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电气专业英语课后练习翻译
PART1U1T1、 In addition to the various power transformers, two special-purpose transformers are used with electric machinery and power systems. The first of these special transformers is a device specially designed to sample a high voltage and produce a low secondary voltage directly proportional to it. Such a transformer is a potential transformer. A power transformer also produces a secondary voltage directly proportional to that the potential transformer is designed to handle only a very small current. The second type of special transformer is a device designed to provide a secondary current much smaller than but directly proportional to its primary current. This device is called a current transformer.除了各种电源变压器、两个专用变压器使用电动机械和电力系统。第一个特殊变压器是一 个高电压设备专门设计的样品和生产较低的二次电压成正比。这样一个变压器电压互感器。 电力变压器也产生二次电压成正比的电压互感器的设计目的是处理只有一个很小的电流。 第二种类型的特殊变压器是一个装置,旨在提供一个次级电流小得多,但它的主要电流直接 成比例。这种装置称为电流互感器。 U1T2、In electronic power supplies there is often a need to isolate the output from the input and reduce the weight and cost of the unit. In other applications, such as in aircraft, there is a strong incentive to minimize weight. These objectives are best achieved by using a relatively high frequency transformer. Thus, in aircraft the frequency of transformers is typically 400Hz, while in electronic power supplies the frequency of transformers may range from 5kHz to 50kHz.在电子电源通常需要隔离的输出输入,减少单位的重量和成本。 在其他应用程序,如飞机,有强 烈的动机来减少体重。这些目标是最好通过使用一个相对高频变压器。因此,在飞机变压器 通常是 400 赫兹的频率,而在电子电源变压器可能范围从 5 khz 的频率 50 千赫 U2T1、In general, the outstanding advantage of DC machines lies in their flexibilityand versatility. Before the widespreaded availability of AC motor drives, DC machines were essentially the only choice available for many applications requiring a high degree of control. Their principal disadvantages stem from the complexity associated complexity increase the cost over competing AC machines, it also increases the need for maintenance and reduces the potential reliability of these machines.一般来说,直流机的突出优势在于他们的灵活性和通用性。交流电动机驱动的广泛可用性之 前,直流机基本上是唯一可用的选择对于许多应用程序要求高度的控制。主要缺点源于复杂 关联的复杂性增加了成本在竞争交流的机器,它也增加了对维护的需要,减少了潜在的这些 机器的可靠性。U2T2、There are three basic type of rotating machines: synchronous, induction, and DC machines. In all of them the basic principles are essentially the same. Voltages are generated by the relative motion of a magnetic field with respect to a winding, and torques are produced by the interaction of the magnetic fields of the stator and rotor windings.有三种基本类型的旋转机器:同步,感应,直流机器。 在所有这些基本原则基本上是相同的。 电 压的相对运动产生的磁场对绕组,和扭矩的交互作用是由定子和转子绕组的磁场。 U3T1、Synchronous machines can be classified as cylindrical-rotor or salient-pole machines. The cylindrical-rotor construction is used in high-speed steam-turbine-driven generators. The armature windings consist of laminated conductors placed in the stator slots. The rotor carries the DC field winding. Most of turbine generators being built at present for 60 Hz service are 2-pole 3600 revolutions per minute machines. Because of the economies of high-speed high-temperature high-pressure steam turbines, much study and some real pioneering work have been devoted to improvements in materials and design of both generators and turbines同步机可分为圆柱形转子或凸极机。圆柱形转子建设用于高速 steam-turbine-driven 发电 机。电枢绕组由叠层导体放置在定子槽。转子直流磁场绕组。目前大部分涡轮发电机建 60 赫兹服务 2-pole 每分钟 3600 转的机器。因为经济的高速高温高压蒸汽涡轮机,多学习和一 些真正的开创性工作一直在致力于改进材料和设计的发电机和发电机 U3T2、Rotating electric machines take many forms and are known by many names: DC, synchronous, permanent-magnet, induction, etc. Although these machines appear to be quite dissimilar and require a variety of analytical techniques, the physical principles governing their behavior are quite similar, and in fact these machines can often be explained from the same physical picture. An induction machine, in spite of many fundamental differences, works on exactl one can identify flux distributions associated with the rotor and stator, which rotate in synchronism and which are separated by some torque-producing angular displacement.旋转电机采取多种形式和已知许多名字:直流、同步、永磁、感应,等等。虽然这些机器似乎 是相当不同的,需要各种分析技术,管理他们的行为非常相似的物理原则,事实上这些机器通 常可以解释从相同的物理图像。 感应式电机,尽管许多根本性的差异,同样的原理工作;一个可 以识别通量分布与转子和定子,在同步旋转,由一些 torque-producing 角位移U4T1、The significance of VRMs in engineering applications stems from their low cost, reliability, adn controllability. Because their torque depends only on the square off applied stator currents and not on their direction, these machines can be operated from unidirectional drive systems, reducing the cost of the power electronics. However, it is only recently, with the advent of low-cost, flexible power electronic circuitry and microprocessor-based control systems, VRMs have begun to see widespread application in systems ranging from traction drives to high-torque, precision control systems for robotics applications.VRMs 在工程应用的意义源于他们的低成本、可靠性、可控性。因为他们的转矩只取决于广 场采用定子电流,而不是他们的方向,这些机器可以从单向操作驱动系统 ,减少电力电子的成 本。然而,直到最近,随着低成本、灵活的电力电子电路和基于微处理器控制系统,VRMs 已经 开始看到广泛应用系统从牵引驱动高扭矩,为机器人精度控制系统应用程序 U4T2、The hybrid stepping motor combines characteristics of the variable-reluctance and permanent-magnet stepping motors. The hybrid stepping motor can achieve small step sizes easily and with a simple magnet structure while a purely permanent-magnet motor would require a multipole permanent magnet. In addition, the hybrid stepping motor will tend to maintain its position when the stator excitation is removed, as does the permanent-magnet design.混合式步进电机结合可变磁阻和永磁步进电动机的特性。混合式步进电机可以实现小步大 小很容易和磁铁结构简单而纯粹的永磁电动机需要多极永磁。此外,混合步进电机将倾向于 保持其位置移除定子励磁时,永磁设计一样。U5T1、Relay is a key component in any power system protection scheme. It is a device that, based on information received from the power system, performs one or more switching actions. The information referred to consists of signals and currents, typically the output of instrument transformers. The relay decides to close(or open)one or more sets of normally open(or close) contacts. The switching action typically energizes the trip coil of a circuit breaker, which then opens the power circuit.继电器是一个关键的组件在任何电力系统保护方案。一个设备,从电力系统根据收到的信息, 执行一个或多个开关动作。指由信号和电流的信息,一般仪器的输出变压器。继电器决定关 闭(或打开)一个或多个组常开(或接近)接触。 开关行动通常激发断路器的脱扣线圈,然后打开 电源电路。U5T2、A contactor is a large relay, usually used to switch current to an electric motor or other high-power load. Large electric motors can be protected from overcurrent damage through the use of overload heaters and over load contacts. If the series-connected heaters get too hot from excessive current, the normally-closed overload contact will open, de-energizing the contactor sending power to the motor.