高压断路器用合闸电阻碳陶瓷研究

Research on the Material Formula of Carbon Ceramic Materials for Closing Resistors Used in High-Voltage Circuit Breakers

合闸电阻是高压断路器重要组成部分,其作用下是在线路合闸中承受电网中的L-C振荡电能转化为热能并释放到外界环境,以达到抑制合闸过电压的目的。该电阻主要成分为碳陶瓷材料,由粘土、氧化铝和碳粉等成分混合成型,其热学和电气性能是产品应用的关键,需要选择适当的原料和配比。随着先进陶瓷粉体工艺的成熟,采用化学纯的原料而不是直接使用矿物原料,能够减少杂质的引入,避免矿物原料成分的不稳定造成烧结产品电阻性能不稳定、成品率低的问题。本文主要研究合闸电阻片的原料与陶瓷相、导电相的成分配比,首先选择了化学纯的导电碳材料、氧化铝骨料和粘土原料,通过成分优化确定了导电碳材料为石墨、氧化铝骨料为α-Al_(2)O_(3)、粘土材料为高岭土;陶瓷相的配比应在二次莫来石生成量最多时的理论配比附近,此时弯曲强度较高达到67MPa。导电相配比应当在材料由绝缘突变到导电的渗流阈值附近,本体系中渗流阈值在13%左右。

The closing resistor is an important component of high-voltage circuit breakers.Its function is to withstand the L-C oscillation in the power grid during line closing,convert electrical energy into thermal energy,and release it to the external environment to achieve the purpose of suppressing closing overvoltage.The main component of this resistor is carbon ceramic material,which is formed by mixing clay,alumina,and carbon.Its thermal and electrical properties are key to product application,and appropriate raw materials and ratios need to be selected.With the maturity of advanced ceramic powder technology,using chemically pure raw materials instead of directly using mineral raw materials can reduce the introduction of impurities and avoid the problems of unstable resistance performance and low yield of sintered products caused by the unstable composition of mineral raw materials.This article mainly studies the raw materials of closing resistors and the composition ratio of ceramic and conductive phases.Firstly,chemically pure conductive carbon materials,alumina aggregates,and clay raw materials were selected.Through composition optimization,it was determined that the conductive carbon material is graphite,the alumina aggregate isα-Al_(2)O_(3),and the clay material is kaolin;The ratio of ceramic phase should be near the theoretical ratio with the highest amount of secondary mullite generation,at which point the bending strength is higher and reaches 67MPa.The conductive phase ratio should be around the percolation threshold of the material's transition from insulation to conductivity.In this system,the percolation threshold is around 13%.