There are many types of cables, but they can basically be divided into low-voltage and high-voltage cables. But how do we distinguish between the two? Some say 250V, others 1000V. So how do we distinguish between high and low voltage?
According to my country's industry standard, electrical equipment is divided into high-voltage and low-voltage types: High-voltage: Equipment with a voltage of 250V or higher to ground. Low-voltage: Equipment with a voltage of 250V or lower to ground. According to the 2009 Power Line Safety Regulations, electrical equipment is divided into high-voltage and low-voltage types:
High-voltage electrical equipment: Voltage levels of 1000V or higher; Low-voltage electrical equipment: Voltage levels of less than 1000V.
Typically, high-voltage lines refer to 3-10 kilovolt lines; low-voltage lines refer to 220/380 volt lines.
Here's how to visually identify the voltage of high-voltage power lines:
Understanding Voltage Levels
In my country's power industry, common voltage levels include 220V, 380V, 1000V, 10,000V, 35,000V, 110,000V, 220,000V, and 500,000V. Generally, 220V and 380V are considered low voltage, primarily for household use; 35,000V and above are considered high voltage, primarily for transmission. Medium voltage is considered between these two levels. It's important to note that touching high-voltage power lines or performing live work under them is extremely dangerous.
Identifying Low-Voltage Lines
Outdoor low-voltage power lines have several distinct characteristics:
1) They are typically supported by short, concrete poles, typically no more than 5 meters.
2) The wires are of uniform thickness and are multiples of 4. This is because low-voltage power lines generally use a three-phase, four-wire system. If these characteristics are present, the line voltage is 380V and the phase voltage is 220V. (Phase voltage is the voltage between the line and ground, and line voltage is the voltage between two wires.)
Identifying Medium- and High-Voltage Lines
Medium- and high-voltage lines also have distinct characteristics:
1) If the wires are of the same thickness, the number of wires is a multiple of three. This is because power lines typically use three-phase transmission. If these characteristics are present, the line is essentially 10,000 volts.
2) If the wires are of varying thickness, the number of thick wires is a multiple of three, while there are only two thin wires, and these are assumed to be located at a higher altitude. This is because the thin wires are not used for power transmission but for lightning protection, also known as lightning conductors. If these characteristics are present, the line is clearly a high-voltage line.
Further Identifying High-Voltage Lines
To increase transmission capacity, high-voltage lines typically use split conductors. In layman's terms, instead of a single wire per phase, several wires are bundled together. Knowing this makes it easier to determine the voltage level of a line.
1) One phase, one wire is 110,000 volts;
2) One phase, two wires is 220,000 volts;
3) One phase, four wires is 500,000 volts.
We don't often encounter high-voltage power lines in our daily lives, but we still need to be careful with medium and low-voltage lines. Countless people die from electric shock every year. Therefore, no matter what type of cable you use, be sure to use quality-assured, nationally standardized cables.
