Gradually realize industrial application and reduce import dependence.


  domestic high-voltage cable insulation materials successfully broke the ground

  The domestic high-voltage cable insulation materials used for 110 kV, 220 kV, and 500 kV are gradually industrialized, which will significantly improve my country’s long-term dependence on imports for high-voltage cable insulation materials. "The achievement of the goal contributes an important force.

  Recently, Yanshan Petrochemical’s 110 kV cable insulation demonstration project for cable insulation was officially launched.

For the first time, this project applied high-voltage cable insulation materials independently developed and produced, marking the realization of industrial demonstration applications of domestic high-grade insulation materials.

  Before the start of the demonstration project, in March this year, the first (set) of 220 kV high-voltage AC cable system using domestic insulating materials was connected to the grid on the 220 kV new coal line in Fuxin, Liaoning. It has been operating stably so far; In April, the first 500 kV DC cable system using domestic insulation materials also passed the completion test of the Zhangbei Rouzhi Project.

  High-voltage cables are a key link in long-distance power transmission, and insulating materials play a vital role in ensuring their safe operation.

Several breakthroughs have been made in the localization of high-voltage cable insulation materials, and the gradual realization of industrial applications will significantly improve its long-term dependence on imports. It will contribute to my country's energy security and the realization of the "dual carbon" goal.

  High-voltage cables have high requirements for insulating materials

  To understand the importance of insulating materials, we need to start with power transmission.

The long-term phenomenon of "separation of source and load" has existed in my country's power pattern, and the energy-rich land is inconsistent with the concentrated power load. The resulting long-distance power transmission is inevitable.

With the gradual advancement of the "dual carbon" goal, how to carry out long-distance power transmission more safely and efficiently has always been an unavoidable issue in the development of my country's power industry.

  Generally, when the transmission distance and power are constant, the higher the transmission voltage, the smaller the loss of the transmission energy.

Therefore, high-level high-voltage power transmission plays an important role in long-distance power transmission.

  However, the higher the transmission voltage level, the higher the requirements for cable insulation materials.

Chen Xin, director of the Institute of Electrical and Advanced Materials of the Global Energy Internet Research Institute, introduced to reporters that compared to the insulation materials of low-voltage cables, high-voltage cable insulation materials need to withstand higher electric field strength; the space charge accumulation and resistivity temperature of the materials The sensitivity is also lower. For example, for ultra-high-voltage cables, the high and low-temperature volume resistivity change rate must be less than 100, but there are no relevant requirements for low-voltage cables.

In addition, ultra-high-voltage cable insulation materials have more stringent requirements for the control of defects and impurities. "Ultra-high-voltage cable insulation materials are not allowed to contain impurities above 50 microns, while ordinary low-voltage cables are allowed to contain impurities above several hundred microns." Chen Xin said.

  The development of high-voltage cable insulation materials has gone through a long process.

Taking the currently widely used HVDC transmission method as an example, the development of its power cable insulation materials has experienced three stages: oil-filled insulation (OF), oil-paper insulation (MI), and cross-linked polyethylene (XLPE) insulation.

“DC cables with oil-filled and oil-filled paper insulation have been around for more than 100 years.” Chen Xin said that early oil-filled cables used hollow conductors as the oil flow channel, and the insulating layer outside the conductor was continuously impregnated with oil to achieve insulation. Effect.

However, this insulation method requires continuous oil filling during the operation of the cable. Once the outer layer of the cable is damaged, it will cause oil leakage, which is easy to cause environmental pollution and is difficult to maintain. It has been basically eliminated.

  In the high-voltage direct current transmission projects built in recent years, the rapidly developing cross-linked polyethylene extruded cable has become a more common choice.

According to Chen Xin, XLPE extruded cables have higher operating temperature than oil-paper cables, better mechanical and insulation properties, convenient installation and maintenance, and simple production processes. They have been widely used in power systems.

"Almost all current high-voltage DC cables use cross-linked polyethylene as an insulating material."

  Joint research to find the "recipe" of high-voltage insulation materials

  my country is the world's largest cable manufacturer, but in the field of high-voltage cable insulation material manufacturing, it has long relied on imports, with an annual import volume of 100,000 tons, which severely restricts the independent and controllable development of my country's high-end power equipment.

