问题 问答题 简答题

发电机在运行中定子电流三相不平衡的原因是什么?怎样处理?

答案

参考答案:

发电机定子电流三相不平衡的原因是:

(1)发电机及系统外发生不对称短路。

(2)发电机出口断路器、隔离开关等设备非全相运行,造成发电机定子电流不平衡。

(3)发电机定子电流表及二次回路故障。

如果发电机在运行中静子电流三相不平衡超过规定值,应根据全部表针的指示判断故障性质,正确处理。

(1)当确定为发电机出口短路接地时,应立即安排停机。

(2)当确定为系统外部故障引起不平衡电流时,应立即降低发电机负荷,使发电机定子电流不平衡程度降到允许范围以内,并与上级联系,尽快消除。

(3)当确认为发电机出口隔离开关或主断路器非全相运行造成三相电流不平衡时,应立即将发电机解列停机。

(4)当确定为发电机定子电流表或其二次回路问题引起不平衡时,应密切监视发电机其他表计的变化,并通知尽快检修处理。

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How to apply (申请) for a free mailbox (邮箱)? First you have to connect to the Internet and go to the homepage of the ICP providing free mailboxes. Then you will find an icon (图标), an agreement about the rules for using the free mailbox will appear. If you want to go, click the icon “I agree”. Then you have to fill in a form about your basic personal data, and the name and PIN (密码) of the mailbox. The PIN is the key to the mailbox. After finishing these, you will get a mailbox like this:your name @ mail server (for example:tvguide@mail.cctv.com.cn. “tvguide” is the name of the mailbox, and “mail.cctv.com.cn” is the name of the mail server.). The mailbox is separated (分隔) into two parts by a separator “@”, which is read as “at”. The former part is the name of the mailbox. The latter is the domain name (域名) of the mail server. All mails to you will be received by the server and put into your mailbox. You can read these mails on any computer on the Internet in the world, if you have the name and PIN of the mailbox.

1 If you want to send or receive an e-mail, you should first ____ .

A. apply for a mailbox                 B. buy a computer

C. go to the post office                D. fill in a form

2 When you get a FREE mailbox, you can send an e-mail ____ .

A. by paying some money            B. to anyone

C. without paying money            D. anywhere

3 The mailbox’s name in the e-mail address “editor@ew.com.cn.” is ____ .

A. ew                B. ew.com.cn     C. com.cn          D. editor

4 The writer mainly wants to tell us how to ____ in this passage.

A. send a letter by e-mail            B. read the e-mail on computers in the world

C. get a free mailbox                   D. find out one’s e-mail address

5 We can find the similar information in the book “____”.

A. Who Moved My Cheese           B. Surfing on the Internet

C. Bill Gates’ Story                      D. Harry Potter