Investigation of the transient disturbances on industrial mains supplies

Published papers and standards (e.g., IEC 61000-4-5, IEC 61000-4-4) suggest that transients on the mains system often exceed 2 kV in amplitude. During a number of incident investigations involving machinery, one of the authors had monitored the level of transients on the mains wiring. The levels that were measured were far lower than was anticipated from published data and an explanation was sought. All of the monitoring described in this paper was carried out using a Sontay three-phase disturbance monitor type LM21. Data were recorded using a Psion 3 personal organizer. The sites monitored are briefly outlined and the results are discussed.