Arc Resistance Testing Service – Comprehensive Evaluation of Electrical Insulation Performance Under High‑Voltage Arc Stress
As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised arc resistance testing services to manufacturers, engineering contractors, and quality assurance teams across the electrical equipment, electronics, automotive, aerospace, and power transmission sectors. Arc resistance – the ability of an insulating material to withstand the thermal, chemical, and electrical stresses caused by an electric arc – is a critical safety parameter for components that may be exposed to arcing faults, short circuits, or switching surges. The test measures the time (in seconds) required for a material to develop a conductive path under a high‑voltage, low‑current arc, simulating the conditions that can occur in electrical panels, connectors, switchgear, and high‑voltage cables. Our test protocols are executed in accordance with ASTM D495 (Standard Test Method for High‑Voltage, Low‑Current, Dry Arc Resistance of Solid Electrical Insulation), IEC 61621 (Dry, solid insulating materials – Resistance test to high‑voltage, low‑current arc discharges), GB/T 1411 (Test method for resistance of insulating materials to high‑voltage, low‑current arc discharges), and UL 746A (Polymeric Materials – Short‑Term Property Evaluations). Our inspection and test reports are recognised by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance.
Materials and Products We Regularly Test
Our arc resistance testing facilities accommodate a wide range of insulating materials and finished products. Typical test articles include:
- Electrical insulating materials – thermosetting plastics (epoxy, phenolic, polyester), thermoplastics (ABS, PC, PA, PBT, PPS), elastomers (silicone, EPDM, natural rubber), and ceramic insulators
- Printed circuit boards (PCBs) and laminate materials – FR‑4, CEM‑1, CEM‑3, and high‑frequency laminates
- Connectors, terminals and switchgear components – for high‑voltage and low‑voltage applications
- Wire and cable insulation – XLPE, PVC, PE, and rubber insulation
- Electrical enclosures and housings – for distribution panels, control cabinets, and junction boxes
- Moulded and machined insulating parts – bushings, standoffs, and insulating spacers
- Coated and surface‑treated materials – powder coatings, varnishes, and conformal coatings
- Composite insulating materials – glass‑reinforced plastics, mica‑based materials, and laminated composites
Test Principle – High‑Voltage, Low‑Current Arc Discharge
- Test voltage and current – standardised conditions for reproducible results – The test is performed at a voltage of 2.5 kV (or 5 kV for certain standards) and a current of 10‑12 mA. The arc is struck between two spring‑loaded electrodes (fixed distance of 2.5‑3.0 mm) that are pressed against the surface of the test specimen. The arc is maintained for a specified time interval (typically 1‑3 seconds on, 1‑3 seconds off) or until the material fails (forms a conductive path).
- Arc duration and failure criterion – time to track or failure – The test continues until either the material develops a conductive path (tracking) that allows the current to exceed the set limit (typically 20‑30 mA), or until the specified test time (e.g., 60 seconds, 180 seconds, or 360 seconds) is reached. The arc resistance is expressed as the total time (in seconds) that the material withstands the arc discharge before failure.
- Environmental conditions – controlled temperature and humidity for consistent results – The test is performed at standard laboratory conditions (23 °C ± 2 °C and 50 % ± 5 % RH). The specimens are conditioned for a minimum of 48 hours at these conditions to ensure that moisture does not affect the results.
- Electrode arrangement – reproducible geometry for standardised arcing – The test uses two metal electrodes (typically stainless steel or brass) that are pressed against the specimen surface with a specified force (typically 0.5‑1.0 N). The electrodes are arranged in a specific geometry (either parallel rods or a pin‑to‑pin configuration) to ensure reproducible arcing conditions.
- Arc sequence – intermittent or continuous arcing – The arc is applied either continuously (for the duration of the test) or in a sequence of on‑off cycles (e.g., 1 second on, 1 second off). The intermittent method allows the material to cool between arcing cycles, simulating the type of stress that occurs during repetitive fault conditions.
