Discussion on DC Withstand Voltage Test of High Voltage Cable
2017-04-25
With the advancement of the national "West-East Power Transmission" and "South-North Power Transmission" projects, high-voltage DC cables will become the main force in application. The large-scale access of new energy and the cable construction of urban transmission require the application of high-voltage DC cables. HVDC cable is the only means of transmission for offshore wind power and offshore islands.
High-voltage and ultra-high-voltage cables have become indispensable materials in modern urban power grid projects. However, the field of high-voltage and ultra-high-voltage cables in my country started late, and materials, equipment and manufacturing technologies have long relied on introduction and imitation. Let's talk about the following, high-voltage cable DC withstand voltage test problems are mainly manifested in what aspects?
1. Under DC voltage, the electric field distribution of cable insulation depends on the volume resistivity of the material, while the electric field distribution under AC voltage depends on the dielectric constant of each medium, especially the distribution of DC electric field strength in cable accessories such as cable terminals and joint boxes is completely different from that of AC electric field strength, and the aging mechanism of insulation under DC voltage is different from that under AC voltage. Therefore, the DC withstand voltage test cannot simulate the operating conditions of high-voltage cables.
2. High-voltage cables will produce a "memory" effect under DC voltage, storing and accumulating unipolar residual charge. Once there is "memory" due to the DC withstand voltage test, it takes a long time to release this DC bias. If the cable is put into operation before the DC residual charge is not fully released, the DC bias will be superimposed on the peak value of the power frequency voltage, making the voltage value on the cable far exceed its rated voltage, which may lead to cable insulation breakdown.
3. DC withstand voltage test, there will be electrons injected into the polymer medium, the formation of space charge, so that the electric field strength is reduced, so that it is difficult to break down. The space charge is easy to be generated at the semiconductor protrusion and dirt point of the high voltage cable. However, if the surface flashover of the cable terminal or the breakdown of the cable accessories occurs during the test, it will cause wave oscillation on the cable core. At the place where the space charge has been accumulated, the polarity of the oscillating voltage will rapidly change to hetero-polarity, which will significantly increase the electric field strength and may damage the insulation and cause multi-point breakdown.
4. A fatal weakness of high voltage cable is that it is easy to produce water branches in the insulation. Once the water branches are produced, they will quickly turn into electrical branches under DC voltage, and form discharge, which accelerates the insulation deterioration, so that breakdown is formed under the action of power frequency voltage after operation. The simple water branch can maintain a considerable pressure value under the AC working voltage, and can maintain a period of time.
Life safety is above all else. High-voltage and low-voltage fire-resistant cables are widely used in high-rise buildings, underground railways, underground streets, large power stations and important industrial and mining enterprises and other places related to fire safety and fire rescue because of their unique advantages. We believe that there will be fewer and fewer accidents due to cable problems.
Related Documents
Related dynamics
WeChat Sweep to Learn More Guda Information
-
E-mail:guda@188.com
Website:www.xjixo.com
Consumer Hotline:400-8379-000
Wire Anti-Counterfeiting and Red Packet Inquiries:18185354668
-
Sales Hotline：0851-34754829、0851-34754819
-
0851-34754816
-
After-Sales Service:17630129055
Recruitment Hotline:18385386544
Advertising Cooperation:18166782513
Address: 02-04, 02-06, Xiayun Industrial Park II, Liyang High-Tech Zone, Pingba District, Anshun City, Guizhou Province
Copyright© Guda Wire and Cable (Group) Co., Ltd. 2024. Website Construction: www.300.cn - GuiYang | Cloud News | City Branches | 
贵公网安备 52040002000107号
电缆.网址
SAF Coolest v1.3.1.2 设置面板 PJBSD-ZDIA-SDXZE-ZQZ
无数据提示
Sorry, the current column is being updated, please look forward to it!
You can view other columns or returnHome Page