Patent ID: 6157196
Filing Date: 2000-12-05
Classification: G01R,G05F,H01H

Abstract:
A method for monitoring an on-load tap changer, comprising:initiating recording of sound and conversion of the sound into a sound signal at a beginning of a connection operation of the tap changer;rectifying the sound signal;converting the sound signal into a signal envelope;digitally sampling the sound signal;continuously evaluating the sound signal with respect to a condition of the tap changer by comparing the envelope with at least one fixed or one continuously updated reference envelope, wherein the comparison is selectively carried out by calculating, at each sample point with index I, a dimensionless comparison figure T.sub.i that is based on a quantity measure and a variation measure, where the quantity measure and the variation measure relate to a statistical distribution; andreleasing an alarm or a warning when the comparison figure T.sub.i for one or more sample points exceeds a predetermined value.