电力专业英语
1A
Although our concern in this book is with the electrical aspects of power systems, it is important to know what basic energy sources can be used to produce electrical energy on a large scale. Electrical energy sources can be broken down into two broad categories，thermal and non-thermal. A brief discussion of varying alternatives follows below.
.尽管本书所耍讨论的是关电力系统电能牛产的各个力面，但了解一下都宥哪些基本能源可以用作大规模发电，也是十分重要的。从广义上讲.我们可以把电能源分为两类：热能源和非热能源。下面简单介绍几种重要的能源。
Thermal Sources
Coal. Substantial reserves and the development of the necessary technology mean that coal is and will continue to be a major energy source. Presently coal represents about 45% of total electrical energy sources.
热能源
煤。由于煤的储量丰富和所需的采煤技术高度发展，不但现在，而且在将来，煤仍然 是主要的能源。目前，用煤发电占电能源总量的45%。
Oil and Natural Gas. In the 1950s and 1960s there was a trend toward greater utilization of these fuels because of their superior combustion properties. However, the cost，scarcity, and competition from petroleum products indicate that while these fuels will remain important for electrical energy production, their percentage share of total energy supply will de?crease.
石油和天然气。在20世纪50年代和60年代，有一种大量利用这两种燃料作为电能源 的趋势，因为这两种物质有着较好的燃烧性能。然而，其高额费用、储量的短缺及石油产品 的竞争等诸多因素表明，尽管这两种燃料在电能生产中仍然占有重要地位，但在总的电能源 中所占的比例将会下降。
Nuclear Fission from Uranium. Since the 1950s fission reactors have been used commer?cially for the production of electrical power. Uranium resources in the U. S. are slightly less than oil and gas reserves. Serious problems relating to environmental impact have accentuated social concern and some legal and regulatory constraints have been placed upon the devel?opment of this resource. A prudent growth in the comparative importance of this source is expected，along with a legitimate and proper concern for the environment.
铀的核裂变。从20世纪50年代以来，已经建起一些商业性的核裂变反应堆来发电。 在美国，铀的储量仅比石油和天然气的储量稍少一点。应用此能源对环境所产生的严重 影响已经引起了社会的关注，并在法律上制定了一些规章来限制此能源的发展。可以预 计，如果依照法律并对环境影响加以适当的注意，人们对此能源会越来越重视。
Solar. It is possible to collect solar energy directly and concentrate it on steam boilers. The major problems are the diffuse nature，which requires large areas for collection, and the unreli
ability of atmospheric conditions. At present there are no coinmercial installations. This source is particularly attractive as no “fuel” is required and because of its non-polluting characteristics.
太阳能。可以直接收集太阳能并将其集中到锅炉里生产热能。存在的问题是：由于它 具有扩散性，因而需占用大量的土地来建立收集器，同时，气候条件也影响了它的可靠性。 目前，还没有这样的商业设施。由于利用太阳能不需要“燃料”、没有污染，它尤其引人注
Nuclear Fusion. Certain types of nuclear reaction are possible，where certain light nucle?ar particles can be combined，or fused, into heavier particles. Such reactions produce pure energy. The most attractive feature here is that common elements such as hydrogen isotopes can be used as fuel，making this source essentially inexhaustible. The difficulty is that a sus?tained fusion reaction requires production of extremely high temperatures and particle concentrations for a sufficiently long time. The technical problems associated with this are formidable and most experts will not predict commercial installation until well into the next century.
核聚变。人们知道，在某种核反应中，轻核粒子可与重核粒子相结合，即溶于其中。 这种反应生成的最终产物是一种纯能源。令人感兴趣的是，像氢同位素这样普通的元素可以 作为燃料，成为一种永不枯竭的能源#难题是，维持持久的核聚变反应需要极高的温度和足 够的时间，以利于粒子的聚集。同时，相应的一些技术问题也是难以克服的。多数专家预 言，这样的工业设施到下个世纪才能出现。
Geothermal. Heat from the earth's interior and subsurface water combine to produce natural steam which can be used for electricity produGtion, Total reserves are estimated at up to about half of the total gas and oil reserves. Expectations are that this resource will con?tinue to be developed，but that it will only make a minor contribution to the total energy supply.
地热。地壳内部的热与地下水相结合生成天然蒸汽可用来发电。据估计，蒸汽的总储 量是石油和天然气总储量的1/2。可以预料，这种资源将会不断地开发出来，但它只占总能 源的一小部分。
Biomass. Synthetic gas can be produced from organic material grown expressly for this purpose. Cerrently the amount of electrical energy produced from this source is negligible， and is not Expected to be Very significknt in the future.
生物。可以从专门为生产能源而培育的有机材料中获得合成气体。目前，用此能源所 生产的电量是微不足道的&预计将来的产量也不会很大。
Garble and Sewage. There are combustible components in garbage that can be used as fuel ； these components are separated from noncombustible items and mixed with coal. Sewer gasses are also combustible
In certain situations utilization of these fuels may prove to be economical； however, such installations should be viewed as supplementary, arid would contribute only a small fraction of the total energy supply.
垃圾和污水。将垃圾中的可燃成分从不可燃物质中分离出来并与煤混合可以作为燃料。 阴沟中的沼气也是可燃的。:虽然利用这些燃料是很经济的，但需要增加额外的设备。它也仅 占总能源的一小部分。
Nonthermal Sources
Hydro. Hydroelectric power has been an economical and pollution free course of energy. It currently stands at about 12% of the total energy supply. It has the advantage of being im?mediately (within seconds at least) available, whereas thermal sources meet demand at a much slower rate. Hydroelectric sources are constrained by navigational requirements and actual or predicted rainfall.
非热能源
水力。有史以来，水力发电就是一种既节约又无污染的能源。目前，水电能源占总能 源供给的12%。此能源的益处在于可以立即利用(几秒钟内），而利用热能源达到要求的程 度则慢得多。水力能源的缺欠是受到水上航运要求和实际或预计降雨量的限制。
Tidal. There are a few sites around the world where it proves economical to convert thfe change in potential energy caused by tide levels into an electrical form. The percentage bf to?tal energy supply output is quite small，and expected to remain so.
