强热烈焰下典型高压输电线路状态受损及机理分析

Analyses on damage behaviors and mechanism of operation properties of typical high-voltage transmission line under intense heat and blaze

利用电炉和酒精喷灯分别模拟易诱发输电线路跳闸的地表火和树冠火对应的高温辐射和高强火焰效应,利用高精度电子天平、拉力试验机和扫描电镜测试模拟火源中35 kV电压等级LGJ--120/20型钢芯铝绞线（ACSR）质量、力学性能和表面形貌等的受损行为,探讨模拟热环境映射实际山火条件下高压输电线路的可能跳闸机理.结果表明,在电炉模拟高温辐射作用下.钢芯铝绞线出现轻微质量受损（0.012％～0.073％）,外层铝线表面形成氧化铝白色无定形粉末区域,铝线电阻增加,产生局部过热现象造成电缆故障;在酒精喷灯模拟高强火焰下,钢芯铝绞线外层铝线表面出现气孔甚至缝隙并形成一定弧度,导线力学性能明显受损（拉伸和拉断后长度分别减少83.4％和增加17.3％）,内层铝线和镀锌层也遭到破坏,电学性能受损;类似实际地表火和树冠火条件下热烟气流和高温火焰可使导线质量、表面形貌、微观结构和力学性能发生破坏性变化,更易促使表面电离和热游离,与地面或树冠可燃物燃烧释放的大量带电质点形成地面 输电线路端口内多个不同强度非均匀电荷区,导线与地面或树木正常安全距离无法保持,区间内电荷量不断积累,电子崩逐渐建立,最终形成流注通道产生放电.诱发跳闸.

The electric furnace and alcohol blast burner were used respectively to simulate the high temperature radiation and high intensity flame sources corresponding to practical surface fire and crown fire in wildfires induce trips of high-voltage transmission lines. Damage behaviors of operation parameters （i. e. quality, mechanical property, surface morphology, etc. ） of 35 kV aluminum conductor steel reinforced （ACSR） conductor under simulated fires were measured by High Precise Electronic Balance, Pulling Force Test Machine and Scanning Electron Microscope （SEM）. Furthermore, the simulation results were mapped to the real wildfires and the possible mechanisms of transmission line trips induced by wildfires were explored. Results showed under the influence of high temperature radiation posed by the electric furnace, the qualities of the ACSR conductors reduced slightly （about 0. 012 %- 0. 073 % ）, white amorphous aluminum oxide powders formed on the surface af outer aluminum wires and increased the resistances, local overheating was caused and finally lead to the transmission line faults; under the effect of intense blaze posed by alcohol blast burner, stomata and even crevices were produced on the surface of outer aluminum wires, the wires were also curved to certain degree, mechanical properties of the ACSR conductors were weakened significantly （the tensile force and the length of bro ken conductor decreased by 83. 4% and increased by 17. 3%, respectively）, the inner aluminum wires and galvanized layer were also destroyed, the electrical properties were therefore impaired; hot thick smoke and high temperature blaze similar to the real surface fire and crown fire both can cause destructive changes （including quality, surface morphology, micro structure and mechanical property, etc. ） of the ACSR conductors, the ionization and thermal ionization become easy on the surface of conductors, and multiple uneven discharge regions of various field intensities are formed between the ground and transmission lines, inside which massive discharged particles released by the flaming ground and crown combustibles are directly accumulated, apparently the normal safety distance between overhead transmission lines and ground or trees can＇t be kept. With the aggregation of negative and positive electric charges, the electron avalanche is gradually built and a streamer channel is ulti mately established, a big discharge occurs and finally induces a trip.