Water mist is one of the effective candidates for halon replacement used in electrical environment fire protec-tion. Water mist additives may greatly enhance fire suppres-sion effectiveness. In electrical environment,...Water mist is one of the effective candidates for halon replacement used in electrical environment fire protec-tion. Water mist additives may greatly enhance fire suppres-sion effectiveness. In electrical environment, electrical breakdown field strength (E) is one of the important factors that control the performance of electrical equipment. In this study the variation principles of electrical breakdown field strength and the electrical characteristics of MC additives were investigated by electrode discharging experiments. Ex-perimental results showed that electrical breakdown field strength was impacted obviously by the conductive metal ions and insulated fluorocarbon surfactants in MC additives. The attenuation percentages of E in different experimental cases were described, thus providing scientific guidance for the use of water mist and MC additives in electrical fire sup-pression.展开更多
A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the ...A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.展开更多
采用熔盐法制备α-Al_(2)O_(3),采用硅烷偶联剂γ-氨丙基三乙氧基硅烷(KH550)对α-Al_(2)O_(3)进行表面改性,得到KH-α-Al_(2)O_(3)。以低密度聚乙烯(LDPE)为基体、不同的α-Al_(2)O_(3)为添加剂,制备α-Al_(2)O_(3)/XLPE和KH-α-Al_(2)...采用熔盐法制备α-Al_(2)O_(3),采用硅烷偶联剂γ-氨丙基三乙氧基硅烷(KH550)对α-Al_(2)O_(3)进行表面改性,得到KH-α-Al_(2)O_(3)。以低密度聚乙烯(LDPE)为基体、不同的α-Al_(2)O_(3)为添加剂,制备α-Al_(2)O_(3)/XLPE和KH-α-Al_(2)O_(3)/XLPE接地线绝缘材料。对α-Al_(2)O_(3)和KH-α-Al_(2)O_(3)的晶体结构、微观结构以及基团进行分析,考察不同α-Al_(2)O_(3)含量对α-Al_(2)O_(3)/XLPE接地线绝缘材料电学性能和热学性能的影响。结果表明:熔盐法制备的α-Al_(2)O_(3)是具有六方结构、结晶度高、直径5~10μm的不规则圆片,KH550的改性不会造成α-Al_(2)O_(3)结晶度的变化。KH-α-Al_(2)O_(3)在KH-α-Al_(2)O_(3)/XLPE接地线绝缘材料中沿材料厚度方向排列,且分散更为均匀,有利于抑制电荷在基体中的传输。KH-α-Al_(2)O_(3)有利于提高XLPE的直流击穿场强和直流电导率。当KH-α-Al_(2)O_(3)的添加质量分数为1.5%时,KH-α-Al_(2)O_(3)/XLPE的直流击穿场强达到320 k V/mm,电导率为1.043×10^(-13)S/m。KH-α-Al_(2)O_(3)的引入使XLPE基体和KH-α-Al_(2)O_(3)之间的界面产生一定数量的陷阱,有效实现了对注入电荷的抑制。KH-α-Al_(2)O_(3)可以明显降低XLPE的热失重速率,提高KH-α-Al_(2)O_(3)/XLPE接地线绝缘材料热稳定性。当KH-α-Al_(2)O_(3)的质量分数达到1.5%时,分解温度升高至475.44℃,90℃条件下的导热系数从0.390 W/(m·K)增加到0.545 W/(m·K)。展开更多
基金This work was supported by the China National Key Basic Research Special Funds(Grant No.2001CB409600)the National Natural Science Foundation of China(Grant No.50323005)the Anhui Development Fund of Person with Ability(Grant No.2003Z019).
文摘Water mist is one of the effective candidates for halon replacement used in electrical environment fire protec-tion. Water mist additives may greatly enhance fire suppres-sion effectiveness. In electrical environment, electrical breakdown field strength (E) is one of the important factors that control the performance of electrical equipment. In this study the variation principles of electrical breakdown field strength and the electrical characteristics of MC additives were investigated by electrode discharging experiments. Ex-perimental results showed that electrical breakdown field strength was impacted obviously by the conductive metal ions and insulated fluorocarbon surfactants in MC additives. The attenuation percentages of E in different experimental cases were described, thus providing scientific guidance for the use of water mist and MC additives in electrical fire sup-pression.
文摘A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.
文摘采用熔盐法制备α-Al_(2)O_(3),采用硅烷偶联剂γ-氨丙基三乙氧基硅烷(KH550)对α-Al_(2)O_(3)进行表面改性,得到KH-α-Al_(2)O_(3)。以低密度聚乙烯(LDPE)为基体、不同的α-Al_(2)O_(3)为添加剂,制备α-Al_(2)O_(3)/XLPE和KH-α-Al_(2)O_(3)/XLPE接地线绝缘材料。对α-Al_(2)O_(3)和KH-α-Al_(2)O_(3)的晶体结构、微观结构以及基团进行分析,考察不同α-Al_(2)O_(3)含量对α-Al_(2)O_(3)/XLPE接地线绝缘材料电学性能和热学性能的影响。结果表明:熔盐法制备的α-Al_(2)O_(3)是具有六方结构、结晶度高、直径5~10μm的不规则圆片,KH550的改性不会造成α-Al_(2)O_(3)结晶度的变化。KH-α-Al_(2)O_(3)在KH-α-Al_(2)O_(3)/XLPE接地线绝缘材料中沿材料厚度方向排列,且分散更为均匀,有利于抑制电荷在基体中的传输。KH-α-Al_(2)O_(3)有利于提高XLPE的直流击穿场强和直流电导率。当KH-α-Al_(2)O_(3)的添加质量分数为1.5%时,KH-α-Al_(2)O_(3)/XLPE的直流击穿场强达到320 k V/mm,电导率为1.043×10^(-13)S/m。KH-α-Al_(2)O_(3)的引入使XLPE基体和KH-α-Al_(2)O_(3)之间的界面产生一定数量的陷阱,有效实现了对注入电荷的抑制。KH-α-Al_(2)O_(3)可以明显降低XLPE的热失重速率,提高KH-α-Al_(2)O_(3)/XLPE接地线绝缘材料热稳定性。当KH-α-Al_(2)O_(3)的质量分数达到1.5%时,分解温度升高至475.44℃,90℃条件下的导热系数从0.390 W/(m·K)增加到0.545 W/(m·K)。
