The type and use of medium voltage cable > medium voltage ca

Medium voltage power cable refers to 35 thousand volt and below power cables.
Power cables can be divided into medium and low voltage power cables (35 thousand volts and below), high voltage cables (110 thousand volts above), ultra high voltage cables (275~800 kilovolts) and UHV cables (1 million volts and above).
Power cable is a cable used for transmission and distribution of electrical energy. Power cables are often used in urban underground power grid, power station elicited lines, power supply in industrial and mining enterprises, and river water transmission lines across the river. In electric power lines, the proportion of cables is 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 all kinds of voltage levels, all kinds of insulated power cables.

Type of medium voltage cable
The main types of medium voltage cables are YJV cable, VV cable, YJLV cable and VLV cable.
YJV cable full name XLPE insulated PVC sheathed power cable (copper core).
VV cable full name PVC insulated PVC sheathed power cable (copper core).
YJLV cable full name XLPE insulated PVC sheathed aluminum core power cable.
VLV cable full name PVC insulated PVC sheathed aluminum core power cable.
Because of the excellent electrical conductivity of copper conductor, more and more engineering uses copper core power cable as the main trunk of power supply system, but the application of aluminum core power cable is less, especially in the power system with high pressure, the more copper core cable is chosen.

Medium voltage cable
Structure of medium voltage cable
The components of high voltage cable from inside to outside include conductor, insulation, inner sheath, filler (armor) and external insulation. Of course, the armored high voltage cables are mainly used for ground burying, which can resist high strength compression on the ground and prevent other external damage.

Use characteristics of medium voltage cable
The product is suitable for the AC rated voltage 35KV and below the power transmission and distribution. The maximum working temperature of the cable conductor is 90 degrees, short circuit (the longest time is not more than 5S), and the maximum temperature of the cable conductor is not more than 250 degrees.

UHV cable
1.8kV and below are low voltage cables, 3.6KV~35KV is medium voltage cable, 35KV~110KV is high voltage cable, 110~220KV is UHV cable.
UHV cable is a kind of power cable with the continuous development of cable technology. UHV cable is generally used as a central link in the large transmission system. It belongs to a high voltage cable with high technical content, which is mainly used for long distance power transmission.

Failure cause of medium voltage cable
Cable is a bridge between power supply equipment and electrical equipment, and plays the role of transmitting electric energy. It is widely used, so the fault often occurs. The following is a brief analysis of the causes of the common problems of high voltage cable. According to the causes of the failure, the classification is divided into the following categories: the manufacturer manufacturing reason, the construction quality reason, the design unit design reason, the external force destruction four major categories.

Medium voltage cable manufacturers
The cause of the manufacturing of the cable body
Generally, in the process of cable production, the problems often occur in the process of cable production, such as insulation eccentricity, uneven thickness of insulation shielding thickness, impurities in insulation, penetration of internal and external shielding, uneven crosslinking degree, cable dampness, and poor sealing of cable metal sheath. It exists in the cable system in the form of defects, causing serious hidden danger to the cable's long-term and safe operation.

Cause of cable joint manufacturing
Before the high-voltage cable joints, such as wrapping, mold casting, molding, and other types, it is necessary to make a large amount of work in the field. And because of the limitation of the field conditions and the reasons for the production process, there will inevitably be air gaps and impurities between the insulating layers, so it is easy to have problems. The types commonly used in China are assembled and prefabricated.
Cable connector is divided into cable terminal joint and cable intermediate joint. No matter what joint form, the cable joint failure usually occurs at the cable insulation shield fracture, because it is the part of the electrical stress concentration. Because of the cause of the failure of the cable joint, the cause of the cable joint failure is the defect of the stress cone body, the problem of insulation filler, the seal. Ring oil leakage and other reasons.

Pearl River cable
Cable grounding system
The cable grounding system includes cable grounding box, cable grounding protection box (with sheath protector), cable cross interconnect box, sheath protector and so on. Generally, the main problem is that the box is not well sealed, and the water leads to multi point grounding, which leads to the excessive induction current of the metal sheath. Besides, the parameter selection of the sheath protector is unreasonable or the quality is not good. The unstable Zinc Oxide crystal is also easy to cause damage to the protective layer protector.

The cause of construction quality
Because of the construction quality, there are many cases of high voltage cable system failure. The main reasons are as follows: one is that the conditions of the field are very poor, the environment and the technological requirements of the cable and joint in the factory are very high, and the temperature, humidity and dust of the construction site are not well controlled. Two is the cable construction process in the insulation surface will inevitably leave small slippery marks, semi conductive particles and sand cloth on the sand may also be embedded in the insulation, in addition to the joint construction process, insulation exposure in the air, insulation will also breathe water, which leave hidden dangers for long-term safe operation. Three, installation is not strictly considered according to process construction or process regulations. The four is the completion acceptance. The DC voltage withstand test results in the formation of the anti electric field in the joint, resulting in insulation failure. The five is caused by poor sealing treatment. The intermediate joint must adopt the metal copper shell and the sealing structure of the PE or PVC insulation anticorrosion layer, and ensure the sealing of the seal in the field construction, so as to ensure the sealing and waterproof performance of the joint effectively.

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