Which tests are used for insulating oil?
Transformer Oil Testing
- Standard Specification for Mineral Insulating Oil Used in Electrical Apparatus (ASTM D3487)
- Acid number (ASTM D664)
- Dielectric breakdown voltage (ASTM D877)
- Liquid power factor (ASTM D924-08)
- Interfacial tension (ASTM D971)
- Specific resistance (ASTM D1169)
- Corrosive sulfur (ASTM D1275)
What are the steps for testing of insulating oil?
To assess the insulating property of dielectric transformer oil, a sample of the transformer oil is taken and its breakdown voltage is measured. The lower the resulting breakdown voltage, the poorer the quality of the transformer oil. The transformer oil is filled in the vessel of the testing device.
How do you check the oil on a transformer?
New transformer oil generally have no acid content by may develop because of oxidation and contamination. The test is carried out by measuring the amount of potassium hydroxide (KOH in mg) required to neutralize the acid in one gram of oil. This test is conducted using the international standard ASTM D974.
How often should transformer oil be tested?
twice a year
Routine testing of transformer oils and insulating oils on a regular schedule is an accepted industry practice. General and physical tests are suggested twice a year, dissolved gas analysis once a year, and Furan testing every 2 years for transformers in operation at least 5 years.
What is crackle test?
The crackle test is a standard laboratory test to detect the presence of water in lubricating oil. A drop of oil is placed on a hotplate that has been heated to approximately 400° F. The sample then bubbles, spits, crackles or pops when moisture is present.
How do you check the ppm of a transformer oil?
Measurements are made using high-performance liquid chromatography (HPLC). Measured in parts per million (ppm) using the weight of moisture divided by the weight of oil. Moisture content in oil lowers the insulating system dielectric strength and allows flashover that can damage a transformer.
Which test detect the presence of water in transformer oil?
The simplest way to determine the presence of water in oil is to use the Visual Crackle test.
Is standard for BDV test?
That means at which voltage dielectric strength of transformer oil between the electrodes has been broken down. A typical value of BDV Test result for 220 / 6.6 kV Transformer oil is 65 kV and moisture content should be less than 10 ppm.
Is BDV of transformer oil used in 11kV substation?
As per IEC, the minimum breakdown voltage of transformer oil should be not less than 30 KV. The BDV of transformer oil does not depend on the voltage rating of the transformer. Minimum transformer BDV value for either 11 KV, 22 KV, 132 KV is the same. The minimum transformer oil BDV is 30 KV.