外文翻译--电力系统介绍

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2024年7月25日发(作者：)

外文翻译

Electric Power System

Electric Power System, components that transform other types of energy

into electrical energy and transmit this energy to a consumer. The production

and transmission of electricity is relatively efficient and inexpensive, although

unlike other forms of energy, electricity is not easily stored ad thus must

generally be used as it is being produced.

Components of an Electric Power System

A modern electric power system consists of six main components: (1) the

power station, （2）a set of transformers to raise the generated power to the

high voltages used on the transmission lines, (3) the transmission lines, (4) the

substations at which the power is stepped down to the voltage on the

distribution lines, (5) the distribution lines, and (6) the transformers that lower

the distribution voltage to the level used by the consumer’s equipment.

Power Station, the power station of a power system consists of a prime

mover, such as a tribune driven by water, steam, or combustion gases that

operate a system of electric motors and generators. Most of the world’s

electric power is generated in steam plants driven by hydroelectric (water

power), diesel, and internal-combustion plants.

Transformers, Modern electric power systems use transformers to convert

electricity into different voltages. With transformers, each stage of the system

can be operated at an appropriate voltage. In a typical system, the generators at

the power station deliver a voltage of from 1,000 to 26,000volts (v).

Transformers step this voltage up to values ranging from 138,000 to 765,000 V

for torture transfer on the distribution system. Another set of transformers step

the voltage down again to a distribution level such as 2,400 or 4,160 V or 15,

27, or 33 kilovolts (kV). Finally the voltage is transformed once again the

distribution transformed near the point of use to 240 or 120 V.

Transmission Lines, The lines of high voltage transmission system are

usually composed of wires of copper, aluminum-clad steel, which are

suspended form tall latticework towers of steel by strings of porcelain

insulators. By the use of clad steel wires and high towers, the distance between

towers can be increased, and the cost of the transmission line thus reduced. In

modern installations with essentially straight paths, high-voltage lines may be

built with as few as six towers to the kilometer. In some areas high-voltage

lines are suspended from tall wooden poles spaced more closely together.

For lower voltage distribution lines, wooden poles are generally used

rather than steel towers. In cites and other areas where open lines create a

safety hazard or are considered unattractive, insulated underground cables are

used for distribution. Some of these cables have a hollow core through which

oil circulates under low pressure. The oil provides temporary protection from

water damage to the enclosed wires should the cable develop a leak. Pipe-type

cables in which three cables are enclosed in a pipe filled with oil under high

pressure (14 kg per sq cm/200psi) are frequently used. These cables are used

for transmission of current at voltage as high as 345,000V (or 345 kV).

Supplementary Equipment Any electric-distribution system involves a

large amount of supplementary equipment to protect the generators,

transformers, and the transmission lines themselves. The system often includes

devices designed to regulate the voltage or other characteristics of power

delivered to consumers.

To protect all elements of a power system from short circuits and

overloads, and for normal switching operations, circuit breakers are employed.

These breakers are large switches that are activated automatically in the event

of a short circuit or other condition that produces a sudden rise of current.

Because a current forms across the terminals of the circuit breaker at the

moment where the current is interrupted, some large breakers (such as those

used to protect a generator or a section of primary transmission line) are

immersed in a liquid that is a poor conductor of electricity, such as oil, to

quench the current. In large air-type circuit breakers, as well as in oil breakers,

magnetic fields are used to break up the current. Small air-circuit breakers are

used for protection in shops, factories, and in modern home installations. In

residential electric wiring, fuses were once commonly employed for the same

purpose. A fuse consists of piece of alloy with a low melting point, inserted in

the circuit, which melts, breaking the circuit if current rises above a certain

value. Most residences now use air-circuit breakers.

Power Failures

In most parts of the world, local or national electric utilities have joined

in grid systems. The linking grids allow electricity generated in one area to be

shared with others. Each utility that agrees to share gains an increased reserve

capacity, use of larger, more efficient generators, and the ability to respond to

local power failures by obtaining energy from a linking grid.

These interconnected grids are large, complex systems that contain

elements operated by different groups. These systems offer the opportunity for

economic saving and improve overall reliability but can create a risk of

widespread failure. For example, the worst blackout in the history of the

United States and Canada occurred august 14, 2003, when 61,800 megawatts

of electrical power was lost in an area covering 50 million people. (One

megawatts of electricity is roughly the amount needed to power 750 residential

homes.) The blackout prompted calls to replace aging equipment and raised

questions about the reliability of the national power grid.

Despite the potential for rare widespread problems, the interconnected

grid system provides necessary backup and alternate paths for power flow,

resulting in much higher overall reliability than is possible with isolated

systems. National or regional grids can also cope with unexpected outages

such as those caused by storms, earthquakes, landslides, and forest fires, or

due to human error or deliberate acts of sabotage.