接触器是一种大型继电器,通常用于切换当前电动马达或其他大功率负载。大型电动机可以 免受过载损坏通过使用超载加热器和过载联系人。如果过度的串联暖气太热电流,将打开闭 合过载来接触,接触器断开的发送功率电动机。U6T1、Circuit-interrupting devices in power systems are of many forms, ranging from the small key switches to the enormous circuit breakers that flow of power in high-voltage networks. Circuit breaker is a device for interrupting a circuit between separable contacts under normal or abnormal conditions. The abnormal conditions during which a circuit breaker may be asked to operate are primarily those which exist during short circuits. The circuit breaker is designed to withstand these short-duration, high-magnitude currents and to interrupt them if necessary.断路装置在电力系统的多种形式,从巨大的小钥匙开关在高压断路器,流动的权力网络。断路 器是中断的设备电路在正常或异常条件下分离之间的联系。异常条件中断路器操作可能会 被要求主要是那些存在在短路。断路器的设计能够承受这些短期高震级水流和必要时打断 他们。U6T2、The main contacts of a circuit breaker are commonly made of copper, silver, or silver alloy, and are subject to diverse temperature limitations. Copper contacts are not normally fit for
their temperature tends to rise with time. Most circuit breaker contacts are therefore made of silver alloy, which provides good conductivity and low stable temperature rise.的主要联系人断路器通常由铜、银或银合金,受不同温度的限制。铜接触通常不适合连续操 作;他们的温度趋向于上升时间。 大多数断路器接触因此银合金做的,它提供了良好的导电性 和较低的稳定的温度上升。U7T1、 A switch can be constructed with any mechanism bringing two conductors into contact with each other in a controlled manner. This can be as simple as allowing tow copper wires to touch each other by the motion of a lever, or by directly pushing twometal strips into contact. However, a good switch design must be rugged and reliable, and avoid presenting the operator with the possibility of electric shock. Therefore, industrial switch designs are rarely this crude. The conductive parts in a switch used to make and break the electrical connection are called contacts. Contacts are typically made of silver or silver-cadmium alloy, whose conductive properties are not significantly compromised by surface corrosion or oxidation. Gold contacts exhibit the best corrosion resistance, but are surface corrosion or oxidation. Gold contacts exhibit the best corrosion resistance, but are limited in current-carrying capacity and may &cold weld& if brought together with high mechanical force. Whatever the choice of metal, the switch contacts are guided by a mechanism ensuring square and even contact, for maximum reliability and minimum resistance.一个开关可以由任何机制带来了两个导体接触彼此以一种受控制的方式。这可以简单允许 两个铜导线相互接触的运动杆,或通过直接将两个金属条接触。然而,一个好的开关设计必须 坚固,可靠,并避免呈现的操作符电击的可能性。因此,工业开关设计很少这原油。 开关的导电部分用于制造和打破的电气连接被称为联系。联系人通常由银或银镉合金,其导 电性能没有显著的表面被腐蚀或氧化。黄金接触表现出最好的耐腐蚀性能,但表面腐蚀或氧 化。黄金接触表现出最好的耐蚀性,但在载流容量是有限的,可能“冷焊”如果与机械力高。任 何金属的选择,开关接触是由一种机制确保广场甚至接触,最大可靠性和最小阻力。U7T2、If the parting contacts are made of low-melting-point material such as brass of copper, the arc will go out at the first current zero as the voltage is insufficient to reestablish a cathode spot after current reversal. The necessary insulation must be so positioned as to avoid charring from the heat of the arc. If charring occurs the carbon produced may serve as an electrode from which thermionic electrons may be released and so reignite the arc following current zero.如果分开联系是由低熔点材料如铜、 黄铜弧将出去第一电流零的电压不足以重建一个阴极电 流换向后现货。必要的绝缘必须定位,避免电弧的热量烧焦。如果发生炭化生成的碳可以作 为一个电极的热离子电子可能被释放,所以重燃弧后电流零。U8T1、IN order to confirm and guarantee the reliability of electrical contacts, a lot of experience is required, especially on how to develop additional testing methods on top of the requirements given through national and international standards. It is very important that the manufacturers of devices with electrical contacts are developing such methods(temperature rise tests, short circuit tests, high voltage tests, etc.) and continuously are using them as routine tests in order to confirm the reliability of electrical contacts.为了确认和保证电接触的可靠性 ,需要丰富的经验,特别是在如何开发额外的测试方法的要 求通过国家和国际标准。是非常重要的 ,设备的制造商与电接触正在开发这种方法 (温升测 试、短路测试,高压测试,等等),不断使用它们作为常规检测,以确认电接触的可靠性。U8T2 、 The reliability means the ability that the product fulfills the stipulated conditions. The reliability working scope is quite large, for example: the reliability organization management, the reliability date, the reliability can give a reference to improve the circuit-breaker quality.可靠性意味着产品满足规定条件的能力。可靠性工作的范围是相当大的,例如:组织管理、可 靠性可靠性日期,可以给一个参考改善断路器可靠性质量。Part II u1 Text AElectromechanical devices which employ magnetic fields often use ferromagnetic materials for guiding and concentrating these fields.Because the magnetic permeability of ferromagnetic materials can be large(up to tens of thousands times that of the surrounding space),most of the magnetic flux is confined to fairly well-defined paths determined by the geometry of the magnetic material.机电设备,采用磁场经常使用铁磁材料进行指导和集中这些字段。因为铁磁材料的磁导率可 以大(成千上万倍,周围的空间),大多数的磁通量局限于相当明确的路径由磁性材料的几何形 状决定。 Text BDue to the hystersis effect,the relationship between B and H for a ferromagnetic material is both nonlinear and multivalued.In general,the characteristics of the material cannot be described analytically.They are commonly presented in graphical from as a set of empirically determined curves based on test samples of the material.The most common curve used to describe a magnetic material is B-H curve or hystersis loop.由于磁滞效应,B 和 H 之间的关系对铁磁材料的非线性和多值。一般来说,材料的特性不能被 描述分析。 它们通常在图形从一组经验确定曲线基于测试的样品材料。 最常见的曲线用于描 述磁性材料磁化曲线和磁滞回路。 Unit 2 Text AThe Mesh Current Method is quite similar to the Branch Current Method in that it uses simultaneous equations,Kirchhoff`s Voltage Law,and Ohm`s Law to determine the unknown currents in a network.It differs form the Branch Current method in that it does not use Kirchhoff`s Current Law,and it is usually able to solve a circuit with less unknown variables and less simultaneous equations,which is especially nice if you`re force to solve without a calculator.当前网格方法非常类似于分支电流方法,它使用联立方程,基尔霍夫电压定律和欧姆定律来确 定网络中未知的电流。形式分支电流方法不同,它不使用基尔霍夫电流定律,而且通常能解决 电路更少的未知变量和更少的联立方程,这是特别好的如果你力量来解决没有计算器。 Text BThe strategy used in the Superposition Theorem is to eliminate all but one source of power within a network at a time,using series/parallel analysis to determine voltage drops (and/or current)within the modified network for each power sourceseparately.Then,once voltage drops and/or currents have been determined for each power source working separately,the values are all “superimposed” on top of each other to find the actual voltage drops/currents with all source active.