ASTM D2759-00(2017)

Standard Practice for Sampling Gas from a Transformer Under Positive Pressure

SIGNIFICANCE AND USE
2.1 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.  
2.2 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.  
2.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2017
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.07 - Physical Test

Relations

• Replaces: ASTM D2759-00(2010) - Standard Practice for Sampling Gas from a Transformer Under Positive Pressure
• Effective Date: 01-Oct-2017

Overview

ASTM D2759-00(2017), titled Standard Practice for Sampling Gas from a Transformer Under Positive Pressure, establishes guidelines for collecting representative gas samples from the gas space above insulating liquids in transformers and similar electrical power apparatus. Developed by ASTM International, this standard helps ensure early detection of fault conditions within transformers by outlining procedures to accurately sample gases formed from the breakdown of insulating materials under thermal or electrical stress. By adhering to these procedures, users can help protect equipment reliability and optimize maintenance activities in the power industry.

Key Topics

• Significance of Gas Sampling: Sampling gas above the insulating liquid provides an early indication of developing faults in transformers and related equipment. Elevated concentrations of combustible gases signal the need for timely investigation and corrective measures.
• Sampling Location: The standard emphasizes that samples must be taken from the gas space directly above the liquid level, not from remote expansion compartments, to maintain integrity and representativeness.
• Sampling Apparatus: Recommended apparatus includes a gas sampling bottle (of stainless steel, Monel, or glass, at least 250 cm³) equipped with valves and hose connectors. Proper cleaning and drying of the sampling bottle is critical to prevent contamination.
• Step-by-Step Procedure: The procedure covers purging and connecting the sampling bottle, ensuring leakproof connections, purging air from the system, collecting the gas sample, and proper closure of the sampling system.
• Sample Documentation: Each gas sample must be clearly labeled with information including the transformer's serial number, sampling date, oil temperature, and location for traceability and analysis.

Applications

• Condition Monitoring: Utilities apply ASTM D2759-00(2017) to monitor transformer health, facilitating early detection of faults and extending asset lifespan.
• Preventive Maintenance: Accurate gas sampling helps maintenance teams prioritize interventions, reduce the risk of catastrophic transformer failures, and schedule repairs proactively.
• Quality Assurance in Manufacturing: Transformer manufacturers may implement this standard to validate the performance of insulating materials and assembly processes under stress.
• Compliance and Safety: The standard aligns with international practices, supporting adherence to safety, health, and environmental requirements when handling gas sampling under positive pressure.

Related Standards

• ASTM D3612 - Practice for Analysis of Gases Dissolved in Electrical Insulating Oil by Gas Chromatography
• ASTM D923 - Practices for Sampling Electrical Insulating Liquids
• IEEE C57.104 - Guide for the Interpretation of Gases Generated in Oil-Immersed Transformers
• IEC 60567 - Oil-filled Electrical Equipment – Sampling of Gases and Analysis of Free and Dissolved Gases

Keywords: transformer gas sampling, positive pressure, ASTM D2759, power transformer monitoring, electrical insulating liquids, fault detection, gas sampling procedure, electrical asset maintenance

Implementing ASTM D2759-00(2017) is critical for utilities and manufacturers seeking reliable transformer operation, early fault detection, and compliance with international best practices for gas sampling and analysis in high-voltage equipment.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D2759 − 00 (Reapproved 2017)
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. Apparatus
1.1 This practice covers the sampling of gas above the 3.1 Gas Sampling Bottle—stainless steel, Monel metal, or
insulating liquid of a transformer. A gas sampling bottle glass, of at least 250-cm capacity, with a valve and a hose
collects the gas sample from the gas space that is at a positive connector on each end.
pressure. 3.1.1 The gas sampling bottle must be free of dirt, moisture,
oil, or other contaminants. It should be cleaned by washing
1.2 Representative samples of gas are taken for analysis to
with anhydrous isopropyl alcohol, or other suitable cleaning
determine their compositions.
agent that is free from residue upon evaporation. The bottle
1.3 The values stated in SI units are to be regarded as
should then be dried by blowing out with dry air or nitrogen,
standard. No other units of measurement are included in this
oven baking, or be dried under vacuum.
standard.
3.2 Plastic Bag—The bag should have only one opening
1.4 This standard does not purport to address all of the
arranged to fit over one of the hose connectors on the sampling
safety concerns, if any, associated with its use. It is the
bottle. The plastic bag should have a volume, when fully
responsibility of the user of this standard to establish appro-
expanded, of approximately 15 times the volume of the
priate safety, health, and environmental practices and deter-
sampling bottle.
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
4. Procedure
dance with internationally recognized principles on standard-
4.1 Before connecting the sampling bottle to the
ization established in the Decision on Principles for the
transformer, purge the outlet valve on the transformer by
Development of International Standards, Guides and Recom-
exhausting a small amount of gas to remove any moisture, oil,
mendations issued by the World Trade Organization Technical
or other contaminants.
Barriers to Trade (TBT) Committee.
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
2.1 A gas sample from above the insulating liquid in sampling bottle to the plastic bag, making sure that a leakproof
transformers and other electrical power apparatus can be used connection is obtained.
to give an early indication of developing fault conditions.
4.3 Purge the sampling bottle and hose of air by first
Combustible gases are formed from the breakdown of the
opening both valves of the sampling bottle and then sligh
...