Patent ID: 6124726
Filing Date: 2000-09-26
Classification: H01H

Abstract:
A method of monitoring a tap selector for interruption-free selection of voltage taps of a power transformer under load, comprising the steps of:(a) displacing the tap selector with an electric drive motor and during tap-selection operation of said electric drive motor measuring effective values of voltage applied to and current drawn by said electric drive motor;(b) automatically calculating true power of said electric drive motor from the effective values of voltage applied to and current drawn by said motor as measured in step (a) and determining a torque developed by said motor from the calculated true power;(c) simultaneously with the determination of the torque developed by said motor, generating a position value representing an actual setting of the tap selector and thereby forming a corresponding pair of determined values of developed torque and tap-selector setting;(d) comparing said pairs of determined values with previously stored apparatus-specific setpoint pairs of corresponding values, optionally corrected for ambient temperature; and(e) upon deviation of a determined value pair from a setpoint value pair exceeding a predetermined threshold difference, generating a signal for inactivating the drive of the tap selector or initiating a maintenance operation thereof.