潮汐。现在世界上一些电站已将潮水落差的潜能变为电能，这样发电是很经济的。利 用潮汐作能源只占总能源的很小一部分，预计将来也会保持相同的比例。
Wind. Wind can be used to drive turbines that in turn drive electricity generators, be?cause wind is intermittent，such a system must include energy storage devices，such as bat?teries, or supply loads that are tolerant of unpredictable source interruptions. As isolated e- lectric power supplies, such systems are now commercially available in sizes up to about 50 kW. Research on much larger units is currently under way； presently, wind energy is negli?gible as a fraction of the total energy output.
风。可以用风驱动叶轮转动，叶轮再带动发电机发电。由于风具有周期性，这样的系 统必须包括能源储存设备，诸如蓄电池、可承受意外能源中断的供电负载等。作为独立的发 电设施，这种系统的最大发电量可达到50kW。更大规模的设施正在研制之中。目前，风能 的比例在总能源中是微不足到的》
Wave. There have been several experimental machines designed to convert kinetic wave energyinto electricity. None as of now appears to have been feasible for large-scale economic electrical energyproduction.
波。已经设计出几种实验设备将波能转变为电能。到目前为止，还没有哪种波能实验 设备可以经济地用于大规模的电能生产上。
2A
Generators change mechanical energy into electrical energy. Motors change electrical energy into mechanical energy.
发电机把机械能转换为电能。电动机将电能转换为机械能。
Generators and motors are a lot alike. They are made in the same general way. Further, they both depend on the same electromagnetic principles for their operation.
发电机和电动机有许多相似之处。它们的制定方法基本相同。此外，它们运行的电磁原 理相同。
The first principle is called GENERATOR ACTION. It is also called INDUCTION. Voltage can be induced into a wire that is in a magnetic field. This happens when the magnetic flux is cut by the wire. In some cases，the wire moves. In other cases，the field moves. In still others，both are moving，but at different speeds. It takes mechanical energy to cause the motion. This motion causes electricity to be generated.
第一个原理称为发电机作用，亦称为感应，即磁场中的线圈切割磁力线时线圈中产生感 应电压。在某些情况下，线圈运动，在另一些情况下磁场运动。有时两者都运动，但运动速 度各异。机械能产生运动，运动产生电。
The second principle is called MOTOR ACTION. This is simply the mechanical forces between magnets. When two magnets (or electromagnets) approach each other，one will be either pulled toward or pushed away from the other.
第二个原理称为电动机作用。简单来说就是两块磁铁间的机械力作用。当两块磁铁(或 电磁铁)相互靠近时，一块将吸引或排斥另一块。
Some motors use one permanent magnet and one electromagnet. Others use two electromagnets. Either way, electrical energy creates at least one of the magnetic fields. Then, the forces between the two magnetic fields cause the motion.
有的电动机使用一块永磁铁和一块电磁铁。有的电动机则使用两块电磁铁。无论哪种方 式，电能至少产生一个磁场。然后，两个磁场之间力的作用产生运动。
CONSTRUCTION
Each type of motor and generator is built to do its own special job. All of them have two main parts. One part is called the stator. The stator is stationary； it does not move. The other part, the rotor，is mounted on bearings so it can rotate. The rotor shaft sticks out beyond the housing. For a generator，a prime mover is coupled to this shaft. For a motor, the rotor shaft is coupled to a mechanical load.
结构
人们制造的各种类型的电动机和发电机都有其特定的功能。它们都由两大部分构成：一 部分称为定子。定子是静止的，它不产生运动。另一部分称为转子，它安装在轴承上，可以 转动。转轴伸出机壳外。对于发电机来说，转轴联接原动机。?对于电动机而言，转轴联接机 械负荷。
GENERATORS
The input power to a generator is mechanical power. If the output is a direct current, the generator is called a DC GENE
RATOR. If the output is an alternating current, it is known as an ALTERNATOR. Prime movers apply mechanical power to turn the rotor. Water wheels，windmills，, steam and hydroturbines, diesel and jet engines，and hand cranks are all examples of prime movers.
发电机
输入发电机的是机械功率。若发电机输出直流电，则称其为直流发电机。若输出交流 电，则称其为交流发电原动机，提供机械功率驱动转子。水车(轮）、风车、汽轮机和水轮 机、柴油机和喷气发动机、手摇曲柄等都是原动机。
To make a rotor turn.the prime mover applies TORQUE. Torque simply means turning force. For example，when you tighten a nut on a bolt，you apply torque with a wrench.
原动机提供转矩使转子转动。转矩就是转动力。例如：当你把螺栓上的螺帽拧紧时，你 就在扳手上施加了转矩。
TORQUE
The amount of torque applied to a shaft is proportional to two things ：
1. The amount of force applied.
2. The distance the force is applied away from the center of the shaft
转矩
施加到转轴上的转矩与下述两因素成正比：
1.所施加的力的大小；
2.施加的力离转轴中心的距离。
The torque，or turning force，is directly proportional to both force and distance. The ,ore force you apply，the greater the torque. Also，the longer the crank handle，the greater le torque. The equation is：
Torque (T) = force (F) X distance (d)
In conventional units of measurement, force is expressed in pounds. The abbreviation is ?f? for POUNDS FORCE. One lbf is the amount of force that would be applied by the eight of one pound. Distance is measured in feet (ft. ). Torque is expressed in pound 丨rcefeet (lbf-ft. ). Torque may also be expressed in ounce force-inches (ozf-in.).
转矩或转动力，与力和力臂成正比。力越太，转矩越大。手柄越长转矩越大。其公式如下：
丁(转矩)=F(力）X炎距离）
在常用的计量单位中，力用磅表示。磅力缩写为lbf。一个lbf表示施加一磅重量的力。 距离用英尺表示。转矩表示为磅力一英尺(lbf ? ft),转矩也可用盎司一英寸(ozf ? in)表示。
MOTORS
The power input to a motor is electrical. Voltage is applied to a motor’s terminals resul-ig in a current. The power output of a motor is mechanical. This power is transmitted by te rotor shaft as a torque. This torque tends to rotate a load,such as a fan or pump.
