| 摘要 |
<p>1. Method for the detection of insufficient dielectric properties of the insulation of coil windings of an electrical machine, according to which method - the capacitor (1) constituted by the conductors of the said windings, the insulation, and the portions of the mass of the machine which are situated around these windings, is connected into the measuring branch of a capacitance measuring bridge, - the measuring bridge is supplied with a measurement A.C. voltage whose value is taken from a range of predetermined values around the nominal voltage of the machine and whose frequency is selected from the frequencies appearing at the windings in the operating conditions of the machine, - the equilibrium of the measuring bridge is established by means of an equilibrium indicator (7) connected into the measuring diagonal of the measuring bridge for the value of the measurement voltage applied to the measuring bridge, characterised in that the mean current pulses due to partial discharges in the insulation and having a first portion constituted by a steep front peak (Ip ) and a second portion constituted by a decreasing tail (Iq ) are detected for each of the predetermined values of the measurement voltage by means of a measuring device (8, 9) of high selectivity tuned to a frequency corresponding to the inverse of the duration 2D, D being the duration of the tail (Iq ) of one of the said predetermined mean current pulses, the measuring device (8, 9) being arranged in the place of the equilibrium indicator after the establishment of the equilibrium of the measuring bridge of the applied measurement voltage.</p> |
