An investigation of incoming lightning surges from a communication line

A communication system is protected by a protective device and requires proper grounding. The protective device is significant to decrease an incoming lightning surge. In Japan, there are two grounding methods, i.e. individual and common grounding. The methods differ in the characteristic of lightning surge. In this paper, the characteristic of the protective device and the lightning surges from a communication line are investigated based on experiments and FDTD simulations. Additionally another method to decrease a lightning surge is proposed and investigated. It is found experimentally that voltage appearing in the common and proposed methods is lower than in the individual method. Also, the maximum voltage in the proposed method is lower than in the common one. Thus, the proposed method is effective to protect customer appliances. FDTD simulation results show a reasonable agreement with the measured results. Therefore, the FDTD simulation can be used to investigate the effect of the protective device.