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D2656-20 – Standard Test Method Technical Guide
ASTM D2656-20 establishes the standard for crosslinked polyethylene (XLPE) insulation designed for power cables rated from 2001 V to 35 000 V. This specification applies to conductor sizes 8 AWG (8.37 mm²) and larger, with a base polymer consisting substantially of polyethylene. It is recognized as a primary standard for medium voltage cable insulation used in both wet and dry locations.
⚙️ Scope and Application Conditions
This insulation is suitable for single- and multiple-conductor power cables operating under a range of thermal and electrical conditions. The standard defines specific emergency and short-circuit ratings alongside continuous operating limits.
| 📊 Condition | 🌡️ Maximum Conductor Temperature | ⚡ Applicable Voltage Rating |
|---|---|---|
| Continuous Operation | 90 °C | 2001 V – 35 000 V (100% Level) 2001 V – 25 000 V (133% Level) |
| Emergency Overload | 130 °C | — |
| Short-Circuit | 250 °C | — |
📏 Physical, Electrical, and Testing Requirements
The physical properties of the insulation must meet the requirements specified in Table 1 of the standard. Electrical qualification is mandatory, with tests conducted in accordance with Test Methods D470.
The standard prescribes a strict sequence for electrical evaluation to ensure material integrity and performance under high voltage stress.
💡 Critical Testing Sequence: When electrical tests are required, they must be performed in this order: Partial-Discharge (Corona)