High-voltage cables and low-voltage cables belong to a kind of power cables, mostly used for transmission lines. There is a big difference between high-voltage cables and low-voltage cables, which are mainly reflected in the following aspects:
 

1. different voltage levels: according to GB/T2900.50-2008 "GB/T2900.50-2008 Electrotechnical Terms for Power Generation, Transmission and Distribution General Terms", 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 class cables.

2. structural differences:

1. High-voltage cable:

YJV22-8.7/15KV-3*70: High-voltage 15KV copper core XLPE insulated PVC sheathed steel tape armored three-core 70m2 cable.

(1) Stranched copper conductor: A conductor used to transmit electrical energy, made of stranded hard wires.

(2) Conductor shielding layer: Because the conductor is twisted by several hard wires, there are gaps on the surface, which will cause uneven electric field and partial discharge. Therefore, it is filled with conductive non-metallic soft material to ensure a perfect match with the insulating layer to uniform the electric field and increase the service 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 polyvinyl chloride material with good performance to play the main Insulation effect. The thickness of the insulation layer of the 8.7/15KV model is generally not less than 4.5mm.

(4) Insulation shielding layer: In addition, there will be a gap in the direct combination of the insulating layer and the outer sheath, so a conductive semiconductor layer is added outside the insulating layer to uniform the electric field and prevent partial discharge.

(5) Metal shielding layer: In order to ensure the reliable grounding of the semiconductor layer, a metal shielding layer is wrapped on the outside. When the metal shielding layer works normally, it is directly grounded to discharge the distributed capacitive current between the cable and other conductors, and at the same time can shield some electromagnetic interference to prevent interference with other equipment.

(6) Filling material: In order to solve the mutual inductance between the three-phase cables, the three-phase cables need to be arranged in a symmetrical zigzag shape. The space left inside needs to be filled with a filling material to ensure the stability of the core and the mechanical strength of the cable.

(7) Winding tape: Most of the material is PVC, non-woven fabric is mainly used to protect the cable from external influences, and the wound core wire and filler are round and not loose.

(8) Inner sheath: The inner sheath is a protective layer covering the cable insulation layer to prevent the insulation layer from being affected by moisture, mechanical damage, light and chemically aggressive media.

(9) Steel tape armor layer: armored cables are used to increase the mechanical strength of the cable and improve corrosion resistance. Designed for use in areas susceptible to mechanical damage and erosion.

(10) PVC outer sheath: mainly used for protection, isolation and waterproof, providing a very outer layer of protection.

2. Low voltage cable:

YJV22-0.6/1KV-3*70: Low voltage 1KV copper core XLPE insulated polyethylene sheathed steel tape armored three core 70m2 cable.

The structure of low-voltage cables and high-voltage cables is different in the conductor shielding layer, insulation shielding layer and metal shielding layer. This difference is mainly due to the different insulation capacity of the voltage level. The electric field capacity of low voltage 0.4KV is much weaker than 10KV, such as air breakdown or insulation breakdown.

3. usage differences

High-voltage cables can only be used after the cable head is made in accordance with the strict manufacturing process, while low-voltage cables do not need to make cable heads. The laying requirements of high-voltage cables and low-voltage cables are also different. In short, the difference between high-voltage cables and low-voltage cables comes from the difference in voltage and insulation capacity. These distinctions are made to ensure electrical safety.