Testing Of Transformer Or Insulating Oil Transformer oilTransformer oil, a type of insulating and cooling oil used in transformers and other electrical equipment, needs to be tested periodically to ensure that it is still fit for purpose. This is because it tends to deteriorate over time. Testing sequences and procedures are defined by various international standards, many of them set by ASTM. Testing consists of measuring breakdown voltage and other physical and chemical properties of samples of the oil, either in a laboratory or using portable test equipment on site

Motivation For Testing The transformer oil (insulation oil) of voltage- and current-transformers fulfills the purpose of insulating as well as cooling. Thus, the dielectric quality of transformer oil is essential to secure operation of a transformer.

Testing Of The Transformer Oil Color ASTM D1500

Dielectric breakdown voltage ASTM D877

Dissolved gas analysis (DGA) ASTM D3612

Dissolved metals ASTM D7151 The D7151 test method is used to cover any dissolved metals that could originate from transformer oil, and also it provides rapid screening of used oils for indications of wear.

Flash point, fire point ASTM D92 1 The flash point is one measure of the tendency of the test specimen to form a flammable mixture with air under controlled laboratory conditions. It is only one of a number of properties that should be considered in assessing the overall flammability hazard of a material. 2 Flash point is used in shipping and safety regulations to define flammable and combustible materials. Consult the particular regulation involved for precise definitions of these classifications.

3 Flash point can indicate the possible presence of highly volatile and flammable materials in a relatively non volatile or non flammable material. For example, an abnormally low flash point on a test specimen of engine oil can indicate gasoline contamination. 4 This test method shall be used to measure and describe the properties of materials, products, or assemblies in response to heat and a test flame under controlled laboratory conditions and shall not be used to describe or appraise the fire hazard or fire risk of materials, products, or assemblies under actual fire conditions. However, results of this test method may be used as elements of a fire risk assessment that takes into account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use. 5 The fire point is one measure of the tendency of the test specimen to support combustion.

Interfacial tension ASTM D971 Interfacial tension measurements on electrical insulating oils provide a sensitive means of detecting small amounts of soluble polar contaminants and products of oxidation. A high value for new mineral insulating oil indicates the absence of most undesirable polar contaminants. The test is frequently applied to service-aged oils as an indication of the degree of deterioration.

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