The structure and specification of YJV cable

Let me introduce to you what YJV means, yj means cross-linked polyethylene, v means polyvinyl chloride, then YJV is cross-linked polyethylene insulated PVC sheathed cable, and the range of use is for the rated voltage (U0/U) 0.6/1—26/35kv power line transmission and distribution, the rated temperature of the cable conductor is 90 degrees when in use, and the temperature of the cable conductor does not exceed 250 degrees when short-circuited (the duration does not exceed 5S). It has the advantages of light weight and simple structure, so it is widely used in urban power grids.
YJV cable model specification

The cores of YJV cables are single core, 2 cores, 3 cores, 4 cores, 5 cores, 3+1, 3+2, 4+1. 3+1 represents 3 phase wires and 1 ground wire, 3+ 2 represents 3 phase wires and 2 ground wires, 4+1 represents 4 phase wires and 1 ground wire. According to the standard model, the specific size specifications include: 1 square, 1.5 square, 2.5 square, 4 square, 6 square, 10 square, 16 square, 25 square, 35 square, 50 square, 70 square, 95 square, 120 square, 150 Square, 185 square, 240 square, 300 square. For example, the YJV 3*120+2*70 cable is a cable composed of three 120 square phase wires and two 70 ground wires.

The combination between the ground wires is regulated by the standard, so the 70 square behind the YJV 3*120+2*70 cable can be omitted. The main specifications of the YJV cable range from 1 square to 240 square meters (also can be customized separately). It is a cable used for transmission and distribution of electric energy. It is often used in urban underground power grids, lead-out lines of power stations, internal power supply of industrial and mining enterprises, and underwater transmission lines that cross rivers and seas. In power lines, the proportion of cables is gradually increasing. Power cable is a cable product used to transmit and distribute high-power electrical energy in the main line of the power system, including 1-500KV and above various voltage levels, various insulated power cables.

How to protect cables from damage in cold winter

In winter, when laying and installing Aerial Bundle Cable (ABC) XLPE Insulated, many construction personnel will find that the wire and cable products with good quality usually have some problems, such as wire body hardening, insulation sheath falling off and damage. Many construction personnel think that the quality problems of wire and cable products have occurred, and the cable manufacturers insist that the products have been inspected before leaving the factory and are qualified Products often lead to misunderstanding between both sides. In fact, it is not the quality of the product itself, but the cold in winter.

The outer skin of PVC insulated AS / NZS 3560.1 power cable products is mostly ordinary plastic (PVC) or rubber. When they are in the environment below zero, they will become hard, and the whole wire and cable product line body will be hard and brittle, resulting in the skin may fall off and be damaged under slight external force. In winter, especially in the northern region, the outdoor temperature is often below zero, and the surface temperature may be lower. Therefore, if the wire and cable products are placed outdoors or directly on the ground, the product skin may fall off. So, how can we prevent the phenomenon of wire and cable sheath falling off in winter? Take the following measures from each stage.

1. When laying and installing the product: it is better to operate under the condition of relatively warm temperature in the middle and afternoon. If possible, the product can be “warmed up” in advance by using air heater and other equipment before use, so that the product can reach the best performance state. If buried, a protective layer can be laid in the cable trench, such as cloth and foam. If it is through the tube, the inside and outside of the pipe must be smooth in advance, so as not to scratch the wire. Special attention should be paid to the iron pipe. If the quality of the iron pipe is qualified, there may be a large number of sharp convex points in the poor quality iron pipe, which is likely to scratch the wire skin.

2, storage: it is best to store products in the room, and lay a layer of isolation layer on the surface of the storage, such as boards, bedding, foam and so on, to prevent the product from getting cold and damp.

3. When arriving at the destination or construction site, it is better for the product supplier to send personnel to supervise to prevent rough operation during unloading.

4. Ex factory transportation: when the products are loaded on the transport tools, they need to be kept warm and protected. For example, the use of closed means of transport to prevent direct exposure of products; put a soft cushion on the product, such as bedding or other softer foam, etc. when loading, gently handle lightly, do not load rough, at the same time avoid excessive bending of the product.

All in all, in winter, wires and cables will become very fragile, we need to “take care of”.

What is Difference Between XLPE Cable and PVC cable?