Test Specimen Preparation – Ensuring Representative and Reproducible Results
- Specimen dimensions – standardised size for the arc test – The test specimen is typically a flat plate of 50 mm × 50 mm (minimum dimensions) and a thickness of 3‑6 mm (or the thickness of the finished component). The surface is cleaned with a solvent (e.g., isopropanol) to remove any contamination, and the specimen is conditioned at the specified temperature and humidity for a minimum of 48 hours.
- Surface preparation – flat and smooth surfaces for consistent arc contact – The surface of the specimen must be flat and free of irregularities (e.g., bubbles, scratches, or raised edges). If the material is supplied as a moulded part, the test is performed on the moulded surface (or on a representative section).
- Number of specimens – statistical significance and repeatability – We test a minimum of five specimens per material (or per condition). The average arc resistance and the coefficient of variation (CV) are reported.
- Conditioning and pre‑treatment – for moisture and thermal equilibrium – The specimens are conditioned at 23 °C and 50 % RH for 48 hours (or until the mass is constant). For some materials, additional conditioning at elevated temperatures (e.g., 70 °C for 24 hours) or high humidity (e.g., 95 % RH) may be required to simulate service conditions.
Data Analysis and Interpretation – Quantifying Arc Resistance
- Arc resistance time – the primary output of the test – The arc resistance time (in seconds) is the time from the start of the test to the moment of failure (tracking, conduction, or arcing through the material). A high arc resistance time (> 120 seconds) indicates that the material has good resistance to arcing; a low value (< 30 seconds) indicates that the material is susceptible to arc tracking.
- Failure mode – classification of the type of failure (tracking, carbonisation, or melt‑through) – We examine the specimen after the test to determine the failure mode: (a) tracking – a conductive carbonised path forms on the surface; (b) carbonisation – the material becomes blackened and charred; (c) melt‑through – the material melts and burns through, allowing the arc to penetrate.
- Visual inspection – recording the track path and the extent of surface degradation – We record the length and the width of the track (or the area of charring) to provide additional information on the severity of the degradation.
- Statistical analysis – for batch‑to‑batch consistency and material qualification – For multiple specimens, we report the mean arc resistance time, the standard deviation, and the coefficient of variation (CV). A CV of less than 15 % is considered excellent for arc resistance testing.
Test Standards and Specification Compliance – Supporting Regulatory and Contractual Requirements
Our arc resistance testing is performed in accordance with the most widely used international and national standards. The most commonly requested include:
- ASTM D495 – Standard Test Method for High‑Voltage, Low‑Current, Dry Arc Resistance of Solid Electrical Insulation – the primary North American standard for arc resistance testing
- IEC 61621 – Dry, solid insulating materials – Resistance test to high‑voltage, low‑current arc discharges – the international standard for arc resistance testing
- GB/T 1411 – Test method for resistance of insulating materials to high‑voltage, low‑current arc discharges – the Chinese national standard for arc resistance
- UL 746A – Polymeric Materials – Short‑Term Property Evaluations – for arc resistance testing in UL certification
- ISO 16406 – Electrical insulating materials – Determination of resistance to high‑voltage, low‑current arc discharges – a more recent ISO standard
Report Acceptance and Regulatory Recognition
All arc resistance tests are conducted under our ISO/IEC 17025 accreditation, using calibrated arc testers, voltage and current monitors, and environmental chambers, all traceable to national and international reference standards. Our final test reports include: a complete description of the test article (material type, thickness, surface finish, manufacturer), the test method and conditions (voltage, current, arc sequence, temperature, humidity), the measured parameters (arc resistance time, failure mode, track length), a statistical summary (mean, standard deviation, CV), and a clear pass/fail verdict against your specified acceptance criteria. These reports are accepted by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance. Bilingual (English/Chinese) versions are available to facilitate submissions to domestic and international authorities and to support your global market access.
