问题 问答题 简答题

简述雷电是如何通过对局外金属缆线的危害而影响到机房内的通信设备的。

答案

参考答案:

雷电通过对局外金属缆线的危害而造成通信机房内设备雷击故障主要是通过如下3个方面:

(l)局外金属缆线长度比较长,所经之处的雷电(包括地闪和云闪)发出的雷电磁脉冲(LEMP)会在金属电缆上产生感应电压,整条金属缆线上雷电压累积起来,最终沿电缆涌入局(站)内,造成通信设备损坏;

(2)当雷电直接打在缆线上或打在金属缆线附近而击穿电缆绝缘流入缆线时,大雷电流会沿缆线侵入局内,造成通信设备损坏;

(3)局(站)建筑物附近落雷时,强大的雷电磁脉冲也会通过空间电磁感应,直接在局(站)附近的金属电缆上产生感应电压,并通过线缆的金属构件进入通信机房而造成通信设备的损坏。

阅读理解

Saturday, June 16th

In the morning, we went camping in Green Natural Park. We were happy because it was a sunny day. We were looking forward to a wonderful two-day holiday. On the way, we kept singing and making jokes.

However, in the afternoon, when we finished our picnic at one o’clock, it was dark and windy. Soon, there was a shower(阵雨). Unluckily, none(没有人) of us brought an umbrella. We ran about but we could find no place to hide.

Twenty minutes passed and it was still raining. There were hours to go before we reached the campsite (野营地). It was even worse that our small compass (指南针) showed that we went to the wrong way. We lost our way!

We had to make a quick decision(决定)because it was raining heavily. Chris said we could put up a tent to hide in, so Mary and Tom helped to put up the tent. Chris and I tried to make a fire to keep us warm. But we weren’t able to light(点燃) the fire, because everything was wet. We dried ourselves, chatted and waited inside the tent. At about five o’clock, it stopped raining. We decided to give up (放弃)the camping trip because all of us were very tired.

This camping trip may not be successful (成功的) but we know each other better. And the most important thing I’ve learned from this camping trip is team spirit(合作精神).

Answer the following questions with No More Than 4 Words

小题1:Where did they go camping?

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小题2: When did they finish their picnic?

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小题3:Why weren’t they able to light(点燃) the fire?

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小题4:How long did the rain last(持续)?

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小题5:What’s the most important thing that the writer has learned from the camping trip?

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