电动机
输人电动机的是电能。施加到电动机端子上的电压产生电流。电动机输出机械功
率。机械功率通过转轴以转矩形式输出。转矩可以驱动负荷转动，诸如一台风扇或一 台栗
To drive a load at a particular speed, you need a certain amount of torque. If the motor? output is large enough, the load will turn. If the motor’s torque output is too small, however，it will not drive the load. Torque requirement is one of the most
important things to insider in selecting a motor.
需要一定的转矩才能驱动负荷以特定的速度转动。若电动机输出的转矩足够大，负荷将 转动。若电动机输出的转矩太小，则不能驱动负荷。在选择电动机时所考虑的最重要的一个 指标就是转矩要求。
As a motor drives a load，mechanical power is drawn from the motor. The motor, in irn, draws electrical power from the source at the same rate.
电动机驱动负荷时，电动机输出机械功率。而电动机又从电源得到等量的电功率。
2B
When you turn on a light switch, the room gets brighter. An electric heater makes you warm. A fan or air conditioner cools you. We have become so used to electrical devices like these that we seldom think about the electricity that makes them work. The power company, however, thinks about it 24 hours a day. Their equipment must be on the job every nute, producing and delivering electricity. Fig. 2-1 shows the generation, transmission, distribution of electricity by a utility.
当你打开电灯时，房间会变亮。电热器可以使你暖和。电扇或空调使你感到凉爽。我们 经常使用这些电器却很少想到是电使它们工作的。然而电力公司却一天24小时都注意着电。 它们的设备必须连续工作，生产和输送电能。图2-1表示了电力公司的发电、输电和配电三部分。
Unlike other products, electricity cannot be stored. The utility must generate it only when it is needed. When you turn on a light, the electricity it uses was produced the instant before. STORAGE BATTERIES，like those installed in cars，do not store electricity. They merely convert chemical energy to electrical energy and vise versa.
与其他产品不同的是，电能不能够储存。电厂只有在需要电的时候发电。当你打开电灯 时，电灯消耗的电能是刚刚生产出来的。像那些安装在汽车上的蓄电池，它们并不能储存电 能，它们仅仅是将化学能转化为电能，反之亦然。
NATURE OF ELECTRICITY
Electrical energy is somewhat like KINETIC ENERGY，which is the energy of motion.
电能与运动的能量即动能有些相似。
This may seem strange at first. After all, you can see a ball moving, but you cannot see electricity moving through a wire. Still, electricity is the result of motion. The reason we cannot see anything move in a wire is that the particles, called ELECTRONS, are so tiny. In fact, they cannot even be seen with the most powerful microscope.
一开始你也许觉得很奇怪。毕竟，你能看到小球运动，但你却看不到导线中电荷的运 动，虽然电能由电荷运动而产生。我们看不到导线中有任何东西运动的原因，是因为电子的 粒子太小。事实上，甚至在高倍显微镜下也看不到电子。
电子理论
ELECTRON THEORY
Benjamin Franklin，a scientist as well as a statesman, made many electrical d
iscoveries. He thought there were two kinds of ELECTRICAL FLUID，as he called electricity. The names Franklin suggested，POSITIVE and NEGATIVE, are still in use today. We speak of positive electrical charges and negative electrical charges. The behavior of electricity was still not understood，however, until the early 1900s. It was then that scientists came up with the ELECTRON THEORY.
本杰明?富兰克林是位政治家，同时也是一位科学家，在电领域有许多发现。他认为有两 种电荷流体，并将其命名为正电和负电。直到今天，我们仍在使用该名词，称为正电荷和负电 荷。然而直到20世纪初，人们才认识到电荷特性。随后，科学家提出了电子理论。
According to the electron theory, all matter is made up of ATOMS. The atoms，in turn, have a centre，around which ELECRTRONS move in orbits (circular paths). As shown in Fig. 2-2，it is a little like our solar system where planets orbit around the sua In the center are PROTONS， which contain positive electrical charges. The centre，called the nucleus，also contains NEUTRONS, which have no charge. The orbiting electrons contain negative electrical charges. Atoms normally contain the same number of electrons as protons.
按照电子理论，一切物质都由原子组成。而原子有一个核，所有的电子在一定的轨道上 绕核运动(环行)。如图2-2所示，这与太阳系中行星围绕太阳旋转有些相似。原子中心即原 子_核有带正电荷的质子，还包含中子，中子不带电。绕核旋转的电子带负电荷。原子通常含 有相等数量的质子和电子。
THE FLOW OF ELECTRICITY
Electrical pressure is built up in what is called a POWER SOURCE. The power source uses chemical energy ( or some other form of energy) to force electrons from one side (terminal) to the other. Then，electricity can flow from the terminal that has extra electrons to the terminal that has fewer electrons.
电荷流动
电荷压力产生于所谓的电源。电源利用化学能(或其他形式的能)迫使电子从一侧(极)移 到另一侧(极）。然后，电荷会从电子多余的极流向电子较少的极。
This flow takes place outside the source if there is an electrical path (conductor) between them. This is illustrated in Fig. 2-3. Negative electrical charges rush through the conductor, trying to balance out the positive charges. Electrons, themselves，move along the conductor rather slowly. Negative charges，however，move extremely fast-approximately 300，000，000 metres per second (186，411 miles per second).
电源两极间存在一条导电的电路时，将发生电荷流动，如图.2-3所示。负电荷穿过导 体，试图中和正电荷。电子本身在导体内运动相当慢，然而负电荷运动极快《约30万公 里/秒(186 411英里/秒）。
electricity. The displacement of electrons inside a power source produces electrical pressure,
or voltage.
Voltage is measured in volts，named for Alessandro Volta，inventor of the electrical storage battery. The symbol for voltage is either E (for electromotive force) or V (for voltage). When we talk about the voltage of a power source，we are really referring to the a-mount of energy necessary to move electrons from their normal positions toward one of the terminals.
电压用伏特来表示，是根据蓄电池的发明者阿莱斯德诺?伏特的名字命名的。电压符号 为￡(用于电动势)或V(用于电压)。我们所说的如电源电压实际上是指使电子从其正常位置 移动到另一极所必需的能量。
3A
Consider the situation shown in Fig. 3-1. The rate of electrical energy flow (power) from network A to network B is
考虑图3-1所示的情况。从网络A送到网络B的功率为
Lowercase letters are used to indicate instantaneous values，that is，that p，v, and i may vary with time. High power levels require high voltage and current values. For a given value of current, higher power flows may be obtained by increasing the voltage，and vice versa. Unfortunately, the existing technology sets practical upper limits on allowable currents and voltages.
