问题 单项选择题

某高层办公楼供电电源为交流10kV,频率50Hz,10/0.4kV变电所设在本楼内,10kV侧采用低电阻接地系统,400/230V侧接地形式采用TN-S系统且低压装置采用保护总等电位连接系统,请回答下列问题,并列出解答过程。 楼内某办公室配电箱配电给除湿机,除湿机为三相负载,功率为15kW,保证间接接触保护电器在规定时间内切断故障回路的动作电流为756A,为降低除湿机发生接地故障是与邻近暖气片之间的接触电压,在该办公室设置局部等电位联结,计算该配电箱除湿机供电线路中PE线的电阻值最大不应超过下列哪项数值?()

A.66mΩ

B.86mΩ

C.146mΩ

D.291mΩ

答案

参考答案:A

阅读理解

阅读理解。

     What would you do if you were ill? Of course, we would eat some medicines. The most

common disease in the world is the cold. It often starts with a sore throat. If you catch a cold,

you sneeze and your nose runs. You usually have a headache, too. Often you have a cough.

It's not a serious disease, but you can feel quite ill.

     There isn't a cure (良方) for a cold, but you can take medicines to make you feel better.

For example, you can take aspirin to get rid of your headache. It is good to rest and to drink

a lot of water, too. A doctor once told me, "With the right medicine, a cold will last for seven

days. With no medicine, it will go on for a whole week!"

     Where does our medicine come from? A long time ago, people understood that some plants

made them feel better when they were ill. They ate leaves, the roots, the fruit, or the seeds of

plants. For example, the juice of lemons makes a sore throat feel better.

     In modern times, scientists have looked at these plants, and found out which chemicals

(化学物质) are in them. Many of our medicines today are made from those chemicals. There

are some diseases which we can't cure (治愈) yet. Such as, AIDS, cancers...

     And nobody has found a cure for old age. But because of modern medicines, the average

person now lives longer than their grandparents.

1. How does a cold often start?

    _________________________________________

2. What is aspirin used to do?

    _________________________________________

3. How long does a cold usually last?

    _________________________________________

4. What makes a sore throat feel better?

    _________________________________________

5. What are modern medicines usually made from?

    _________________________________________

单项选择题