Insulating materials.Test methods for electric strength.Part 2:Additional requirements for tests using direct voltage
1Key Takeaways
This part of GB/T 1408 supplements GB/T 1408.1 with the requirements for determining the electric strength of solid insulating materials under DC voltage stress.
2Expert Interpretation
This expertly interprets the additional requirements for DC voltage electrical strength testing of insulating materials in the GB/T 1408.2-2016 standard, covering key technical points such as electrode configuration, voltage control, and breakdown determination. It also compares and analyzes the differences between DC and AC testing, and provides implementation guidelines that comply with the IEC 60243-2:2013 standard.
Analysis of the core content of the standard
This part of the standard is a supplement to GB/T 1408.1-2016, and specifically specifies the special requirements for equipment such as DC high-voltage generators in the testing of solid insulating materials. The main technical changes include:
- Updated the reference standard to GB/T 1408.1—2016
- Deleted 10 outdated reference documents
- Optimized the test report content structure
Key differences between DC and AC tests
| Comparison dimensions | DC voltage test | AC voltage test |
|---|---|---|
| Voltage distribution characteristics | Resistive distribution after steady state | Always capacitive distribution |
| Typical breakdown voltage ratio | Can reach more than 3 times the AC peak value | Baseline value |
| Current component | Contains capacitance/absorption/leakage current | Mainly capacitive current |
Key test requirements
Power system specifications
DC power supply must meet the following requirements:
- Voltage ripple ≤2% (when voltage>50% breakdown value)
- Rising voltage step ≤2% of expected breakdown voltage
- Must be equipped with a current sensing circuit breaker
Safety discharge requirements
After the test, the electrodes must be short-circuited to ground for at least:
- Basic requirement: twice the total charging time
- Large specimens: ≥1 hour
Implementation Recommendations
Key Points for Heterogeneous Material Testing
For multi-layer composite insulation materials, it is recommended that:
- A 1000pF compensation capacitor be connected in parallel to the DC withstand voltage tester
- The voltage rise rate should be controlled within the range of ±20% of the nominal value
- The automatic voltage rise control mode should be used preferentially
Data Recording Specifications
The report must include:
- Voltage polarity marking (positive/negative)
- Thickness measurement of each sample
- Media parameters (temperature and humidity for gases, temperature for liquids)