小写字母表示瞬时值，即声，t;和i会随时间而变化。传输大容量功率需要高电压和大 电流。对于一给定电流值，升高电压可以提高传输容量，反之亦然。不幸的是，现有技术使 额定电流和额定电压存在上限。'
What are the limiting factors for current? We fabricate power conductors using materials with high conductivity, appropriate mechanical characteristics，and that are economical： aluminum is the most common choice，with copper used for some applications. The current-carrying capacity of a conductor is related to its maximum allowable current density and its cross-sectional area：
限制电流的因素是什么？我们用具有高导电性和适当机械性能的材料制造导体，从经济 方面考虑：通常选用铝，有时也选用铜。导体传导电流的大小与其最大允许电流密度和截面 积有关：
I = T A
The maximum current density is determined by the maximum conductor temperature that will not damage the conductor or its insulation system.
最大电流密度(J_)取决于不损坏导体及其绝缘系统所允许的最大导体温度。
What are the limiting factors on voltage? The fundamental consideration is to provide electrical isolation ( or insulation ) between adjacent parts that can conduct current-that is，to confine current to the paths through which it was intended to flow. When the voltage exceeds the breakdown strength for a given insulation system, undesirable conduction paths will be created and the system will be either temporarily or permanently disabled. Fluid insulation tends to be “self-healing” ( the system will recover from a breakdown if it is de-energized for a short time and then re-energized)，w
hereas solid insulation is permanently damaged by a breakdown.
限制电压的因素是什么？基本考虑是在可以传导电流的相邻部件间提供电气隔离？（或 绝缘)即：使电流在规定的路径上流通。当电压超过所给绝缘系统的击穿电压值时，电流将 通过不希望导通的路径使系统暂时或永久性损坏。液体绝缘物能“自恢复”(如果短时去激励 后又重激励，系统会由击穿状态恢复到绝缘状态），而固体绝缘物击穿后是永久性损坏。
The meaning of “ground” is important ； we quote from the IEEE Standard Dictionary of Electrical and Electronic Terms：
ground ( earth ) {electric system). A conducting connection, whether intentional or accidental, by which an electric circuit or equipment is connected to the earth, or to some conducting body of relatively large extent that serves in place of the earth.Note： It is used for establishing and maintaining the potential of the earth ( or of the conducting body ) or approximately that potential, on conductors connected to it，and for conducting ground current to and from the earth (or the conducting body).
“接地”的意义是重要的；从IEEE电气和电子标准术语词典中可得到解释：
接地(电力系统)是一种导体联接形式，：导体无论是有意或无意通过电路或设备连接到地 上，或连接到可作为地用途的相当大的导体上。说明：接地用于建立或维持地的电位，（或 导体电位)或所连的导体对地的大概电位，并用以导通流人和流出大地(或导体)的电流。
We understand this to mean that at a given location in the power system, accessible parts of power apparatus and earth constitute an equipotential surface when perfectly grounded. Insulation of conductors from ground is a basic problem.
我们对此的理解是电力系统的给定位置，当接地良好时，电力仪表的可触及部分和地之 间构成一个等势面。导体与地之间的绝缘是一个基本问题。
Let us consider some different schemes for implementing the transmission line indicated in Figure 3-1. For a fair comparison we select constraints that all schemes must satisfy. We allow any number of conductors to be used, as long as each scheme uses the same amount of conducting material. Given that networks A and B are separated by a fixed physical length, this means that in viewing the lines in cross section we must observe the same cross-sectional conducting area (A) for all schemes. Also，we argue that no conductor shall carry current greater than that constrained by some maximum current density Jo.
让我们考虑一些不同类型作为对图3-1所示输电线路的补充。为了公平比较，我们选择 所有类型都满足的限制条件，并允许使用任何数量的导体，只要每种类型都使用等量的导体 原料。假设用固定的物理距离将网络A和网络B分隔开来，这意味
着在察看线路截面积时 我们必须观察所有类型同样的导线截面积(a)。此外，e可以说所有导体传导的电流均不大于 其最大电流密度人。
We require that at least one conductor be grounded and shall refer to such a conductor as the neutral, designated as “n.” If it is not required to conduct any appreciable current, we will not include its cross-sectional area in A. This condition is achieved under certain symmetrical loading conditions，referred to as “balanced” loading, and can be maintained in a practical situation； therefore we allow all schemes to make this assumption . We require that for all schemes，no voltage to ground exceed Vo. It is assumed that the reader has a background in basic circuit theory. The adjective “dc” essentially means time invariant or constant with time. Recall that the term “ac".which historically stood for “alternating cur-rent”，in modern usage means “sinusoidal steady state. ” These terms are used to describe voltages and currents in time invariant (constant) steady-state and sinusoidal steady-state modes.
至少需要一个导体接地并称该导体为中性点，记为“n”。若中性点无需传导任何电流， 则不需要截面积A。这种情况在某种称为“平衡”负荷的对称负荷条件下出现，,也可在实际情 况下得到。因此允许对所有类型作这种假设。.同时要求对于所有的类型，其对地电压不超过 V。。假定读者已具有电路理论的基本知识。|“dc”主要含义是时间不变的或不随时间变化。 回想一下“ac”，以往代表“交流电流”，现在用于表示“正弦稳定状态”。这些术语用来描述电 压和电流随时间是恒定不变的稳定状态和正弦稳定状态。
3B
Transformers come in many sizes. Some power transformers are as big as a house. Electronic transformers，on the other hand，can be as small as a cube of sugar. All transformers have at least one coil； most have two although they may have many more.The usual purpose of transformers is to change the level of voltage. But sometimes they are used to isolate a load from the power source.
变压器大小不一。有的变压器像房子一样大。而电子变压器可能小如糖块。所有的变压 器至少有一只线圈；大多数变压器具有两个或两个以上的线圈。 通常使用变压器的目的是改变电压等级，但有时也用于隔离电源和负荷。
TYPES OF TRANSFORMERS
Standard power transformers have two coils. These coils are labeled PRIMARY and SECONDARY. The primary coil is the one connected to the load. There is no electrical connection between the primary and secondary. The secondary gets its voltage by induction.
