Process for identifying abnormalities in power transformers

A method, comprising:

• measuring a dielectric frequency response of a section of insulation within a power transformer;
• calculating a theoretical dielectric frequency response for the section;
• generating a dielectric frequency response signature for the section;
• and
• comparing the dielectric frequency response signature to the dielectric frequency response signature of other sections of the insulation known to have particular types of abnormalities.

A method for classifying a type of abnormality in a section of insulation in a power transformer, comprising:

• energizing a conductor insulated by the section of insulation with an alternating-current voltage;
• varying a frequency of the alternating-current voltage between a plurality of discrete frequencies within a predetermined range;
• measuring the dielectric loss in the section of insulation at each of the discrete frequencies;
• calculating a theoretical dielectric loss for the section of insulation at each of the discrete frequencies;
• calculating a percent difference between the measured dielectric loss and the theoretical dielectric loss at each of the discrete frequencies;
• generating a substantially curvilinear representation of the percent differences between the measured dielectric loss and the calculated dielectric loss at each of the discrete frequencies;
• and
• comparing a shape of the substantially curvilinear representation to a shape of one ,or more predetermined curvilinear representations of a percent difference between a measured dielectric loss and a calculated dielectric loss for a section of insulation known to have a particular type of abnormality.

A method, comprising:

• measuring a dielectric loss in a section of an insulation system of a power transformer in response to an alternating-current voltage varied over a predetermined range of frequencies;
• calculating a theoretical dielectric loss for the section based on the material properties, geometry, and temperature of the section of insulation;
• generating a representation of a percent difference between the measured and calculated dielectric losses;
• and
• determining whether a shape of the representation substantially differs from a representation of a percent difference between measured and calculated dielectric losses in another section of the insulation previously identified as having a specific type of abnormality.

A method for identifying a type of abnormality in an insulation system of a power transformer, comprising:

• measuring dielectric losses in a section of the insulation system;
• calculating theoretical dielectric losses for the section;
• identifying the section as having an abnormality by comparing the measured dielectric losses in the section to the theoretical dielectric losses for the section;
• generating a graphical representation of a percent difference between the measured and calculated dielectric losses;
• and
• comparing a shape of the graphical representation with a shape of one or more graphical representations of a percent difference between measured and theoretical dielectric losses in one or more other sections of the insulation each known to have a specific type of abnormality.

A method, comprising:

• measuring a dielectric frequency response of a section of insulation within a power transformer;
• calculating a theoretical dielectric frequency response for the section;
• identifying the section as having an abnormality therein by comparing the measured dielectric response and the theoretical dielectric response;
• generating a dielectric frequency response signature for the section;
• and
• comparing the dielectric frequency response signature to a dielectric frequency response signature of other sections of the insulation known to have particular types of abnormalities.