【判断题】
在系统发生故障而振荡时,只要距离保护的整定值大于保护安装点至振荡中心之间的阻抗值就不会误动作
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相关试题
【判断题】
对于双重化保护的电流回路，电压回路，直流电源回路，双套跳闸线圈的控制回路等，不宜合用同一根多芯电缆
【判断题】
中性点经消弧线圈接地系统，不采用欠补偿和全补偿的方式，主要是为了避免造成并联谐振和铁磁共振引起过电压
【判断题】
高频闭锁负序功率方向保护，当被保护线路上出现非全相运行时，只有电压取至线路电压互感器时，保护装置不会误动
【判断题】
大接地电流系统系指所有的变压器中性点均直接接地的系统
【判断题】
正序电压是越靠近故障点数值越小，负序电压和零序电压是越靠近故障点数值越大
【判断题】
一般距离保护振荡闭锁工作情况是正常与振荡时不动作、闭锁保护，系统故障时开放保护
【判断题】
大接地电流系统中接地短路时，系统零序电流的分布与中性点接地点的多少有关，而与其位置无关
【判断题】
电流互感器本身造成的测量误差是由于有励磁电流的存在
【判断题】
在双母线母联电流比相式母线保护中，任一母线故障只要母联断路器中电流为零，母线保护将拒动。为此要求两条母线都必须有可靠电源与之联接
【判断题】
如果开关偷跳时负荷电流太小不足以使起动元件动作。WXB－11型微机保护可由不对应起动重合，此时不检查同期
【判断题】
在大接地电流系统中，线路始端发生两相金属性短路接地时，零序方向电流保护中的方向元件将因零序电压为零而拒动
【判断题】
与电流电压保护相比，距离保护主要优点在于完全不受运行方式影响
【判断题】
LFP─901A微机保护零序方向元件所使用的电压是外接的
【判断题】
相间距离保护的Ⅲ段定值，按可靠躲过本线路的最大事故过负荷电流对应的最大阻抗整定
【判断题】
结合滤波器和耦合电容器组成的带通滤波器对50周工频应呈现极大的衰耗，以阻止工频串入高频装置
【判断题】
发电机的过电流保护应装于出口端侧，而不应装于中性点
【判断题】
发电机低压过流保护的低电压元件是区别故障电流和正常过负荷电流，降低了电流的整定值，提高整套保护灵敏度的措施
【判断题】
谐波制动的变压器保护中设置差动速断元件的主要原因是为了提高差动保护的动作速度
【判断题】
如果两测量点的阻抗相同，则该两点间的电压相对电平和功率相对电平相等
【判断题】
当带频阻波器损坏后，分流衰耗一定会增加
【判断题】
允许式保护控制载波机发信的接点为闭锁式保护停信的接点，该接点只有在正方向发生故障时才可能动作
【判断题】
只要测得收发信机发送到高频电缆的电压电平，即可知道发送到高频电缆的功率电平
【判断题】
为提高抗干扰能力，微机型保护的电流引入线，应采用屏蔽电缆，屏蔽层和备用芯应在开关场和控制室同时接地
【判断题】
在大接地电流系统中，两相短路对系统的危害比三相短路大，在某些情况下，单相接地短路电流比三相短路电流还要大
【判断题】
两个同型号、同变比的CT串联使用时，会使CT的励磁电流减小
【判断题】
重合闸前加速保护比重合闸后加速保护的重合成功率高
【判断题】
开关液压机构在压力下降过程中，依次发压力降低闭锁重合闸、压力降低闭锁合闸、压力降低闭锁跳闸信号
【判断题】
变压器各侧电流互感器型号不同，变流器变比与计算值不同，变压器调压分接头不同，所以在变压器差动保护中会产生暂态不平衡电流
【判断题】
对Y/△－11接线的变压器，当变压器△侧出口发生两相短路故障，Y侧保护的低电压元件接相间电压，该元件不能正确反映故障相间电压
【判断题】
对三绕组变压器的差动保护各侧电流互感器的选择，应按各侧的实际容量来选择电流互感器的变比
【判断题】
线路出现断相，当断相点纵向零序阻抗大于纵向正序阻抗时，单相断相零序电流小于负序电流
【判断题】
系统振荡时，线路发生断相，零序电流与两侧电势角差的变化无关，与线路负荷电流的大小有关
【判断题】
线路发生接地故障，正方向时零序电压滞后零序电流，反方向时，零序电压超前零序电流
【判断题】
系统运行方式越大，保护装置的动作灵敏度越高
【判断题】
线路发生单相接地故障，其保护安装处的正序、负序电流，大小相等，相序相反
【判断题】
平行线路之间的零序互感，对线路零序电流的幅值有影响，对零序电流与零序电压之间的相位关系无影响
【判断题】
在大接地电流系统中，线路的零序功率方向继电器接于母线电压互感器的开口三角电压，当线路非全相运行时，该继电器可能会动作
【判断题】
中性点不接地系统中，单相接地故障时，故障线路上的容性无功功率的方向为由母线流向故障点
【判断题】
电容式电压互感器的稳态工作特性与电磁式电压互感器基本相同，暂态特性比电磁式电压互感器差
【判断题】
五次谐波电流的大小或方向可以作为中性点非直接接地系统中，查找故障线路的一个判据
推荐试题
【单选题】
( ) 39. The water in the river is polluted because of _____________.
A. people's drinking water too much B. people's swimming in the river too much
C. chemicals and other materials D. people's building a dam across a river
【单选题】
( ) 40. The best title of the passage is ___________.
