Research on switching operation transient electromagnetic environment of substations in a coal mine

摘要

Research of switching operation transient electromagnetic field in substations is fundamental to the protection of mine monitoring systems against electromagnetic interference. Three models, which are the equivalent circuit of switching on/off inductive load, transient radiation of short dipole, and transmission line of long cable, are built for numerical analysis. The results indicate that switching operation does not produce transient pulse when the breaking angle is close to 90°. Electric fields are the primary form of transient pulse radiation, and the effect of the magnetic field on the environment can be ignored. Long cables are naturally resistant to differential mode transient pulse propagation, but the effect of common mode transient pulse cannot be ignored. Energy distribution of transient pulse in different frequency ranges is calculated by using theParserval equation. Furthermore, the measurement frequencies and the instruments used in the coal mine are determined, and on-site data is then obtained. Measurement results show that switching operation may produce a series of transient pulses, causing the electric field to grow larger than before. Specifically, conducted emissions have large impacts on the monitoring circuitry of the mine equipment, causing the mine monitoring system to frequently record erroneous data and omit information.