Transformer maintenance tests are a series of diagnostic procedures conducted periodically to assess the health, performance, and integrity of transformers. These tests help identify potential issues, predict future failures, and ensure the reliable operation of transformers over their lifespan.
This article is related to Transformer Maintenance Tests, and what assessment is needed in transformer.
Transformer Maintenance Tests.
Following table shows quick summary for this assessment and maintenance of transformer. Following test list includes about what tests are used for maintenance, their detection and tools and equipment used.
Some common transformer maintenance tests include:
| Test | Detects | Tool |
| Online Tests | ||
| 1. Dissolved Gas Analysis. | Internal arcing; bad electrical contacts; hot spots; partial discharge; and overheating of conductors, oil, tank, and cellulose insulation. | Requires laboratory analysis. |
| 2. Oil Physical and Chemical Tests. | Moisture, degraded IFT, acidity, furans, dielectric strength, and power factor. | Requires laboratory analysis. |
| 3. 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. |
| 4. External Temperatures (Main tank and load tap changer). | Temperature monitoring with changes in load and ambient temperature | Portable temperature data loggers and software |
| 5. Infrared Scan. | Hot spots indicating localized heating, circulating currents, blocked cooling, tap changer problems, and loose connections. | Thermographic camera and analysis software. |
| Offline Tests | ||
| Doble 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) Resistance Measurements. | 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. | Doble 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. |
What is Insulation Resistance Test?
Measures the resistance of insulation between windings and between windings and ground to detect insulation degradation.
What is Transformer Turns Ratio Test?
Determines the turns ratio between primary and secondary windings to ensure proper voltage transformation.
What is Power Factor Test?
Measures the power factor to assess the dielectric losses in the insulation and detect any insulation deterioration.
What is Dissolved Gas Analysis (DGA)?
Analyzes gases dissolved in insulating oil to detect and identify potential internal faults, such as overheating, arcing, or partial discharge.
What is Moisture Content Test?
Determines the moisture content in insulating oil to assess its dielectric properties and identify any moisture-related issues.
What is Dielectric Breakdown Voltage Test?
Measures the dielectric strength of insulating oil to evaluate its ability to withstand electrical stress.
What is Partial Discharge (PD) Test?
Detects and monitors partial discharge activity within the transformer, which could indicate insulation degradation and potential failure.
What is Thermography (Infrared Imaging)?
Utilizes thermal imaging to identify any hotspots or abnormal temperature distributions within the transformer, indicating potential issues.
What is Load Tap Changer (LTC) Testing?
Evaluates the operation and performance of load tap changers, ensuring proper voltage regulation and control.
What is Mechanical Inspection?
Conducts visual inspections and checks for mechanical wear, corrosion, loose connections, and other physical abnormalities.
By performing these maintenance tests regularly, utilities and operators can identify and address potential problems early, optimize transformer performance, extend its lifespan, and minimize the risk of unexpected failures and downtime.