叠加定理中使用的策略是消除网络内的所有只有一个电源,使用串联/并联分析来确定电压下 降(和/或电流)在修改网络分别为每个电源。然后,一旦电压下降和/或电流已经被确定为每个 单独电源工作,的值都是“叠加”的发现实际的电压/电流与所有源活性下降。Unit 3 Text AThe finite element procedure consists of partitioning or discretizing interior domain Ω into a number of subdomains or finite elements.The field is approximated over each element by an interpolating or shape function depending on values at discrete nodes on or in the element.To provide some degree of field continuity across element boundaries,most of the discrete nodes are defined on the element surface and shared by adjacent element.Provided that they cover the domain, the elements and shape functions may be completely arbitrary.有限元程序由分区或离散化内部域Ω 成子域或有限元素的数量。 字段由插值近似在每个元素 或形状函数根据值在离散节点或元素。提供某种程度的领域跨元素边界连续性,大多数离散 节点上定义元素的表面和共享的相邻元素。提供覆盖域,马英九的元素和形状函数。 Text BDiscrete numeral methods like finite elements or finite differences are necessarily formulated on finite spatial grids-whether actual domain being modeled is finite or infinite.This domain truncation introduces artificial boundaries that must be treated with special care in order to minimize nonphysical wave reflections.These trap energy that would otherwise be radiated and establish undesirable resonances within the grid.Note that this is true regardless of the solution scheme applied,in either the time-domain or frequency-domain.离散的数字方法如有限元素或有限的差异必然是制定有限空间 grids-whether 实际域建模是 有限的还是无限的。 这个领域截断引入了人工边界,必须特别小心处理,以减少非物质波反射。 这些陷阱能量,否则被辐射,建立不良网格内的共振。 注意,这是真正的不管应用解决方案,无论 是在时间 Unit 4 Text ACoupling can also occur in circuits that share common impedances.For instance,two circuits that share the conductor carrying the supply voltage and the conductor carrying the return path to ground.If one circuit creates a sudden demand in current,the other circuit`s voltage supply will drop due to the common impedance both circuits share between the supply lines and the source impedance.This coupling effect can be reduced by decreasing the supply lines and the common impedance.Coupling also can occur with radiated electric and magnetic fields which are common to all electrical circuits.Whenever current changes,electronmagnetic wares are generated.These waves can couple over to nearby conductors and interfere with other signals within the circuit.耦合也可以发生在共享公共阻抗的电路。例如,两个电路共享导体携带电源电压和导体携带 的返回路径。如果一个电路产生电流的突然需求,其他电路的电压供应将会下降,由于公共阻 抗电路供给线之间的分享和源阻抗。 这种耦合效应可以减少减少供应线和常见的阻抗。 耦合 也可能发生Text BThe majority of modern digital integrated circuits(IC) are manufactured using complementary metal oxide semiconductor (CMOS) technology.The static power consumption of COMS devices may be lower,but with fast switching rates the CMOS device demands transient power from the supply.The dynamic power demand of a high speed clocked COMS devices may exceed an equivalent bipolar device.Therefore,decoupling capacitors must be used on these devices to reduce the transient power demand from the power supply.大多数的现代数字集成电路(IC)制造使用互补金属氧化物半导体(CMOS)技术。设备的静态 功耗 COMS 可能较低,但快速交换率的互补金属氧化物半导体元件要求瞬时功率供应。的动 态电力需求高速时钟 COMS 设备可能超过一个等价的双极型设备。因此,去耦电容器必须在 这些设备上使用,以减少瞬态电源的电力需求。 Unit 5 Text AGiant Magnetostrictive Material(GMM)is new functional material which has bi-directional transduction effects,it can be made into Giant Magnetostrictive Actuator (GMA) by using the direct,also can be made into sensors by using the pared with piezoelectric actuator,GMA owns the advantages of larger load capacity,rapider response,higher reliability and lower voltage drive,etc.It has a promising prospect in precision positioning,active noise and vibration control and fluid control (pump,value)fields.超磁致伸缩材料 (GMM)是新型功能材料具有双向传导效果 , 它可以制成超磁致伸缩驱动器 (GMA)通过使用直接,也可以制成传感器利用相反的效果。与压电致动器相比,该协会拥有的 优势更大的负载能力,更快捷的反应,高可靠性和低电压驱动等。它在精密定位,具有广阔的发 展前景,积极的噪声和振动控制和流体控制(泵、瓦尔 Text BMagnetostrictive (MS) linear position sensors constitute an interesting possibility as generic all-use sensors because they are by principle non-contract and absolute.These are very desirable characteristics for machine tool operation,as well as their non-optical nature which makes them resistant to typical contaminants of the machine tool environment like shavings and metalworking coolant fluid.磁致伸缩(MS)线性位置传感器构成传感器一般都使用一个有趣的可能性,因为他们是由原则 non-contract 和绝对的。机床操作,这些都是非常可取的特征以及他们为了自然使他们对机床 的典型污染物环境刨花和金属加工冷却液等。PartIII Unit1 ASo far ,all the power semiconductor devices discussed exclusively use silicon as the basic raw material ,and this will possibly continue,at least in the near future.however,new types of large band-gap materials,such as silicon carbide and semi-conducting diamond,are showing high promise for the future generation of power devices.silicon carbide is particularly more promising because its technology is more “mature” than for diamond.The material has high carrier mobility,faster minority carrier lifetime,and high electrical and thermal conductivities.These properties permit high-voltage and high-power capabilities,fast switching (i. e. ,high switching frequency),low conduction drop ,good radiation hardness ,and high junction temperature.All key devices,such as diodes,power MOSFETS,thyristors,GTO,etc,are possible with new material.到目前为止,专门讨论的所有电力半导体器件用硅作为基本原料 ,而这可能会持续下去,至少 在不久的将来。然而,新类型的大带隙材料、碳化硅和半导体等钻石,显示高承诺未来一代的 电力设备。碳化硅尤为更有前途,因为其技术比钻石更“成熟”。该材料具有高载流子迁移 率,更快的少数载流子寿命,高电气和热导率。这些属性允许高压和大功率功能,快速交换(即 高开关频率),低传导,辐射硬度好,和高结温。 所有关键设备,如二极管,功率 mosfet,晶体闸流管, 之所以与新材料等,是有可能的。 BPower semiconductor devices constitute the heart of modern power electronic apparatus.They are used in power electronic converters in the form of a matrix of on-off switches,and help to convert power form AC-to-AC at the same (AC controller) or different frequencies (cycloconverter).The switching mode power conversion gives high efficiency,but the disadvantage is that due to the nonlinearity of switches,harmonics are generated at both the supply and load sides.The switches are not ideal,and they have conduction and turn-on and turn-off switching losses.Converters are widely used in applications such as heating and lighting controls,AC and DC power supplies,electrochemical processes,DC and AC motor drives,active harmonic filtering,etc.Although the cost of power semiconductor devices in power electronic equipment may hardly exceed 20~30 percent , the total equipment cost and performance may be highly influenced by the characteristics of the devices.An engineer designing equipment must understand the devices and their characteristics thoroughly in order to design efficient ,reliable,and cost-effective systems with optimum performance.It is interesting to note that the modern technology evolution in power electronics has generally followed the evolution of power semiconductor devices.The advancement of microelectronics has greatly contributed to the knowledge of power device materials,fabrication ,packaging,modeling,and simulation.