变压器的类型
标准电力变压器有两只线圈。这些线圈标记为一次绕组(一次侧)和二次绕组(二次侧）。 一次绕组连接电源，二次绕组连接负荷。在一次和二次
绕组间没有电的连接。二次绕组通过感应获得电压。
The only place where you will see a STEP-UP transformer is at the generating station. Typically, electricity is generated at 13，800 volts. It is stepped up to 345，000 volts for transmission. The next stop is the substation where it is stepped down to distribution levels， around 15，000 volts. Large substation transformers have cooling fins to keep them from o-verheating. Other transformers are located near points where the electric power is used
大概只有在发电厂才能见到升压变压器。典型的发电机出口电压为13 800V,升压至 345 000V用来输送。下一站是变电所，把电压降到配电电压等级，约15 000V。大型的变 电所变压器具有冷却叶片，以防止变压器过热。有的变压器安装的位置靠近用户。
TRANSFORMER CONSTRUCTION
The coils of a transformer are electrically insulated from each other. There is a magnetic link, however. The two coils are wound on the same core. Current in the primary magnetizes the core. This produces a magnetic field in the core. The core field then affects current in both primary and secondary.
变压器的结构
变压器的线圈之间是绝缘的，但存在磁联系。两只线圈绕在同一个铁芯上。一次绕组电 流使铁芯磁化，并在铁芯中产生磁场。铁芯磁场影响一次和二次绕组的电流。
There are two main designs for cores ：
1. The CORE type has the core inside the windings.
2. The SHELL type has the core outside.
铁芯主要有两种型式：
1.芯型。铁芯在线圈内部。
2.壳型。铁芯在线圈外部。
Smaller power transformers are usually of the core type. The very large transformers are of the shell type. There is no difference in their operation, however.Coils are wound with copper wire. The resistance is kept as low as possible to keep losses low.
小型电力变压器通常为芯型。特大型变压器为壳型，但是在运行时二者并无区别。线圈用铜线绕成。电阻应尽量小，从而保持低损耗。
IDEALIZED TRANSFORMERS
Transformers are very efficient. The losses are often less than 3 percent. This allows us to assume that they are perfect in many computations.
理想变压器
变压器效率很高，损耗通常低于3%。因此这使我们假定它在计算时是无损耗的。
Perfect means that the wire has no resistance. It also means that there are no power losses in the core. Further, we assume that there is no flux leakage. That is，all of the magnetic flux links all of the turns on each coil.
无损耗意味着线圈没有电阻，并且铁芯中没有能量损耗。进一步可以假定没有漏磁，即 所有的磁力线穿过线圈的每一匝。
EXCITATION CURRENT
To get an idea of just how small the losses are, we can take a look at the EXCIT AT ION CURRENT. Assume that nothing is connected to the secondary. If you apply rated
voltage to the primary, a small current flows. Typically, this excitation current is less than 3 percent of rated current.
励磁电流
欲知损耗的大小，可以看一下励磁电流。假定二次绕组空载，在一次绕组施加额定电压 后会产生一较小电流。典型情况是该励磁电流小于额定电流的3%。
Excitation current is made up of two parts. One part is in phase with the voltage. This is the current that supplies the power lost in the core. Core losses are due to EDDY CURRENTS and HYSTERESIS.
励磁电流由两部分组成。一部分与电压同相，该电流供给铁芯中的能量损耗。铁芯损耗 的原因是涡流电流和磁滞。
Eddy currents circulating in the core result from induction. The core is，after all，a conductor within a changing magnetic field.
涡流电流在铁芯中旋转，产生感应现象，因为铁芯毕竟是变化磁场的导体。
Hysteresis loss is caused by the energy used in lining up magnetic domains in the core. The alignment goes on continuously ，first in one direction，then in the other?
磁滞损耗是由于用来排列铁芯中的磁畴需要能量。这种排列调整是连续不断的，开始是 一个方向，然后是另一个方向。
The other part of the excitation current magnetizes the core. It is this magnetizing current that supplies the “shuttle power”. Shuttle power is power stored in the magnetic field returned to the source twice each cycle. Magnetizing current is quadrature (90 degrees of phase) with the applied voltage.
另一部分励磁电流磁化铁芯。磁化电流供给“往复能量”，往复能量就是储存在磁场中的 能量，并在每个周期内返回电源两次。磁化电流与所加电压正交(相位差为90°)。
5A
Power is distributed from central power plants and other generating facilities at various voltage levels. Starting at the generator itself，the voltage may be in the area of 18，000 to 24，000 V，similar to the machine where the generated voltage is 22，000 V. Higher generating voltage aggravates the insulation problem and lower voltages increase the conductor size and cooling requirements. The generated voltage is stepped up to meet transmission requirements. An old rule of thumb is to allow 1，000V per mi. when we judge transmission line levels. A llOkV line would serve loads of 100 per mi. or more from the generating point. With sources of water power oftentimes far removed from cities and other major loads, transmission levels have increased dramatically over the past years in order to bring the power from remote stations.
电是从中心电厂和其他发电设备中，以几种不同的电压等级发送出的。与发电机发出的 电压22kV大致相同，电机的出口电压是在18?24kV之间。更高的发电电压会带来绝缘问 题，而低电压则增加导体的尺寸并对冷却要求较高。发电电压需逐步增加，以满足输电要
求。判断输电线路电压等级，通常所采取的办法是：每英里lkV，一条llOkV的线路可供 电100英里，或离发电地点更远的距离。通常，由于水电资源远离城市和其他主要负荷区， 为了将电能从远处电站输出，输电压等级在最近几年中已明显增高。
Lower voltages are adequate to the needs of cities and towns. These generally range from 13，800 Vdown to 2，400 V. Almost all these systems go through three phases.
低电压足以满足城镇的需求，其电压水平都在13. 8?2. 4kV之间，几乎所有的电网都 是二相的。
Transmission Line Design
Transmission line design is a somewhat specialized field of engineering . The towers are mostly a structural design problem with the support of the overhead conductors falling into some rather common arrangements. Spacing of the conductors between each other and away from the grounded structure varies with the voltage level.
