问题 问答题 简答题

直线杆塔断线时,应如何确定断线张力?

答案

参考答案:

经验和调查资料表明,高压线路断线事故很少,没有什么规律可循,而且导线截面越大,断线概率越小,用复杂的理论计算断线张力没有必要,所以规程作了如下规定:

(1)断一根导线、而地线未断且无风、无冰时,单导线断线杆塔张力按表4-1所列数据使用。

两分裂导线断线张力,对于平地应取一根导线最大使用张力的40%,对于山地区取50%。

(2)一根避雷线断线,不平衡张力按最大使用张力的15%~20%,拉线铁塔为30%,自立塔为50%。

阅读理解

As we enjoy the summer ocean waves along the beaches, we may think nervously about Steven Spielberg's Jaws and the great fear that sharks inspire in us. Yet we are happy to see global efforts to protect the declining number of sharks. The world has realized that we need the species, like sharks, to keep a balanced ecosystem.

Sharks, in particular, are “in” these days. Thanks to good public policy and famous stars such as Jackie Chan and Ang Lee, killing sharks for fin soup is no longer cool.

The demand for shark fins has been rising for decades, threatening sharks with extinction(灭绝)—up to 100 million sharks are killed each year just for their fins. But we have started to reverse the trend, particularly in many areas of the United States and overseas where restaurants once proudly provided delicious shark fins on the menu.

In California, a ban on the sale and possession of shark fin soup has gone into effect this year through the efforts of Wild Aid and other organizations.

Overseas marketing and public efforts featuring posters on public transportation systems and TV ads have been underway for the past few years. These efforts all show signs of success, on both the supply side and the demand side of trade in shark fins.

Actually, stopping the killing of sharks is part of a broader movement to stop the killing of wild animals and the buying and selling of wildlife products. These products come from hunting elephants, tigers and rhinos, besides killing marine life.

Whether it is shark fin soup or ivory piano keys, killing animals is big business. The hunting of elephants in search of ivory tusks for luxury(奢侈的)goods has become a full­scale war. The decrease of African elephant populations is alarming. Together with international partners, the United States is leading the worldwide effort to reduce demand for high­end products that rely on killing animals.

小题1:The underlined word “reverse” in Paragraph 3 probably means ________.

A.show

B.keep

C.follow

D.change小题2:From the passage, we know ________.

A.Jackie Chan and Ang Lee make fin soup popular

B.a lot of wild animals have been killed for products

C.Steven Spielberg's Jaws inspires us to protect sharks

D.the number of African elephants has been increased小题3:.What can we infer from the passage?

A.More animals for high­end products will be saved.

B.People have kicked the habit of having shark fin soup.

C.Shark fins will not be available any more in restaurants.

D.Global efforts have succeeded in stopping killing wild animals.

单项选择题