功率半导体器件构成现代电力电子设备的核心。 它们用于电力电子转换器的形式的一个矩阵 开关开关,同时帮助转换能量形式 AC-to-AC 控制器(AC)或不同频率(回旋转换器)。开关模式 电源转换效率高,但缺点是由于非线性开关、谐波产生供应和负载。开关并不理想,他们有传 导和接通和断开开关损失。转换器广泛用于取暖和照明控制等应用,交流和直流电源、电化 学过程中,直流和交流电机驱动器、有源谐波滤波等。虽然电力半导体器件在电力电子设备的成本可能不超过 20 ~ 30%,设备总成本和性能可能会受到设备的特点。一个工程师设计设 备必须了解设备及其特点完全为了设计高效、 可靠和具有成本效益的系统最优性能。 有趣的 是注意到,现代电力电子技术发展已普遍遵循电力半导体器件的发展。微电子技术的进步极 大地促进了知识的力量设备材料、制造、包装、建模和仿真。 UNIT 2 AThe modern power devices include the diode,SCR,GTO,BJT,power MOSFET,IGBT,MCT and IGCT.Power semiconductor devices constitute a vast and complex subject,and the technology is going through continuous evolution.It is needless to say that a power electronics engineer responsible for designing an apparatus should be thoroughly familiar with the different devices to achieve optimum cost and the performance goals of the system.Traditionally,SCR-type devices have been very popular in power electronic systems and many applications can be found on this area .MOS-gated devices,particularly power MOS-FETs and IGBTs,have been applied extensively in recent years. The IGCT is a recent member in the devices family with good potential,and we are yet to see its growth of applications in competition with IGBTs and GTOs.It is interesting to see that the advent of new power semiconductor devices,growth of their power ratings,and improvement of their characteristics are continually driving the power electronics and motor drives technologies forward.Suffice it to say that if the devices evolution would have stopped at the SCR level,the power electronics technology would have stalled hopelessly in the primitive stage.现代电力设备包括二极管、可控硅,之所以是机器、电力 MOSFET、IGBT,MCT 和 IGCT。功 率半导体器件构成一个庞大而复杂的话题,和技术正在经历不断进化。不用说,电力电子工程 师负责设计一个装置应该彻底熟悉不同的设备来实现最优成本和系统的性能目标。传统 上 ,SCR-type 设备已经非常流行在电力电子系统和许多应用程序可以在这个地区找到。 MOS-gated 设备,特别是电力 MOS-FETs 和 igbt,近年来已被广泛应用。 IGCT 是一个最近设备家族成员具有良好的潜力,我们尚未看到经济增长的应用程序的竞争 对手 igbt 和矩形脉冲断开。有趣的是发现新型功率半导体器件的出现,增长他们的力量评级, 改善他们的特点是不断推动电力电子和电机驱动技术。我只想说,如果设备进化会停止在可 控硅层面,电力电子技术将会停滞在原始阶段的不可救药。 BOnly a few define statements can ba made in comparing these devices since a number of properties must be considered simultaneously and because the devices are still evolving at a rapid pace.However,the qualitative observations given in Table 3-1 can be made. It should be noted that in addition to the improvements in these devices,new devices are being investigated.The progress in semiconductor technology will undoubtedly lead to higher power ratings,faster switching speeds,and lower costs.On the other hand,the forced-commutated thyristor,which was once widely used in circuits for controllable switch applications,is no longer being used in new converter designs with the possible exception of power converters in multi-MVA ratings.This is a pertinent example of how the advances in semiconductor power devices have modifiedconverter design.只有几个定义语句可以英航在比较这些设备,因为许多属性必须同时考虑,因为设备仍在快速 发展。然而,表 3 - 1 中给出的定性观察。 应该指出的是,除了这些设备的改进,新设备正在接受调查。半导体技术的进步无疑将导致更 高的评级,更快的开关速度,并降低成本。另一方面,forced-commutated 晶闸管,曾广泛应用于 电路可控开关应用,不再是被用于新的转换器设计可能除了 multi-MVA 电力转换器的评级。 这是一个相关的例子半导体电力设备的进步转换器设计修改。 UNIT 3 ADiodes and phase converters constitute the largest segment of power electronics that interface to the electric utility today.The history of these converters extends nearly one hundred years,and often defined as classical power electronics.Before the advent of solid-state diodes and thyristors,which are invariably used presently,gas-filled glass-bulb devices such as mercury-arc rectifiers,phanotrons,and thyratrons,and ignitrons were dominant in the early part of this century.Then,during World War 2,saturable-core magnetic amplifiers were introduced.This class of converters mainly conversion 50/60 Hz AC to DC(rectification),but a select group can also function for DC to AC conversion (inversion).The efficiency of the converters is high because of soft switching,accompanied with low conduction loss.二极管和相位转换器构成最大的电力电子接口的部分电力。 这些转换器扩展了近一百年的历 史,而且经常定义为古典电力电子。 出现之前的固态二极管和晶体闸流管,总是使用目前,充气 玻璃灯泡设备如汞弧整流器、phanotrons,和闸流管,引燃管是在本世纪初占统治地位。然后, 在二战期间,饱和铁芯磁放大器。这类转换器主要转换 50/60 Hz 交流到直流(整流),但选择组 还可以为 DC AC 转换函数(反演)。转换器的效率很高,因为软切换,伴随着低传导损耗。 BThe voltage and currents in a power circuit are frequently not pure sine waves.The line voltages usually have a satisfactory wave-shape but the currents are sometimes badly distorted.The distortion maybe caused by magnetic saturation in the core of a transformer,by the switching action of thyristors.Harmonic voltage and currents are usually undesirable,but in some ac circuits they are also unavoidable.Harmonics are created by nonlinear loads,such as electric arcs and saturated magnetic circuits. It is important to know how a circuit responds to harmonics.In linear circuits composed of resistors,inductors, capacitors,and transformers,the various harmonics act independently of each other.The fundamental and each harmonics behave as if the others were not here.In solving such a circuits for a particular harmonic, the voltages sources of the other harmonics, including that of the fundamental, are replaced by a short-circuit,.Then , the totalrms current in each branch is equal to the algebraic sum of the effective fundamental current and the effective values of the individual harmonic currents. In AC circuits, the fundamental current and fundamental voltage together produces a fundamental power. This fundamental power is the useful power that causes a motor to rotate and an arc furnace to heat up. The product of a harmonic voltage times the corresponding harmonic current also produces a harmonic power. The latter is usuallydissipated as heat in the AC circuit and , consequently ,does no useful work. Harmonic current and voltages should therefore be kept as small as possible .电源电路中的电压和电流常常不是纯正弦波。线电压通常有一个令人满意的波形,但电流有 时被严重扭曲。磁饱和引起的失真也许在变压器的核心,通过晶体闸流管的开关动作。谐波 电压和电流通常是不受欢迎的,但在一些交流电路也是不可避免的。谐波是由非线性负载,如 电弧和饱和磁回路。 重要的是要知道电路谐波响应。在线性电路由电阻、电感、电容和变压器,各种谐波彼此独 立的行动。的根本,每个谐波表现得像其他人并不在这里。在解决这样一个特定谐波电路,其 他谐波的电压源,包括基本的、被短路,取代。然后,totalrms 在每个分支电流的代数和等于有 效基本电流和单个谐波电流的有效值。 在交流电路中,基本电流和基本电压在一起产生一个基本力量。这个基本权力是有用的力量, 使电动机的旋转和电弧炉加热。 谐波电压的产品时间也相应的谐波电流产生谐波功率。 后者 通常以热能的形式散失的交流电路,因此,没有有用的工作。 谐波电流和电压应保持尽可能小。 