Incipient fault conditions — disruptions in the normal electrical and mechanical operation of electrical equipment — cause the oil to break down, generating combustible gases. The profile of those gases can be interpreted to diagnose whether fault conditions exist, and how severe those faults may be. DGA is also used to determine the concentration of dissolved atmospheric gases oxygen, nitrogen, and carbon dioxide so that the operation of oil preservation systems such as conservators, continuous nitrogen systems, and nitrogen blankets can be evaluated. Gas content of new oil installed in equipment is frequently run.

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More D The power-frequency breakdown voltage of a liquid is reduced by the presence of contaminants such as cellulosic fibers, conducting particles, dirt, and water.

A low result in this test method indicates the presence of significant concentrations of one or more of these contaminants in the liquid tested. See Appendix X1. Test Method D is not sensitive to low levels of these contaminants.

Breakdown in this test method is dominated by events occurring at the electrode edges. The voltage stress distribution between the parallel disk electrodes used in this test method are quasi-uniform and there is substantial stress concentration at the sharp edges of the flat disk faces.

Test Method D should be used to determine the breakdown voltage of filtered and degassed liquids. Scope 1. The breakdown test uses ac voltage in the power-frequency range from 45 to 65 Hz. It is no longer applicable to new insulating liquids upon receipt, in which case Test Method D shall be used. It is recommended to move all new and in-service electrical discharge voltage testing of electrical insulating liquids to Test Method D For further information refer to RR:D These liquids include petroleum oils, hydrocarbons, natural and synthetic esters, and askarels PCB used as insulating and cooling liquids in transformers, cables, and similar apparatus.

Procedure B, modified in accordance with Section 17 of Test Methods D, is acceptable for testing silicone dielectric liquids if the requirements of 1. These may include samples taken from circuit breakers, load tap changers, and other liquids heavily contaminated with insoluble particulate material.

These examples represent samples that may have large differences between replicate tests. The use of Procedure B will result in a more accurate value of breakdown voltage when testing such liquids. Procedure A may be used once the single operator precision of The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.

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.

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More D The dielectric breakdown voltage serves to indicate the presence of contaminating agents such as water, dirt, cellulosic fibers, or conducting particles in the liquid, one or more of which may be present in significant concentrations when low breakdown voltages are obtained. However, a high dielectric breakdown voltage does not necessarily indicate the absence of all contaminants; it may merely indicate that the concentrations of contaminants that are present in the liquid between the electrodes are not large enough to deleteriously affect the average breakdown voltage of the liquid when tested by this test method see Appendix X1. Scope 1.


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