电气毕业设计外文翻译

本科毕业设计

外文文献及译文

文献、资料题目：《Special English for Architectural Electric Engineering and Automation》

文献、资料来源：期刊（著作、网络等）

文献、资料发表（出版）日期：2006.4

院（部）：信息与电气工程学院学院

专业：电气工程与自动化

班级：电气093

姓名：孙德艺

学号：2009081102

指导教师：陈红艳

翻译日期：2013.6.30

外文文献一：

Transformer

One of the most valuable apparatus in electric power system is the transformer, for it enables us to utilize different voltage levels across the system for the most economical value. Generation of power at the synchronous machine level is normally at a relatively low voltage，which is most desirable economically．Stepping up of this generated voltage to high voltage，extra-high voltage or even to ultra-high voltage is done through power transformers to suit the power transmission requirement to minimize losses and increase the transmission capacity of the lines．This transmission voltage level is then stepped down in many stages for distribution and utilization purposes．

A transformer is a static device for transferring electric energy from one circuit to another electromagnetically，that is，by induction instead of by conduction．Its usual function is to transfer energy between circuits of different voltage．A transformer has a magnetic core on which there are two or more windings．These windings are insulated from each other and from ground．In autotransformers，however，the windings are connected together．The assembly of core and coils is normally insulated and cooled by immersion in mineral oil or other suitable liquid within an enclosing tank．Connection to the windings is by means of insulating bushings，usually through the cover.

The “ratio of transformation” is determined by the relative number of turns in each of he windings．This is known as the “turn ratio” and it is the ratio of the no-load voltages．When the unit is carrying load, the ratio of the actual voltages is slightly different because of the drop caused by the flow of 1oad current through the impedance of the transformer windings．At rated load, this drop is known as the "voltage regulation". The amount of voltage drop varies with the power factor of the output even when the kilovolt-amperes remain constant．

Practically all power transformers and many distribution transformers have taps in one or more windings for changing the turn ratio．Changing the ratio is desirable

for two reasons to compensate for varying voltage drop in the system and to assure that the transformer operates as nearly as possible at the correct core density．For the latter purpose, the taps should be in the winding subject to the voltage variation. De-energized tap changers are used when it is expected that the ratio will need to be changed only infrequently, because of load growth or some seasonal change．The desired tap is selected by means of a ratio adjuster(no load taps)．Load tap changer(LTC)is used when changes in ratio may be frequent or when it is undesirable to de-energize the transformer to change a tap．It seldom makes much difference to the user which winding or windings are tapped；therefore，the choice is usually made by the designer on the basis of cost and good design. Both winding current and voltage must be considered when applying LTC equipment．High voltage and high current applications require special considerations to arrive at an optimum location for the LTC equipment．Step down units usually have LTC in the low-voltage winding and de-energized taps in the high voltage winding．

When energy is to be transferred between two circuits of nearly the same voltage．The use of autotransformers affords cost savings over two-winding units．The nearer the voltages are to each other, the smaller will be the autotransformer per kilovolt-ampere of output，and the greater the savings．The simplicity of phasing out systems has increased its use．Most autotransformers are Y-connected，and it has been a standard American practice to add a low capacity, delta winding．This is frequently referred to as a “delta tertiary“．Its primary purpose has been to provide an internal path for the third harmonic currents (required for excitation)，thus reducing those currents on the power system．It also helps to stabilize the neutral and to ground the system better．In recent years，the use of shielded telephone cable has reduced the requirements for the delta tertiary. Because an autotransformer does not afford electrical separation between the two circuits, disturbances originating on one circuit can be communicated to the other．This difficulty is minimized by solidly grounding the neutral of the autotransformer. Solidly grounding the neutral，however, causes(among other things)current of short-circuit magnitude to flow through the delta-connected tertiary winding during ground faults on either system.

Autotransformers are not inherently self-protecting and, therefore，all windings must be examined for mechanical strength as applied to the system where they will be used . Tertiaries are normally 35％of the physical size of the largest winding of the autotransformer, unless otherwise specified by the user.

