Experimental study on new type earth mesh in railway substations aimed at lightning protection

In Japanese electrical railways, earth meshes are normally utilized as earthing electrodes in the traction substations. The earthing meshes are designed and optimized for low-frequency phenomena, such as earth-fault whose frequency is about between zero (dc) and few kilo hertz (power frequency and its low-order harmonics). Because the earthing impedance of the earthing mesh has positive frequency dependence, it is difficult to design or construct an earthing mesh so as to be also suitable for high-frequency phenomena, such as lightning. This paper proposes a new design of earthing meshes for railway substations aimed at lightning protection and also at fault protection. Experimental validations are carried out through the comparison between the conventional design and the proposed one.