- 學位論文
電氣火災一次痕影響因子之探討
Evaluation of Factors for Primary Shorting in Electric Fires
摘要
本研究經由改變實驗環境因子，針對一次短路熔痕，以金相分析法加以探討其熔痕之孔洞、成分等金相組織之跡象，並以定性定量的方式做研究。並結合實際案例分析影印機之鑑定，其事件經火災鑑定員判定影印機為起火點。但經本研究之實驗發現，當此日本廠牌影印機內部電源線發生電線負載、電線短路時，結果發現其所使用之難燃電線經過負載高電流通電後，內部銅線燒斷但其披覆僅發生熱膨脹及龜裂的現象，並未因高溫而起火燃燒，且不會引燃影印機內部其他電線或是影印機之塑料外殼甚至是影印機周圍紙張等物品；相對於一般家用常用電線(同樣為16AWG)則承受不了高溫整條電線起火燃燒，證明了不同披覆材料之電線，發生過負載之現象並不相同。由此案例可知其電線披覆材料設計之重要性。而當影印機周圍擺設如汽油等易燃性液體，使其影印機內部發生過負載，不管內部電源線材質為何皆會將汽油引燃。因此建議易燃性液體與影印機等電器設備需有適當的安全距離因而不可擺設太近。 此外，本研究亦利用金相分析，進行一次短路熔痕、過載熔痕之金相組織微結構觀察，以高解析掃描電子顯微鏡(Scanning Electron Microscope)觀察氣孔之外觀及氣孔深度並結合X光能譜散佈分析儀(Energy Dispersive Spectrometer, EDS)進行氣孔成分分析。應用Image J生物影像軟體分析金相試片上其一次短路熔痕及過載熔痕之面積、氣孔孔洞等特徵，分別計算出氣孔孔洞之數量、粒徑、面積等數據，並繪製成圖表。研究結果顯示，一次短路痕之氣孔小而多且平均粒徑皆很小，不管其環境之相對濕度為乾溼或是高濕，亦不管環境中是否含有汽油煙氣、塑膠煙氣或其他物質，皆不受其影響。
並列摘要
This research focused on a primary shorting mark by altering the ambient factors while using metallurgic analysis to analyze the holes and compositions in the melted marks; qualitative and quantitative methods were used during the research. From the assessment of a photocopier fire case, the fire investigators determined the origin of fire to be the photocopier. However, experiments made by this research showed that when overloads or short-circuits occurred on the Japanese photocopier, the wires inside the flame resisting cables would break and the outer coating would expand and crack, but there would be no fire caused by the high temperatures. Also, objects around the cables, such as other cables inside the machine, the plastic case of the copier and paper placed beside the machine, would not ignite either. As compared with the cables of other household appliances (also using 16AWG), those cables would be unable to withstand the high temperatures and ignite, which proves that cables with different outer coatings have different situations during overload. This case shows the importance of outer coatings of cables. When gasoline and other flammable liquids were placed beside the photocopier, the gasoline would ignite regardless of the outer coating used, therefore it is recommended that flammable liquids should be kept at a safe distance from photocopiers and other electric appliances. This research also used metallurgic analysis to observe the microstructures of the primary shorting marks and overload melted marks. High resolution Scanning Electron Microscopes were used to observe the appearance and depth of the air holes, while using Energy Dispersive Spectrometer (EDS) to analyze the composition of the air holes. Using Image J bio-imaging software, the area of the melted marks and air holes were observed, while the quantity, particle size, area of the air holes were calculated and drawn into graphs. Results show that primary shorting melted marks possessed small air holes and were small in particle size, regardless of if the relative humidity was dry or humid, or if the surroundings contained gasoline fumes, plastic fumes or other substances.