field. The experimental results have been reproduced by the computer simulations. The performance of the arc phenomenon is examined using a typical Finnish distribution network design. Using the modified arc model, the lightning arc performance of the MV/ LV network under the influence of nearby trees and the network characteristics is evaluated.
Supervising professor
Lehtonen, Matti, Prof.
overvoltage, lightning arc, medium voltage distribution lines, tree
Other note
  • [Publication 1]: M. A. Omidiora and M. Lehtonen. 2008. An approach to the lightning overvoltage protection of medium voltage lines in severe lightning areas. In: Sio-Iong Ao, Mahyar A. Amouzegar, and Su-Shing Chen (editors). Current Themes in Engineering Technologies. Selected Papers of the World Congress on Engineering and Computer Science 2007 (WCECS 2007). San Francisco, California, USA. 24-26 October 2007. Melville, NY, USA. American Institute of Physics. AIP Conference Proceedings, volume 1007, pages 140-151. ISBN 978-0-7354-0526-4.
  • [Publication 2]: Michael A. Omidiora and Matti Lehtonen. 2009. Simulation performance of lightning discharges around medium voltage underground cables. In: Proceedings of the 44th International Universities' Power Engineering Conference (UPEC 2009). Glasgow, UK. 1-4 September 2009. IEEE. 5 pages. ISBN 978-0-947649-44-9.
  • [Publication 3]: Michael A. Omidiora and Matti Lehtonen. 2010. Protection of lightning disturbances on MV underground cable. International Review of Electrical Engineering (I.R.E.E.), volume 5, number 1, pages 317-326.
  • [Publication 4]: M. A. Omidiora and M. Lehtonen. 2009. Performance analysis of lightning overvoltage on medium voltage distribution lines equipped with covered conductors. In: Amoakoh Gyasi-Agyei and Tokunbo Ogunfunmi (editors). Proceedings of the 2nd International Conference on Adaptive Science & Technology (ICAST 2009). Accra, Ghana. 14-16 December 2009. IEEE. Pages 290-295. ISBN 978-1-4244-3522-7.
  • [Publication 5]: M. A. Omidiora and M. Lehtonen. 2008. A comparative study on the shielding effect of tree, concrete building on direct lightning strokes to medium voltage distribution line. In: Proceedings of the 40th North American Power Symposium (NAPS 2008). Calgary, Alberta, Canada. 28-30 September 2008. IEEE. 7 pages. ISBN 978-1-4244-4283-6.
  • [Publication 6]: Michael A. Omidiora and Matti Lehtonen. 2010. Experimental performance of induced voltage on power line due to lightning discharge to nearby tree. In: Proceedings of the 4th International Symposium on Modern Electric Power Systems (MEPS 2010). Wrocław, Poland. 20-22 September 2010. Wrocław, Poland. Wrocław University of Technology. Paper 14.5. 5 pages. ISBN 978-83-921315-7-1.
  • [Publication 7]: Michael A. Omidiora, Nagy I. Elkalashy, Matti Lehtonen, Petri Hyvönen, and Mansour H. Abdel-Rahman. 2011. Investigation of lightning arc between conductor and nearby tree under artificial rainfall. IEEE Transactions on Dielectrics and Electrical Insulation, volume 18, number 2, pages 620-630.
  • [Publication 8]: Michael A. Omidiora, Nagy I. Elkalashy, Matti Lehtonen, and Mansour H. Abdel-Rahman. Modelling and evaluation of the lightning arc between a power line and a nearby tree. European Transactions on Electrical Power, published online on June 24th, 2011.
    DOI: 10.1002/etep.606. View at publisher