Technical Insight: Significance of Voltage Rating $U_0/U (U_m)$ in VDE 0250 Specifications
安徽飞纯特种电缆有限公司 (Anhui Feichun Special Cable Co., Ltd) — Professional Cable Solutions for Mining and Heavy Industry.
1. Overview of the $U_0/U (U_m)$ Notation / 额定电压 $U_0/U (U_m)$ 符号概述
In international and German VDE standards (specifically VDE 0250), the voltage rating of a cable is not a single value but a set of three parameters. For example, a 6/10 (12) kV rating defines the electrical limits under different operating conditions.
在国际和德国 VDE 标准（特别是 VDE 0250）中，电缆的额定电压不是单一数值，而是一组三个参数。例如，6/10 (12) kV 额定值定义了不同运行条件下的电气极限。
| Parameter (参数) | Definition (定义) | Technical Meaning (技术含义) |
|---|---|---|
| $U_0$ | Phase-to-Earth Voltage (导体对地电压) | The RMS voltage between the main conductor and the earth or metallic screen. |
| $U$ | Phase-to-Phase Voltage (相间电压) | The RMS voltage between any two phase conductors in a multi-core cable. |
| $U_m$ | Maximum System Voltage (系统最高电压) | The highest permissible continuous operating voltage for which the cable is designed. |
2. Detailed Breakdown of 6/10 (12) kV / 6/10 (12) kV 详细解析
When a cable like the (N)3GHSSHCH or NSHTÖU (common in VDE 0250-813) is rated as 6/10 (12) kV, it implies:
- $U_0 = 6$ kV: Designed for systems where the voltage to ground does not exceed 6 kV. / 设计用于对地电压不超过 6 kV 的系统。
- $U = 10$ kV: The nominal operating voltage between phases. / 相间的额定工作电压。
- $U_m = 12$ kV: The cable can withstand sustained peaks or fluctuations up to 12 kV, which is 20% higher than the nominal $U$. / 电缆可承受高达 12 kV 的持续峰值或波动，比额定电压 $U$ 高出 20%。
3. Industrial Significance and Safety / 工业意义与安全性
Properly identifying these values is crucial for heavy machinery such as cranes, stacker-reclaimers, and mining equipment. Using a cable with an insufficient $U_m$ can lead to dielectric breakdown during transient surges.
正确识别这些数值对于起重机、堆取料机和矿山设备等重型机械至关重要。使用 $U_m$ 不足的电缆可能会在瞬态浪涌期间导致介电击穿。
Note: According to VDE Standards, $U_m$ is the “highest system voltage” and is used to determine test voltages during manufacturing.
4. Comparison of Common Voltage Classes / 常见电压等级对比
| Cable Type (电缆型号) | $U_0/U$ (kV) | $U_m$ (kV) | Application (应用场景) |
|---|---|---|---|
| Low Voltage (LV) | 0.6/1 | 1.2 | Conveyor belts, light cranes |
| Medium Voltage (MV) | 3.6/6 | 7.2 | Standard industrial power |
| High-Stress MV | 6/10 | 12 | Heavy-duty mining, reeling |
| Extreme MV | 12/20 | 24 | Deep shaft mining, tunneling |
