Transformer oil are mainly used in electrical industry to transfer electrical energy from one circuit to another. Oil surrounding the coils in a power transformer provide cooling, insulation and protection against corona and arcing. Transformer Oil is failure results in production loss, unavailability of critical services and loss of revenue. Hence testing of oil can minimize these loss and down time. Generally,many reasons of failure results include some external factors. Like lighting strikes, system overload,short circuit, whereas internal factors such as deterioration, transformer winding,system overheating,moisture and solid oxygen etc. So transformer oil testing is essential for improve all these internal and external factors.

Following some methods for Transformer oil testing:

1.Color D1500(standard):

Color is determine meaning of transmitted light and give a numerical value based on series color stranded.Therefore Transformer oil testing colors are indicate arcing is take place of the oil.

2.Dielectric breakdown voltage D877: 

This standard is measured by apply voltage between two electrodes and oil entered between both of them. Finally Measuring of this voltage are indicate which amount of moisture in transformer oil.

3.Dissolved gas analysis D3612:

The transformer oil generate different gases are indicates occurring various types of thermal and electrical stress. So an internal faults are remove in oil can earliest using this test method.

4.Dissolved metals D7151: 

It is identify to these testing after that can generate overheating or arcing from transformer oil. Rather it is measured by inductively dissolved metals in micrometers.

5.Flash and fire point D92:

 It indicates the moisture in insulating oil by measuring the minimum temperature at insulating oil .Which is heated transformer oil to gives a sufficient vapor in form of unstable and mix with air.

6.Interracial tension D971:

Its define as interracial tension to decrease value indicates an increase in oxidation products within the transformer oil. Measures to oxidation products in  oil are expressed in mN/m. It is a test of interracial tension surface tension in that the surface, after testing the water is contact with oil instead of air.

 7. Furanic compound D5837:

The determines testing of furanic compound that present of degradation in cellulose materials such as paper, press board, and cotton, etc. Measurements of furanic compound are made using high-performance liquid to used Insulating oil.

8.Moisture content D1533:

It does not measure the water content in the insulation paper. Measured weight of moisture divided by the weight of oil. Hence Moisture content in oil to insulate dielectric strength and allows flash overheating that can damage a oil.

9.Neutralization number D974:

 This stranded after testing measures the acids formed by oxidation. Transformer oils can contain no acids. As a result after measurements that can acid occur the high amount of potassium hydroxide (KOH in mg) in  oil.

10.Oxidation inhibitor content D2668: 

Its define testing the amount of transformer oil as protection against oxidation. The oil it measures the amount remaining after oxidation has reduced its concentration to used material.

11. Polychlorinated biphenyls content D4059: 

It is tested by these content to detects the concentration level of polychlorinated biphenyls in insulating oil by gas chromatography. Another measured it also applies to the determination of PCB present in mixtures known as askarels.

12.Pour point D97:

 It indicates the lowest level of temperature at which the oil will flow. So this test the oil is particularly useful in cold climates. To ensure that the  transformer oil will circulate and serve properly. Since the  purpose of oil as an insulating and cooling medium.

13.Power factors D924:

Testing of power factor the dielectric losses of oil are dissipate as form of heat. While measure of power factor equals to cosine phase angle between an ac voltage and current. Since mineral oil of power factor not exceed 0.05 percent at 25 degrees  Increase.

14.Relative density D1298:

 To determines relative density, or API gravity of  oil by use of hydrometer at a reference temperature. After the testing process high specific gravity to indicates the oil’s ability to suspend in mineral water. All whether ice will float on the transformer oil.

15. Resistivity D1169: 

Measures the electrical insulating properties of oil under conditions comparable to those after testing method. In addition a low resistivity to indicates reflects a high content of free ions and  particles of insulating oil.

16.Visual examination D1524:

Oil is passing a beam of light transparency medium and identify foreign matters. It has Contamination of the transformer oil testing is poor transparency and cloudiness.