The bulk of a11 transformers，except for large extra-high voltage(EHV)and distribution units are three-phase units．In the early days of the industry，It was almost universal practice in the United States to use three single-phase units connected in a three-phase bank．Insulation clearances and shipping limitations for certain large EHV units now require this design．The distribution systems serve mainly single-phase loads in residential areas and are served from single-phase transformers．

中文译文一：

变压器

在电力系统中最有价值的一个装置是变压器,因为它使我们能够在系统中利用不同的电压水平获得最经济的价值。同步电机的发电电压水平通常是在一个相对较低的电压,这是最令人满意也是最经济的。把发电电压升高到高电压,超高压甚至超高电压是通过电源变压器实现的,这样可以适应电力传输要求,减少电压损失,提高线路的传输容量。在不同的阶段，我们可以根据配电和使用目的的要求把高电压通过变压器降到低电压。

一个变压器是一个静态装置，因为电能量从一个电路转移到另一个电路是通过电磁的形式实现的,也就是说,能量的转移是通过感应而不是通过传导。变压器通常的功能是传递不同电压等级电路之间的能量。变压器有一个磁芯，磁芯上有两个或两个以上的绕组，这些绕组相互之间是绝缘的并且与大地也是绝缘的。然而自藕变压器中的绕组是直接连在一起的的。磁芯和绕组的组装通常是在密闭容器内进行的并且浸没在矿物油或其他适当的液体中。线圈的连接是通过绝缘套管,通常穿过表面。

“变压比”是由每个绕组上线圈的相对匝数决定的。我们称为“匝数比”,这也是空载电压比。当变压器承载负荷时,实际电压的比例略有不同,因为当负载电流通过变压器时会因为绕组阻抗而使电压产生降落。在额定负载下,这种电压

降落被称为“电压调整”。电压降落的大小随输出的功率因数的变化而变化即使总的视在功率保持不变。

几乎所有的电力变压器和输电变压器在一个或多个线圈上都有改变变压器变比的开关。改变变比有两个令人满意的理由：补偿系统中变化的电压降落以及确保变压器尽可能的在正确的中心密度下操作。为了达到后边的目的，改变变比的开关通常放在变压器的绕组中并且受电压变化的控制。当变比不经常改变时，例如负荷的增加或者季节的变化，我们常用断距抽头转换开关。理想的开关是由比例调节器选择的。当变比变化比较频繁或者不希望断开变压器去改变抽头时，我们常用负载抽头转换开关(LTC)。当线圈或线圈组都是抽头时对使用者这几乎没有任何区别；因此,设计师通常根据成本和良好的设计来做出选择。应用LTC设备时绕组电流和电压都是必须考虑的。高电压和大电流在应用中需要特殊考虑才能达到负载抽头转换开关（LTC）设备的最佳使用条件。在降压变压器中，低压绕组通常用LTC（负载抽头转换开关），高压绕组通常用断距抽头转换开关。

当两个具有相同的电压的电路之间转移能量时,使用自耦变压器要比使用两个绕组单元更能够节约成本。两个电路的电压越接近,自耦变压器输出的每千伏安越小,也就越节约成本。一些简单落后的系统往往常用它。很多自耦变压器是星形连接,这已经成为一个标准，但美国人尝试采用低容量三角形连接的自耦变压器。这是经常被称为是一个“三角洲三级“牵引,主要目的是为三次谐波(用来激发)提供一个内部路径,从而减少在电力系统的谐波。这也有助于稳定中性点并且使接地系统更好的工作。在最近几年,屏蔽电话电缆的使用已经降低了对三角洲三级的要求。？？

因为一个自耦变压器不负担两个电路之间的电气隔离, 来源于一个电路的干扰可以传达到另一个电路。这一困难可以通过将自耦变压器的中性点直接接地来解决。然而,中性点直接接地,在系统发生接地故障时会(在其他事物之中)引起短路电流流过三角接法的第三相绕组。第三绕组的物理尺寸通常为自耦变压器最大的绕组的35%,除非用户另有指定。自耦变压器就不具有自我保护的功能,因此, 所有的绕组在使用之前都必须经过机械强度检查以确定是否适用于该系统。

