问题 问答题 简答题

电网设置解列点的原则是什么?什么情况下应能实现自动解列?

答案

参考答案:

电网解列点的设置原则是:解列后各电网应各自同步运行与供需(包括有关和无功)基本平衡的要求。解列的断路器不宜过多。

一般在下列情况下,电网应能实现自动解列:

(1)当电两中非同期运行的各部分可能实现再同期,且对负荷影响不大时,应采取措施,以促使将其拉人同期。如果发生持续性的非同期过程,则经规定的振荡周期数后,应在电网间联网的联络线弱联系处将电网解列。

(2)主要由电网供电的带地区电源的终端变电站或在地区电源与主网联络的适当地点,当电网发生事故、与电网相连的线路发生故障或地区电网与主电网发生振荡时,应在预定地点解列。

(3)大型企业的自备电厂,为保证在主电网电源中断或发生振荡时,不影响企业重要用户的供电,应在适当的地点设置解列点。

(4)并列运行的重负荷线路中一部分线路断开后,或并列运行的不同电压等级线路中主要高压送电线路断开后,可能导致继续运行的线路或设备严重过负荷时,应在预定地点或暂时未解环的高低压电磁环网预定地点解列或自动减负荷。

(5)事故时专带厂用电的机组。

(6)当故障后难以实现再同期或者对负荷影响较大时,应立即在预定地点将电网解列。

阅读理解

A simple piece of clothesline hangs between some environmentally friendly Americans and their neighbors.

On one side stand those who see clothes dryers(干衣机) as a waste of energy and a major polluter of the environment. As a result, they are turning to clotheslines as part of the “what-I –can do environmentalism(环境保护主义).”

On the other side are people who are against drying clothes outside, arguing that clotheslines are unpleasant to look at. They have persuaded Homeowners Associations (HOAs) access the U.S. to ban outdoor clotheslines, because clothesline drying also tends to lower home value in the neighborhood. This had led to a Right-to-Dry Movement that is calling for laws to be passed to protect people’s right to use clotheslines.

So far, only three states have laws to protect clothesline. Right-to-Dry supporters argue that there should be move.

Matt Reck, 37, is the kind of eco-conscious(有生态意识的) person who feeds his trees with bathwater and reuses water drops from his air conditioners to water plants. His family also uses a clothesline. But on July 9, 2007, the HOA in Wake Forest, North Carolina, told him that a dissatisfied neighlzir had telephoned them about him clothesline. The Recks paid no attention to the warming and still dried their clothes on a line in the yard. “Many people say they are environmentally friendly but they don’t take matters in their own hands,” says Reck. The local HOA has decided not to take any action, unless more neighbors come to them.

North Carolina lawmakers are saying that banning clotheslines is not the right thing to do. But HOAs and housing businesses believe that clothesline drying reminds people of poor neighborhoods. They worry that if buyers think their future neighbors can’t even afford dryers, housing prices will fall.

Environmentalists say such worries are not necessary, and in view of global warming, that idea needs to change. As they say, “The clothesline is beautiful”. Hanging clothes outside should be encouraged. We all have to do at least something to slow down the process of global warming.”

小题1:One of the reasons why supporters of clothes dryers are trying to ban clothesline drying is that ____.

A.clothes dryers are more efficient

B.clothesline drying reduces home value

C.clothes dryers are energy-saving

D.clothesline drying is not allowed in most U.S. states小题2:Which of the following best describes Matt Reck?

A.He is a kind-hearted man.

B.He is an impolite man.

C.He is and experienced gardener.

D.He is a man of social responsibility.小题3:Who are in favor of clothesline drying?

A.housing businesses.

B.Environmentalists.

C.Homeowners Associations.

D.Reck’s dissatisfied neighbors.小题4:What is mainly discussed in the text?

A.Clothesline drying: a way to save energy and money.

B.Clothesline drying: a lost art rediscovered.

C.Opposite opinions on clothesline drying.

D.Different varieties of clotheslines.

单项选择题