Transformer Oil

Transformer oils are subject to electrical and mechanical stresses while a transformer is in operation. In addition there is contamination caused by chemical interactions with windings and other solid insulation, catalyzed by high operating temperature. As a result the original chemical properties of transformer oil changes gradually, rendering it ineffective for its intended purpose after many years. Hence this oil has to be periodically tested to ascertain its basic electrical properties to make sure it is suitable for further use and to ascertain the need for maintenance activities like filtration or regeneration.

To avoid expensive and unnecessary maintenance, the testing must be performed quickly and accurately. PDC Laboratories maintains rigorously controlled laboratory conditions along with specially trained and experienced chemists to assure the accuracy of your oil tests.

Dissolved Gas Analysis

Dissolved gas analysis (DGA) is the most efficient and cost effective alternative to emergency change outs and premature equipment failure. Unlike your typical oil quality tests, DGA is often your first warning of failure and provides essential information for maintenance. No other test can pinpoint faults as accurately in the early stages of oil deterioration. DGA is the most reliable test available for locating and monitoring the progress of faults in transformers before costly damage is done.

Oil Quality Tests

Neutralization Number 

(ASTM D-974)

This test is important for determining the amount of acidic or basic constituents resulting from additives or degradation. It is used as an indication of the oil's propensity to form sludge which is the result of oxidation of various transformer components. Sludge diminishes the dielectric strength of the oil, and hinders the oil's ability to circulate through cooling ducts.

Color (ASTM D-1500)

Color changes predictably and measurably with the general deterioration of oil. The darker the oil is, the more deterioration there is. Although this test is not specific, it is a valuable indicator, especially when used with more specific tests.

Dielectric (ASTM D-877)

Dielectric tests measure oil's ability to withstand electrical stress without breaking down. With the ability to withstand stress within reasonable limits, transformers are vulnerable to rapid destruction.

Specific Gravity

This is used to identify oil and can be used as a measure of gross contamination.

Water (ASTM D-1533)

Detects soluble in oil. soluble water strongly affects the electrical insulating characteristics of oil. Levels of soluble water as little as 35 ppm can diminish dielectrics strength enough to require maintenance.

Interfacial Tension (ASTM D-971)

Indicates the level of deterioration due to sludging and contamination, and monitors gradual deterioration of oil over time.

Visual (ASTM D-1524)

Detects solid and liquid insoluble contaminants not indicated by other tests.

Power Factor (ASTM D-924)

Detects the power lost when an insulating liquid is subjected to an AC field. It is performed to determine the quality of new or used transformer oil. The test is sensitive to ionic contaminants such as water or oxidation by-products.

Other Tests

VDE Dielectric (ASTM D-1816)
Flashpoint (ASTM D-92)
DBPC (ASTM D-1473)
Corrosive Sulfur (ASTM D-1275)

 

For more information, please contact Keith Earhart at kearhart@pdclab.com or 1-800-333-FAST x7339.