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Attention should be paid to the application of silicone rubber insulator

20 Jul 2019 - silicone rubber insularor,LSR silicon insulator development,electrical insulator

 silicone rubber insulator

Mechanical strength

The mechanical strength of pure silicone rubber is very small, and white carbon black is generally used as reinforcing filler, which can significantly improve the strength of insulator.Due to its small size and large specific surface area, silica particles can interact strongly with polysiloxane molecules to improve the interface. Meanwhile, the surface of silica contains many hydroxyl groups, which can form network structure through hydrogen bond and van der Waals force.The average particle size of silica white surface area and porosity in the appropriate range can achieve an optimal performance of silicone rubber.The tensile strength of the composite insulator mandlet can reach 7000 MPa, which is 5 times higher than that of high quality carbon steel.Some regions and departments put forward the use of synthetic insulators, whose mechanical strength is one level higher than that of traditional porcelain and glass insulators.For example, porcelain insulator is l60kN, while synthetic insulator is 210kN.In fact.When the load is less than 40% of the rated mechanical load, it can ensure the reliability of operation.Therefore, synthetic insulators can be used in the way of porcelain insulators without increasing the allowable mechanical load.The results show that the composite insulator has good bending resistance, dancing resistance and breeze vibration resistance.When used in tensile tower, it can bear certain bending moment.

Clean the

There is no unanimous opinion on whether the pollution of silicone rubber insulator is heavier than that of porcelain insulator.Due to the occurrence of some pollution flashover accidents and excessive insulator pollution in heavy pollution areas, the problem of silicone rubber insulator cleaning gradually surfaced.Due to the high pollution lightning voltage of silicone rubber insulators, even if the hydrophobicity drops or even nearly disappears for a short time, its pollution and voltage resistance is 20% higher than that of porcelain insulators.Therefore, clean areas and areas of general filth may be exempted from cleaning.Periodic replacement may be used in areas of particularly severe industrial and saline contamination.

Reliability of seal

Insufficient attention has been paid to the sealing of the joint between the end fittings of the composite insulator and the mandle-sleeve.It may be the cause of mandrel breakage and interface breakdown.Most of the end connection structure of silicone rubber insulator is wedge joint. It is inevitable that there will be slippage between the mandrel and the fittings during long-term heavy load operation.When sealant and metal adhesive poor, small slip enough to open the seal;When sealant elasticity is not enough, excessive slip can make sealant disconnect.From this point of view, the end structure of pressure joint is one of the ways to prevent seal damage.In addition, the engineering application of sealant is mostly room temperature silicone rubber, its anti-aging performance is obviously not as high temperature silicone rubber, in the end of the corona may lead to premature deterioration.There is a greater risk when the equalizer ring is not used for products 110 kV and below, or when the equalizer ring is not installed at the position of 220 kV and above.In short, the end of the seal under the long-term mechanical and electrical action whether long-term maintenance still need to test demonstration and long-term operation test.

Aging of silicone rubber

The chemical composition and structure of insulators will be affected by various factors in use, which will affect their properties.For composite organic insulators, aging and performance degradation are mainly caused by the following factors: ultraviolet radiation, corona discharge and arc discharge.

1) ultraviolet radiation

Ultraviolet light, as a high-energy beam, ACTS on chemical bonds, causing them to break and reorder.Compared with ceramic and glass materials, ultraviolet radiation has a significant effect on polymer materials.Experiments have shown that as uv exposure increases,

The hydrophobic property of silicone rubber decreases gradually.According to the analysis, this is because the low energy c-h bond and si-c bond in silicone rubber will break under the irradiation of ultraviolet radiation, generating hydrophilic silanol groups.In addition, the free radicals generated by the fracture reaction will cross link with the low molecular chain, which will lead to the reduction of the number of low molecular chain silicone oil.

2) corona discharge

In a certain period of time, corona discharge can accelerate the recovery of hydrophobic property.However, with the extension of discharge time, the hydrophobic property decreases gradually.This is because the corona discharge can produce low molecular weight silicone oil, so as to accelerate the hydrophobic properties of the recovery, however, corona discharge at the same time can produce silicon alkoxide groups with hydrophilic groups such as carbonyl group, with the increase of the content of hydrophilic groups and the hydrophilic group can interact with low molecular weight chain segment and hinder the chain to the movement of the silicone rubber surface, leading to hydrophobic performance decline.

3) arc discharge

The action of arc discharge on insulator includes two aspects: electrical action and thermal action.First of all, the high thermal energy generated by arc discharge can break the main chain of silicone rubber polymer and generate low molecular chain silicone oil. However, due to the high temperature (> 500℃), which is far higher than the boiling point of oligomer silicone oil, a large number of oligomers volatilized, and the hydrophobic property decreased.Secondly, arc discharge has an extremely significant impact on the surface of silicone rubber. Due to the action of discharge and intense heat release, a series of chemical changes have taken place on the surface of silicone rubber, and the hydrophilic porous inorganic thin layers of amorphous SiO2, SiO2 hydrate (SiO2·xH2O) and silicocarbon are generated.Therefore, even if the low molecular chain segment with restored hydrophobic property is not volatile, the hydrophilic surface generated will lead to the loss of hydrophobic property of the insulator.

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