电力专业英语第十五讲

1、山东交通学院电气系张建军 词汇flashover n. 闪络, 跳火 ，闪燃synchronous condenser 同步调相机attenuate tenjuet v. 减弱（使） 变细; （使） 变薄; （使） 变小; unduly ndju:li ad. 过分地 ，过度地; 不适当地; 不相称地; configuration knfgren n. 外形， 配置; 布局，构造compromise kmprmaz v. 平衡，兼顾 折中解决; 妥协，退让;galvanized lvnazd a. 镀锌的， 激起某人行动起来disposition dspzn n. 配置， 性情，性格; 意向，

2、倾向; 安排empirical mprkl a. 以实验为基础的， 经验主义的; 凭经验的; 以观察或实验为依据的;arcing hore 角形避雷器nonlinear a. 非线性的amplitude mpltju:d n. 振幅， 广大，广阔，充足; （思想的） 广度; 角度距离;spark gap 避雷器co-ordination n. 协调sparkover sp:kvr n. 跳火，打火花; 课文内容Part ALightning and Transmission LinesWhen lightning makes a direct hit on a transmission lin

3、e, it deposits a large electric charge, producing an enormous over voltage between the line and ground. The dielectric strength of air is immediately exceeded and a flashover occurs. The line discharges itself and the overvoltage disappears in typically less than 50 s.deposits放置；(使)沉淀；存储；付(订金等)；寄存n.

4、存款；定金；electric charge 电荷; 电费;dielectric strength 电介质强度，绝缘强度;flashover闪络：沿面放电发展到气体或液体破坏性放电称闪络：沿面放电发展到气体或液体破坏性放电称为闪络为闪络闪络效应 闪络效应，当人体被闪电击中后,99%的电流不是通过人体导入地下，而是会以电弧的形式从人体表面穿过，导入地下，降低对人体的伤害，这就是有些人被闪电打击后还能存活的缘故，这种现象就叫闪络效应，也叫闪络现象。在高电压作用下，气体或液体介质沿绝缘表面发生的破坏性放电。其放电时的电压称为闪络电压。发生闪络后，电极间的电压迅速下降到零或接近于零。闪络通道中的火花或电

5、弧使绝缘表面局部过热造成炭化，损坏表面绝缘。Unfortunately, the arc between the line and ground (initiated by the lightning stroke), produces a highly ionized path which behaves like a conducing short-circuit. Consequently, the normal ac line voltage immediately delivers a large ac current that follows the ionized path. U

6、nfortunately 可惜; 不幸地，遗憾地; 不巧;the normal ac line voltage正常的交流线电压delivers a large ac current that follows the ionized path.通过电离通道把大量的交流电流传导至大地This follow-through current may sustain the arc until the circuit breakers open at the end of the line. The fastest circuit breakers will trip in about 1/15th o

7、f a second, which is almost 1000 times longer than the duration of the lightning stroke itself.This follow-through current may sustain the arc until the circuit breakers open at the end of the line.译文：这个穿越电流能在线路首端断路器断开之前一直维持该电弧。The fastest circuit breakers will trip in about 1/15th of a second动作最快的断

8、路器能在1/15秒分闸which is almost 1000 times longer than the duration of the lightning stroke itself这个时间几乎比雷电流自身持续时间长1000倍Direct hits on a transmission line are rare; more often, lighting will strike the overhead ground wire that shields the line. In the latter case, a local charge still accumulates on the

9、 line, producing a very high local overvoltage. Direct hits on a transmission line are rare输电线路上的直击雷是很罕见的lighting will strike the overhead ground wire that shields the line雷电击中屏蔽输电线路的架空底线（避雷线）a local charge still accumulates on the line在线路上的局部出现电荷的积累producing a very high local overvoltage.产生出非常高的局部过

10、电压This concentrated charge immediately divides into two waves that swiftly move in opposite directions at close to the speed of light (300m/s). The height of the impulse wave represents the magnitude of the surge voltage that exists from point to point between the line and ground. This concentrated

11、charge集中的电荷immediately divides into two waves that swiftly move in opposite directions at close to the speed of light立即分成两个向相反方向快速流动的涌流，速度接近于光速The height of the impulse wave冲击雷电波的高度the magnitude of the surge voltage浪涌电压的幅值that exists from point to point between the line and ground（这个电压）存在于线路和大地的点对点之

12、间The peak voltage (corresponding to the crest of the wave) may attain one or two million volts. Wave front is concentrated over a distance of about 300 m, while tail may stretch out over several kilometers. crest 山顶; 羽毛饰; 鸡冠; The peak voltage may attain one or two million volts.峰值电压可以达到两百万伏。Wave fro

