Look at the Cable Structure.
High-voltage cables have many layers, peel off the outermost layer inside there are armor, shielding layer, insulation layer, conductors, etc.
Low-voltage cables generally set aside the outermost layer, which is the insulation layer or conductor.
Look at the Insulation Layer.
The high-voltage cable insulation layer is thicker, the low-voltage cable insulation layer is thinner.
The low-voltage cable insulation layer is generally within 3 mm, the high-voltage cable insulation layer is generally more than 5 mm.
Look at the outermost layer of the cable nameplate.
The outermost layer of the cable is generally printed with the relevant parameters of the cable, which include the cable type, cross-sectional area, rated voltage, length, and other parameters.
High-voltage cables are voltage levels above 1kV volts to 750KV, collectively referred to as high-voltage cables.
The main use is the power sector for the transmission of electricity, and voltage conversion.
Commonly used for long-distance transmission of electricity, substations voltage level change.
Our commonly used voltage levels are below 220KV.
Long-distance transmission of electricity voltage levels are ultra-high voltage, are designated by the power sector special power workers' construction, special maintenance.
There are various types of high-voltage cables according to the voltage resistance level:
1 Oil-Impregnated Paper-Insulated Cable
The voltage resistance level is from 1KV to 750KV.
2 Plastic Insulated Cable
Voltage resistance level 1KV ~ 220KV.
3 Rubber-Insulated Cable
Pressure resistance level 1KV ~ 138KV.
4 Gas Insulated Cable
Withstanding voltage level 220KV～500KV.
Low-voltage insulated cables are suitable for electrical equipment with a voltage resistance of 450V/750V or less.
General industrial plastic insulated cable for fixed laying.
Low-voltage insulated cables with rubber jackets for mobile use.
Building installation is mainly used for the laying of the main power circuit, the main branch, branch circuit, there are also special flat elevator cables for elevator installation.
We first look at the low-voltage cable and high-voltage cable structure
High-voltage cable from the inside to the outside of the conductor - inner semiconductor layer - insulation layer - outer semiconductor layer - metal armor - sheath layer.
Low-voltage cables are conductor-insulation-steel ribbon-sheath from inside to outside, and many low-voltage cables do not have steel ribbons.
The main difference between high-voltage cables and low-voltage cables in structure is that high-voltage cables have more semiconductor layers and shield layers than low-voltage cables.
Therefore, the insulation layer of high-voltage cables is much thicker than that of low-voltage cables, the structure is complicated, and the process requirements are high.
Semiconductor Layer
The main role of the inner semiconductor layer is to improve the electric field effect, as there is a gap between the conductor and insulation layer of high-voltage cable, it is easy to produce partial discharge to destroy the insulation layer.
To improve the situation, the metal conductor and insulation layer between the addition of a layer of semiconductor material shielding layer, play a transitional role.
The outer semiconductor layer plays the same role as the inner semiconductor layer, and its role is to avoid partial discharge between the insulation layer and the metal sheath.
Shielding Layer
The metal shield of the high-voltage cable has three main roles:
1. Shielding Electric Field
Since the shield, as the name implies, is to play the role of shielding.
The voltage inside the high-voltage cable is very high, it produces a very strong electric field, and the shield can effectively prevent the interference of high-voltage cable to the outside world.
2. Operation Through the Capacitive Current
The innermost layer of the high-voltage cable is the conductor, with an insulating layer in the middle and a metal sheath outside.
The two conductors (internal copper wire + metal sheath) are separated by an insulating medium (insulation layer), which can be seen as a capacitor.
The basic principle of a capacitor is two metal plates separated by an insulating medium.
AC will charge and discharge the capacitor, so the shield can provide a circuit for capacitor charging and discharging.
In addition, both the metal shield and metal armor of the high-voltage cable need to be grounded at one end.
3. Can be used as a Short-Circuit Current Channel
When the insulation of high-voltage cable is damaged, if there is no shield layer cable will leak into the earth, there is a safety hazard.
If there is a shield, the leakage current will flow to the earth through the shield.
The above is the introduction of high-voltage cables and low-voltage cables. If you have any questions about the purchase, welcome to email us, we will have professional cable sales representatives to solve your questions.
