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How to distinguish between high voltage cables and low voltage cables?


There are many types of wires and cables, but the most basic ones can be divided into two types: high-voltage cables and low-voltage cables. What is the difference between the cables?

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              How to distinguish between high voltage cables and low voltage cables?

 

                                                 

一、Different voltage levels

In my country's power industry, the common voltage levels are 220V, 380V, 1kV, 10kV, 350kV, 110kV, 220kV, 500kV, etc. Under normal circumstances, 220V and 380V are considered low voltage, mainly for household electricity; 35kV and above are high voltage, mainly used for power transmission; those in between are medium voltage.

                                                     

二、 The cable structure is different

 

1. High voltage cable:

High-voltage 10KV copper core XLPE insulated PE sheathed steel tape armored three-core 70 square cable: YJV22-8.7/15KV-3*70
(1) Stranded copper conductor: a conductor that transmits electrical energy, made of multiple strands of hard wire.

(2) Conductor shielding layer: Since the conductor is made of multiple hard wires twisted together, there are gaps on the surface, which will cause uneven electric field and easy partial discharge, so it is filled with conductive non-metallic soft material to ensure insulation The perfect fit of the layers can even out the electric field and increase the life of the cable.

(3) Insulation layer: Since the electrical gap between the 10KV bare conductors is 125mm, the gap between the two conductors in the cable is very small, so it needs to be made of cross-linked polyethylene material with better performance, which plays the main role of insulation . Generally, the thickness of the insulating layer of the 8.7/15KV model is not less than 4.5mm.

(4) Insulation shielding layer: Also, due to the direct combination of the insulation layer and the outer sheath, there will be gaps, so a conductive semiconductor layer is added outside the insulation layer to even out the electric field and prevent partial discharge.

(5) Metal shielding layer: In order to ensure that the semiconductor layer can be reliably grounded, a metal shielding layer is wrapped outside, and the metal shielding layer is directly grounded when it is working normally to discharge the distributed capacitance current between the cable and other conductors, and at the same time It can also shield some electromagnetic interference and prevent interference with other devices.

(6) Filling material: In order to eliminate the mutual inductance between the three-phase cables, the three-phase cables need to be arranged in a symmetrical shape, and the empty space inside needs to be filled with filling materials, so as to ensure the stability of the core and the stability of the cable. Mechanical strength.

(7) Wrapping tape: the material is mostly PVC, non-woven fabric, etc. It is mainly used to protect the cable from external influences, and wrap the core tightly and the filling material is round and not loose.

(8) Inner sheath: The inner sheath is a protective coating covering the cable insulation to prevent the insulation from moisture, mechanical damage, and light and chemical corrosive media.

(9) Steel tape armor layer: Armored cable is used to increase the mechanical strength of the cable and improve the anti-corrosion ability. It is designed for areas that are vulnerable to mechanical damage and corrosion.

(10)PVC outer sheath: It mainly plays the role of protection, isolation and waterproof, and provides the outermost layer of protection.

 

Low voltage cables:

Low-voltage 0.4KV copper core XLPE insulated PE sheathed steel tape armored three-core 70 square cable: YJV power cable.
The structure of low-voltage cables is different from that of high-voltage cables. The conductor shielding layer, insulating shielding layer, and metal shielding layer are mainly due to the differences in insulation capabilities of different voltage levels. The electric field capability of low-voltage 0.4KV is much weaker than that of 10KV. Through air or insulation breakdown.
 

三、 Different uses

High-voltage cables are mainly used by the power sector to transmit power and transform the voltage level of substations. Our common and commonly used voltage levels are all below 220KV, and the voltage levels of long-distance transmission power are all ultra-high voltage, which are designated by the power department for construction and maintenance by specialized electric workers.

Low-voltage cables are suitable for electrical equipment with a withstand voltage of 450V/750V or less, and are widely used and classified. General industrial plastic insulated cables are used for fixed laying; rubber-sheathed low-voltage insulated cables for mobile use; building installations are mainly used for the laying of the main power circuit, each branch, and branch roads, and there are also special flat elevator cables for elevator installation.

四、Production process

Low-voltage cables can use two kinds of insulating materials, polyvinyl chloride and cross-linked polyethylene. Medium and high-voltage cables only have cross-linked cables, and 6kV-35kV use three-layer co-extruded, high-density cross-linked polyethylene production.

High-voltage cables must be used after the cable head is made according to the strict manufacturing process, while low-voltage cables do not require the cable head to be made. In addition, the laying requirements of high-voltage cables and low-voltage cables are also different.