A. Rivers in Cities B. The importance of Rivers
C. Transportation D. Natural Resources
【单选题】
1.—Hello! This is Henry Speaking．I’d like to speak to your father．
—Sorry, he has Shanghai．
A. been in B. been to C. come to D. gone to
【单选题】
2. — It’s difficult for the village children to cross the river for school．
— I think a bridge ______ over the river．
A. was built B. is being built C. has been built D. should be built
【单选题】
3. —Where would you like to go, Jinan or Qufu?
— ．I only want to go to Qingdao．
A. Each B. Either C. Neither D. All
【单选题】
4. — The documentary A Bite Of China II is quite popular around China recently. How do you like it? — ______.
A. I think so B. Pretty good C. It’s my pleasure D. All right
【单选题】
5. There are three English-books on the shelf, but ______ of them is mine.
A. both B. neither C.all D. none
【单选题】
6. When the parents arrived at the hall, the students _______ their projects.
A. have finish B. finished C. had finished D. are finishing
【单选题】
7. This week, the _______ seems to change every day: one day is hot; the next day is cold.
A. time B. weather C. season D. way
【单选题】
8. He never does his work _______ Mary.
A. as careful as B. so careful as C. carefully as D. as carefully as
【单选题】
9. — Can he jump high?
— Yes, he ______. He is a good high jumper.
A. must B. need C. can D. shall
【单选题】
10. The shop _____ at 8:00 a．m．and it ________ for ten hours every day．
A. is open; has opened B. is opened; opens
C. opens; is open D. opened; opens
【单选题】
11. —Excuse me, may I use your bicycle? ______ is broken.
—Certainly. But remember to return it before lunch.
A. Mine B. Me C. Myself D. I
【单选题】
12. —Simon, what do I need to take for the hiking?
—You’d better ________ more water than usual. It’s hot today.
A. to take B. taking C. take D. took
【单选题】
13. Helen ______ to a language school when she was seven.
A. sent B. is sent C. will send D. was sent
【单选题】
14. — Is this park you’ve visited recently?
— Yes, it's the most beautiful one I’ve ever visited before.
A. that B. the one C. which D. the one which
【单选题】
15. — It’s difficult for the village children to cross the river for school.
— I think a bridge ________ over the river.
A. should be built B. is being built C. has been built D. was built
【单选题】
16. — Could you tell me when Mr. Li ________ in Huaibei?
