The chemical industry standard HG/T 3330—2026 *Test Method for Dielectric Breakdown Strength of Insulating Varnish Films* has been officially released and will come into force on December 1, 2026. Replacing HG/T 3330—2012, this standard further specifies the methods for measuring the dielectric breakdown strength of insulating varnish films using AC voltage method and DC voltage method. It sets more rigorous requirements covering tester configuration, electrode specifications, test panel preparation, voltage boosting modes and result calculation, providing a reliable basis for verifying the electrical performance of insulating materials.

With over 90 years of expertise in electrical measurement, HIOKI has taken part in the formulation of this standard. Mr. Ruifeng Li, expert from our company, serves as one of the primary drafters. During the standard compilation, HIOKI leveraged its extensive experience in high-voltage insulation and withstand voltage measurement, contributing professional insights on key aspects including technical requirements for dielectric breakdown strength testers and test condition setup, to better align industry testing methods with practical applications.

Dielectric breakdown strength of varnish films is a core indicator for evaluating the electrical performance of insulating materials. In the power battery sector, the insulation performance of cells, modules and battery packs is critical to vehicle safety. Insulation failure may lead to performance degradation at minimum, or severe accidents such as thermal runaway at worst.

To meet the stringent requirements of battery insulation measurement, HIOKI officially launched the DC Withstand Voltage Insulation Resistance Tester ST5680A in June 2026. Equipped with three core technologies: international standard compliance, contact check, and waveform recording & analysis (Intelligent Waveform), this instrument is specially designed for the production lines of EV battery cells, modules and packs. It can perform all-in-one measurements of insulation resistance, DC withstand voltage and breakdown voltage (BDV).

- DC Withstand Voltage Test: Output DC 0.010～8.000 kV, maximum current 20 mA, minimum current resolution 0.001 μA

- Insulation Resistance Test: Output DC 10～2000 V, measurement range 100.0 kΩ～200.0 GΩ for accurate evaluation of battery insulation

- Breakdown Voltage (BDV) Measurement: Supports continuous and stepwise voltage rise, directly reads breakdown voltage (kV) and breakdown strength (kV/mm)

- Intelligent Waveform Technology: Synchronously records waveforms of voltage, current and insulation resistance, with maximum sampling rate of 500 kS/s and maximum recording duration of 128 seconds. Waveform analysis close to production line scenarios can be realized without an oscilloscope

- ARC Detection: Monitors the rate of change of test voltage to sensitively capture minor discharges caused by foreign matter and burrs

- Contact Check Function: Verifies probe contact reliability via capacitance measurement to reduce false PASS results induced by poor contact

- Comprehensive Safety Features: Automatic discharge (residual voltage below 30 V), voltage upper limit, interlock functions to ensure safe and efficient high-voltage testing

On battery production lines, ST5680A covers insulation testing across the full process: cell, module and battery pack. After cell electrolyte filling, DC withstand voltage and insulation resistance tests are carried out between electrodes and housing. After assembly and welding of modules and packs, ARC discharge detection identifies potential defects such as burrs and foreign impurities. Combined with contact check function, it simplifies wiring and PLC programming, improving production line efficiency and stability.

This instrument holds international certifications including CE, UKCA and CSA (NRTL). Manufacturers can deploy the same model with unified test standards across global production sites, supporting battery enterprises in international expansion.