Transient Response of Shielded Non Braided Coaxial Cable due to Lightning Indirect Effect
The development of dispersed but highly interconnected systems of telecommunication centers, computers, and control equipment‘s leads to an extensive use of shielded cables to avoid interference and protection problems. Under the excitation of the external electromagnetic wave, the current and voltage can be generated along the cable. An analysis of the voltage induced onto the inner wire of a cable above a ground plane shows that this voltage does not depend on the resistance of the cable shield, where the current is limited by the shield's self-inductance. The electromagnetic field may couple into interconnecting wiring and thus induces voltage and current into the avionics systems. Electromagnetic effects may also occur due to nearby lightning flashes which can affect sensitive avionics systems even without contacting the aircraft. Electrical energy from lightning can enter a system by direct injection, usually the most severe, or by electromagnetic coupling; the latter being more frequent. Coupling can occur even when lines are underground because the attenuation of earth at normal burial depths is minimal. Lightning is a destructive natural phenomenon that can bring about serious damages to an aircraft. Protection from the indirect effects of lightning should be provided to ensure that all lightning critical systems, equipment, components, and propellants tolerate the lightning-induced voltages and currents appearing at their interfaces. A high frequency electromagnetic influence such as lightning or a surge current creates electromagnetic fields that interfere with the cable. A Transmission Line coupling model is developed for determining the transient currents and voltages induced within braided and non-braided shielded cables. Keywords - Avionics, Shielded Cable, Non-Braided, Electromagnetic, Transmission Line Coupling.