远距离电能输送采用高压输送的原因.doc

Page2.The reasons of long-distance power transmission adopts high voltage transmission(远距离电能输送采用高压输送的原因) 1. English textLong-distance transmission power why want to adopt high transportation can be from the following several aspects that:Firstly,the electric power plants emit, need is used electric power transmission lines conveying out, because of transmission lines are resistance, and the transmission is longer, the more resistance. When an electric current passes through the transmission will produce hot, part of electric energy into internal energy and lost. By including joule law: Q = I2Rt knowledge, in transmission time certain circumstances, current heat generation and transmission of the current is proportional to the square, and transmission line resistance become direct ratio. Want to reduce power loss, one is to reduce the transmission line resistance, 2 it is to reduce the current transmission intensity. In transmission line resistance cannot change circumstances, take to reduce the flow of electric current method, it can obviously reduce electricity losses, if the current reduced to the original 1/2, loss of power is reduced to the original 1/4. According to P = UI, we can conclude that when power, voltage must rise, can reduce the current strength. Therefore, the actual conveying electricity is to adopt the method of hv transmission to reduce the current strength transmission, thus reduce transmission process electricity consumption. Therefore, high voltage grade lines to transmit power low voltage level line loss is small, the transmission distance long. In conveying certain power and transportation distance certain premise, the higher the voltage, current and smaller. This can bring as follows: (1) the benefits of the current line flows is small, can reduce line cross-sectional area, save nonferrous metals; (2) line of small current flows in a circuit, can reduce power loss and voltage loss.Secondly,electricity transmission, whether ac power or HVDC transmission, the general trend is increasingly high voltage level, its main reason is: 1.Lines corridor consideration. In a country with plenty more narrow country, land price high or by topography constraints, the factors will show delirious. Economical comparison shows: each raise a voltage grade, the utilization rate of electric power transmission corridor can improve 2 to 3 times. In addition to the stability of the consideration, the same voltage grade multiple transmission line total transmission ability is not the sum of every circuit transmission capacity, but transmission voltage level enhancement, transmission capacity will greatly improve. 2.Short-circuit current consideration. Transmission systems allow the shortcircuit current cap is by the system structure and breaker open circuit ability of the decision. By higher voltage shouldering the main transmission task, low voltage system short circuit current are not increase, and can satisfy the existing breaker open circuit ability. 3.And system operation reliability and economical efficiency consideration. Ultrahigh pressure and uhv transmission, give power equipment, especially the transformer, transformer, circuit breakers, lightning arrester and other manufacturing development, operation management brings a new task and goal. Power transmission areas, high pressure concept is constantly changing. In view of the actual research and operation needs, now usually divided into: 35kV voltage level below level, called distribution voltage, 110kV 220kV voltage grade, called high-pressure, 330kV 500kV voltage grade, called ehv, 1000kV class above voltage grade, called uhv.Key words:Long-distance power lost，High-voltage transmission2.中文翻译及分析远距离输送电能为什么要采用高压输送可从以下几个方面说明： 1、 电厂发出的电，需要用输电线路将电能输送出去，由于输电线路是有电阻的，且输电线越长，电阻越大。当电流通过输电线时就会产生热，一部分电能转化成内能而损失掉。 由焦耳定律：QI2Rt知，在输电时间一定的情况下，电流产生的热量与输电线中的电流的平方成正比，与输电线的电阻成正比。要想减小电能损耗，一是减小输电线的电阻，二是减小输电线中的电流强度。在输电线的电阻不能改变的情况下，采取减小电流的方法，可以明显地降低电能的损耗，如果把电流减小到原来的1/2，损失的电能就降为原来的1/4。 根据PUI可知，当电功率一定时，电压升高，可以减小电流强度.因此，实际输送电能时是采用高压输电的方法来减小输电线中的电流强度，从而减少输电过程中电能的损耗。因此，高电压等级线路传输电能较低电压等级线路损耗小、传输距离长。 在输送一定功率及输送距离一定的前提下，电压越高，电流越小。这样可以带来如下的好处：（ 1 ）线路中流过的电流小，可以减小线路截面积，节约有色金属；（ 2 ）线路中流过的电流小，可减小线路中的功率损失和电压损失。2、 电能的传输，无论交流输电还是直流输电，总的趋势是输电电压等级越来越高，其主要原因是： 1、线路走廊的考虑。在幅员较窄小的国家、地价很高或受地形限制时，此因素就显特出。经济性比较显示：每提高一个电压等级，走廊输送电能的利用率可提高2至3倍。此外出于对稳定性的考虑，同一电压等级多条输电线路总输电能力并非是各条线路输电能力的总和，但输电电压等级提高，输送容量会大大提高。 2、短路电流的考虑。输电系统允许的短路电流上限是由系统结构和断路器的开断的能力所决定的。由于更高电压担负主要输电任务，较低电压系统的短路电流则不会增加，并能满足已有断路器的开断能力。 3、系统运行可靠性和经济性的考虑。 超高压和特高压输电，给电力设备，特别是变压器、互感器、断路器、避雷器等制造研发、运行管理提出了新的课