输电线设计是一项专门的工程领域。杆塔的设计主要是结构问题，即如何支撑按通用方 式排列的架空导线。导线之间、导线与地之间的间隔随着电压水平的不同而改变。
Distribution Lines
Design of the common distribution systems seen throughout the countryside are generally created from long-standing standard designs that have been developed by the utility companies who generally build these lines. If the system is an overhead one，each pole design has usually been drafted into a standard so the corner pole, the transformer pole, street lighting pole，etc.，are part of design standards. Naturally variations must be handled as they occur and unique designs may need to be made based on the standards. Underground design has been developed in much the same way. Manholes，duct banks，and cable arrangements in manholes，transformer vaults，etc.，are standardized as much as possible.
配电线
旷野中所见到的普通配电网通常是按架高标准规范架设的，该标准是由架设这些线路的 设备公司制定的。如果这是一条架空线路，每根线杆的设计都应标准化，因此，角杆、传输 杆塔、街道照明线杆都属标准设计的部分。当然还要根据他们出现的不同场合进行调整并按 其标准进行个别的设计，地下部分的设计也与此相同，检查孔、管道组（群）、变压器电压 以及探井入口中的电缆排列都应尽可能标准化。
Arrangement of Primary Distribution Circuits
Primary distribution circuits generally range from 13，800V down to 2，400V. Higher voltages are used and the tendency toward higher levels is on the increase. Primary systems are usually classified as radial or network . The radial system is usually supplied from a single source and the lines radiate from a substation out along roads and streets to serve the
主配电线路排列
主配电线路的排列，电压范围通常为13.8kV?2.4kV。使用
高电压和高电压水平输电 的趋势正在增长。主系统通常可分为辐射状或网络状两种。辐射系统通常是单电源供电。区 域供电是由道旁的变电站辐射线路供给的。
Primary network systems are used a great deal in metropolitan areas and to some degree n. suburban areas. The basic system provides for tying the feeds from several sources togeth-r in order to feed selected load centres from more than one supply. Failure of any one source Lormally will not shut down the system.
主网络型系统大量使用在大城市和部分市郊，其基本系统是将多处电源供电合并向所指 定的负荷中心集中供电。其中一处电源发生故障通常不会影响正常供电。
6A
It is necessary to make a great amount of effort to maintain an electric power supply within the requirements of the various types of customers served. Large investments are necessary, and continuing advancements in methods must be made as loads steadily increase from year to year. Some of the requirements for electric power supply are recognized by most consumers，such as proper voltage, availability of power on demand，reliability, and reasonable cost. Other characteristics，such as frequency, wave shape，an phase balance, are seldom recognized by the customer but are given constant attention by the utility power engineers.
为了保证电力供应以满足不同类型用户的要求必须付出很大的努力。随着负荷逐年稳步 增长，需要加大投资并不断改进方法。电力供应的某些要求为大多数用户所认可，如合适的 电压，保障供应，可靠性和合理的费用。虽然用户不注意这些特性，但其他如频率、波形、 相位平衡等特性，却受到电力工程师的格外注意。
The voltage of the power supply at the customer’s service entrance must be held substantially constant. Variations in supply voltage are，from the consumer’s view，detrimental in various respects. For example，below-normal voltage substantially reduces the light output from incandescent lamps. Above-normal voltage increases the light output but substantially reduces the life of the lamp.提供给用户的电源电压必须基本保持不变。从用户的角度看，供电电压的变化在许多方 面是有害的。例如：电压低于正常值实质上是减少了白炽灯的发光效率。电压高于正常值虽 然提高了白炽灯的发光效率但实际上却减少了它的寿命。
Motors operated at below-normal voltage draw abnormally high currents and may overheat, even when carrying no more than the rated horsepower load. Overvoltage on a motor may cause excessive heat loss in the iron of the motor, wasting energy and perhaps damaging the machine. Service voltages are usually specified by a nominal value and the voltage then maintained close to this value，deviating perhaps less than 5 percent above or below the nominal value. For example,
in a 120-volt residential supply circuit, the voltage might normally vary between the limits of 115 and 125 volts as customer load and system conditions change throughout the day.
低压运行的电动机即使在只输送额 定负荷时，也会产生过电流而导致过热。过电压作用于电动机会引起发动机铁芯热量的过度 损失，不但浪费能量而且可能损害电动机。通常明确规定供电电压的额定值，然后使电压保 持接近于此数值，允许产生的偏差在额定值百分之五以内。例如，在120V居民供电电路 中，随着一天内用户负荷及系统情况的变化，电压的正常变化范围限定为115?125V。
Power must be available to the consumer in any amount that he may require from minute to minute. For example, motors may be started or shut down, lights may be turned on or off, without advance warning to the electric power company. As electrical energy cannot be stored (except to a limited extent in storage batteries)，the changing loads impose severe demands on the control equipment of any electrical power system. The operating staff must continually study load patterns to predict in advance those major load changes that follow known schedules，such as the starting and shutting down of factories at prescribed hours each day.
用户在任何时候要用任何数量的电量都必须得到满足。比如说启动或停止电动机，开灯 或关灯，都不会事先预告供电公司。由于电能无法储备（蓄电池中有限的电能除外），变化 着的负荷对任何电力系统的控制设备都提出了严格的要求。操作人员必须不断研究负荷模 式，遵循已知的时刻表，比如工厂每天规定的开工和停工时间，提前预报主要的负荷变化。
The demands for reliability of service increase daily as our industrial and social environment becomes more complex. Modern industry is almost totally dependent on electric power for its operation. Homes and office buildings are lighted, heated，and ventilated by electric power. In some instances loss of electric power may even pose a threat to life itself.
由于我们的工业和社会环境越来越复杂，对服务可靠性的要求日益提高。现代工业的运 行几乎完全依赖于电力。住宅和办公楼要用电来照明、取暖、通风。在某些情况下，突然断 电甚至会对生活本身造成威胁。
Electric power, like everything else that is man-made, can never be absolutely reliable. Occasional nterruptions of service in limited areas will continue. Interruptions affecting large areas re-nain a possibility, although such occurrences may be very infrequent Further interconnection of electric supply systems over wide areas ； continuing development of reliable automated :ontrol systems and apparatus； provision of additional reserve facilities； and further effort in leveloping personnel to engineer，design, construct, maintain and
operate these facilities will continue to improve the reliability of the electric power supply.
