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.

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.