ASTM D149 Standard Test Method for Dielectric Disruption Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies

EUROLAB laboratory provides testing and compliance services within the scope of ASTM D149 standard. The ASTM D149 standard covers procedures for determining the dielectric strength of solid insulating materials at commercial power frequencies under certain conditions.

Dielectric Strength is a measure of the electrical strength of a material as an insulator. Dielectric strength is defined as the maximum voltage required to cause a dielectric breakdown in the material and is expressed in Volts per unit thickness. A higher dielectric strength represents a better insulator quality.

There are three basic procedures that can be used to determine the dielectric strength of an insulator. These procedures are the short time method, the slow rate of increase method, and the step-by-step method. Each of these three methods has the same basic setup consisting of a test sample placed between two electrodes in air or oil.

Unless otherwise stated, tests will be performed at 60 Hz. However, this test method is suitable for use at any frequency between 25 and 800 Hz. At frequencies above 800 Hz, dielectric heating is a potential problem.

This test method is intended for use with any ASTM standard or other documentation that refers to this test method. References to this document should specify the specific options to be used.

For the short-term method, which is the most common test, voltage is applied across the two electrodes and increased at an equal rate from zero to dielectric breakdown. Failure occurs when an electrical burn punctures or decomposes the sample. The rate of voltage rise is determined by the time it takes for the sample to reach dielectric breakdown.

The slow rate of rise method starts at 50% of the breakdown voltage determined by the short time method and is increased at a uniform rate. The step-by-step method starts at 50% of the short-term test, then the voltage is increased in equal increments for a specified period of time until failure. The test is sometimes performed in oil to prevent electrode-to-ground arcing.

It is suitable for use at various temperatures and in any suitable gas or liquid surrounding environment. This test method is not designed to measure the dielectric strength of materials that are fluid under test conditions. This test method is not intended for use in determining intrinsic dielectric strength, direct voltage dielectric strength, or thermal failure under electrical stress.

This test method is most commonly used to determine the dielectric breakdown voltage across the (puncture) thickness of a test sample. It is also suitable for use to determine the dielectric breakdown voltage across the interface between a solid sample and a gas or liquid surrounding medium (flashover). With the addition of instructions, this test method is also suitable for use for evidence testing.

This standard does not purport to address all, if any, safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health and environmental practices and to determine the applicability of regulatory restrictions prior to use.

Our organization, EUROLAB, provides standard test method services for the dielectric breakdown voltage and dielectric strength of solid electrical insulation materials at commercial power frequencies, within the framework of national and international standards, with its trained and expert staff and advanced technological equipment, among numerous test, measurement, analysis and evaluation studies. Provides testing services within the scope of ASTM D149 standard.