Testing Of Transformer Or Insulating Oil

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Testing Of Transformer Or Insulating Oil

• Transformer 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

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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.

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Testing Of The Transformer Oil

Color ASTM D1500

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Dielectric breakdown voltage ASTM D877

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Dielectric breakdown voltage ASTM D877

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Dissolved gas analysis (DGA) ASTM D3612

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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.

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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.

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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.

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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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