Safety analysis of electromagnetic wave energy for multiloop small loop receiving antenna equivalent to underground circular metal structure

Along the narrow tunnel underground, metal structures are concentrated, such as long wires, rails, winch steel wires, brackets, wire rings, and other different forms of metal structures. Underground metal structures may receive electromagnetic wave energy from transmitting antennas through magnetic coupling or radiated electromagnetic waves. If there are breakpoints in the metal structure, an induced voltage can be generated at the breakpoint. If there is scraping at the breakpoint of the metal structure, it will generate scraping discharge sparks at a very low voltage in the form of scraping discharge at the breakpoint, which poses a risk of igniting and detonating gas. Different forms of metal structures, such as circular metal structures and columnar metal structures, have different characteristics in coupling electromagnetic wave energy. Small circular metal structures widely exist along underground tunnel with the characteristics of small volume and large freedom of placement and installation. The safety of underground small circular metal structures equivalent to circular receiving antennas receiving electromagnetic wave energy is worthy of attention and research. This paper studies the safety of electromagnetic wave energy of circular metal structures along underground tunnel, and analyzes its safety by equating underground circular metal structures to multiloop small loop receiving antennas to receive electromagnetic wave energy. The equivalent circuit has been established and the power consumption on the load has been calculated by equating the circular metal structure to multiloop small loop receiving antenna. When the multiloop small loop receiving antenna equivalent to circular metal structure resonates, the input impedance of the small loop receiving antenna is exactly resistive. The equivalent circuit of the multiloop small loop receiving antenna equivalent to circular metal structure can be used to calculate the maximum power consumption on the load, as well as the safety distance that should be maintained between the multiloop small loop receiving antenna equivalent to circular metal structure and the transmitting antenna. The influence on the maximum power consumption on the load and safe distance by the equivalent radius, conductor diameter, number of turns, and the angle between the equivalent multiloop small loop receiving antenna of the circular metal structure and transmitting antenna is simulated. The simulation results show that the safety distance increases with the increase of the equivalent radius of the circular metal structure equivalent to the multiloop small loop receiving antenna, and the change is not significant with the increase of the conductor diameter of the circular metal structure equivalent to the multiloop small loop receiving antenna. It decreases with the increase of the angle representing the relative height relationship between the transmitting antenna and the equivalent receiving antenna. This study provides reference for the safety issues of electromagnetic wave energy caused by the application of new wireless communication technologies in underground coal mines.