Quality control of technical indexes of the hottes

2022-08-24
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Abstract: 10kV and SF6 load switchgear has the advantages of safety, easy installation, less maintenance, small size, low price, safety and reliability. At the same time, load switches and current limiting fuses can better protect transformers, so they have been widely used abroad. For example, in industrialized countries (such as Europe and Japan), the ratio of circuit breaker to load switch is 1:5 ~ 6. The circuit breaker is mainly used for primary power distribution, while the load switch is used for secondary power distribution

key words: 10kV SF6 load switch secondary power distribution Untitled Document 10kV, SF6 load switch equipment has the advantages of safety, easy installation, less maintenance, small volume, low price, safety and reliability. At the same time, load switches and current limiting fuses can better protect transformers, so they have been widely used abroad. For example, in industrialized countries (such as Europe and Japan), the ratio of circuit breaker to load switch is 1:5 ~ 6. At present, circuit breakers are mainly used for primary distribution, while load switches are used for secondary distribution. In China, with the continuous development of urban construction and transformation, the application of load switchgear in the loop power supply and terminal power transmission of 10kV distribution system is also increasing. In recent years, it has been gradually promoted nationwide from Guangdong, Beijing, Shanghai and Tianjin. However, at present, the domestic market of 10kV and SF6 load switches is mainly occupied by foreign companies (such as abb, Schneider, etc.). With the gradual mastery of SF6 load switch technology by domestic manufacturers, the number and quality of domestic SF6 load switches have been steadily improved. At present, more than a dozen manufacturers in China have produced various types of SF6 load switches. Taking the SF6 load switch produced by Beijing Longyuan switchgear Co., Ltd. as an example, this paper introduces the quality control of several key technologies. 1、 Quality control of oxygen resin insulating shell epoxy resin has become the first choice for manufacturing high-quality insulating parts because of its good mechanical, insulation, aging resistance and manufacturing process performance. Because the pressure gel process gives full play to the performance advantages of epoxy resin, the insulating shells of SF6 load switches of various international and domestic brands are all made of epoxy resin by pressure gel process

because the switch shell simultaneously undertakes the functions of insulation, air tightness and mechanical support, it has complex structure and high requirements for mechanical performance and precision, which undoubtedly puts forward strict requirements for material selection and manufacturing process. Epoxy resin is selected as the material: basic epoxy resin (i.e. epoxy resin with an annual output of thousands of tons produced by large resin plants) and curing agent cannot be directly used in the production of insulating parts, especially the epoxy resin and curing agent used in the insulating shell of SF6 switch need special modification treatment to improve its mechanical strength, toughness, cold and heat shock resistance and processing performance. The modification technologies of different manufacturers have their own merits, so they are suitable for the product requirements of different work priorities. As for the SF6 switch insulation shell, because it is a support, it receives a certain impact in the opening and closing process of the switch, which puts forward higher requirements for the strength of the epoxy resin; The switch shell should be filled with SF6 gas and ensure a very low leakage rate, which puts forward higher requirements for the adhesion of epoxy resin to the insert; In recent years, the shell cracking accident of SF6 load switch has occurred in production or work. After testing, the tensile strength and bending strength of the material used for the cracked shell are not low, but the impact strength representing the toughness of the material is low. It can be seen that the impact strength of SF6 switch insulation shell is the top priority of various performance indicators. The domestically produced he2082-hh2082 material is particularly suitable for the production of SF6 switch insulation shell. The measured glass transition temperature of the system is 104 ℃, which meets the requirements of an internationally renowned brand of 100 ℃ ~ 110 ℃, and the impact strength is 15kj/m2, which is 50% higher than the general formula system. It has excellent toughness. At the same time, due to its excellent adhesion, the produced switch shell has a very low air leakage rate. Silicon powder: adding silicon powder to epoxy resin can improve the heat resistance, hardness and dimensional stability of the cured product, and reduce the production cost. Due to different mineral sources and production processes, silica fume has a great impact on the properties of epoxy resin cured products. In the production of general products, the viscosity of the mixture or the amount of silicon powder that can be added are often regarded as the main indicators to measure the quality of silicon powder. However, as the formulation system for the production of important insulating parts, the high performance of the cured product is the preferred index to measure the quality of silicon powder. After adding high-quality silicon powder and epoxy resin, the viscosity is high, making the amount that can be added low. After analysis, it is due to the high content of needle particles in silicon powder, which is easy to disassemble in May and June this year, and this just improves the mechanical strength of epoxy resin

colorants: no wonder there are two kinds of colorants used for epoxy resin, organic colorants and inorganic colorants. Organic colorants have no significant effect on the electrical insulation performance of epoxy resin cured products; Inorganic colorants are mostly metal oxides based on iron oxide, which will increase the dielectric loss of cured products after adding epoxy resin. Therefore, in order to ensure the electrical insulation performance of products, inorganic colorants should not be added to the formula system as far as possible. In order to ensure the electrical insulation performance, the technical index of Fe2O3 content of electrical grade silicon powder is required to be ≤ 0.01%. If 1.5% iron oxide red powder is added to the formula system according to the epoxy resin ratio, it is equivalent to increasing the Fe2O3 content of silicon powder to 0.5%, reaching 50 times the basic content. It can be imagined that there is a great negative impact on the electrical insulation performance. Insert pretreatment: in order to ensure the good adhesion of epoxy resin to the insert, a good pretreatment of the insert is also crucial. The pretreatment of the insert includes sandblasting, cleaning oil and dust, accurately preheating to the same temperature as the mold, and paying attention not to excessive oxidation, so as to prevent the copper oxide with very low strength from affecting the bonding strength of the epoxy resin to the insert. And ensure that the inserts cannot be secondary polluted in the process of turnover. The good bonding of epoxy resin to the insert not only ensures the extremely low air leakage rate, but also makes the product have extremely low partial discharge. Yulian group insists on honesty. When the discharge is 15kV, only 5pc is measured. Post curing, shaping and cooling: elasticity of epoxy resin at room temperature

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