ASTM
ASTM D1816 is a standard test method published by ASTM International for determining the dielectric breakdown voltage of insulating oils of petroleum origin using VDE electrodes. It defines how an oil sample is placed in a test cell, stirred and stressed with rising alternating voltage until it breaks down, so that results from different laboratories can be compared.
Editions cited: ASTM D1816
The method is a measure of the ability of the oil to withstand electrical stress. It is sensitive to contamination by free water, dissolved moisture and particles, which is why it is widely used as an indicator of oil condition. The VDE electrode geometry and the stirring of the sample make it more responsive to certain contaminants than a method with flat discs and a still sample. It applies to mineral oil in transformers, load tap changers, circuit breakers and similar apparatus, and it is used on new oil at receipt, on oil after processing and on in-service oil during routine sampling. Utilities, oil laboratories and field testing firms rely on it, and the cell, electrode and sample handling details determine whether a result is meaningful. The pages in this encyclopedia that cite ASTM D1816 explain the related tests in general terms and point the reader to the method and to the applicable apparatus standards for procedures and values.