Radiated Electromagnetic Fields of Surge Current in Coal Mines

The radiated electromagnetic fields from the cable excited by surge current in mine environment were studied. The mathematical models for the radiated electromagnetic fields in time domain were deduced by using the theories of retarded vector potential and traveling wave antenna. The analytical expressions and simulation results of the radiated electromagnetic fields were given. The results show that surge current can cause high transient radiated electromagnetic fields nearby a cable, but the strength of radiated field attenuates quickly with increasing radial distance from a cable; the radiated field strength is proportional to the peak value of surge current and, within the radial distance of the same transverse section in a tunnel, the radiated field strength is inversely proportional to the distance from a cable. It has been obtained from simulation that, when the surge peak current reaches 1 kA, the transient peak radiated electric field strength is about 15 kV/m and the peak magnetic field strength is about 40 A/m at the field point 4 m away from the cable. That indicates, if there is no shielding measures to be taken, the radiated electromagnetic fields of surge current could cause malfunction of monitoring system and communication system in tunnels.