Transformer Maintenance Tests – Transformer Condition Assessment
This article is related to Transformer Maintenance Tests, and what assessment is needed in transformer.
Transformer Condition Assessment Summary – Transformer Maintenance Tests
Following table shows quick summary for this assessment and maintenance of transformer.
|Dissolved Gas Analysis||Internal arcing; bad electrical contacts; hot spots; partial discharge; and overheating of conductors, oil, tank, and cellulose insulation||Requires laboratory analysis|
|Oil Physical and Chemical Tests||Moisture, degraded IFT, acidity, furans, dielectric strength, and power factor||Requires laboratory analysis|
|External Physical Inspection||Oil leaks, broken parts, worn paint, defective support structure, stuck indicators, noisy operation, loose connections, cooling problems with fans, pumps, etc.||Experienced staff and binocular|
|External Temperatures (Main tank and load tap changer)||Temperature monitoring with changes in load and ambient temperature||Portable temperature data loggers and software|
|Infrared Scan||Hot spots indicating localized heating, circulating currents, blocked cooling, tap changer problems, and loose connections||Thermographic camera and analysis software|
|Double Tests (bushing capacitance, insulation power factor, tip up, excitation current)||Loss of winding insulation integrity, loss of bushing insulation integrity, and winding moisture||Double test equipment|
|Turns Ratio||Shorted windings||Double test equipment or turns ratio tester|
|Short Circuit Impedance||Deformation of the core or winding||Double or equivalent test equipment|
|Core to Ground Resistance (External test may be possible depending on transformer construction)||Bad connection on intentional core ground and existence of unintentional grounds||Megger Tester|
|Winding Direct Current (dc)
|Broken strands, loose connections, bad tap changer contacts||Wheatstone Bridge (1 ohm and greater)
Kelvin Bridge micro-ohmmeter(less than 1 ohm).
|Frequency Response Analysis||Shifted windings||Double or equivalent sweep frequency analyzer|
|Internal Inspection||Oil sludging, displaced winding or wedging, loose windings, bad connections, localized heating, debris and foreign objects||Experienced staff, micro-ohmmeter|
|Degree of Polymerization||Insulation condition (life expectancy)||Laboratory analysis of paper sample|