— Sure．．When he ________, I’ll call you．
A. arrives; will arrive B. will arrive; will arrive
C. arrives; arrives D. will arrive; arrives
【单选题】
) 17.There is ________ 800-metre-long road behind ________ hospital．
A. an; an B. an; the C. a; a D. a; the
【单选题】
18. — Did you see a girl in yellow pass by just now?
— No, sir. I ________ a magazine.
A. read B. am reading C. was reading D. would read
【单选题】
19.In fact, my parents are not only kind to me, but also strict ________ me.
A. at B. to C. for D. with
【单选题】
20. The boy_____ a yellow sweater can_____ himself now．
A. wearing; dress B. putting on; wear C. put on; dress D. dressing; wear
【单选题】
21. —Jack, I haven’t seen your brother for a long time．
— He ________Shanghai on business for two months．
A. went to B. has gone to C. has been in D. has been to
【单选题】
22. The meat with eggs tastes ______. Would you like some more?
A. nice B. well C. bad D. wonderfully
【单选题】
23. — Look! The man standing at the gate ______ be our headmaster．
— No, it _______ be him．He is holding a meeting in the office now．
A. must; can’t B. must; mustn’t C. can’t; can’t D. can’t; mustn’t
【单选题】
24. The Japanese government must do everything ________ polluted water from running into rivers, lakes, seas and oceans．
A. keep B. kept C. Keeping D. to keep
【单选题】
25. —Hi, Jack．Did you go to Jim’s birthday party?
—No, I felt so sad．I ．
A. didn’t invite B. am not invited C. wasn’t invited D. hadn’t invited
【单选题】
( ) 26. Where does the writer of "The little Prince" come from?
A．England． B．France． C．America． D．China．
【单选题】
( ) 27. What does the prince do after the fox tells him a secret?
A．He cares more about a flower and a sheep．
B．He meets many more strange adults on other planets．
C．He realizes his love for the rose and he goes back to his planet．
D．He discovers interesting things such as a snake, other roses and a fox．
【单选题】
( ) 28. What does "The little Prince" mainly talk about? It' s about _________．
A．the adult world B．the planet B -612
C．a rose and a fox D．the adventure of a young prince
【单选题】
( ) 29. What is the writer's main purpose（目的）in writing this passage？
A．To tell the readers his life story．
B．To tell people what kind of person his father was．
C．To tell the readers what present he got from his father．
D． To let people know how poor he was．
【单选题】
( )30 Why did the father not ask his son not to do this and do that？
A．Because he felt quite confident of his son．
B．Because he was born from a poor family．
C．Because he was a man of few words．
D．Because he didn't want to be much too strict with his son．
【单选题】
( ) 31. What would someone learn from this passage？
A．How to live by oneself． B．How to stand on one's own feet．
C．What a good father should do． D．What the self-important is like．
【单选题】
( ) 32. What may be the proper Chinese for the underlined part in the passage？
A．闲暇时光 B．学费 C．精神空虚 D．经济不足
【单选题】
( ) 33. It’s good for children to ________ on the Internet.
A. give password to others
B. go into a chat room as they’d like to
C. give out a credit card number
D. get useful knowledge and information
【单选题】
( ) 34. The underlined phrase “leak out” in the third paragraph may mean “________.”
A. give away B. give out C. leave out D. put away
【单选题】
( ) 35.If your parents don’t agree, never ________.
A. read anything on the Internet
B. relax in your free time
C. have a face-to face meeting with anyone you met online
D. treat other people as you’d like to be treated
【单选题】
( ) 36. This passage is mainly about “________”.
A. Internet Safety Rules B. Surfing on the Internet
C. Information on the Internet D. How to use Computers
【单选题】
( ) 37. When was canned food invented?
A. In 1870. B. In 1810. C. In 1902. D. In 1926.
【单选题】
( ) 38. After the trip to the Arctic, Clarence Birdseye invented ____________.
A. canned food B. can openers
C. frozen food D. air conditioning
