In the early 1990s, China introduced a groundbreaking innovation in high-voltage electrical equipment by using an oil-free, gas-free, and porcelain-free fluoroplastic as internal insulation. This marked a significant departure from traditional designs both domestically and internationally. The new products featured silicone rubber as the outer insulation, offering a completely different structure and design approach. These innovations were particularly evident in wall bushings, which stood out for their unique concept and modern engineering. Several of their technical specifications even exceeded international standards like IEC and national Chinese standards GB, leading to growing adoption across the industry.
To date, the dry series of products—including wall bushings, current transformers, and cable terminations—has seen remarkable progress and rapid development. Their advantages are clear: they are oil-free, gas-free, and porcelain-free, with a compact size, lightweight, fire-resistant, explosion-proof, and resistant to pollution flashover. Since 1990, over 10,000 of these units have been operating safely within the power system without any reported incidents.
As widely known, traditional high-voltage components such as wall bushings, cable terminations, and current transformers rated at 66kV and above have typically relied on oil-filled porcelain designs. However, this approach comes with several drawbacks, including leakage risks, flammability, explosiveness, susceptibility to pollution flashover, and heavy maintenance requirements. Additionally, as environmental conditions worsen, the likelihood of flashover increases, especially on the porcelain surface. Historically, increasing the creepage distance was a common solution, but this method had its limits. As the creepage ratio increased, the firing rate of the porcelain casing decreased.
To address these challenges, a new generation of products was developed, featuring innovative structural designs and advanced materials that differ significantly from conventional approaches.
The development of dry high-voltage wall bushings gained momentum in the early 1990s, driven by the rapid expansion of urban power networks and the growth of indoor substations. This surge in demand prompted the need for a novel solution to replace the traditional oil-ceramic insulation with organic insulating materials.
In 1990, the first STA-type through-wall bushing was developed and successfully deployed at the Dalian Laohutan Substation. It was later installed in more than 200 units across Northeast China and Yunnan. Despite their success, the STA-type bushings still had limitations, as they required post insulators at both ends due to their construction using XLPE cables. To overcome this issue, we introduced the STB high-voltage wall bushing in 1994. To date, over 10,000 STB casings have been installed across the grid, covering more than 20 provinces and municipalities—from Hainan in the south to Daqing in the north, and from the eastern coast to Xinjiang in the west.
NINGBO DOTEC manufactures various water solenoid valves in China for many years.
Options:
1. Port Size: 1/8'' to 3'', etc
2. Connection: Threaded, Flanged, Push-In, etc
3. Body Material: Brass, Stainless Steel, Aluminum Alloy, PA, PP, POM, etc
4. Seal Material: NBR, EPDM, FKM, PTFE, PEEK, Silicone, etc
5. Function: 2 way, 3 way or Multi ways; normally closed or normally open, etc
6. Voltage: 12VDC, 24VDC, 24VAC, 110VAC, 220VAC, other voltage can be customzied
Water Solenoid Valve 24V, Water Solenoid Valve 110V, Water Solenoid Valve 220V, Brass Water Solenoid Valve, Stainless Steel Water Solenoid Valve
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