Lan Lei

Research on characterization of RTV silicone rubber/LS (layered silicate) electrical insulation nanocomposites

Presently, the security of power system is seriously threatened by pollution flashover. Room temperature vulcanized (RTV) silicone rubber has been widely used into coat porcelain insulators to render water repellency to prevent the formation of water filming on the surface and thus to suppress the leakage current and consequently flashover, due to their hydrophobicity and migration of hydrophobicity. However, in order to obtain an increase of service life and better service effect, some properties of RTV silicone rubber (RTVSR) coatings still need to be improved, especially the abilities of mechanics performances. In this paper, nanotechnique is used for the reformation of RTVSR, by which RTVSR/layered silicate nanocomposite is synthesized by means of solution. The mechanical properties, such as tensile strength, elongation at break and adherence grade are theoretically and experimentally analyzed and compared with that of RTV silicone rubber without nano fillers with the help of SEM, FTIR and XRD. The test results prove that layered silicate can be dispersed in the silicone rubber matrix uniformly. Moreover tracking tests and hydrophobicity contact angle test are conducted, and the influences to the electrical parameters such as tan /spl delta/, and /spl rho//sub v/ are also found, considering that RTV silicone rubber is a kind of electrical insulation materials.

Study on RTV silicone rubber/SiO/sub 2/ electrical insulation nanocomposites

Surface contamination and leakage current have caused operating problems for utilities since electric power was its infancy. A flashover in a substation may result in the destruction of an insulator or many others electrical equipments. In order to reduce the incidence of insulator flashover and damage, the liquid silicone RTV (room temperature vulcanized) has been used for coating porcelain and glass insulators to provide water repellency (hydrophobicity) on the surface. Nano science and technology (nano-st) is a promising research field. In this paper, from previous research results in the other research fields, we decide to select nanoSiO/sub 2/ to try to reform RTVSR. First, different kinds of nano SiO/sub 2/ from different fabrication methods such as sol-gel and gas phase method etc are selected. Then dispersal situation of nano SiO/sub 2/ synthesized by different ways and disposed with or without coupling agents in RTV silicone rubber were studied and analyzed with SEM. Some basic properties of RTVSR/SiO/sub 2/ nanocomposites and pure RTVSR were compared and analyzed in detail. In addition, some electrical performances tests are also conducted, and the influences to the electrical parameters such as tan /spl delta/, and /spl rho//sub v/ were found as well, considering that RTV silicone rubber was a kind of electrical insulation materials. The resulting hybrid had more excellent mechanical, thermal stability than pure RTV silicone rubber.

Corona ageing tests of RTV and RTV nanocomposite materials

Silicone rubber insulating materials are superior to conventional porcelain materials, whose special water repellency and transfer of water repellency is favorable in power industry. However, two points are concerned in its application, and these are long-term reliability and lack of methods to assess their long-term performance. Corona and arc are important factors that induce degradation of RTV insulating materials during operation. Nanomaterials are used to modify the properties of RTV silicone rubber. Corona aging tests have been conducted, and the results of water repellency and IR analyses show that these nanomaterials can markedly improve its corona aging performance.

Technical and Economic Performance Analysis on Vertical Grounding Electrodes of ±800KV UHVDC

According to alternative grounding place situation of plusmn800 KV DC project, this paper selects the theoretically suitable place to design several different arrangement scenarios of vertical grounding electrodes and then compares the technical and economic performance when the sub-electrode length remains invariable while other parameters are changed and when the sub-electrode quantity remains invariable while other parameters are changed. The results show that both step voltage and grounding resistance conform to the system requests in these scenarios, but soil temperature near ground rods can not satisfy the request. Simultaneously, a series of conclusions are reached by selecting a best one of these scenarios to compare with level two-rings grounding electrode.

Resistance to high and low temperature of RTV nanocomposite

Room temperature vulcanized silicone rubber (RTV-SR) is widely applied to outdoor insulation in power system. It is aged under the conditions of outdoor environment. Temperature is one of the ageing factors. So the resistance to high and low temperature of RTV is important to its ageing performance. In the paper, two kinds of RTV nanocomposite are achieved, and the resistance to high and low temperature is tested with the help of TG (thermogravimetry)/DTG (differential thermogravimetry) and DSC (differential scanning calorimeter). The decomposing temperature and glass transition temperature of RTV nanocomposite are obtained. The test results show that RTV nanocomposite has better resistance to both high and low temperature, which may lead to better ageing performance of RTV material. The mechanisms are also discussed.

Simulation for Shielding Performance of Transmission Line

A novel method that is been used to simulate the lightning progress process was presented. The base of the simulation the calculation of electric field intensity, the purpose of the simulation is to find out whether the lightning will strikes phase conductors or not. In the simulation model, the descending leader is been considered as cylinder discharge, and placing a concentrated discharge in the tip of the cylinder, choosing gap-criterion to judge the upward-directed leader inception. The system voltage and the ground obliquitys influence to the electric intensity are both considered. The calculation result of a transmission line is a little smaller than the statistical data.

GRNN applied to study the Lightning Shielding Performance for EHV&UHV Transmission Line

Lightning shielding failure is the main factor to threat the safety and reliability of EHV transmission lines. In this paper, the small-scale model experiments of lightning shielding performance of EHV transmission lines were made, taking the various influencing factors into account, including protection angle alpha , the gradient of the hillside thetas, the height of the gully H , the conductor potential U , non-vertical leader angle beta and the position of lightning stroke point (X,y) , showing the lightning stroke probability Pa has the hidden non-linear function relation with the factors above. Due to the fact that the generalized regression neural network (GRNN) has several advantages over the back-propagation network (BP) such as very short training time and guaranteed performance even with sparse data, it is applied to simulate the complex non-linear function relationship between the lightning stroke probability Pa and these various influencing factors. A lot of simulation was carried out in Matlab and the feasibility and accuracy of the proposed GRNN are verified.

Study of Discharge Process and Characteristics of Discrete Water Droplets on the RTV Hydrophobic Surface in the Non-uniform Electric Field

According to simulating test on the model sample by using high speed digital camera (10000 fps) and combining with finite elements analysis software, this paper studies the discharge process of discrete water droplets on the hydrophobic surface in the non-uniform electric field ( needle-board electrodes ) and computes electric field intensity along hydrophobic surface. The results show that the development trend of the arc is stretching from the double ends to the intermediate on the RTV surface and obvious extinguishing and restriking phenomena can be observed. Furthermore, the paper compares electric field intensity along the RTV hydrophobic surface with no-droplet, one droplet and multi-droplets, and computes the maximum value of electric field intensity. It can be found that the maximum value of electric field intensity with the existence of droplets on the sample surface is 1.22-1.44 times as it without the existence of them in the non-uniform electric field.