Measurements and computations of electromagnetic fields in electric power substations

The magnetic fields generated by a typical distribution substation were measured and calculated based on a computer model which takes into account currents in the grounding systems, distribution feeder neutrals, overhead ground wires and induced currents in equipment structures and ground grid loops. Both measured and computed results indicate that magnetic fields are significantly influenced by ground currents, as well as induced currents in structures and ground system loops. All currents in the network modelled were computed, based on the measured currents impressed at the boundary points (ends of the conductor network). The agreement between the measured and computed values is good. Small differences were observed and are attributed mainly to uncertainties in the geometry of the network model and phase angles of some of the currents in the neutral conductors which were not measured in the field. Further measurements, including more accurate geometrical information and phase angles, are planned