ASTM D2759-00(2005)

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 This standard does not purport to address all of the safety problems, 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.

General Information

• Status: Historical
• Publication Date: 30-Sep-2005
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.07 - Physical Test

Relations

• Replaces: ASTM D2759-00 - Standard Practice for Sampling Gas from a Transformer Under Positive Pressure
• Effective Date: 01-Oct-2005
• Replaced By: ASTM D2759-00(2010) - Standard Practice for Sampling Gas from a Transformer Under Positive Pressure
• Effective Date: 01-Nov-2010

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D2759–00 (Reapproved 2005)
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 with anhydrous isopropyl alcohol, or other suitable cleaning
agent that is free from residue upon evaporation. The bottle
1.1 This practice covers the sampling of gas above the
should then be dried by blowing out with dry air or nitrogen,
insulating liquid of a transformer. A gas sampling bottle
oven baking, or be dried under vacuum.
collects the gas sample from the gas space that is at a positive
3.2 Plastic Bag—The bag should have only one opening
pressure.
arranged to fit over one of the hose connectors on the sampling
1.2 Representative samples of gas are taken for analysis to
bottle. The plastic bag should have a volume, when fully
determine their compositions.
expanded, of approximately 15 times the volume of the
1.3 The values stated in SI units are to be regarded as
sampling bottle.
standard. No other units of measurement are included in this
standard.
4. Procedure
1.4 This standard does not purport to address all of the
4.1 Before connecting the sampling bottle to the trans-
safety concerns, if any, associated with its use. It is the
former, purge the outlet valve on the transformer by exhausting
responsibility of the user of this standard to establish appro-
a small amount of gas to remove any moisture, oil, or other
priate safety and health practices and determine the applica-
contaminants.
bility of regulatory limitations prior to use.
4.2 Attach one end of the gas sampling bottle by plastic
2. Significance and Use hose to the transformer outlet valve, and the other end of the
sampling bottle to the plastic bag, making sure that a leakproof
2.1 A gas sample from above the insulating liquid in
connection is obtained.
transformers and other electrical power apparatus can be used
4.3 Purge the sampling bottle and hose of air by first
to give an early indication of developing fault conditions.
opening both valves of the sampling bottle and then slightly
Combustible gases are formed from the breakdown of the
opening the outlet valve on the transformer. As the gas flows
insulating materials under thermal and electrical stress. Exces-
through the sampling bottle, the plastic bag will expand.
sive concentrations of combustible gases indicate the need to
4.4 When the bag has expanded to its full volume, first close
take appropriate action.
the valve adjacent to the bag; then close the valve at the other
2.2 Itisimportantthatgassamples
...