像其他一切人造的东西一样，电永远不可能完全可靠。对某 些地区偶尔的限电现象还会时有发生。尽管类似事件将非常罕见，但仍有可能大面积断电。 大面积供电系统的进一步互连，继续开发可靠的自动化控制系统，提供额外的储备设施，进 一步开发、策划、设计、建造、维修和操作这些设备的人员都将继续提高电力供应的可靠 性。
The cost of electric power is a prime consideration in the design and operation of electric power systems. Although the cost of almost all commodities has risen steadily over the past nany years, the cost per kilowatt-hour of electrical energy has actually declined. This de-rease in cost has been possible because of improved efficiencies of the generating stations nd distribution systems. Although franchises often grant the electric power company exclu-ive rights for the supply of electric power to an area，there is keen competition between electric power and other forms of energy, particularly for heating and for certain heavy-load industrial processes.
在电力系统的设计和运行过程中，主要考虑的是电费。多年以来，尽管几乎所有日用品 的费用稳步增长，电能（千瓦时）的费用实际上却下降了。费用的降低之所以成为可能主要 归因于发电厂和配电系统效率的提高。虽然专营权使供电公司对一个地区的供电拥有特权， 但电和其他形式的能源，特别是供暖和某些高负荷工业流程之间仍存在激烈的竞争。
6B
A modern electric power system is an assembly of many components, each of which influences the behavior of every other part. Proper functioning of the system as a whole makes it necessary to monitor conditions existing at many different points on the system in order to assure optimum operation.
现代供电系统是许多部分的组合，每个部分都影响其他部分的运转。为使系统作为整体 正常运作，有必要监控系统中许多不同位置的情况，才能确保最佳运转。
The concern of the customers is primarily that the frequency and voltage of the supply are held within certain rather narrow limits. Since frequency of the system is the same everywhere ,it may be monitored by a single frequency meter located at any convenient point. In contrast, the voltage of the system may be quite different at different points. Consequently, it is necessary to make continuous observation of the voltage at certain key points in the system in order to provide acceptable service.
用户主要关心的是频率和把供电电压限制在某些相当有限的范围内。因为在任何地方系 统的频率都相同，所以可在任一方便的地方安装单个的频率测试仪来监控。相反，系统的电 压可能在不同的地方差别很大。因此，必须
在系统某些关键位置对电压不断进行观察，才能 提供令人满意的服务。
Efficient operation of the system is obtained by assigning proper load schedules to each of the generators of the system. Newer plants, although individually more efficient, may be located at points of the system where their loading occasions large system losses. It is desirable to operate with such a division of the load between generators that the total cost of fuel consumed is minimized. To provide reliability of the power supply in the event of unexpected conditions，it is desirable for all machines in operation to have the total kilowatt rating somewhat greater than the total load plus losses.
将合适的负荷计划分配给系统中每台发电机，才能使系统达到高效运转。新的设备虽然 单机效率较高，但它们在系统中被安装的位置可能会由于它们的加载而造成系统巨大的损 失。应该将负荷在发电机之间分配后进行运作，才能使所消耗燃料的费用总额降至最低。为 在意外情况下可靠供电，最好使运行中的所有机器的千瓦定额比负荷加上损耗的总数高一 些。
Instrumentation is necessary to permit billing of customers for energy used. Many interconnections exist between different power systems. Instruments must be provided at interchange points to permit billing for energy transferred from one system to another. The continuous monitoring of energy transfer is necessary to assure that interchanged power is within the limits of contract agreements.
要想把用户的用电量记人账目，就必须安装测试设备。在不同的供电系统间存在着许多 互连。必须在连接点配备测量仪器才能将从一个系统转换到另一个系统的能量记入账目。必须对能量转换不断监测，才能保证交换的电力在协议规定的限度之内。
The continuous measurement of conditions of major pieces of equipment is necessary to avoid damage due to overload. Instrumentation serves as a guide for future construction in a growing power system.
要避免由于超载造成的损害，必须对大件装置的状态不断测量。测试设备在未来扩充供 电系统的建设中起指导作用。
Occasionally, under emergency conditions, a system operator observes that his system load exceeds the ability of the available generating and transmission equipment. He is then faced with the problem of load shedding or, more properly, load conservation. It is then necessary to drop selected loads where service interruption is least objectionable. In such an event，he relies on the many instruments which provide information relative to system-opera-tion conditions.
有时在紧急情况下，一位系统操作人员注意到他的系统负荷超过了现有发电和输电设备 的能力。于是他就面临着限制用电的问题，更恰当地说，是保持负荷的问题。于是就有必要 在最合适中断
供电服务的地方减少一定的负荷。在此情况下，他依赖于许多测试仪表来提供 有关系统运行状况的信息。
Instruments may sound alarms as advance warnings of conditions requiring action to avoid damage to equipment operating beyond its design limitation. In the event of extreme conditions such as powersystem faults，defective equipment is switched out of service automatically. Instruments that continuously monitor current, voltage，and other quantities must be able to identify the faulted equipment and to bring about operation of the circuit breakers which remove it from service，while leaving in service all other equipment on the operating system.
当要求采取操作避免超过限定运行设计给设备带来损害时，测量仪会发出警报声，作为 提前警告。万一出现最糟的情况，如电力系统出现故障，有毛病的设备将会自动关闭，停止 运行。要对电流、电压和其他量的测量仪器进行监控，必须能够辨别出产生故障的设备，使 断路器开始起作用并将有故障的设备排除在供电服务之外，而让运行系统中其他所有设备继 续运行。
The many different electrical devices in a power system and those owned by the customers are designed for operation within certain specified ranges. Operation outside these designed limits is undesirable，as it may result in inefficiency of operation, excessive deterioration, or (in extreme cases) the destruction of the device. Careful attention to the conditions under which equipment is operating may indicate corrective action that must be taken.
