For Critical Infrastructures, there is a special approach to testing of Transformer Main Tank with OCTC (Off-Circuit Tap Changer). We carry out Oil Testing according to IS: 1866 (Nine Parameters) to ensure that the dielectric properties of your insulating oil meet the highest safety standards.
BDV (Breakdown Voltage) Test
The BDV test determines the dielectric strength of the insulating oil by measuring the maximum voltage that it can withstand. A low breakdown voltage is an indication of the presence of moisture, conducting particles, or other contaminants in the oil. This test is performed strictly per the IS 6792 standard. This test is recommended as a part of the annual maintenance schedule, after oil filtration, or when the transformer is tripped. It helps ascertain the oil’s ability to withstand electrical stress and avoid internal short circuits.
Moisture Content Analysis
This test helps determine the amount of water in the insulating oil, which is expressed as parts per million. Moisture in the oil reduces the life of the solid paper insulation, which ultimately reduces the life of the asset. As per the IS 13567 standard, we ensure that the moisture content is within acceptable limits for the voltage rating of your equipment. This test is recommended as a part of the biannual maintenance or when the oil analysis report shows a sudden drop in the dielectric strength of the oil. It helps the engineers determine if the oil needs dehydration or online filtration before it causes permanent damage to the insulation.
Acidity Test
The acidity test determines the amount of acidic constituents in the oil, which is an indication of the oxidation and thermal degradation of the oil. High levels of acidity in the oil can lead to the formation of sludge, which coats the internal components of the transformer and reduces the cooling efficiency while causing corrosion to the copper windings. By estimating the acidity of the oil as per the IS 1448 standard, we can determine the oxidation rate of the oil. This test is recommended as a part of your annual Electrical Transformer Oil Testing to keep track of the long-term chemical stability of the oil. It helps determine if the oil needs reclaiming before it causes permanent damage to the asset due to the formation of corrosive byproducts.
Dissolved Gas Analysis (DGA)
The dissolved gas analysis is a powerful tool that helps detect the type of fault in the transformer by determining the type and amount of gases that have been dissolved in the oil due to thermal or electrical stresses. This test is considered the gold standard in the field of transformer oil analysis. The gas content in the oil is evaluated using the standard IS 10593 to identify the type of fault that has occurred in the transformer. This test is recommended at least once a year for the critical power transformers or whenever the gas relay of the transformer is tripped. It helps identify the exact nature of the fault without having to shut down the transformer.
Interfacial Tension Test
The interfacial tension test determines the molecular attraction of the oil sample with water, which helps determine the amount of polar contaminants present in the oil. This test is recommended as a part of the advanced Transformer Oil Quality Testing to determine the early signs of chemical degradation of the oil before the sludge formation begins. The test is performed as per the IS 6104 standard to estimate the presence of undesirable contaminants in the oil. It is recommended to perform this test when the acid content of the oil starts to increase to dangerous levels. It helps determine the structural integrity of the internal parts of the transformer.
Flash Point Test
The flash point test helps determine the lowest temperature at which the vapors of the oil are ignited when exposed to an open flame. A sudden decrease in the flash point of the oil indicates the presence of highly volatile and flammable contaminants in the oil. This test is performed as per the IS 1448 standard to ensure that the flash point of the oil is not dropping due to the presence of contaminants. This test is recommended after electrical faults, high-temperature excursions, or whenever there is a suspicion of cross-contamination of the oil. It helps ensure the safety of the equipment by determining the stability of the oil under high-temperature conditions.
Resistivity Test
The resistivity test is a diagnostic test that helps determine the ability of the oil to resist the flow of current when a direct current is applied across two electrodes. The high specific resistance of the oil is required to ensure that the leakage current between the windings does not exceed acceptable limits. The oil resistivity is estimated in the laboratory as per the IS 6103 standard to ensure that the oil is free from conductive contaminants. This test is recommended as a part of the Transformer Oil Testing Services to ensure the purity of the fluid. It is highly sensitive to the presence of any soluble conductive contaminants in the oil, making it an excellent test for estimating the overall cleanliness of the oil.
Tan Delta Test
The tan delta test is a sensitive test that helps determine the dielectric dissipation factor of the oil, which is an indication of the amount of power loss in the oil. An increase in the tan delta value indicates the progressive deterioration of the dielectric properties of the oil, which can be due to structural aging, contamination, or the presence of conductive moisture in the oil. The tan delta test is performed as per the IS 6262 standard and is recommended as a part of the Electrical Transformer Oil Testing to detect the early signs of insulation degradation. It helps ascertain the overall power loss in the transformer windings and is an excellent test for determining the maintenance schedule of the asset.
Furan Analysis
The furan analysis helps determine the amount of 2-furfural and other byproducts that have been generated due to the thermal degradation of the paper insulation. Since the paper insulation cannot be sampled directly to estimate the degree of polymerization, the furan content in the oil is estimated to determine the health of the solid insulation. This test is performed as per the IS 15668 standard and is recommended for the transformers that are more than 20 years old or are operated under severe overloading conditions. It helps estimate the mechanical strength of the paper insulation and determines the remaining life of the asset.
For every test explain:
- Purpose
- Importance
- When it should be performed
- Benefits