Silicone Rubber or Porcelain, Which Housing Type Is Better for Use on Bushings?
The first generation of silicone rubber composite insulators began to operate in North America in the early 1970s. It has a history of nearly 50 years. Therefore, silicone rubber is successfully used in high-voltage bushing industry really not as a brand-new insulation material. Practical experience of composite insulators has shown that silicone rubber is excellent in anti-pollution-flashover performance， it also has durable service life and high reliability. Needless to say, the service life of the silicone rubber sheds is severely depend on the raw materials, production technology, design, and quality assurance system of it.
Therefore, ChinSun bushing has taken into account:
- In terms of electrical performance, in addition to the long-term working voltage, high-voltage bushings must also withstand transient operating over voltages and lightning over voltages. The bushings must be able to withstand these voltages without insulation failure, nor flashover occurring along the surface, nor breakdown in its internal insulation.
- In terms of mechanical performance, the bushing is required to work stably and reliably under the long-term mechanical load, and it also requires the ability to withstand hurricanes and earthquakes. In addition to the requirements of excellent electrical and mechanical properties, the bushings must also have good weather resistance and aging resistance. The bushing is required to be able to withstand rain, snow, hail, wind and sunrays, even extreme cold and heat. It must work stably and reliably under various severe weather conditions and have a service life exceeding 30 years.
Based on mentioned above, the silicone rubber composite bushings produced by ChinSun has the following excellent properties:
- Lighter weight. The density of the silicone rubber is much lower than the density of ceramics; so the overall weight of bushing is significantly reduced by using silicone rubber sheds instead of porcelain housing. Light weight of bushing leads to several benefits, for instance, easy transportation & installation, convenient design of sealing, better mechanical performance, and so on.
- Better anti-pollution flashover effect. ChinSun silicone rubber material has more excellent hydrophobic properties. Under severe weather conditions such as heavy fog, light rain, dew, snow melting, and ice melting, the surface of the silicone rubber material forms separated water beads instead of continuous water films. The conductivity of the pollution layer is very low, so the leakage current is also very weak, and a strong local arc is not easy to occur. It is also difficult for the local arc to further develop and lead to external insulation flashover. After running for a period of time, and the surface of the silicone rubber sheds being dirty, the hydrophobicity migrates to the surface of the pollution layer. This characteristic is unique to the silicone rubber material! Under the same contamination level and the same leakage distance, the pollution-flashover voltage for silicone rubber insulator can reach more than twice of that for porcelain insulator.
- Easieroperation and maintenance. Due to the excellent anti-pollution flashover performance of silicone rubber materials, the reliability of power system operation is improved. In polluted areas, it is not necessary to clean the bushing regularly like a porcelain one, which greatly reduces the operation and maintenance costs of substations in polluted areas.
- Difficult — broken. The composite bushings of ChinSun Company have strong impact resistance, which reduces external damage probability during installation and transportation and can effectively reduce damage consequence caused by human factors such as gunshots.
- According to a survey conducted by the CIGRE insulator working group in 2000, covering more than 70 companies in different regions of the world, 54% of companies chose composite bushings to use in the pollution areas. In the region, 47% of companies choose composite bushings because of their superiority in installation and transportation, and 35% of companies chose composite bushings from an economic perspective.
Therefore, ChinSun Company widely uses internationally recognized silicone rubber materials with UV protection in its external insulation design of the composite bushings, including wall bushings, transformer bushings and switchgear bushings. This kind of silicone rubber material makes the outer insulation of the bushings much more excellent than porcelain housing. The outstanding anti-pollution-flashover function has guaranteed an opportunity for the application of silicone rubber bushings in electric power systems.