？？除了大型超高压(超高压)和配电设备，大部分变压器都是三相的。在美国早期的工业中, 把三个单相单位连接成一个三相的组合设备是一个非常普遍的经

验。某些大型超高压单位的绝缘间隙和运输限制现在就需要这个设计。配电系统主要服务于居民区的单相负载并且电能是引自单相变压器。

外文文献二：

Selection and Cooling of Power Transformer The selection of the transformer can have a major impact on the cost a substation，since the transformer represents the major cost item．Nameplate rating is only a guide to transformer application，and should only be used as a first step in the selection process. The transformer is available as a self-cooled unit，or it can be purchased with additional steps of forced cooling that use fan or fans and oil pumps．Transformer ratings can be increased from 25％to 66％by the addition of fans and pumps．The nameplate rating is based on a continuous load producing a 55℃to 65℃conductor temperature rise over ambient. Since many transformers do not carry continuous loads，advantage can be gained from the thermal time lag to carry higher peak loads without exceeding the temperature limits .Transformer ratings are based on the assumption that only an extremely slow deterioration of insulation will take place with normal operation．A substantial increase in rating can be achieved by accelerating the loss of insulation life．This increase in rating might approach 200％for an hour or two, and approximately 120％for 24 hours．For substations that are designed to carry full load under the outage of any one transformer, a high emergency rating for a 24-hour period (e.g. until the failed unit can be replaced) could mean the selection of smaller transformers and a substantial saving in substation cost．The selection of the transformer should involve a careful evaluation of a number of other factors：

(1)Impedances should be selected considering their effect on short-circuit duties and low-side breaker ratings both for initial and future station developments．In addition，impedance is important to achieve a proper load division in the parallel operation of transformers.．

(2)No load tap ranges should be selected to provide an adequate low-side bus voltage.

(3)If the high-side or low-side voltages vary over a wide range during the load cycle, it may be necessary to provide bus regulation．The actual regulation can be calculated using the system and load characteristics．If regulating equipment is needed，it may be desirable to provide it in the transformer by using load tap changer(LTC) equipment. If the need for bus regulation is not presently evident, but may be required in the future, it may be economical to leave space in the station for future regulators, and buy transformers without LTC equipment.

A great many transformers, including all the large ones and all the high voltage ones are immersed in mineral oil which serves the double purpose of cooling and insulating the windings. Small transformers have enough tank surface to radiate a11 the heat caused by their losses without exceeding the permissible temperature rise．As size increases，the losses increase faster than the tank surface which soon becomes inadequate．V arious methods have been developed to get the heat out of the tank more effectively．Large power transformer being built today are commonly of the forced-oil-cooled type．In this design the oil is pumped both through the external cooling devices(air or water heat-exchangers)and through internal channels that are located nearest the points where the heat is generated．Thus the transfer of heat to and from the oil is far more effective than in the plain self-cooled or fan-cooled unit where the oil is allowed to circulate by convection. When oil-to-air heat exchanger(a group fans on each radiator)is used，this cooling type is designated as type of FOA．While oil-to-water heat exchanger is used，it is called FOW．

For applications where any liquid，even a nonflammable one，is objectionable，the dry-type transformer is used．The ventilated dry-type unit is cooled by a continuous natural draft of air and consequently is not suitable for locations where the air is wet or dirty. For these locations a completely enclosed unit，the sealed dry-type，is available，having a core-and-coil in a tank that is sealed and filled with an insulating gas. Dry-type transformers are completely nonflammable，using organic material such as epoxy resin.

中文译文二：

电力变压器的选择和冷却

变压器的选择对变电所的建造成本具有重大影响,因为变压器是主要的成本项目。铭牌定额只是变压器应用的指南,它只应该用作变压器选择过程的第一步。变压器可以是自冷式单位,也可以购买额外的冷却装置,如强制冷却风机或机组和柴油泵。根据额外的冷却机组和柴油泵，变压器评级可以从25%增加到66%。铭牌评级是基于连续负荷产生超过环境55℃到65℃导体温升而评定的。？？？因为很多变压器不带连续负载,优势可以获得从热滞后时间进行更高的高峰负荷而不超过温度限制。变压器的评级是基于假设：正常操作下的绝缘老化只是一个极其缓慢的过程。通过加速绝缘老化的进程可以大幅度的提高评定等级。在一两个小时左右评级可能增长接近200%,而在在二十四小时左右评级则增长大约120%。因为变电站的设计要保证在任何一个变压器断电的情况下都要满足全负荷运行，为24变电站设计将满载在停机的任何一个变压器,因此在二十四小时内的较高的紧急评级(例如直到失败的单位可以更换)可能意味着选择较小的变压器和节约大量的变电所成本。

变压器的选择应该涉及对其他影响因素的审慎评估:

(1)阻抗应该被选择的考虑到他们对短路职责和下部断路器评级的影响对初始和未来空间站发展。此外,阻抗在并行变压器的操作中获得一个合适的负载也是十分重要的.

