Effects of Electromagnetic Fields due to High Voltage Transmission Lines on Detonator Firing Circuits

High voltage AC transmission is the common mode adopted in transmitting bulk electrical power from one station to the other. Overhead high voltage (HV) transmission lines which carry bulk electric power emanate electric and magnetic fields which could influence the devices in their proximity. Detonator is one such electro explosive device (EED) that is susceptible to electromagnetic coupling when placed in proximity to the transmission lines which in turn could cause inadvertent misfires. This paper focuses on the computational modeling of electric and magnetic fields around overhead high voltage transmission lines at various voltage levels and line configurations, starting from fundamental electromagnetic principles and the verification of those models by field measurements. MATLAB software was used in modeling the field profiles and the developed model is capable of accommodating any configuration with any combination of conductors. The overhead transmission line parameters used in this paper are from the present line configurations practiced in Sri Lanka. For the validation of the model, electric and magnetic fields of transmission lines were measured in the field and compared with the modeled values. Using the developed electric and magnetic field models, the impacts of electric and magnetic fields of HV transmission lines coupling with detonator firing circuits were investigated. Possible unintentional misfires under different scenarios and safe distance levels for operation of detonators in the proximity of transmission lines are proposed.