Effect of bending degree of down conductor on lightning current diversion in lightning protection system installation

The major role of protection against lightning are to secure structures and every component connected to it from lightning damage by directing the high currents and dispersed it to the ground safely. Lightning protection of structures and premises becomes crucial in order to provide the safety and to ascertain that the installation of Lightning Protection System (LPS) is reliable and comply with the standards and specification assigned by the authority to assure the quality of services. LPS have been designed deliberately to get the overall protection via an external grid arrangement depends on the building constructions and level of protection needed as per standard. A LPS is composed of three main parameters which are the air termination network, the down conductor and the earth termination. The down conductor is the medium to divert the lightning current from the air termination to the earth termination system of protected structures. This research focused on the down conductor and its effects when it meets the bending part in the LPS installation. According to the standards and specifications, the down conductor shall be installed as short and straight as possible with particular attention shall be carried out eliminating sharp bends and curves to provide a low impedance path between the air termination network to the earth termination. However, due to the modern architecture and to fulfill aesthetical requirement of the building, the bending seems unavoidable. The aim of the research is to investigate and analyze the effect of the bending degree of the down conductor in the LPS installation since no particular experiment has been channeled away to this topic so far. Numerical (simulation) analysis has been applied using Ansoft Maxwell software. The down conductor in concern for the simulation is an Annealed Copper Tape that was injected with lightning impulse current waveforms as per standard at the various bending degree.The potentials and the fields involved are analyzed and the result was discussed in comparison with the straight conductor and the standard. The main findings conclude that the bending of the down conductor does give an effect where the distribution properties of magnetic field, electric field and current densities can be seen nonuniform along the conductor. The maximum value of magnetic field and current densities located at the vertex of the bent part and are influenced by the bent angle. The magnetic field strength concentrated at the location of the bent and getting stronger as the bending angle getting sharper which is could lead to self-induced coupling and this behavior could cause current to directly flow or short through it and ignite dangerous sparking during lightning strike. The stronger the magnetic field, the greater will be the induced voltage produced along the bent conductor compared with the straight conductor which is hazardous in practice. The magnetic forced also may cause distribution of current densities at the bent part nonuniform in the sectional area and form a void. This phenomenon known as skin effect where current concentrated near the surfaces of the conductor caused by electromagnetic induction and current crowding that could reduce the cross sectional area for current conducting ability to the ground.

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