Electric power distribution and environment: interference of power installation magnetic fields on computer systems

The present study analyzes the electromagnetic interference produced on vis ual display units (VDUs) in domestic and industrial environments. The main sources of disturbance may be identified in three-phase lines, unbalanced c urrents, currents in earthing systems, proximity of power installations, pr oximity of railway tracks, and presence of harmonics on the neutral conduct or. Magnetic-field interference for PCs is practically limited to the defle ction of the cathode-ray tube (CRT) electron beam. The vertical magnetic fi eld determines a horizontal electron beam motion. The distortion depends li nearly on magnetic field intensity and on the difference between the freque ncy of the CRT vertical raster scan and the frequency of the interfering ma gnetic field. Herein are analyzed two actual cases of interference produced by the DC-supply line of a metropolitan tram network and by the public ele ctric power distribution network. (C) 1999 Elsevier Science Ltd. All rights reserved.