Tests and Diagnosis in Generators and Rotating Machines

As with any other substation equipment, many things could go wrong during the transformer operation.
For example, temperature indicators could stuck; Buchholz relay’s mechanism could falsely detect faults,
oil pump failure, oil leaks that can often indicate a potential for oil contamination, loss of insulation, or
environmental problems. These are all severe problems that substation maintenance staff must take care
of very carefully when inspecting a transformer. Such transformer inspection requires maintenance staff
experienced in these techniques.
These are some of the mechanical inspections to check:
Capacitance Measurement, Dissipation Factor (Tan) / Power Factor
Partial Discharge Measurement (DP)
DP Online Monitoring
Non-Disruptive Stress Tests
Measurements of Insulation Resistance,[IR] Polarization Index,[PI] and Dielectric Absorption Ratio [DAR]Winding Resistance
Contact Resistance Measurement
Polo Drop Tests
Frequency Response Sweep Analysis
Dielectric Response Analysis (SFRA)