During this test, insulating oil in an evacuated cell is subjected to a high voltage discharge between two electrodes. The discharge generates free electrons. These electrons collide with the oil molecules causing many of them to become electronically excited. Some of these molecules lose this energy as a quanta of light emitting fluorescent radiation. Some of the other excited molecules decompose into gases, ionized molecules and free radicals. These changes can provide an indication of the stability of oils under the conditions of this test method. The measures of these changes are the increase of the pressure in the test cell and the increase in the dissipation factor of the test specimen.

During the test, the gas content increases in the cell and the concentration of charge carriers increases in the oil.

1. Scope

1.1 This test method covers a laboratory technique that measures the stability of new, used, or reclaimed insulating oils, similar to those described in Specification D 3487 in the presence of a controlled electric discharge. When subjected to this type of discharge, insulating oils absorb energy and produce gases as well as ionized molecules (charge carriers). The quantity of these decay products can be measured and can provide an indication of the stability of oils under the conditions of this test.

1.2 The gases are retained in the discharge cell and their pressure measured. The charge carriers remain in the test specimen. The change in the dissipation factor before and after the discharge is determined.

1.3 The values stated in SI units are to be regarded as the standard. The values stated in parentheses are for information only.

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. Specific cautionary statements are given in and .

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

D923 Practices for Sampling Electrical Insulating Liquids

D924 Test Method for Dissipation Factor (or Power Factor) and Relative Permittivity (Dielectric Constant) of Electrical Insulating Liquids

D3487 Specification for Mineral Insulating Oil Used in Electrical Apparatus

IEEE Standard

Keywords

dissipation factor; electrical discharge; gas formation; gassing tendency; insulating oil; oxidation stability; stability;

ICS Code

ICS Number Code 29.040.10 (Insulating oils)

Citing ASTM Standards

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