ASTM D2759-00(2010)
(Practice)Standard Practice for Sampling Gas from a Transformer Under Positive Pressure
Standard Practice for Sampling Gas from a Transformer Under Positive Pressure
SIGNIFICANCE AND USE
A gas sample from above the insulating liquid in transformers and other electrical power apparatus can be used to give an early indication of developing fault conditions. Combustible gases are formed from the breakdown of the insulating materials under thermal and electrical stress. Excessive concentrations of combustible gases indicate the need to take appropriate action.
It is important that gas samples from equipment be taken from the gas space directly above the liquid level, and not from remote expansion compartments, such as tank bracing bands.
The procedure described should be carefully followed to ensure that the sample is not diluted by air or nitrogen, or contaminated by residual materials in the sampling bottle.
SCOPE
1.1 This practice covers the sampling of gas above the insulating liquid of a transformer. A gas sampling bottle collects the gas sample from the gas space that is at a positive pressure.
1.2 Representative samples of gas are taken for analysis to determine their compositions.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D2759 − 00 (Reapproved 2010)
Standard Practice for
Sampling Gas from a Transformer Under Positive Pressure
This standard is issued under the fixed designation D2759; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 The gas sampling bottle must be free of dirt, moisture,
oil, or other contaminants. It should be cleaned by washing
1.1 This practice covers the sampling of gas above the
with anhydrous isopropyl alcohol, or other suitable cleaning
insulating liquid of a transformer. A gas sampling bottle
agent that is free from residue upon evaporation. The bottle
collects the gas sample from the gas space that is at a positive
should then be dried by blowing out with dry air or nitrogen,
pressure.
oven baking, or be dried under vacuum.
1.2 Representative samples of gas are taken for analysis to
3.2 Plastic Bag—The bag should have only one opening
determine their compositions.
arranged to fit over one of the hose connectors on the sampling
1.3 The values stated in SI units are to be regarded as
bottle. The plastic bag should have a volume, when fully
standard. No other units of measurement are included in this
expanded, of approximately 15 times the volume of the
standard.
sampling bottle.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 4. Procedure
responsibility of the user of this standard to establish appro-
4.1 Before connecting the sampling bottle to the
priate safety and health practices and determine the applica-
transformer, purge the outlet valve on the transformer by
bility of regulatory limitations prior to use.
exhausting a small amount of gas to remove any moisture, oil,
or other contaminants.
2. Significance and Use
4.2 Attach one end of the gas sampling bottle by plastic
2.1 A gas sample from above the insulating liquid in
hose to the transformer outlet valve, and the other end of the
transformers and other electrical power apparatus can be used
sampling bottle to the plastic bag, making sure that a leakproof
to give an early indication of developing fault conditions.
connection is obtained.
Combustible gases are formed from the breakdown of the
4.3 Purge the sampling bottle and hose of air by first
insulating materials under thermal and electrical stress. Exces-
opening both valves of the sampling bottle and then slightly
sive concentrations of combustible gases indicate the need to
opening the outlet valve on the transformer. As the gas flows
take appropriate action.
through the sampling bottle, the plastic bag will expand.
2.2 Itisimportantthatgassamplesfromequipmentbetaken
4.4 When the bag has expanded to its full v
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