  Chen Xin believes that the main difficulties that hindered the localization of high-voltage cable insulation materials came from three aspects.

First of all, the basic raw materials used in the manufacture of high-voltage cable insulation materials in China have insufficient performance. "The electrical performance is obviously lower than that of foreign countries, and the breakdown field strength is less than 60% of foreign countries. At the same time, the basic raw materials contain high impurity content and poor flow stability. "Secondly, the domestic research on the formulation components of UHV cable materials and the interaction between the components is very weak, and there is no experience in developing UHV cable insulation materials for reference.

In addition, the performance of insulating materials of different formulations may change during the transition from small batch testing in the laboratory to large-scale industrial production, and it is difficult to control the process to maintain the performance of the amplified formulations.

  Facing the situation that related foreign technologies are tightly sealed, and there is no relevant domestic experience to start from scratch, Global Energy Internet Research Institute Co., Ltd. takes the lead, and universities, manufacturers, and research institutes within the United Nations carry out multi-party collaborative research.

The project team has overcome many difficulties and carried out research on key technologies such as simulation design, material research and development, cable manufacturing, system matching, and test evaluation. It has successively solved the optimization of the molecular structure of domestic insulating base materials, and the suppression of space charge and conductance nonlinearity under multi-field effects. , Multi-layer dielectric interface insulation conductivity matching of cable system, large-size cable extrusion defect control and breakdown size thickness effect suppression, and many other technical problems.

  Researching and developing insulating materials and making samples in the laboratory is only the first step.

How to get out of the laboratory and move towards industrialized mass preparation is often the key.

From the research and development of experimental materials calculated in "grams", to the production tests of the "hundred kilograms" level, to the mass production of "tons", changes in the quantity level may lead to instability of material properties.

To this end, the research team coordinated manufacturing companies, testing units and other advantageous resources to participate in scientific research, trial-produced hundreds of tons of material samples and thousands of meters of cable samples, and went through 9 types of tests before and after, and finally realized continuous iteration of insulation materials and cable systems. Optimization and steadily improving performance, successfully developed 320kV and 500kV DC cable insulation materials, and initially established the process formula of domestic high-voltage cable insulation materials.

  The market potential of domestic insulation materials is brewing

  Although it has successfully broken the game, domestic insulation materials still have a long way to go.

Chen Xin said that at present, my country's high-voltage DC cable insulation materials are basically equivalent to foreign insulation materials in terms of high-temperature resistance strength and high-temperature volume resistivity stability, and can meet the manufacturing needs of short-distance 500 kV terrestrial high-voltage DC cables.

However, there is still a certain gap between it and foreign countries in terms of long-term continuous extrusion. "Foreign countries can achieve a single continuous extrusion of 70-130 tons, while the domestic is still at a level of less than 35 tons."

  However, the breakthrough has been successfully opened, and the market potential has been brewing.

According to Chen Xin's estimation, the current annual import volume of insulation materials for high-voltage cables of 110 kV and above in my country is nearly 100,000 tons, and the output value of related cables exceeds 100 billion yuan.

At the same time, domestic products also have advantages in price. For example, the price of domestic 500kV high-voltage cable insulation materials is only about 70% of that of similar foreign products.

The high-voltage cable industry chain involves many upstream and downstream related industries such as petrochemical base materials, insulation compounding, cable extrusion, test evaluation, installation, operation and maintenance. The industry has a very obvious pulling effect.

  For example, in the rapidly developing field of offshore wind power generation, as the "dual carbon" goal advances in the future, this field will have a huge demand for high-voltage cables.

In Europe, which has the largest offshore wind power generation capacity, Germany has planned a 640 km ±525 kV HVDC transmission corridor; the United Kingdom has also planned a HVDC transmission project with a total length of more than 3,000 km.

In September of this year, the acceptance test of Asia's first ±400 kV DC submarine cable in Rudong, Jiangsu was also successfully completed, and the conditions for power transmission and operation have been met.

In the future, with the completion of a number of offshore wind power projects along the eastern coast, my country is expected to become the world's second largest country with wind power on the sea.

  Chen Xin said that the next domestic high-voltage cable insulation materials will further improve the performance, especially the large-length cable performance, and focus on the research of the submarine cable factory soft joint technology, the development of large-length submarine cable insulation materials and submarine cable systems.