Power quality

In recent years electricity has been used to power more sophisticated and

technically complex manufacturing processes, computers and computer

network, and a variety of other high-technology consumer goods. These

products and processes are sensitive not only to the continuity of power supply

but also to the constancy of electrical frequency and voltage. Consequently,

utilities are taking new measure to provide the necessary reliability and quality

of electrical power, such as by providing additional electrical equipment

assure that the voltage and other characteristics of electrical power are

constant.

Voltage Regulation long transmission lines have considerable inductance

and capacitance. When current flows through the lines, inductance and

capacitance have the effect of varying the voltage on the line as the current

varies. Thus the supply voltage varies with the load. Several kinds of devices

are used to overcome this undesirable variation in an operation called

regulation of the voltage. The devices include induction regulation and

three-phase synchronous motors (called synchronous condensers), both of

which vary the effective amount of inductance and capacitance in the

transmission circuit.

Inductance and capacitance react with a tendency to nullify one another.

When a load circuit has more inductive than capacitive reactance, as almost

invariably occurs in large power systems, the amount of power delivered for a

given voltage and current is less than when the two are equal. The ratio of

these two amounts of power is called the power factor. Because

transmission-line losses are proportional to current, capacitance is added to the

circuit when possible, thus bringing the power factor as nearly as possible to 1.

For this reason, large capacitors are frequently inserted as a part of

power-transmission systems.

World Electric Power Production Over the period from 1950 to 2003, the

most recent year for which data are available, annual world electrical power

production and consumption rose from slightly less than 1 trillion

kilowatt-hours (

kwh

) to 15.9 trillion

kwh

A change also took place in the

type of power generation. In 1950 about two-thirds of the world’s electricity

came from steam-generating sources and about one-third from hydro electric

sources. In 2003thermal sources produced 65 percent of the power, but

hydropower had declined to 17 percent, and nuclear power accounted for 16

percent of the total. The grown in nuclear power showed in some countries,

notably the United States, in response to concerns about safety. Nuclear plants

generated 20 percent of U.S. electricity in 2003; in France, the world leader,

the figure was 78 percent.

Conservation

Much of the world’s electricity is produced from the use of nonrenewable

resources, such as natural gas, coal, oil, and uranium. Coal, oil, and natural gas

contain carbon, and burning these fossil fuels contributes to global emissions

of carbon dioxide and other pollutants. Scientists believe that carbon dioxide

is the principal gas responsible for global warming, a steady rise in Earth’s

surface temperature.

Consumers of electricity can save money and help protect the

environment by eliminating unnecessary use of electricity, such as turning off

lights when leaving a room. Other conservation methods include buying and

using energy-efficient appliances and light bulbs, and using appliances such as

washing machines and dryers, at off-peak production hours when rates are

lower. Consumers may also consider environmental measures such as

purchasing “green power” when it is offered by a local utility, “Green power”

is usually more expensive but relies on renewable and environmentally

friendly energy sources, such as wind turbines and geothermal power plants.