(2)无载分接范围应该选择提供一个足够的下部总线电压。

(3)如果高压侧或低压侧电压在负载周期内变化很大的话,可能有必要提供总线监管。通过系统和负载特性实际监管和控制是可以被计算和描绘的。如果调节设备是必要的,在变压器内使用负载抽头转换开关(LTC)设备来提供监管是可取的。如果需要总线监管目前是不需要的,但可能在未来需要的,那么在变电站预留未来安装设备的空间并且购买没有LTC设备的变压器是十分经济的。

许多变压器,包括所有的大体积的和所有的高电压的变压器都是沉浸在矿物油,矿物油有双重目的：冷却和绝缘绕组。小变压器有足够的容器表面辐射a11热引起的损失而不超过容许温度上升范围。随着体积的增加,损失增加的速度会加快，这时容器表面会变得不适宜。很多的方法已经被改进以使的容器的散热更有效。今天一般建造的大型电力变压器都是强制循环油冷却类型的。在这个设计

中矿物油通过油泵不仅流进外部冷却设备(空气或水热交换器)，而且流过内部最靠近热源的凹槽。因此通过矿物油对热量进行转移的方式要比一般的自冷装置和风冷装置要有效的多,因为油是允许通过对流循环的。当油空气热交换器(在每个散热器有一组风机)被使用时,这种冷却类型被指定为FOA。当油水热交换器被使用时，则被称为FOW。

因为无论变压器是采用何种液体都是不受欢迎的，即使这种液体不易燃，所以干式变压器得到普遍的应用。通风式的干式变压器通常是通过自然风来使变压器冷却的，所以这种变压器不适于潮湿和恶劣的环境。如果铁芯和线圈是在一个充满绝缘气体的封闭装置中则干式变压器在潮湿恶劣环境中是完全可以正常运行的的。干式变压器是完全不燃烧的，因为它使用了有机材料如环氧树脂。

外文文献三：

Circuit Breaks

Within a few years of the introduction of the fuse，the growing electrical industry startedlooking for an alternative method of providing protection for electric circuits．They wanted a device that would not be destroyed by its operation，that could simply be reset to restore power, and that could also be used as a means of switching for the circuit．Out of this development work came the circuit breaker．which is an electromechanical device．The circuit breaker is defined as a device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined over-current without injure to itself when properly applied within its rating.

As with other equipment，circuit breakers are divided into those rated for 1 000 volts and less and those rated for more than 1000 volts．Low-voltage circuit breakers were also divided into two distinct categories，molded-case and power types．However，in the past few years the distinction between these two types has become less clea-cut as a new type of encased breaker are universally operated in air, so it is not necessary to designate them as air circuit breakers as this understood．Medium and high—voltage breakers，on the other hand，use mediums other than air in which to open the circuit and therefore must be designated as being

air, gas，and so on．

Apart from having different voltage and continuous current ratings．breakers have widely different interrupting ratings，response characteristics，and methods of operation．The proper application of circuit breakers requires a good knowledge of all the characteristics and options available for each type．

The simplest circuit—opening device is the manually operated knife switch．This switch has the basic parts required of any circuit—opening device：a fixed contact, a moving，an operating handle，and a base—plate or flame．However as anyone who has opened a knife switch under load has witnessed，there is a luminous discharge drawn between the separating contacts of the switch．This discharge is called an arc，and it consists of a stream of positive and negative ions. The current flowing in a circuit cannot be instantaneously interrupted．As a result，the arc continues until the switch contacts have separated far enough to finally extinguish the arc．

The arc can make the opening of the switch very unsafe and unreliable when interrupting a circuit breaker must provide a safer and more reliable interrupting action. The following are the means by witch low—voltage circuit breakers can be made to safely interrupt large fault currents with a minimum of contact damage．1．Fast speed of operation．The duration and severity of an arc depends in part on the speed

with witch the contacts can be separated，therefore powerful spring are used to rapidly force the

contacts open．These springs are compressed (charged)during the closing operation．The breaker contacts are then mechanically held closed and are released by a separate trip mechanism．An

operator can initiate the opening of the breaker but has no control over the speed with which the

contacts separate．

2．Use of arcing contacts．The arc burn can cause pitting，which eventually affects the ability

of the contacts to carry the load current when closed．To offset this, two parallel sets of contacts are used for each pole of the breaker，a main current carrying set and an auxiliary or arcing set．When the breaker is tripped open, the main contacts separate first，transferring the current flow to the arcing contacts．The arcing contacts then separate a split second late，drawing the arc between them and leaving the main contacts free of any arcing．This allows the surfaces of the main current carrying contacts to be made of high—conductivity metal such as silver，the surfaces of the arcing contacts are then made of a tougher alloy better able to withstand the effects of arcing．

