发电机定子绕组内部单相接地故障时,使用零序电流或零序电压实现的保护存在死区。死区内故障可使接地故障发展为匝间、相间故障,严重损坏发电机,需使用无死区100%定子绕组接地短路的保护。( )
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用于植物油抗氧化效果较好的是
AP
B. TBHQ
C. BHA
D. BHT
被世界卫生组织食品添加剂联合委员会认可的营养型抗氧化剂是
A. L-抗坏血酸
B. L-抗坏血酸棕榈酸酯
C. 异抗坏血酸
D. 异抗坏血酸钠
Which analysis indicates whether a particular element or compound is in the sample?
A. Qualitative analysis.
B. Quantitative analysis.
Chemical analysis.
D. Instrumental analysis.
Modern analytical chemistry can be used for many fields, for example.
A. in industrial production
B. in evaluation of commodity quality
C. in health area and in the environment
D. above of all
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