What kind of transformer oil test should be done?
For the transformer oil test’s plan, Both new transformer oil and running oil need to be tested. According to the transformer operating regulations, transformer oil must be tested every year. Depending on the voltage level, the test cycle and items are also different. The test cycle for 66~550kV transformers is 1 year, and the test cycle for transformers of 35kV and below is 3 years. The test items generally include oil dielectric strength test, oil dielectric loss factor tanδ test, simplified test, etc. For transformers of 330kV and above, other test items should be added.
It is designed for testing dielectric strength (Breakdown Voltage) of insulating oil, transformer oil, and it refers to the minimum voltage indicated by the voltmeter when the oil medium between the two electrodes of the tester breaks down. The dielectric strength value indicates the content of water and impurities in the oil; According to DL/T 596-1996 “Preventive Test Regulations for Power Equipment”, the higher the dielectric strength of transformer oil, the better.
2.Transformer oil dielectric loss test(power factor tanδ)
The insulation loss factor tanõ of transformer oil is measured under the action of an applied voltage, which reflects the quality of the oil and the degree of purification. The insulation loss factor of transformer oil in operation(tanδ) is required＜4% @90℃ for below 330kV, ＜2% @90℃ for 550kV.
3.Simplified Test
In order to know the situation of transformer oil in operation, the following simplified test items can be done:
a. PH: The water-soluble acid pH value of the oil in operation is ≥4.2.
b. Acid value: The acid value of the oil in operation is ≤0.1KOHmg/g.
c. Flashpoint: The flashpoint of the oil in operation>135℃ (#10, #25 oil), the flash point> 130℃ (#45 oil)
d. Moisture: The moisture of the oil in operation, 66~110kV≤35PPM; 220kV≤25PPM; 330~550kV≤15PPM.
e. Gas content: 330kV and above transformer gas content <3%
Having transformer oil test analysis done on a regular basis establishes a baseline of normal wear and can help indicate when abnormal wear or contamination is occurring. ASSEN company specializes in providing a variety of transformer oil test instruments, in line with European IEC standards and American ASTM standards
Hot Oil Testing Kit
Click on the images below to learn more about each of these test methods.
You can also view all of our testers and their methods on the Complete Tester List.