Unit 4 Text AIn some power systems there is a need to transform DC power from one DC voltage level to either a higher or lower DC level. For example, in a public transportation system, a 4000V DC overhead line many be the source to drive a 300V DC motor in a bus. In other cases, a 12V battery many have to power a device rated as 120V DC. In alternating current systems the voltage step-up or step-down can be done with a transformer. But in DC systems, an entirely different approach is required. It involves the use of a DC-to-DC switching converter, sometimes called a chopper. In the DC-DC converters the switch is actually a GTO, MOSFET, or IGBT whose on/off state is controlled by a signal applied to the gate. The combination of electronic switch, inductor, and diode constitutes what is known as a step-down DC-DC converter, or buck chopper. In any converter circuit operating in steady state, a capacitor can be represented by its instantaneous voltage as an equivalent voltage source. Similarly, an inductor can be represented by its instantaneous current as an equivalent current source.在一些电力系统需要直流电源转换从一个直流电压级别较高或较低的直流级别。例如,在公 共交通系统中,4000 v 直流架空线路多源驱动一个 300 v 直流电机在一辆公共汽车。 在其他情 况下,一个 12 v 电池许多设备被评为 120 v 直流。在交流系统的电压升压或降压变压器可以 做。但在直流系统中,一个完全不同的方法是必需的。它涉及 DC-to-DC 开关转换器的使用, 有时也被称为直升机。 直流-直流转换器的开关实际上是一个 GTO、MOSFET、IGBT 的开/关状态由一个信号控制 应用于门。电子开关、电感、二极管构成所谓的降压直流-直流转换器,或巴克直升机。 在任何变换器电路操作在稳定状态,电容器可以表示为其瞬时电压作为等效电压源。同样,一 个电感可以表示为其瞬时电流作为等效电流源。 Unit 4 Text BThere is an increasing requirement in equipment such as computers for power supplies with voltages of even lower than 5V, for example, in a 2~3V range, as a consequence of increasing integration of logic gates on a single monolithic substrate. In switching power supplies with low output voltage, the diodes in the output rectifierstage can be the biggest source of power loss. Even the commonly used Schottky diodes have a relatively large voltage drop and, hence, a large power loss in such low-output-voltage applications. As a remedy, low-voltage MOSFETs with a very low on-state resistance and low-voltage BJTs with a very low on-state voltage can be used replace the diodes in the output stage. These devices in this application are commonly referred to as synchronous rectifiers.越来越要求在设备如电脑电源甚至低于 5 v 电压,例如,在一个 2 ~ 3 v 范围内,因此提高集成逻 辑门在一个单片衬底。在较低的开关电源输出电压,二极管整流器的输出阶段可以功率损耗 的最大来源。即使是常用的肖特基二极管有一个相对较大的电压降,因此,大功率损失在这样 low-output-voltage 应用程序。补救,低压 mosfet 开态电阻很低,低压是一个非常低的开态电压 可以用替代二极管的输出级。这些设备在这个应用程序中通常称为同步整流器。 Unit 5 Text AThe voltage-source inverters can be divided into the following three categories: Pulse-width modulated (PWM) inverters. In these inverters, the input DC voltage is essentially constant in magnitude. Therefore, the inerter must control the magnitude and the frequency of the AC output voltage. This is achieved by PWM of thr inveter switches and hence such inverters are called PWM inverters. Square-wave inverters. In these inverters, the input DC voltage is controlled in order to control the magnitude of output AC voltage, and therefore the inverter has to control only the frequency of the output voltage. The output AC voltage has a waveform similar to square wave and hence these inverters are called square-wave inverters. Single-phase inverters with voltage cancellation. In case of inverters with single-phase output, it is possible to control the magnitude and the frequency of inverter output voltage, even though the input to the inverter is a constant DC voltage and the inverter switches are not pulse-width modulated, therefore, these inverters combine the characteristics of the previous two inverters.电压源逆变器可分为以下三类: 脉宽调制(PWM)逆变器。这些逆变器输入直流电压大小本质上是不变的。因此,惰性必须控 制级和交流输出电压的频率。 这是通过 PWM 刺 inveter 交换机,因此这种逆变器被称为 PWM 逆变器。 方波逆变器。这些逆变器输入直流电压控制,以控制输出交流电压的大小,因此逆变器必须控 制输出电压的频率。输出交流电压有类似方波的波形,因此这些逆变器被称为方波逆变器。 单相逆变器电压取消。与单相逆变器的输出,可以控制级和逆变器输出电压的频率,即使逆变 器的输入是一个恒定的直流电压和逆变器开关脉宽调制,因此,这些逆变器结合前两个逆变器 的特点。 Unit 5 Test BThe control and estimation techniques of variable frequency drives have been a fascinating and challenging area of research in recent years. Although many different types of scalar and vector control methods have been proposed in the literature, the industry is settling with simple open loop volts/Hz control for economical low performance applications and vector control for high performance applications. Manyproblems related to vector control, such as speed estimation, vector-flux estimation, slip gain tuning, and complete auto-commissioning of drive base on on-line parameter extraction are receiving wide attention in literature, and have indicated a successful trend.变频驱动器的控制和评估技术一直是近年来引人入胜的和具有挑战性的研究领域。 尽管许多 不同类型的标量和矢量控制方法被提出的文学,产业是解决简单的开环伏特/赫兹控制经济的 低性能的应用程序和为高性能矢量控制应用程序。许多与矢量控制相关的问题,如速度估计, 矢通量估算、 滑动得到优化,并完成 auto-commissioning 传动基础上的在线参数提取收到广泛 关注在文学,并表示一个成功的趋势。 Unit6 Text AIn a given controllable power semiconductor switch, its switching speed and on-state losses depend on how it is controlled. Therefore, for a proper converter design, it is important to design the proper drive circuit for the base of a BJT or the gate of a MOSSFET, GTO, or IGBT. The future trend is to integrate a large portion of the drive circuitry along with the power switch within the device package, with the intention that directly. Besides optocouplers, fiber cable can be used to provide very high electrical isolation and creepage distance. When using fiber optic cables, the LED is kept on the printed circuit board of the control electronics, and the optical fiber transmit s the signal to the receiver transistor, which is put on the drive circuit printed board.在一个给定的可控电力半导体开关,其开关速度和使用状态取决于它是如何控制损失。因此, 适当的转换器设计,重要的是要设计合适的驱动电路的基础是机器或 MOSSFET 门口,GTO、 IGBT。未来的趋势是将大部分的驱动电路以及电源开关在设备包中,直接的意图。 除了光耦合器,光纤电缆可用于提供非常高的电气隔离和爬电距离。当使用光纤电缆,LED 电 子印刷电路板上的控制,和光纤传输信号到接收机晶体管,这是驱动电路印制板。 Part III Unit6 Text BSnobber circuits are used to modify the switching weave-forms of controllable switches.In general, snubbers can be divided into three drive categories: Turn-on sunbbers to minimize large over-currents through the device at turn-on, Turn-on sunbbers to minimize large over-voltages across the device during turn-off. Stress reduction sunbbers that shape the device switching waveforms such that the voltage and current associated with a device are not high simultaneously. The future trend is to design devices that can withstand high voltage and current simultaneously during the short switching interval and thus minimize the stress reduction requirement. However, for a device with a given characteristic, an alternative to use of snubbers is to alter the converter topology such that large voltages and currents do not occur at the same time.