Low cost method for on-line remote monitoring of power transformers and induction motors

Abstract

The application of Finite Element Method (FEM) to the analysis of the magnetic flux in power transformers and asynchronous motors has allowed the design of two new diagnosis procedures for the early detection of failures. These new methods are by its simplicity and low cost very suitable tools for remote monitoring of power transformers and motors. In the case of transformer diagnosis the installation of search coils on the machine windings for the measurement of leakage flux allows the detection of interturn shortcircuits and winding deformation. For motor condition monitoring the measurement of the magnetic flux linked by a stator tooth permits the detection of broken bars even in the case of oscillating mechanical loads. This is an important advance with respect to the conventional motor current signature analysis techniques (MCSA), which are not reliable when the driven machine provokes mechanical oscillations in the rotor shaft. The results of simulations have been validated by means of experimental measurements on actual motors, and the utility of both methods has been demonstrated.