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D1352-02 – Standard Test Method Technical Guide
ASTM D1352 – 02 establishes the standard specification for an ozone-resisting crosslinked rubber insulating compound whose polymer consists substantially of butyl rubber, intended for electrical wires and cables. This document defines the physical, electrical, and aging requirements necessary to ensure reliable performance in demanding service environments.
📐 Scope and Operating Conditions
The insulation covered by this specification is suitable for use at service voltages not exceeding 15,000 V between phases at an insulation level of 133% or 28,000 V between phases at an insulation level of 100%. Conductor temperature limits are strictly defined: a maximum of 85°C for operating voltages of 15,000 V or less, and a maximum of 80°C for voltages exceeding 15,000 V.
💡 Interpretation of Material Testing: In many instances the insulation material cannot be tested unless formed around a conductor. Per Section 1.4, tests performed on insulated wire or cable in this document are conducted solely to determine the relevant property of the insulation material itself, not to test the insulated conductor or completed cable.
🧪 Material Performance and Resistance Properties
| 🟦 📏 Property | 📐 Requirement | 🎯 Reference |
|---|---|---|
| Polymer Base | Substantially Butyl Rubber | Section 1.1 |
| Insulation Thickness (Minimum) | ≥ 90% of average thickness per D470 Table 1A | Section 4.2 |
| Ozone Resistance | No visible cracking after 3 h exposure | 0.025 to 0.030% ozone conc. per D470 |
| Thermal Aging Definition | Exposure to air at 100°C for 168 h | Section 3.1.1 |
| Accelerated Water Absorption | Per Table 2, Electrical Method | 75 ± 1°C water temp at 60 Hz (D470) |
The standard mandates strict evaluation of ozone resistance, a critical property for applications exposed to corona. The insulation must show no visible cracking after a 3-hour exposure to an ozone concentration of 0.025 to 0.030% by volume.
⚡ Electrical Verification and Test Sequence
A specific order of electrical testing is required when multiple tests are specified. This sequence ensures valid and repeatable data without cross-contamination of measurements.
⚠️ Mandatory Test Order (Section 7.1): When partial discharge, AC voltage, insulation resistance, and DC voltage tests are all specified, they must be performed in the following order: 1. Partial Discharge ➔ 2. AC Voltage ➔ 3. Insulation Resistance ➔ 4. DC Voltage. Capacitance and dissipation factor tests must be run on a separate sample.
| ⚡ 🟦 Test (in sequence) | 📏 Specification | 🎯 Reference |
|---|---|---|
| 1. Partial Discharge (Corona) | Minimum requirements per Table 3 (for cables ≥ 2001 V) | ICEA T-24-380 / D470 |
| 2. AC Withstand Voltage | 5-minute withstand test at specified voltages | D470 Table 1A |
| 3. Insulation Resistance | Per sequence after AC test | Test Methods D470 |
| 4. DC Voltage Test | Per sequence order | Test Methods D470 |
Combined with strict thermal aging requirements and water absorption limits, this standard ensures a high level of reliability for butyl rubber insulated systems operating in demanding environments.
❓ Frequently Asked Questions
🔍 What specific polymer base is required by this standard?
The polymer must consist substantially of ozone-resisting crosslinked butyl rubber as defined in the scope of the specification.
💡 What are the voltage and corresponding temperature limits?
The insulation is suitable for up to 15,000 V (133% level) with a max conductor temperature of 85°C, and up to 28,000 V (100% level) with a max conductor temperature of 80°C.
⚡ What is the strict sequence for high-voltage testing?
When specified, the mandatory testing sequence is: 1. Partial Discharge, 2. AC Voltage, 3. Insulation Resistance, 4. DC Voltage. Capacitance and dissipation factor tests require a separate sample.
📌 How is the term “aging” defined in this standard?
Per Section 3.1.1, aging is specifically defined as the exposure of materials to air at 100°C for 168 hours.