问题 问答题 简答题

消除电力系统振荡的主要措施有哪些?

答案

参考答案:

1、不论频率升高或降低的电厂都要按发电机事故过负荷的规定,最大限度地提高励磁电流。

2、发电厂应迅速采取措施恢复正常频率。送端高频率的电厂,迅速降低发电出力,直到振荡消除或恢复到正常频率为止。受端低频率的电厂,应充分利用备用容量和事故过载能力提高频率,直至消除振荡或恢复到正常频率为止。

3、争取在3至4分钟内消除振荡,否则应在适当地点将部分系统解列。

单项选择题

I was a single parent of four small children, working at a low paid job. Money was always tight, but we had a (1) over our heads, food on the table, clothes on our backs, and if not a lot, always (2) . Not knowing we were poor, my kids just thought I was (3) . I’ve always been glad about that.
It was Christmas time, and although there wasn’t (4) for a lot of gifts, we planned to celebrate with a family party. But the big (5) for the kids was the fun of Christmas (6) .
They planned weeks ahead of time, asking (7) what they wanted for Christmas. Fortunately, I had saved MYM120 for (8) to share by all five of us.
The big (9) arrived. I gave each kid a twenty-dollar bill and (10) them to look for gifts of about four dollars each. Then everyone scattered. We had two hours to shop; then we would (11) back at the "Santa’s Workshop"
Driving home, everyone was in high Christmas spirits, (12) my younger daughter, Ginger, who was unusually (13) She had only one small, flat bag with a few candies—fiftycent candies I was so angry, but I didn’t say anything (14) we got home. I called her into my bedroom and closed the door, (15) to be angry again. This is what she told me.
"I was looking (16) thinking of what to buy, and I (17) to read the little cards on the ’Giving Trees’. One was for a little girl, four years old, and all she (18) for Christmas was a doll. So I took the card off the tree and (19) the doll for her. We have so much and she doesn’t have anything. "
I never felt so (20) as I did that day.

二、完形填空

A.out

B.over

C.forward

D.around

选择题