Polyethylene abbreviated as PE, it is a polymer of ethylene, non-toxic. Easy to color, good chemical stability, cold resistance, radiation resistance, and good electrical insulation. It is suitable for packaging materials for food and medicine,
Making food utensils, medical equipment, and insulating materials for the electronics industry, etc.;PE cable become the better choice economically.

Polyvinyl chloride is abbreviated as PVC , which is a polymer of vinyl chloride. It has good chemical stability, resistance to acid, alkali and some chemicals. It is resistant to moisture, aging, and flame retardant. The temperature cannot exceed 60℃ when it is used, and it will become hard at low temperatures. Polyvinyl chloride is divided into soft plastic and hard plastic. The soft ones are mainly made into films, which can be used as packaging materials, rainproof products, agricultural seedling raising films, etc., as well as insulation layers for cables and wires, and artificial leather products. Rigid ones are generally made of pipes and plates. The pipes are used as water pipes and pipes for transporting corrosion-resistant fluids. The plates are used as the lining and floor of various storage tanks;PVC cable can divide to many kinds ,such as PVC sheathed power cable ,PVC insulated flexible cable and so on.

Cross-linked polyethylene, abbreviated as XLPE, uses chemical or physical methods to transform polyethylene molecules from a linear molecular structure to a three-dimensional network structure. Thermoplastic polyethylene becomes thermoset cross-linked polyethylene, thereby increasing the polyethylene’s It has aging resistance, mechanical properties and environmental resistance, and maintains excellent electrical properties. The allowable long-term maximum working temperature of the conductor of cross-linked polyethylene insulated power cable is 90 degrees Celsius, which is higher than that of paper insulated cables, polyvinyl chloride insulated cables and polyethylene insulated cables, and has light weight, simple structure, convenient use, chemical resistance and corrosion resistance. Laying is not limited by the drop and other advantages.

It is also an important technology to improve PE performance. Cross-linked modified PE can greatly improve its performance, not only significantly improving the mechanical properties, environmental stress cracking resistance, chemical corrosion resistance, creep resistance and electrical properties of PE , but also The temperature resistance level is significantly improved, and the heat resistance temperature of PE  can be increased from 70°C to above 90°C, which greatly broadens the application range of PE . At present, cross-linked polyethylene (XLPE ) has been widely used in pipes, films, cable materials and foam products.

Comparison of physical properties:
1.Polyvinyl chloride cable: using polyvinyl chloride (PVC) as the insulating material, the maximum operating temperature of the cable does not exceed 70°; the specific gravity of polyvinyl chloride is between 1.35-1.5;
2.Polyethylene cable: Use cross-linked polyethylene (XLPE) as the insulating material. The maximum working temperature of the cable does not exceed 90°; the specific gravity of polyethylene is between 0.922-0.95. The insulation performance is better than PVC;

The difference between XLPE insulated cables and PVC cables:
1. The temperature resistance of XLPE insulated cables can reach 90°C.
2. The temperature resistance rating of polyvinyl chloride (PVC) cables is generally 70°C.
3. Polyvinyl chloride will release toxic HCl fumes when it burns.
4. The current carrying capacity of XLPE insulated cables is greater than that of PVC cables. For cables with the same conductor cross-sectional area, XLPE cables have higher current carrying capacity and stronger overload capacity;
5. Cross-linked polyethylene cables have a long service life (the thermal life of PVC cables is generally 20 years when the environment is better, and the thermal life of XLPE cables is generally 40 years);
6. PVC will decompose and release a large amount of black smoke and toxic gas when burning, while XLPE will not produce halogen toxic gas when burning. The superiority of cross-linked cables is increasingly recognized by the design and use departments.

Ordinary PVC wire and cable (insulation and sheath) burns quickly and promotes the fire. The power supply will be lost within 1 to 2 minutes. The black smoke released by the combustion and decomposition can reach the level of reaching the fingertips, causing difficulty in breathing and evacuation. What’s more serious is that when PVC burns, it will decompose and release highly toxic and corrosive halogen gases such as hydrogen chloride (HCL) and dioxins, which is the main cause of death in fires (accounting for 80% of fire deaths) and becomes rare The hydrochloric acid conductive film is attached to the electrical equipment, seriously reducing the insulation performance of the equipment, and forming a secondary disaster that is difficult to remove.