13、nt波前Tail波尾The wave also represents the point-to-point value of the current flowing in the line. For most aerial lines the ratio between surge voltage and surge current corresponds to a resistance of about 400. A surge voltage of 800 000 V at a given point is therefore accompanied by a local surge cu

14、rrent of 800 000/400=2000A. The wave also represents the point-to-point value of the current flowing in the line.雷电波也表示了线路上点到点的电流值the ratio between surge voltage and surge current corresponds to a resistance of about 400浪涌电压与浪涌电流的比值对应大约400As the wave travels along the line, the I2R and corona losses

15、 gradually cause it to flatten out, and the peak of the surge voltage decreases. corona 电晕As the wave travels along the line当雷电波沿着线路行进时the I2R and corona losses gradually cause it to flatten out焦耳定律中的I2R和电晕损失会使它的波形逐渐变平缓and the peak of the surge voltage decreases并且浪涌电压的峰值减少Should the wave encounter a

16、 line insulator, the latter will be briefly subjected to a violent overvoltage. The over-voltage period is equal to the time it takes for the wave to sweep past the insulator. Should the wave encounter a line insulator假如雷电波遇到线路绝缘子the latter will be briefly subjected to a violent overvoltage后者（线路绝缘子）

17、将会受到严重的过电压The voltage rises from its nominal value to several hundred kilovolts in about 1s, corresponding to the length of wavefront. If the insulator cannot withstand this overvoltage, it will flash over, and the resulting follow-through current will cause the circuit breakers to trip. The voltage

18、 rises from its nominal value to several hundred kilovolts in about 1s, corresponding to the length of wavefront.电压在大约1s内由额定值升高到几百千伏，这与波前的长度相对应。and the resulting follow-through current will cause the circuit breakers to trip.随后的穿越电流会使得断路器动作On the other hand, if the insulator does not fail, the wave

19、will continue to travel along the line until it eventually encounters a substation. It is here that the impulse wave can produce real havoc. if the insulator does not fail如果绝缘子没有出问题the wave will continue to travel along the line until it eventually encounters a substation雷电波将继续沿着线路前行直到最终遇到变电所impulse

20、 wave can produce real havoc雷电冲击波能造成真正的灾难The windings of transformers, synchronous condensers, reactors, etc., are seriously damaged when they flash over to ground. Expensive repairs and even more costly shut-downs are incurred while the apparatus is out of service. The windings of transformers变压器绕组

21、synchronous condensers同步调相机reactors 核反应堆;when they flash over to ground当它们对地闪络时shut-downs 关机; 关闭，倒闭; 停电，停业; 停播The overvoltage may also damage circuit breakers, switches, insulators, and relays, that make up a substation. To reduce the impulse voltage on station apparatus, lightning arresters must be

22、 installed on all incoming lines. The overvoltage may also damage circuit breakers, switches, insulators, and relays, that make up a substation.过电压会损坏断路器、隔离开关、绝缘子、继电器等构成变电所的设备。To reduce the impulse voltage on station apparatus为了减少变电所设备的冲击电压lightning arresters must be installed on all incoming lines避

23、雷器必须要安装在所有的进线上Lightning arresters are designed to withstand an impulse voltage, say 440 kV. In turn, the apparatus within the substation is designed to withstand an impulse voltage, say 550 kV, which is considerably higher than the arrester clipping voltage. Lightning arresters 避雷器are designed to wi

24、thstand an impulse voltage被设计能承受冲击电压say 440 kV从理论上讲为440 kVclipping voltage限幅电压Consequently, if a 1000 kV surge voltage enters a substation, the 400 kV station arrester diverts a substantial part of the surge energy to ground. The residual impulse wave that travels beyond the arrester then has a peak

25、 of only 400 kV. This impulse will not damage station apparatus built to withstand an impulse of 550 kV. Consequently相应的if a 1000 kV surge voltage enters a substation如果1000 kV 的冲击电压进入变电站the 400 kV station arrester diverts a substantial part of the surge energy to ground.这个400 kV 变电站的避雷器把大部分冲击能量转入大地T

26、he residual impulse wave 残余的雷电冲击波travels beyond the arrester 经过避雷器的（未入地部分）课堂练习：Protective DevicesThe devices generally used for overvoltages protection are given below: Spark Gap for overvoltage protection, insulation Co-ordination and Arcing Horn.A spark gap limits the overvoltage by sparkover. Hence the critical sparkover voltage is an index of the protection level. Every sparkover is accompanied by a power-follow current which could be interrupted by de-energization. This constitutes short circuit and currents cause electrodynamics stresses in apparatus. The sparko