Modeling of the Coupling Mechanisms between Lightning and a Complex Telecommunication Network

In this paper, we propose a new modeling of the coupling mechanisms of the lightning with a complex network of telecommunication. The studied network is composed of a building that can be linked to many sections of buried cables and overhead lines. Moreover a protective earth placed in the ground is added to the study. We also take into account the lightning channel and the mismatching existing at the top of the building in the case of a direct lightning strike. The modeling is realized in two difierent parts. On one hand, we show that it is possible to model with a temporal model, the building struck by the lightning channel. The model is an assembly of distributed element by unit length. On the other hand, we have optimized the protection of the buried cables against the lightning direct and indirect efiects. In the flrst part, the building is studied and linked to a ground rod. The characterization is realized by the free solver OPEN TEMSI-FD using the Finite Difierence Time Domain (FDTD) method. The re∞ection coe-cient (S11a) of the building can be obtained, and it permit to know the building's impedance matrix (Z). Then, the building can be described by an assembly of Pi cells by length unit. So, if some buried cables or overhead lines are connected to the building, it becomes possible to know relatively simply the induced and conducted electromagnetic fleld over these cables or lines. In the second part, a theoretical study is set. This study uses a calculation code based on the theory of the Transmission Lines Theory (TLT) associated with a topological approach (1). Previously in 2006, an artiflcial release of lightning campaign has been realized at Cachoeira Paulista in Brazil (2). The test have been realized on a network composed of an overhead line and of a buried cable joined to a protective earth. A comparison is thus realized and the measurement and the simulation results are in quite good agreement. It flnally enables to validate our code. In conclusion, we propose a global modeling of the coupling mechanisms of lightning with a telecommunication network. The proposed tools are very useful because of the implementation simplicity. Furthermore, experimental tests have validated the code based on the TLT. The study realized is a global approach of a network struck by lightning and could be involved by taking into account the presence of non linear element as lightning conductor.