必要时

Moreover, second-winding current waveform of a current transformer is calculated under the transient current of the typical short-circuit fault by numerical method. The analysis shows that the relevant protection equipment may refuse to trip when the fault current is extra high. It will result in the maloperation of protective relays for loss of their selectivity, and cause other protective relays to operate beyond range, and extend the scope of shutdown of power supply.

在这些回路出口处发生相间直接短路等严重故障时，流过相应TA一次侧的故障电流可能达到TA额定工作电流的100倍以上，大大超过了保护用TA的10%误差容许倍数，将使TA严重饱和，从而影响相关的保护设备的动作性能，因此有必要对在这种特大电流作用下的TA的传变特性做一些探讨，以分析其对继电保护装置动作特性的影响及应采取的措施。

Fire Makino supervision of law enforcement officers to examine the scene of the fire in the time that the row fan the fire of a lack of necessary maintenance and periodic testing is a result of the internal electrical fire caused by an aging line.

牧野区消防执法监督人员在对火场进行勘验时了解到，起火的排风扇缺乏必要的维护保养和定期检测，是因内部电机线路老化引起的着火。

I reasoned that once I got to the point where I could run two or maybe three miles, I would be so overwhelmingly pleased with myself that I wouldn't feel any need to fulfill my five-mile objective.

每当我能跑2或3英里时，我就高兴地想，实在没有必要再去跑5英里了。

55 Flagmen 信号旗手 When signs, signals, and barricades do not provide necessary protection on or adjacent to a highway or street, flagmen or other appropriate traffic controls will be provided.

当标志，信号和路障在一公路或大街上或其附近已不能提供必要的保护时，则要提供旗手或其它合适的交通控制措施。

Others have replied that that doctrine is in itself a grave threat to international peace and security – since it might imply that any state has the right to use force whenever it sees fit, without regard to other states' concerns.

宪章》第八十一条重申&联合国会员国受武力攻击时，在安全理事会采取必要办法，以维持国际和平及安全以前，行使自卫之自然权利&。

I scarce knew in what Manner to receive them; but found to draw our selves in a close Line was the only Way: so we form'd in a Moment: But that we might not have too much Interval, I order'd, that only every other Man should fire, and that the others who had not fir'd should stand ready to give them a second Volley immediately, if they continued to advance upon us, and that then those who had fir'd at first, should not pretend to load their Fusees again, but stand ready with every one a Pistol; for we were all arm'd with a Fusee, and a Pair of Pistols each Man; so we were by this Method able to fire six Volleys, half of us at a Time; however, at present we had no Necessity; for upon firing the first Volley, the Enemy made a full Stop, being terrify'd as well with the Noise, as with the Fire; four of them being shot into the Head, dropp'd, several others were wounded, and went bleeding off, as we could see by the Snow: I found they stopp'd, but did not immediately retreat; whereupon remembring that I had been told, that the fiercest Creatures were terrify'd at the Voice of a Man, I caus'd all our Company to hollow as loud as we could; and I found the Notion not altogether mistaken; for upon our Shout, they began to retire, and turn about; then I order'd a second Volley to be fir'd, in their Rear, which put them to the Gallop, and away they went to the Woods.

我简直不知道如何对付它们。结果，我认为最好的办法是我们互相靠拢，排成一行。于是，我们马上照此行事。为了不致使我们的火力中断太久，我下令只许一半人开枪，另一半人作好准备；如果第一排枪响过后，狼群继续向我们冲来，就开第二排枪；同时，在开第二排枪时，那开第一排枪的一半人，不要忙于装他们的长枪，而是应该抽出手枪，作好准备。因为我们每人身上都有一支长枪和两支手枪。用这种办法，我们可以连续开六排枪，每次有一半人开枪。然而，当时还没有必要这样做。放出第一排枪之后，我们的敌人就给枪声和火光吓坏了，马上停止了前进。有四条狼被我们打中头部，倒了下来；另外有几条受了伤，鲜血淋淋地跑掉了。这在雪地上可以看得一清二楚。我发现，狼群停止了攻击，但没有后退。这时，我忽然记起有人说过，就是最凶猛的野兽，听见人的声音也会害怕。于是我就叫大家拼命呐喊。这个办法果然很有效。我们一喊，狼群就开始后退，掉头跑掉了。我又下令朝它们背后开了一排枪。这样一来，它们才撒腿跑回树林里去了。

When building infrastructure, governments walk a tricky line between counterproductive tight-fistedness and unnecessary gold-plating.

基础设施建设之时，政府实际上是在后果不佳的缩衣减食和没有必要的镏金贴瓦之间走钢丝。

In order to reduce the inductive current and the power loss caused by the current when the power system runs naturally, this article brings forward a way to reduce the power loss through a multiple impedance to insulate the lightning shield line and ground, so that the system can run economically.

为减小系统正常运行时避雷线中出现的感应电流及其电能损耗，提出了利用复合阻抗隔离避雷线与杆塔的方法，EMTP程序对该方法数字仿真的结果证明了它的可行性和有效性，但系统序阻抗也会随之改变，故有必要调整系统保护的整定，以满足系统对保护的要求。

I'm Connecting Two Audio Devices. Is It Important to Match Their Impedances?

C.2 在连接两台音频设备时，有必要匹配它们的阻抗吗？

Im Connecting Two Audio Devices. Is It Important to Match Their Impedances?

C.2 在连接两台音频设备时，有必要匹配它们的阻抗吗？

They weren't aggressive, but I yelled and threw a rock in their direction to get them off the trail and away from me, just in case.

他们没有侵略性，但我大喊，并在他们的方向扔石头让他们过的线索，远离我，以防万一。

In slot 2 in your bag put wrapping paper, quantity does not matter in this case.

在你的书包里槽2把包装纸、数量无关紧要。