电力系统和用户拥有的许多不同的电力装置都是为在某些特定范围内运行而设计的，不 可以在设计限定范围之外运行，因为它会导致低效运行、过度磨损或者（在极端的情况下） 设备损坏。认真观察设备运行状态才会知道应该如何采取正确行动。
Overcurrent is undesirable for all electrical devices，as it produces excessive temperatures? inefficient operation, and reduced service life. Overcurrent in residential circuits may bring about disconnection of the circuit by fuse or breaker action. Overcurrent in motors may also damage insulation.
所有电力装置都不可以过电流，因为这会导致温度过高、低效运行并减少使用寿命。居 民电路若电流过载，会导致因熔丝烧断而产生断路，或使断路器动作。电动机若电流过载， 会损坏绝缘，使绝缘失效。
7A
In 200 B. C.，a Greek named Hero designed a simple machine that used steam as a power source. He began with a cauldron of water, placed above a fire. As the fire heated the cauldron, the cauldron shell transferred the heat to the water and the water reached the boiling point of 212°F (100°C). It then changed form and turned into steam. The steam passed through two pipes into a hollow sphere，pivoted at both sides. As the steam escaped the
sphere through two tubes，each bent at an angle，the sphere moved, rotating on its axis. Hero, a mathematician and scientist, labeled the device aelopile，meaning rotary steam engine.
公元前200年，希腊人希罗设计了一台用蒸汽作为动力的简易机器，他把一大锅水放在 火上加热，锅热后，热量被传递给水，使水温达到沸点212华氏度（摄氏100度），由水变成 的蒸汽通过两个管子进入安装在轴两侧的中空的壳体。当蒸汽通过两个弯管散发出去时，壳 体便绕轴转动。数学家、科学家希罗把这一装置称为aelopile，意思是旋转蒸汽机。
The invention was only a novelty. However, even though Hero made no suggestion as to how to use the device，the idea of generating steam to do useful work was born.
这一发明是新鲜事物，尽管希罗对如何使用这一装置未做任何说明，但用蒸汽来做功的 想法却已产生了。
To this day, the basic idea has remained the same-generate heat, transfer the heat to water, and produce steam.
时至今日，其基本方法仍然相同产生热，传递给水进行加热，进而生成蒸汽。
Closely related to steam generation is the steam turbine, a device to change the energy of steam into mechanical work. In the early 1600s，an Italian named Branca made a unique invention. He first produced steam, based on Hero’ s aelopile. Next, he channeled the steam to a wheel and the steam pressure caused the wheel to rotate. This marked the beginning of steam turbine development.
与蒸汽密切相关的是汽轮机，它的作用是把热能转换成机械能。在17世纪早期，意大利 人博兰卡搞了一项极好的发明创造。他先是借助于希罗的旋转蒸汽机产生蒸汽，然后将蒸汽 引入一个轮子，在蒸汽推动下，轮子开始转动，这是汽轮机发展的一个里程碑。
The primary use of steam turbines today is the production of electric power. In one of the most complex systems designed by mankind, superheated high pressure steam is produced in a boiler and channeled to turbine-generators to produce electricity.
现在，汽轮机主要用来发电。在人类设计的最复杂的一个系统中，锅炉产生高温高压蒸 汽，并将其送进汽轮机，生产出电能。
Today’s steam plants are a complex and highly sophisticated combination of engineered elements. They must first obtain heat sources，usually in the form of coal, oil，natural gas, referred to as fossil fuels，or in the form of uranium，called nuclear fuel. Other forms of sources include waste heat and exhaust gases，bagasse and biomass，spent chemicals and municipal waste, and geothermal and solar energy.
今天的蒸汽设备是由复杂尖端的零件组成的。首先它们必须受热，通常用的燃料包括 煤、石油、天然气等矿物燃料和铀等核燃料，以及诸如废热、废气、蔗渣、生物燃料，用过 的化学制
品和城市废品、地热能和太阳能等其他形式的能量。
Each fuel contains potential energy, or a heating value measured in Btu/lb (kj/kg). The first goal is to release this energy，most often by a controlled combustion process or， with uranium, through fission. The heat is then transferred through tube walls and other components or liquids to water. The heated water then changes form, turning into steam. The steam is normally heated further to specific temperatures and pressures.
每种燃料都有一定的发热量，即热值，以kj/kg为单位。首先是要释放这些能量，通常 通过受控的燃烧过程或铀分裂的方法来达到。然后热量通过管壁、其他部件或液体传给水， 加热后的水变成高温高压的蒸汽。
Steam is also a vital resource in industry. It drives pumps and valves，helps produce paper and wood products，prepares foods，and heats and cools large buildings and institutions.steam also propels much of the world’s naval fleets and a high percentage of commercial ma-rine transport. In some countries，steam plays a continuing role in railway transportation.
在工业生产上，蒸汽也是一种极其重要的资源。它驱动水泵和阀门，用来生产纸张和木 制品，生产食品，调节大楼的温度。蒸汽还用来驱动世界上大多数海军舰艇和商业运输船。 在一些国家，蒸汽在铁路运输上也起着重要作用。
Steam generators，commonly referred to as boilers，range in size from those needed to heat a small building to those used individually to produce 1300 megawatts of electricity in a units deliver generating station-enough power for more than one million people. These larger atures deliver more than ten million pounds of superheated steam per hour with steam temper-?es exceeding 1000T (538°C) and pressures exceeding 3800 psi (262 bar).
蒸汽发生器，通常是指锅炉，其容量因需要的不同而异，从用来为住宅供暖的锅炉到那 些在发电厂中单独使用便可生产出1300兆瓦的电能（足够上百万居民使用）的锅炉。这些 更大功率的机组每小时可生产出10万镑的温度超过1000T (538°C)、压力超过3800psi (262bar)的过热蒸汽。
Today’s steam generating systems owe their dependability and safety to more than 125 years of experience in the design, fabrication and operation of water tube boilers，first patented by George Babcock and Stephen Wilcox in 1867.
1867年，乔治?柏博考科和史蒂芬?威尔考科斯首先获得了水管锅炉的专利。有了超 过125年的水管锅炉的设计和运行经验，今天的锅炉更加安全可靠。
Steam is a resource for mankind. It is our challenge and responsibility to further develop and use this resource safely，efficiently and dependably.
蒸汽是人类可利用的一种资源，如何进一步开发并安全、高效地利用这一资源，这是对 我们的挑战，也是我们的责