MaTestLab > ASTM Methods > ASTM D149, IEC 60243 Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials
Last updated 3rd February 2026
ASTM D149, IEC 60243 Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials
ASTM D149/IEC 60243 test method determines the dielectric strength of solid insulating materials at commercial power frequencies under defined experimental conditions. Dielectric strength is the maximum voltage required to produce a dielectric breakdown through the material and is expressed as Volts per unit thickness. This test procedure applies to frequencies ranging from 25 to 800 Hz. Engineers design this test technique in conjunction with any ASTM standard or other document referencing it. ASTM D149 applies at a variety of temperatures and in any acceptable gaseous or liquid medium. Laboratories typically use this test method to calculate the dielectric breakdown voltage through the thickness of a test specimen (puncture).
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Introduction to ASTM D149
ASTM D149 is a standard for measuring the dielectric breakdown voltage of solid electrical insulating materials. The standard specifies the material’s electrical stress-withstanding capability before failure. It is essential to ensure both the safety and reliability of insulating materials. In electrical equipment, cables, and other devices that utilize these materials, preventing electrical failure is crucial. The method involves applying increasing voltage until the material loses its insulating properties, helping evaluate performance under real-world conditions.
ASTM D149 and IEC 60243 standardize methods for determining the dielectric breakdown voltage and dielectric strength of solid electrical insulating materials. These quantities are important to assess the insulation reliability of high-voltage equipment, electronics, motors, transformers, and cable systems, as they are the highest maximum electric field that a material can bear before electrical failure. The test determines the voltage at which sudden dielectric failure occurs, usually through arcing, carbonising, or puncturing. Both have the configuration of electrodes, test mode (AC, DC, or impulse), specimen preparation, raising voltages, and environmental conditions to achieve consistent and comparable breakdown measurements. This test method helps in the performance evaluation and reliability assessment of electrical insulating materials. Better quality insulators have high dielectric strengths. The dielectric strength of a material is calculated by dividing the breakdown voltage by the thickness of the sample in this test method. The results apply for quality control and specification purposes. This test method is applicable for frequencies ranging from 25 to 800 Hz. Dielectric heating is an issue at frequencies exceeding 800 Hz.
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Get Certified ASTM D149 / IEC 60243 for Reliable Insulation Performance
ASTM D149/IEC 60243 certification proves that the laboratories and manufacturers can correctly measure the breakdown voltage and dielectric strength, to make sure that insulating materials meet the requirements of safety, durability, and high-voltage operation. Compliance helps to achieve material qualification, design validation, production quality control, and electrical safety certification of equipment used in power, industrial, automotive, aerospace, and electronic industries. ASTM D149/IEC 60243 certification helps qualify materials for product development, everyday quality monitoring, and failure analysis. It allows to compare the insulation performance of various materials, their thicknesses, and formulations directly and makes informed decisions on the selection of materials and design optimization.
ASTM D149 / IEC 60243 Testing Procedure and Requirements
The short-time method
The most common test is the short-time method. Operators apply voltage across the two electrodes and increase from zero to dielectric breakdown at a uniform rate. When an electrical burn-through punctures the sample or decomposition occurs in the specimen, we assess the breakdown. The time taken by the sample to reach dielectric breakdown determines the rate of voltage rise.
The step-by-step method
The step-by-step method starts at 50% of the short-time test. Operators increase the voltage at equal increments for a specified time period until breakdown. Laboratories also perform the test using oil as a medium to prevent arcing to the ground.
The slow-rate-of-rise method
The slow-rate-of-rise method starts at 50% of the breakdown voltage, as the short-time method determines. The voltage increases at a uniform rate.
ASTM D149
Scope of ASTM D149 / IEC 60243
The standard provides procedures for determining the dielectric breakdown voltage and dielectric strength of solid insulating materials.
The standard covers AC, DC, and impulse tests depending on the required use.
Promotes quality control, certification, material ranking, and reliability.
Provides information critical to insulation design, electric-field modelling, and high-voltage engineering.
ASTM D149 / IEC 60243 Equipment and Sample Preparation
Specimen details
Specimens are solid and uniformly rectangular in shape.
Specimen dimensions
The general sample size is a 4-inch plaque. The thickness range is 0.8 to 3.2 mm.
Specimen preparation
Specimens are injection molded or cut from molded or extruded sheets or plates.
Use of ASTM D149 / IEC 60243
Testing transformer, motor, switchgear, capacitor, and high-voltage equipment insulation materials.
Estimating thickness of use and electric-field withholding factors in polymeric and composite insulations.
Comparing electrical, electronic, automotive, and aerospace applications materials according to dielectric strength.
Supporting research, new material development, and quality-control programs for insulating solids.
Engineers use this standard in failure analysis to identify the cause of electrical breakdown during service or accelerated-aging tests.
The test determines the effect of the environmental conditioning, such as humidity, temperature, and immersion media, on the performance of insulation.
Assists in the approval and certification of the electromagnetic and electronic components in the domestic and global markets.
Common Challenges and Troubleshooting in ASTM D149 / IEC 60243
There is surface contamination, trapped air, misalignment of electrodes, the influence of moisture, and uneven thickness of the specimen; each of these may cause premature or inconsistent breakdown. Lossy or hygroscopic materials can give different results when measured in air and require measurement in an insulating oil. Troubleshooting concerns clean electrode surfaces, proper contact with the specimen, oil baths to provide more stable tests, calibration of the rate of voltage rise, and controlled environmental conditions.
ASTM D149 / IEC 60243 Testing Technique, Process, and Data Collection
The test method conditions the specimen, places it between electrodes, and applies voltage until it breaks; the voltage at which it breaks is recorded. Specimen identification, thickness, electrode type, medium (air/oil), voltage rise rate, breakdown voltage, dielectric strength results, and environmental conditions are all data under collection. This data is useful in the design of insulation systems, material comparison, and reliability analysis of high-voltage applications.
Analysis Results and Interpretation for ASTM D149 / IEC 60243
Laboratories report breakdown voltage and dielectric strength in kV/mm or V/m. Large dielectric strength values indicate resistance to failure from electric fields, whereas lower values may indicate surface flaws, moisture absorption, internal cracks, or poor material quality. Interpretation takes into account the test medium, electrode geometry, thickness dependency, and frequency effects. Trends in dielectric strength assist the engineers in establishing safe operating conditions and insulation life.
Problem & The Solution for ASTM D149 / IEC 60243
Problem: Irregularity in interruption voltage due to moisture, surface defect, electrode gaps, trapped air, or unpredictable thickness. Solution: Stable environmental circumstances and proper specimen handling lead to better repeatability.
Factors to Consider for ASTM D149 / IEC 60243
Speed Laboratories can perform testing relatively quickly, particularly on thin films and sheets, making it easy to compare two or more materials.
Expert Trained technicians ensure alignment of electrodes, high voltage handling, and determination of breakdown occurrences.
Cost Accurate dielectric-strength testing reduces failure risks, improves insulation design, supports compliance, and prevents costly breakdowns in high-voltage equipment.
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The required number of samples or specimens should comply with the procedure given in the astm d149 standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
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The turnaround time for astm d149 test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
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You can share your astm d149 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm d149 test to various testing techniques.
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