Measurement and mitigation of electromagnetic interference from a radio navigation station to nearby power and telephone lines

In this paper, electromagnetic interferences (EMI) occurred in electric power and telephone lines due to radiation at a frequency of 525 kHz from an aeronautical radio navigation station are presented. The induced voltages measured on those lines caused malfunction or even damage to some electrical devices inside the station. To understand those EMI effects further, an FDTD software package, XFDTD, was applied to evaluate the induced voltages. It was found that the major reasons resulting in interferences were due to longitudinally induced voltages and ground potential rises. They were caused by the radiation from the antenna of the station and current flowing through the ground grids, respectively. In addition, mitigation of EMI was performed to correct those problems by applying separate grounding systems, shielding the telephone, and using underground cables instead of overhead lines near the station. Currently, the whole system, including electric power, navigation and telephone, inside the station operates normally