势利眼电路是用来修改的切换 weave-forms 可控开关。 一般来说,阻尼器驱动可分为三种类型: 刺激 sunbbers 减少大型刺激的过电流通过装置, 刺激 sunbbers 减少大型跨设备过电压在让我倒尽胃口。 减压 sunbbers 塑造设备切换电压和电流波形,同时与设备关联不高。 未来的趋势是设计的设备可以同时承受高电压和电流在短切换时间间隔 , 从而减少减压要 求。 与给定的特点,然而,对于一个设备替代使用缓冲器是改变转换器拓扑结构,这样大的电压 和电流不发生在同一时间。Part IV Unit 1 A For a general load composed of RLC elements, the real power absorbed by passive load is always positive. The reactive power absorbed by a load may be either positive or negative. When the lode is inductive, the current lags the voltage, which means β is less than δ ， and the reactive power absorbed is positive. When the load is capacitive ,the current leads the voltage,which means β is greater than δ ,and the reactive power or,alternatively ,the capacitive load delivers positive reactive power.一般 RLC 负载组成的元素,真正的权力被被动吸收负载总是积极的。吸收无功功率的负 载可以是积极的还是消极的。 矿脉是感应时,电流滞后于电压,即β 小于δ ,吸收无功功率是积 极的。当负载电容,电流的电压,这意味着β 大于δ ,和吸收的无功功率为负;或者,或者,电容性 负载提供积极的无功功率。 BIt is appropriate to mention that a balanced △-connected load is more common than a balanced Y-connected load . This is due to the ease with which loads may be added or removed from each phase of a △-connected load. This is very difficult with a Y-connected load because the neutral may not be circulating current that will result in the △-mesh if the three-phase voltage are slightly unbalanced.适当提及,一个平衡的△连接负载比平衡线星形常见负载。这是由于负载的缓解可能添 加或删除从每个阶段的△连接负载。这与星形负载是非常困难的,因为中立可能不是循环电 流,将导致△网三相电压是否有点不平衡。 Unit2 AThe power-flow problem is the computation of voltage magnitude and phase angle at each bus in a power system under balanced three-phase steady-state conditions. As a byproduct of this calculation, real and reactive power flows in equipment such as transmission lines and transformers, as well as equipment losses,can be computed. The starting point for a power-flow problem is a single-line diagram of the power system, from which the input data for computer solutions can be obtained. Input data consist of bus data,transmission line data ,and transformer data.功率流的问题是电压级和相角的计算每个总线在电力系统三相对称稳态条件下。这个计 算的副产品,真实和无功功率流在输电线路和变压器等设备,以及设备的损失,可以计算。 功率流的起点问题是电力系统的一个单行的图,输入数据的电脑解决方案。 输入数据包括 总线数据,输电线路数据,和变压器数据。BA lightning stroke hits a transmission line , “breaking down” the air between a pair of conductors ,or from line to ground and creating an ionized path. Sixty-Hertz line currents also flow trough this ionized path, maintaining the ionization even after the lighting stroke energy has been dissipated. This constitutes a short circuit or “fault” as real a if the conductors were in physical contact. To remove the fault, relays detect the short circuit and cause circuit breakers to open at both ends of the line. The line is deenergized and the air deionizes, reestablishing its insulating properties. Wesay that the fault “clears”. The circuit breakers are set to reclose automatically after a preset interval of time,reestablishing the original circuit. This sequence of events (called a fault sequence) constitutes a shock to the power system and is accompanied by a transient.输电线路雷击击中 , “分解”一对导体之间的空气 , 或从地面和创建一个电离路径。 Sixty-Hertz 线电流也流槽这电离路径,维持照明中风后的电离甚至能源已经消散。这就构成 了一个短路或“断层”真正的身体接触如果导体。消除故障,继电器检测短路和导致断路器 两端开口的。线断开,空气消电离,重建其绝缘特性。我们说错“清除”。断路器将再次接通 自动预设时间间隔时间后,重建原来的电路。 这一系列的事件(称为断层序列)对电力系统构成 冲击,伴随着瞬态。 Unit 3 AIn planning an electric utility system, the physical location of the generating station,transmission lines and substations must be carefully planned to arrive at an acceptable, economic solution. We can sometimes locate a generating station next to the source of energy(such as a coal mine) and use transmission lines to carry the electrical energy to where it is needed. When this is neither practical economical,we have to transport the energy (coal,gas,oil) by ship, train, or pipeline to the generating station. The generating station may, therefore, be near to, or fa from, the ultimate user of the electrical en energy. Some of the obstacles prevent transmission lines from following the shortest route. Due to these obstacles, both physical and legal, transmission lines often follow a zigzag path between the generating station and the ultimate user.在规划一个电力系统,电站的物理位置,输电线路和变电站必须仔细计划到达一个可以接 受的,经济的解决方案。 我们有时可以找到一个电站的能源(如煤矿)并利用输电线路将电能到 需要的地方。当这个既不实用经济,我们必须运输能源(煤、天然气、石油)船,火车,或管道发 电站。因此,发电厂可以靠近,或者从的最终用户 fa 电力能源。的一些障碍防止输电线路最短 的路线。由于这些障碍,包括生理的和合法的,输电线路通常遵循一个锯齿形发电站和最终用 户之间的路径.BThe hydraulic resources of most modern countries are already fully developed. Consequently, we have to rely on the thermal and nuclear stations to supply the growing need for electrical energy. Thermal generating stations produce electricity from the heat released by the combustion of coal ,oil,or natural gas. Most stations have ratings between 200MW and 1500MW so as to attain the high efficiency and economy of a large installation. Such a station has to be seen to appreciate its enormous complexity and size. Thermal stations are usually located near a river or lake because large quantities of cooling water are needed to condense the steam as it exhausts from the turbines. The efficiency of thermal stations is always low because of the inherent low efficiency of the turbines.大多数现代国家已经完全的水力资源开发。因此,我们必须依靠热,核电站供应电能的需 求越来越大。 热发电站发电所释放的热量燃烧的煤,石油,天然气。大多数电视台收视率 200 mw 和 1500 mw 之间,达到高效、经济的安装。这样一个站出现升值其巨大的规模和复杂性。 热站通常是附近的河流或湖泊,因为需要大量的冷却水浓缩蒸汽涡轮机的废气。热力站 的效率总是因为固有的低效率低的涡轮机。 Unit 4 AThe fundamental purpose of a transmission or distribution lines is to carry active power from one point to another. If it also has to carry reactive power,the latter should be kept as small as possible. In addition, a transmission line should possess the following basic characteristic: (1) The voltage should remain as constant as possible over the entire length of the line, from source to load,and for all loads between zero and rated load. (2) The line losses must be small so as to attain a high transmission efficiency. (3) The I^2R losses must not overheat the conductors. If the line alone cannot satisfy the above requirements,supplement equipment ,such as capacitors and inductors, must be added until the requirements are not.传输或配电线路的根本目的是进行有功功率从一个点到另一个地方。 如果它还携带无功 功率,后者应保持尽可能小。此外,输电线路应具备以下基本特征: (1)电压应尽可能保持不变在整个长度的线,从源到负载,负载零至额定负载。 (2)线路损失要小,达到较高的传动效率。 (3)I ^ 2 r 导体不能过热的损失。 如果线路无法满足上述要求,补充设备,如电容和电感器,必须添加到需求没有。