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D2526-02 – Standard Test Method Technical Guide
The ASTM D2526-02 standard defines the properties and test methods for ozone-resisting crosslinked silicone rubber insulation used in wire and cable. This material is engineered for high-temperature performance up to 125°C and voltage ratings up to 5000 V, ensuring reliability in demanding environments.
📐 Scope and Classification
This specification covers an ozone-resisting crosslinked silicone rubber insulating compound for electrical wires and cables. It is suitable for conductor sizes up to 1000 kcmil (507 mm²) at a maximum of 5000 V for both single-and-multiple-conductor cables. Minimum conductor sizes and insulation thicknesses are detailed in Table 1 of the standard.
Values presented in dual units prioritize the first set as standard, with informational equivalents in parentheses.
🟢 Tip: Tests on insulated wire or cable are intended to determine the property of the insulation material, not the conductor or cable completion.
⚙️ Test Requirements and Procedures
The insulation shall meet physical properties as per Table 2 and electrical requirements defined in the standard. Key tests include partial discharge, AC voltage withstand, insulation resistance, and DC voltage testing, performed in that order when specified.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Partial Discharge Extinction Level (100% Insulation) | 4.0 kV |
| Partial Discharge Extinction Level (133% Insulation) | 5.0 kV |
| AC Voltage Withstand Test Duration | 5 minutes |
| Insulation Resistance Constant at 60°F | ≥ 4000 MΩ·1000 ft |
| Accelerated Aging Temperature | 200 ± 2°C |
| Accelerated Aging Duration | 168 hours |
For insulation resistance, temperature correction factors from Table 2 of Test Methods D 470 should be applied if test temperature deviates from 60°F.
📊 Compliance and Performance Data
The standard requires that each length of completed power cable rated for 2001 to 5000 V with insulation shielding must have a partial discharge extinction level as specified. The insulation must also withstand the AC voltage test for 5 minutes as per Table 1 values.
⚠️ Note: For cables with ungrounded neutral (133% insulation level), the partial discharge extinction level is higher at 5.0 kV.
Physical property compliance is confirmed through testing to Table 2 of D2526, ensuring the material’s robustness under operational conditions.
❓ Frequently Asked Questions
🔍 What is the maximum operating temperature for this insulation?
The insulation is suitable for continuous operation at conductor temperatures up through 125°C for power cable applications.
💡 What are the partial discharge extinction level requirements?
For cables rated at 2001 to 5000 V, the partial discharge extinction level is 4.0 kV for 100% insulation level and 5.0 kV for 133% insulation level.
⚡ How is insulation resistance tested and corrected?
Insulation resistance is tested per D 470, and the value is corrected to 60°F using correction factors from D 470, with a minimum requirement of 4000 MΩ·1000 ft.
📌 What is the defined aging condition for the insulation material?
The aging condition is exposure to air at 200 ± 2°C for 168 hours.