第6题:[多选题]变压器绕组变形对变压器的危害有:()。 A. 绝缘距离发生变化,导致局部放电发生,在正常运行电压下,因局部放电的长期作用,绝缘损伤部位逐渐扩大,最终导致变压器发生绝缘击穿故障 B. 固体绝缘受到损伤,当遇到过电压作用时,绕组会发生股间或匝间短路事故 C. 绕组机械性能下降,当再次遭受短路电流冲击时,将承受不住巨大的电动力冲击作用而发生损坏事故 D. 累积效应。运行经验表明,变压器一旦发生绕组变形,将导致累积效应,出现恶性循环
参考答案:ABCD
第13题: [单项选择]Americans eat ______ as they actually need every day. A. twice as much protein B. twice protein as much twice C. twice protein as much D. protein as twice much 参考答案:A 答案解析:[解析] 此题考查比较级的倍数表示方法。much修饰名词,应放在protein之前,twice表示倍数,修饰as much protein as,也应前置。