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What is the relationship between the rated voltage of the cable and the number of cores?

Everything in the world has its own properties and levels, not to mention the wide variety of applications and types of cable products.

Even if you are in the industry, you do not know everything.

Today ZMS cable editorial this article, a simple analysis of the relationship between the rated voltage of the cable and the number of cores of the cable, I hope to help you better understand.


1kV and below for 1-5 core cable selection conditions.

1 Single-Core Cable

Longer lines, circuits with higher operating currents or when laid underwater.

To avoid or reduce the intermediate joints, or single-core cable than multicore cable has a better overall technical economy, single-core cable can be selected.

Low-voltage DC power supply circuit, when necessary, single-core cable can be used.

2 2-Core Cable

1kV and below when the neutral point of the power supply is directly grounded, the number of cores of the single-phase circuit cable.

When the protection wire and neutral wire together with the same conductor, should be used 2 core cable.

DC power supply circuit, it is appropriate to use 2-core cable.

3 3 Core Cable

1kV and below when the neutral point of the power supply is directly grounded, the number of cores of the single-phase circuit cable is the following rule. When the protection line and the neutral line are independent, it is appropriate to use 3-core cable.

4 Core Cable

1kV and below 4 core cable (3 + 1 cable), the fourth core of which, in addition to the protection of grounding, but also to transport the power system in the unbalance current and short-circuit current.

Its size is determined by the unbalance current and short-circuit current, but generally shall not be less than 1/2 of the phase line.

1kV and below three-phase four-wire low-voltage power distribution system.


When the protection line and neutral line are combined with the same conductor, a 4-core cable should be used, instead of a 3-core cable plus a single-core cable combined into a circuit.

Or directly use the metal sheath or armor layer of the 3-core cable as the neutral line.

Otherwise, when the 3-phase current is not balanced.

This is equivalent to the operating state of single-core cable, easy to cause industrial frequency interference.

5 5 Core Cable

1kV and below the three-phase four-wire low-voltage distribution system, some of the reliability requirements of higher electrical installations' distribution lines.

As well as some both to ensure that the electrical is not damaged, but also to resist interference grounding communication and automation equipment. It is advisable to use the TN-C low-voltage distribution system with 5 cores, so that the protection line (PE line) and the neutral line (PN line) are independent.

Cable core cross-sectional area is generally 3 large and 2 small or 4 large and 1 small or 5 large.


Wire and cable is used to transmit electrical (magnetic) energy, information and electromagnetic energy conversion of wire products.

Wire and cable in the broad sense is also referred to as cable, the narrow sense of cable refers to the insulated cable.

It can be defined as a collection of the following components.

One or more insulated wire cores, together with their respective possible cladding, total protective layer and outer sheath.

The cable may also have additional conductors that are not insulated.


Measures to Prevent Wire and Cable Fires are as Follows.

1 ensure the quality of construction, especially the production quality of the cable head, must be strict and meet the requirements of the regulations.

2 strengthen the cable operation monitoring, to avoid cable overload operation.

3 Conduct cable tests on a regular basis and deal with abnormalities promptly when found.

4 Cable trench should be kept dry.

Prevent the cable from getting damp, causing the insulation to drop and causing a short circuit.

5 Regularly sweep the dust accumulated on the cable.

Prevent spontaneous combustion of the accumulated dust causing cable fire.

6 Strengthen the regular calibration and maintenance of the cable circuit switch and protection to ensure its reliable operation.

7 The cable should be laid at a sufficient distance from the heat pipe.

Control cable is not less than 0.5 m, power cable is not less than 1 m.

Control cables and power cables should be divided into slots, layered and arranged separately, not overlapping between layers placed.

For parts that do not meet the requirements, the cable should take fire retardant, thermal insulation measures.

8 Install a fire alarm device to detect fire in time to prevent the cable from catching fire.


Cable Fire Retardant Measures

1 The cable is wrapped with adiabatic and flame-resistant materials.

When the cable around the fire, the cable wrapped by the adiabatic flame resistant materials and fire isolation can be saved from burning. 

If the cable itself is on fire, the lack of oxygen inside the wrap can make the fire extinguish itself and prevent the fire from spreading outside the wrap.

2 cable through the wall, the bottom of the tray, the hole in the shaft with fire-resistant materials sealed tightly.


To prevent the cable from catching fire, high-temperature smoke diffusion and spread caused by the expansion of the fire surface.

3 Apply fireproof paint to the cable surface.

4 Wrap the parts of the cable that need to be protected from fire with fireproof tape.

5 Install a heat-resistant fire barrier between the layers of the cable.

Prevent the fire from spreading between cable layers and expanding the fire.

6 Set up segmental partition walls and fire doors in the cable channel.

Prevent the cable from burning and expanding the fire.

7 equipped with the necessary fire-fighting equipment and facilities.

Overhead cable fire can be commonly used to put out the fire extinguishing equipment.

But in the cable mezzanine, shafts, trenches and tunnels, etc. should be installed automatically or remote control fire extinguishing devices.

For example, 1301 fire extinguishing devices, water spray fire extinguishing devices.

Putting out cable fires

When a cable fire occurs, the alarm should be raised quickly and the system and direction of the burning cable should be identified immediately. 

Adjust the operation of the burning cable as soon as possible, and cut off the power supply of the burning cable to withdraw from operation.

Cable burning produces toxic gases, so cable fires need special attention to protection.


These are some general knowledge about the cable, I hope you can play a certain help in choosing the cable.

ZMS cable company  manufacturer always insists on providing high-quality cables, good value for money, considerate service, and products that have undergone strict manual qualification audits and are trustworthy.