Method for evaluating a remaining life of a rotating machine coil

A method for evaluating a remaining life of a rotating machine coil, comprising the step of

• sampling an insulating layer of a stator coil of a rotating machine adopting a water cooling system;
• finding infrared spectra of the insulating layer;
• comparing the infrared spectra of the insulating layer of a stator coil with infrared spectra of an insulating layer of a healthy stator coil not penetrated by water and finding difference spectra of an ester group in an epoxy resin used as a bonding agent of the insulating layer;
• and
• predicting a period of water penetration into the insulating layer of the stator coil as a wet heat degeneration period, on the basis of the difference spectra of the ester group, with the use of a relation between initially found difference spectra of an ester group and an aging time.

A method for evaluating a remaining life of a rotating machine coil, comprising the steps of:

• obtaining effective sealing lengths on the basis of measured cut faces of brazing sections;
• predicting, by statistical processing, a shortest effective sealing length of all clips of the stator coil in one rotating machine on the basis of the effective sealing length of each cut face;
• predicting a remaining life of the brazing section resulting from a galvanic corrosion of different kinds of metals on the basis of the shortest effective sealing length and an initially found galvanic corrosion rate;
• comparing infrared spectra of the insulating layer of the stator coil with infrared spectra of an insulating layer of a healthy stator coil not penetrated by water and finding difference spectra of an ester group in an epoxy resin used as a bonding agent of the insulating layer;
• predicting a period of water penetration into the insulating layer of the stator coil as a wet heat degeneration period, on the basis of the difference spectra of the ester group, with the use of a relation between initially found different spectra of the ester group and aging time;
• measuring a breakdown voltage of the stator coil;
• predicting a drop rate of a dielectric strength of the insulating layer of the stator coil resulting from the wet heat degeneration on the basis of the period of water penetration into the insulating layer of the stator coil and the breakdown voltage of the stator coil;
• and
• finding a remaining life of the stator coil from a time point of sampling the stator coil on the basis of both the remaining life of the brazing section between clips of the stator coil and the copper wires and the drop rate of the dielectric strength of the insulating layer of the stator coil resulting from the wet heat degeneration.