Technical Analysis: What are the thermal characteristics of the 3GI3 (EPR) insulation compound used in high-voltage VDE cables?
Published by: Anhui Feichun Special Cable Co., Ltd.
Specialists in Medium Voltage and High Voltage Industrial Cabling
1. Executive Summary: Defining 3GI3
2. Thermal Performance Data (VDE 0298-4)
The selection of 3GI3 is primarily driven by its thermal resilience, which directly dictates the current carrying capacity (Ampacity) of the cable.
| Thermal Parameter (热参数) | Value for 3GI3 (3GI3 数值) | Comparison to PVC (对比 PVC) |
|---|---|---|
| Max. Continuous Conductor Temp. 最大连续导体温度 | +90°C +90°C | PVC is limited to +70°C. PVC 限制在 +70°C。 |
| Max. Short-Circuit Temperature (5s) 最大短路温度（5秒） | +250°C +250°C | PVC is limited to +160°C. PVC 限制在 +160°C。 |
| Min. Installation Temperature 最低安装温度 | -40°C (Fixed) -25°C (Flexing) -40°C（固定） -25°C（移动） | PVC becomes brittle below -5°C. PVC 在 -5°C 以下变脆。 |
| Thermal Overload Factor 热过载系数 | 1.2x Current (Emergency) Can run at 130°C for short periods. 1.2倍电流（紧急） 可在 130°C 下短时间运行。 | Melts/Deforms rapidly. 迅速熔化/变形。 |
3. Why 3GI3 is Mandatory for High Voltage (>1kV)
The Ozone Factor: High voltage cables create electrical fields that can ionize the air around the insulation, creating ozone ($O_3$). Standard rubbers (like Natural Rubber) crack rapidly when exposed to ozone. 3GI3 is inherently Ozone Resistant, preventing surface cracking and tracking.
Dielectric Strength: 3GI3 has a significantly higher dielectric strength than 3GI1 or 3GI2, making it the only choice for cables rated 3.6/6 kV up to 18/30 kV (e.g., (N)TSCGEWÖU or PROTOLON cables).
臭氧因素： 高压电缆会产生电场，电离绝缘层周围的空气，产生臭氧 ($O_3$)。标准橡胶（如天然橡胶）在暴露于臭氧时会迅速龟裂。3GI3 天生具有耐臭氧性，可防止表面龟裂和漏电起痕。
介电强度： 3GI3 具有比 3GI1 或 3GI2 明显更高的介电强度，使其成为额定电压 3.6/6 kV 至 18/30 kV 电缆（例如 (N)TSCGEWÖU 或 PROTOLON 电缆）的唯一选择。
4. Comparison: 3GI3 vs. Other Compounds
| Compound Code (VDE 0207-20) | Base Material | Typical Application |
|---|---|---|
| 3GI3 | EPR (High Grade) EPR（高级） | Medium/High Voltage Cables. Reeling, Mining, Marine. 中/高压电缆。 卷盘、矿用、船用。 |
| 3GI1 / 3GI2 | EPR (Standard) EPR（标准） | Low Voltage Cables (H07RN-F). Limited to 1000V. 低压电缆 (H07RN-F)。 限制在 1000V。 |
| YI4 | PVC PVC | Stationary Install. Poor thermal and cold performance. 固定安装。 热性能和冷性能较差。 |
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![The maximum conductor operating temperature is a critical parameter that determines a cable's current-carrying capacity, service life, and application suitability. For VDE-certified cables, EPR (Ethylene Propylene Rubber) insulation permits a continuous conductor operating temperature of 90°C, representing a significant advancement over older rubber insulation technologies which were typically limited to 60°C–70°C.[1][2] 最高导体工作温度是决定电缆载流量、使用寿命和应用适用性的关键参数。对于VDE认证电缆，EPR（乙丙橡胶）绝缘允许90°C的连续导体工作温度，相比传统橡胶绝缘（60°C–70°C）有显著提升。](https://feichuncables.com/blog/wp-content/uploads/image-574-400x225.avif "What is the Maximum Conductor Operating Temperature Allowed for VDE Cables Insulated with EPR (90°C) vs. Older Rubber Types? 4")