Different voltage levels:
According to the provisions of some conventional cable standards, the voltage below 1KV (including 1KV) is defined as low voltage, and 1KV-330KV is defined as high voltage. Therefore, the rated voltage of 1KV and below is called low-voltage cable, and the rated voltage of 1KV-330KV is high-voltage cable. The common cables in our work and life are 0.4KV and 10KV voltage grade cables. The following analysis will focus on these two voltage grade cables.
Structural differences:
1. High voltage cable:
YJV22-8.7/15KV-3 * 70: High voltage 15KV copper core cross-linked polyethylene insulated PVC sheathed steel tape armored three core 70m2 cable
(1) Stranded copper conductor: a conductor used to transmit electric energy, which is made of stranded hard wires.
(2) Conductor shielding layer: because the conductor is twisted by several hard wires, and there are gaps on the surface, which will lead to uneven electric field and partial discharge. Therefore, the conductive non-metallic soft materials are used to fill to ensure the perfect fit with the insulation layer to uniform the electric field and improve the service life of the cable.
(3) Insulating layer: as the electrical gap between 10KV bare conductors is 125mm, and the gap between two conductors in the cable is very small, it needs to be made of cross-linked polyvinylchloride material with good performance to play a major insulating role. Generally, the thickness of insulation layer of 8.7/15KV model is not less than 4.5mm.
(4) Insulation shield layer: also, there will be gaps in the direct combination of the insulation layer and the outer sheath, so a conductive semiconductor layer is added outside the insulation layer to uniform the electric field and prevent partial discharge.
(5) Metal shielding layer: In order to ensure that the semiconductor layer can be reliably grounded, a layer of metal shielding layer is wrapped outside. When the metal shielding layer works normally, it is directly grounded to drain the distributed capacitive current between the cable and other conductors, and at the same time, it can shield some electromagnetic interference to prevent interference with other equipment.
(6) Filler material: in order to eliminate mutual inductance between three-phase cables, three-phase cables need to be arranged in a symmetrical zigzag pattern. The space left inside needs to be filled with filler material to ensure the stability of the core and the mechanical strength of the cable.
(7) Wrapping tape: Most of the materials are PVC, non-woven fabrics are mainly used to protect the cable from external influences, and the wrapped core and filler are round and not loose.
(8) Inner sheath: the inner sheath is a protective covering covering the cable insulation to prevent the insulation layer from being affected by moisture, mechanical damage, light and chemical aggressive media, etc.
(9) Steel tape armor layer: The armored cable is used to increase the mechanical strength of the cable and improve the corrosion resistance. It is designed for areas vulnerable to mechanical damage and erosion.
(10) PVC outer sheath: mainly used for protection, isolation and waterproof, providing the outermost layer of protection.
2. Low voltage cable:
YJV22-0.6/1KV-3 * 70: low-voltage 1KV copper core cross-linked polyethylene insulated polyethylene sheathed steel tape armored three core 70m2 cable
The structure of low-voltage cable is different from that of high-voltage cable in conductor shielding layer, insulation shielding layer and metal shielding layer. The difference is mainly caused by different insulation capacities of voltage grades. The electric field capacity of low-voltage 0.4KV is much weaker than that of 10KV, such as air breakdown or insulation breakdown.
Differences in usage:
High voltage cables can only be used after the cable head is made according to strict manufacturing process, while low-voltage cables do not require the production of cable head. The laying requirements of high-voltage cables and low-voltage cables are also different.
In a word, the difference between high and low voltage cables comes from the difference of voltage and insulation capacity. These differences are to ensure the safety of electricity.