电力系统介绍

电力系统把其它形式的能源转化为电能并输送给用户。尽管不同于其它形式

的能源，电能不容易储存，一旦生产出来，必须得到使用，但是电力的生产和传

输相对高效和廉价。

电力系统的组成

当今的电力系统由六个主要部分组成：电站，升压变压器（将发出来的电升

压至传输线所需高电压），传输线，变电站（电压降至配电线电压等级），配电线

路和降压变压器（将配电电压降至用户设备使用的电压水平）。

1、电站。电力系统的电站包括原动机，如由水，蒸汽驱动的涡轮，或者燃

烧气体操控的电动机和发电机系统，世界上大多数的电能由煤炭、石油、核能或

者燃气驱动的蒸汽发电厂产生。少量电能由水力，柴油和内燃机发电厂产生。

2、变压器。现代电力系统使用变压器把电能转换为不同的电压。有了变压

器，系统的每个阶段都能在合适的电压等级下运行。在典型的系统中，电站发电

机发出的电压范围是1000伏到26000伏。变压器把电压升至138000到765000

伏后，送至主传输线上。因为对于长距离传输，电压越高，效率越高。在变电站，

电压被降至69000到138000伏，以便在配电系统中传输。另外一组变压器把电

压进一步降至配电等级，如2400到4160伏，或者15，27，33KV。最终，在使

用端，经配电变压器，电压再次被降至240V或120V。

3、传输线。高压传输系统通常由铜线、铝线或者镀铜、镀铝的钢线组成，

它们悬挂在高大钢格构塔架上成串的断瓷质绝缘体上。由于含镀层钢线和铁塔的

使用，增大了塔与塔之间的距离，降低了传输线的成本。在当前的直线安装中，

每公里高压线只需建立6个铁塔。在一些地区，高压线悬挂于距离较近的木质电

线杆上。对于低压配电线路，更多的使用木质电线杆，而不是铁塔。在城市和一

些地区，明线存在安全危险或者被认为影响美观，所以使用绝缘地下电缆进行配

电。一些电缆内核中空，供低压油循环。油可以为防止水对封闭线路的破坏提供

临时保护。通常使用管式电缆，三根电缆放入线管中，并填满高压油。这些电缆

用于传输高达345KV的电流。

4、辅助设备。每个配电系统包含大量辅助设备来保护发电机、变压器和传

输线。系统通常还包括用来调整电压或用户端其它电力特性的设备为了保护电力

系统设施，防止短路和过载，对于正常的开关操作，采用断路器。断路器是大型

开关，在短路时或者电流突然上升的情况下自动切断电源。由于电流断开时，断

路器触点两端会形成电流，一些大型断路器（如那些用来保护发电机和主输电线

的断路器）通常浸入绝缘液体里面，如油，以熄灭电流。在大型空气开关和油断

路器中，使用磁场来削弱电流。小型空气开关用于商场，工厂和现代家庭设备的

保护。在住宅电气布线中，以前普遍采用保险丝。保险丝由熔点低的合金组成，

安装在电路中，当电流超过一定值，它会熔断，切断电路。现在绝大多数住宅使

用空气断路器。

供电故障

世界上大多数地方，局部或全国电力设施都连成电网。电网可以使发电实现

区域共享。同意共享的每个电力企业可以获得不断增加的储备功率，使用更大、

效率更高的发电机，从电网中获取电能以应对局部电力故障。

互联的电网是大型复杂系统，包括被不同组织操控的部分。这些系统可以节

约开支，提高整体可靠性，但是也带来了大范围停电的风险。例如，2003年8

月14日，美国和加拿大发生了历史上最严重的停电事故。当时，这个区域61800

兆瓦的电力供应中断，五千万人口受到影响。（一兆瓦大约可以满足750居民的

用电需求）。停电事件迫切要求更新老化设备，提出关于全国电网可靠性的问题。

尽管存在大范围停电危险，互联电网提供了必要的备份措施和供替换的线

路，相对于孤立系统，其整体可靠性要高得多。国家或地区电网还可以应对由暴

风雨、地震、泥石流、森林火灾、人员操作错误或者蓄意破坏造成的意外停电。

供电质量

近年来，越来越多的精密复杂生产过程、计算机和网络及许多高科技消费品

都使用电力为其提供能量。这些产品和生产过程对于供电的连续性和电压、频率

的恒定性很敏感。于是，相关部门正采取新措施来保证供电的可靠性和质量。如

提供附加的电气设备来保证电压和电能其它特性保持恒定。

1、电压调整。长距离传输线存在的电感和电容不容忽视。当电流流过线路

时，随着电流的变化，电感和电容会对线路电压产生影响。这样，供电电压会随

负荷变化。运行中，有几种设备用来克服这个波动，被称为电压调整。这些设备

包括感应调节器、三相同步机（也称同步调相机），它们能够改变传输线路中的

电感和电容的有效量。

电感和电容作用能相互抵消。当负载电流感性电抗大于容性电抗时，这种情

况总是出现在大型电力系统中，对于给定的电压和电流，传送的功率小于两者相

等的时候。这两个量功率之比称为功率因数。由于传输线损耗和电流成比例，如

果可能，将在电路中使用电容，这样功率因数尽可能接近于1。正是这个原因，

在电力传输系统中，经常使用大型电容器。

2、世界电力生产。从1950年到2003年，最近一年的可用数据显示，每年

世界电力生产和消费从小于1万亿千瓦时增长到15.9万亿千瓦时。同样，发电

类型也发生了变化。在1950年，世界电力约2/3来自蒸汽源，约1/3来自水电。

2003年，热源生产65%的电能，水电却降至17%，核电占总量的16%。出于安

全的考虑，在一些国家，特别是美国，核能的增长缓慢。2003年，美国电能的

20%来自核电厂；在世界领先的法国，这个数字是78%。

保 护

世界上大多数电能的生产来自天然气、煤炭、石油和铀等不可再生资源。煤

炭、石油、天然气含有碳元素，它们的燃烧加剧了二氧化碳和其它污染物的排放。

科学家们认为，二氧化碳是导致全球变暖，地球表面温度上升的主要因素。

电力用户通过节约用电，如离开房间时关闭电灯等措施消除不必要消耗，可

以节省资金，有助于环境保护。其它保护措施包括购买和使用节能电器和灯泡，

在费率较低的非用电高峰使用洗衣机和烘干机等电器。消费者也可以考虑环境措

施，如购买当地公共部门提供的绿色能源等。绿色能源通常价格较贵，但依靠可

再生和环境友好型资源，如风力轮机和地热发电厂。

本文标签： 电压使用电流系统