BInsulated cables have many applications in the field of electric power. Small cables are used as extension cords around offices,homes,and factories. Larger cables are used for connections to machines that are movable over restricted distance. In some instances portable cables carry quite heavy electrical loads ,as for example the case of electrically driven drag lines ,which require several thousand horsepower for operation. Overhead cables find application in distribution circuits where tree conditions or proximity to buildings and other structures make the use of open-wire lines impracticable. Underground cables are used in many situations, including major transmission circuits between large stations. Some cable power circuits operate at 765 kilovolts and carry loads of several hundred megawatts. Cables of even higher voltage will probably become available soon.绝缘电缆在电力领域的许多应用程序。小电缆作为延长线在办公室,家庭,和工厂。大电 缆用于连接机器,在限制移动的距离。在某些情况下便携式电缆携带很重电气负载,例如电动 拖线的情况下,需要几千马力操作。架空电缆发现应用程序在分配电路树条件或邻近建筑物及其他设施的使用开放式连接线路行不通的。在很多情况下使用地下电缆,包括主要的大型 站点之间传输电路。 一些有线电源电路工作在 765 千伏及携带大量的几百兆瓦。 电缆的更高 的电压可能会很快变得可用。 Unit 5 AA distinction must be made between a fault and an overload. An overload implies only that loads greater than the designed values have been imposed on system. Under such a circumstance the voltage at the overload point may be low,but not zero. This under-voltage condition may extend for some distance beyond the overload point into the remainder of the system. The currents in the overload equipment are high and may exceed the thermal design limits. Nevertheless ,such currents are substantially lower than in the case of a fault. Service frequently may be maintained,but at below-standard voltage. Overloads are rather common occurrences in homes. To prevent such trouble residential circuits are protected by fuses or circuit breakers which open quickly when currents above specified values persist. Distribution transformers are sometimes overloaded as customers install more and more appliances. The continuous monitoring of distribution circuits is necessary to be certain that transformer sizes are increased as load grows.必须注意区分错误和过载。 一个过载意味着只有负载大于设计值对系统。 在这种情况下 的电压过载点可能较低,但不是零。这个欠压条件可能为一段距离超出了过载点扩展到系统 的其余部分。的电流过载设备高并可能超过热设计限制。然而,这种电流大大低于在错误的 情况下。服务通常可以保持,但在达标的电压。 过载而普遍出现在家里。 防止这样的麻烦住宅电路保护的保险丝或断路器电流超过指定 值时快速打开持续下去。 配电变压器是有时重载为客户安装越来越多的电器。 分布的连续监 测电路必须确定变压器尺寸随着负载增加。BThe IEEE defines a relay as “ a device whose function is to detect defective line s or apparatus or other power system conditions of an abnormal or dangerous nature a nd to initiate appropriate control action ” .In practice,a relay is a device that closes or opens a contact when energized.Relays are also use in low-voltage(600V and below)p ower systems and almost anywhere that electricity is used.They are used in heating,air conditioning,stoves,clothes washers and dryers, refrigerators, dishwashers, telephone networks,traffic controls, airplane and other transportation systems and robotics,as well as many other applications. Problems with the protection equipment itself can occur.A second line of defense ,called primary relays.In HV and EHV systems,separate current-or voltage-measuring devices,separate trip coils on the circuit breaker,and separate batteries for the trip coils may be used.Also,the various protective devices must be properly coordinated such that primary relays assigned to protect equipment in a particular zone operate first.If the primary relays fail,then backup relays shouldoperate after a specified time delay.IEEE 定义了一个继电器为“设备的功能是检测有缺陷的线路或设备或其他电力系统异 常或危险的性质和条件进行适当的控制行动”在实践中,继电器是一种装置,关闭或打开一个 接触当 energized.Relays 也使用在低电压(600 v 及以下)电力系统和电力使用的几乎任何地 方。它们用于供暖、空调、炉灶、服装产品项目,像洗衣机及烘干机、冰箱、洗碗机、电话 网络、交通控制、飞机和其他运输系统和机器人技术,以及许多其他应用程序。 保护设备本身可能出现的问题。第二道防线,叫做主继电器。在高压和超高压系统,单独 当前或电压测量设备,单独旅行在断路器线圈,和单独的电池可以使用的线圈。 同时,必须妥善 协调,各种保护装置主要继电器分配给保护设备在一个特定的区域操作。如果主继电器失败, 那么备份继电器应该运行在指定的时间延迟。 Unit 6 AThe exciter delivers DC power to the field winding on the rotor of a synchronous generator. For older generators,the exciter consists of a DC generator driven by the rotor. The DC power is transferred to the rotor via ship rings and brushes. For newer generators, static or brushless exciters are often employed. For static exciters,AC power is obtained directly from the generator terminals or a nearby station service bus. The AC power is then rectified via thyristors and transferred to the rotor of the synchronous generator via slip rings and brushes. For brushless exciters ,AC power is obtained from an “inverted” synchronous generator whose three-phase armature winding are located on the main generator rotor and whose field winding is located on the stator. The AC power from the armature windings is rectified via diodes mounted on the rotor and is transferred directly to the field winding . For this design,slip rings and brushes are eliminated.磁场绕组的励磁机提供直流电源的同步发电机的转子。对于年长的发电机,励磁机由直 流发电机由转子驱动的。直流电源是转移到转子通过船环和刷子。更新的发电机,静态或无 刷激励器通常使用。 对于静态推荐,获得交流电源直接从发电机终端或附近的车站服务总线。然后纠正交流 电源通过晶体闸流管和转移到同步发电机的转子通过滑环和电刷。 无刷激发器,交流电源获得从一个“倒”同步发电机的三相电枢绕组位于主发电机转子 的磁场绕组位于定子。电枢绕组的交流电源整流二极管安装在转子和直接转移到磁场绕组。 对于这个设计,滑环和电刷是消除。 BAs electric utilities have grown in size and the number of interconnections has increased, planning for future expansion has become increasingly complex. The increasing cost of additions and modifications has made it imperative that utilities consider a range of design options, and perform detailed studies of the effects om the system of each option, based on a number of assumption: normal and abnormal operating conditions, peak and off-peak loadings, and present and future years of operation. A large volume of network data must also be collected and accurately handled.To assist the engineer in this power system planning, digital computers and highly developed computer programs are used. Such programs include power-flow,stability, short-circuit, and transients programs.电力公司已经在大小和相互连接的数量增加,规划未来扩张已经变得越来越复杂。添加 和修改成本的增加使得公用事业必须考虑一系列设计选项,并执行的详细研究影响 om 每个 选项的系统,基于一些假设:正常和不正常的运行条件下,峰和非高峰载荷,现在和未来几年的 操作。大量的网络数据也必须准确收集和处理。协助工程师在这个电力系统规划,使用数字 计算机和高度发达的计算机程序。这些项目包括功率流、稳定、短路和瞬态程序。Part V U1 TADielectrics are materials that are used primarily to isolate components electrically from each other or ground or to act as capacitive elements in devices,circuits,and systems.Their insulating properties are directly attributable to their large energy gap between the highest filled valence band and the conduction band.The number of electrons in the conduction band is extremely low,because the energy gap of a dielectric in sufficiently large to maintain most of the electrons trapped in the lower band.