3．Use of arc chutes Parallel plates enclosed in the form of a chute are mounted directly above the arcing contacts．As the arcing contacts separate, the resulting are creates a strong magnetic field that forces the arc upward into the plates．The arc stream is then broken into a series of small arcs，which are quickly cooled，deionized，and extinguished．The ionized gases created by the are stream must be deionized before they are expelled from the arc chute；otherwise，secondary arcing could occur between the line side terminals of the breaker, which are still energized．

中文译文三：

断路器

在引入保险丝的几年内,越来越多的的电力企业开始寻找一个可替代的保护电气电路的方法。他们想要一个装置,不会因为它的操作而被破坏,可能只是恢复供电,也可以用来作为一种电路转换的手段。断路器，作为一种机电设备，就是这种发展的成果。断路器被定义为这样的一种装置：可以通过非自动的方式闭合或断开电路，也可以在正确应用其评级并且自身不被破坏的情况下根据电路中的过电流自动的断开电路。

与其它设备类似,断路器分为额定1 000伏特,少许被认为超过1000伏低。压断路器也分为两个不同的类别,塑壳和万能式。然而,在过去的几年中这两个类型之间的区别已经变得不那么明确，因为一种新型的微型断路器是通常操作在空气的,所以不需要将它视为空气断路器。另一方面,中压和高压断路器使用空气外的其他的介质断开电路,因此必须指被整定为空气、瓦斯等其他断路器一样。

与其它设备类似,断路器分为额定1 000伏特,少许被认为超过1000伏低。压断路器也分为两个不同的类别,塑壳和万能式。然而,在过去的几年中这两个类型之间的区别已经变得不那么明确，因为一种新型的微型断路器是通常操作在空气的,所以不需要将它视为空气断路器。另一方面,中压和高压断路器使用空气外的其他的介质断开电路,因此必须指被整定为空气、瓦斯等其他断路器一样。除了有不同的电压和不间断电流额定值，断路器有广泛不同的分断能力、响应特性和运行方式，正确的应用断路器需要深入理解断路器的特点并且对断路器的设置要通用。

电路中的电流不能在瞬间打断。因此,电弧会持续存在直到开关触头分离的足够远,直到最终熄灭电弧。最简单的断路设备是手动刀开关。这个开关有任何短路设备都需要的基本组件:一个固定的触头,一个移动的触头,一个操作手柄和一个冷却基板。然而，如果在带负载的情况下打开刀开关,在开关的分断触点之间会有发光放电。这放电称为电弧弧,它由大量的的正负离子组成。电路中的电流不能在瞬间打断。因此,电弧会持续存在直到开关触头分离的足够远,直到最终熄灭电弧。

电弧会使开关的开断变得很不安全,不可靠，因此开断一个断路器必须保证一个更安全、更可靠的开断动作。

以下就是低压断路器以最小的损失安全断开故障电流的方法。

1.迅速操作。电弧的持续时间和严重程度在某种程度上取决于触点断开的速度。因此我们用强大的弹簧来迅速迫使触点断开。在合闸操作时这些弹簧是被压缩的(带电)。开关触点由一个单独的跳闸装置来控制它的接触和断开。一个操作员可以控制断开断路器但无法控制触点断开的速度。

2.使用灭弧装置。电弧燃烧会导致点蚀,最终影响触点带负载电流运行的能力。为了消除这种缺陷, 断路器的每个极都用两组相同的触点,主要载流触点和一个辅助触点或灭弧装置。当断路器跳闸断开时，主触点首先分开并且将当前电流转移到灭弧触点。灭弧触点然后在一瞬间断开,吸引了他们之间的电弧而使主触点不受电弧影响。这就允许主触点的表面可以用超导金属来制作例如银，灭弧触点的表面则是用可以很好灭弧的合金制作的。

3.使用灭弧隔板封。灭弧触点上面直接安插着以斜槽形式排列的平行隔板,

在灭弧触点分开时,会产生一个强磁场使得电弧向上到达隔板。弧流然后分解成一系列的小弧线,迅速冷却,去离子,最后熄灭。电离气体流在被从灭弧隔板中赶出之前必须背去离子化；否则,在断路器的线路终端之间会发声二次放电，而它仍然是带电的。