电介质是主要用于从彼此或地面电隔离的部件或充当在设备用作电容元件的材料， 电路， 和 systems.Their 绝缘性能是直接归因于最高填充价带与传导之间的能隙大 band.The 号中的导 带电子的极低，因为电介质中足够大的能隙，以维持最困在低带中的电子。 Part V U1 TBWhen several conductors are situated in an electric field with the conductors charged,a definite relationship exists among the potentials of the conductors,the charges on them,and the physical location of the conductors with respect to each other. In a conductor,electrons can move freely under the influence of an electric filed.This means that the charges are distributed inside the substance and over the surface such that,E=0 everywhere inside the conductor.Since .....,it is necessary that is constant inside and on the surface of the conductor. Thus, the conductor is an equipotential surface当几个导体位于一个电场与导体带电，有一定的关系存在导体的电位，对他们的费用，以及 导体相对于彼此的物理位置之间。 在一个导体，电子可电气 filed.This 的影响下自由移动装置，该电荷分布内的物质，并在表 面上，使得 E =0 到处 conductor.Since 里面.....，它是必须使内和导体的表面上是恒定的。因 此，该导体是一个等电位表面 Part V U2 TAAs the voltage is increased across a dielectric material ,a point is ultimately reached beyond which the insulation will no longer be capable of sustaining any further rise in voltage and breakdown will ensure, causing a short to develop between the electrodes. If the dielectric consists of a gas or liquid medium ,the breakdown will be self-healing in the sense that the gas or liquid will support an a re application of voltage until another breakdown recurs.In a solid dielectric,however,the initial breakdown will result in a formation of a permanent conductive channel, which cannot support a reapplication of voltage.The dielectric breakdown processes aredistinctly different for the three states ofmatter.作为电压施加的介电材料的增加， 一个点最终达到超出该绝缘将不再能承受任何进一步上升 电压和击穿将确保，从而导致在电极之间的短发展。 如果该电介质包括一气体或液体介质中， 且击穿会自愈在这个意义上， 该气体或液体将支持 电压的重新应用程序，直到 recurs.In 固体电介质另一击穿，但是，在初始击穿将结果在形 成一个永久的导电通道，它不能支持 voltage.The 介质击穿过程的重新申请的是物质的三种 状态明显不同。 Part V U2 TBAs already mentioned,the latest trend in capacitor manfuacture is to replace paper by polypropylene plastic films.This results in a drastic reduction in size .Its use results in cheaper capacitors for high voltage ratings because of its high working stress.As regard impregnants,askarels are harmful to the environment and hence are being banned. The latest trend is to develop other types of materials.With this in view,research is being directed towards the use of oils like castor oil.如已经提到的， 在电容器 manfuacture 的最新趋势是由聚丙烯塑料 films.This 导致大幅减少 尺寸。其在高电压的评分，因为它的高的工作 stress.As 便宜的电容器使用的结果把浸渍剂， askarels 更换纸张是对环境有害，因而正被禁止使用。最新的趋势是发展其他类型的 materials.With 如此看来，研究正在指向像使用蓖麻油油。 Part V U3 TAA fault in an electrical power system is the unintentional and undesirable creation of a conducting path(a short circuit) or a blockage of current(an open circuit).The short-circuit fault is typically the most common and is usually implied when most people use the term fault.We restrict our comments to the short-circuit fault. The causes of faults include lightning, wind damage,trees falling across lines,vehicles colliding with towers or poles,birds shorting out lines,aircraft colliding with lines, vandalism,small animals entering switchgear,and line breaks due to excessive ice loading. power system faults may be categorized as one of four types:single line-to-ground,line-to-line,double line-to-ground and balanced three-phase.The first three types constitute severe un balanced operating conditions在电力系统中的故障是无意的和不希望建立一个导电通路的 （短路） 或电流 （开路） 的堵塞。 短期短路故障通常是最常见的，通常是隐含的，当大多数人使用术语 fault.We 限制我们的 短路故障的注释。 故障的原因包括雷电，大风破坏，树木掉落跨线，车辆塔或电线杆相撞， 鸟短路线， 飞机线， 人为破坏，小动物进入开关碰撞，并因过度负荷冰断行。电力系统的故障可以被分类为四种 类型之一：单线路对地，线到线，双线路对地和平衡的三相，前三种类型构成严重的未平衡 的操作条件 Part V U3 TBEarlier the testing of insulators and other equipment was based on the insulation resistance measurements,dissipation factor measurements and breakdown tests.It was observed that the dissipation factor(tan )was voltage dependent and hence became a criterion for the monitoring of the high voltageinsulation. In further investigations it was found that weak points in an insulation like voids, cracks,and other imperfections being small were not revealed in capacitance measurements but were revealed as power loss components in contributing for an increase in the dissipation factor.In modern terminology these are designated as&partial discharges&which in course of time reduce the strength of insulation leading to a total or partial failure or breakdown of the insulation.较早绝缘子等设备的测试是基于所述绝缘电阻的测量，耗散因数的测量和击穿 tests.It 观察 到的损耗因数（TAN）是电压依赖性，因此成为一个标准的高电压绝缘的监测。在进一步研 究后发现， 薄弱点状空隙， 裂纹和其它缺陷是小的绝缘未揭示的电容测量而被揭露作为功率 损耗分量在用于增加耗散 factor.In 现代术语这些是造成指定为“局部放电”的过程中的时间减 少的绝缘领先的强度以绝缘的全部或部分的故障或崩溃。 Part V U4 TAMany electrical apparatuses like transformers,line conductors,rotating machines,ete.produce unwanted electrical signals in the radio and high frequency ranges.These signals arise due to corona discharges in air ,internal or partial discharges in the insulation, sparking at commutators and brush gear in rotating machines,etc.It is important to see that the noise voltages generated in the radio and other transmission bands are limited to acceptable levels,and hence the radio interference voltage measurements are of importance.It has been found that the surface conditions og the overhead conductors subjected to high voltage stresses and varying atmospheric conditions greatly influence the magnitude of the noise voltage produced.许多电气设备如变压器，线路导线，旋转电机，ete.produce 在无线电和高频信号 ranges.These 由于在空气中，内部或在绝缘局部放电电晕放电不必要的电信号的出现，引 发了在换向器和电刷齿轮在旋转电机，etc.It 地看到，噪声电压在无线电等传动带所产生被 限制到可接受的水平是很重要的，因此，无线电干扰电压测量 importance.It 已发现，表面 条件 OG 的经受高电压应力和不同的大气条件架空导线大大影响所产生的噪声电压的幅 度。 Part V U4 TBTransmission system planning criteria have been developed from the above planning principles and equipment ratings as well as from actual system operating date, probable operating modes,and equipment failure rates.These criteria are used to plan and build the transmission network with adequate margins to ensure a reliable supply of power to customers under reasonable equipment-outage contingencies.The transmission system should perform its basic functions under a wide range of operating conditions.Transmission planning criteria include equipment loading criteria ,transmission voltage criteria ,stability criteria and regional planning criteria.输电系统规划标准已经制定，从上面的规划原则和装备等级，以及实际系统运行日期，可能 的操作模式，以及设备故障 rates.These 标准来规划和建设有足够的利润率传输网络，以确 保可靠的电力供应，客户在合理的设备，停电 contingencies.The 传输系统应该在范围广泛的经营 conditions.Transmission 规划准则执行其基本功能包括设备负荷标准，输电电压标 准，稳定性标准和区域规划的标准。