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[分享] 保护的历史(英文来源于PAC杂志,中文学生自译)

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发表于 2012-2-11 00:17:50 | 显示全部楼层 |阅读模式
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Introduction to the History of Selective Protection


Author: Walter Schossig, Germany

Introduction

The intention of this series of articles is to begin to piece together the true account and timeline associated with PAC developments and to recognize the achievements of the pioneers of early and modern PAC technology.

The technological developments and accomplishments of protection equipment are rarely a cause célèbre within the power industry. It is easy to understand why this is so when one considers that the little black box often pales into insignificance when compared with the physical scale, size and cost of generators, transformers and switchgear. Indeed protection topics are often only discussed after a disturbance or blackout.

Nowadays we achieve a high security of supply thanks in part to the secure and reliable performance of protection, automation and control (PAC) equipment.  Indeed people take the availability of electricity for granted and pay little attention to the effort required to reach this state.

That is why it is useful to consider the first steps of electrical power supply protection and to note the technological development from the early fuse protection up the current state of the art initiatives. Such consideration may provide an insight into the silent, often obscure work on protection and substation automation systems. This will be the first in a series of articles where we will outline the steps in the development of PAC equipment. We admit that there may be information in the articles which may be subject to debate particularly with regard to the historical accuracy of certain events and the fact that we do not have access to all records. Indeed the articles may appear to be biased towards European developers but this Eurocentric perspective is due to access and availability to data. We warmly welcome contributions from our readers, particularly those who may be familiar with historical developments that may have been going on in parallel in other regions, e.g. United States, Japan, former USSR etc.

Technological developments typically follow certain rules and in general you can observe three stages of development. Initially, there can be quite a gentle or silent start-up however this ripple is often followed by a stormy wave of developments which eventually moves towards a more steady state with ongoing incremental activity. This reflects the fact that new ideas are often treated with skepticism and, in the absence of any real need, are not put into practice unless genuine technical or practical reasons exist for doing so. Necessity breeds invention and those ideas that satisfy needs in the industry are more likely to be successfully pursued.  Another driver for inventions is of course the goal to overtake the competition in the market place. In such cases existing ideas are often recycled and improved. One invention supersedes the other. As the German protection pioneer Hans Titze mentioned in his award winning ("Conrad-Matschoß-Medal") publication in 1962, "New ideas sometimes appear like an avalanche: new, up to now unknown and new approaches appear." This observation is valid even today as people rush to exploit the possibilities offered by new technological developments.

100 Years Selective Protection

Developments in PAC equipment were not linear or consistent throughout the years. Some ideas and proposals were rejected initially (perhaps the market conditions were not right or there was not a full appreciation for the proposal's capability or there was no apparent need for the solution). Some ideas were discarded only to be rediscovered by others who recycled them, improved them and exploited them to their full potential driven perhaps by different market conditions or technical challenges facing power system engineers.

The beginning of relay development goes back into the first half of the 19th century. In a paper for the French Academy of Sciences, the Frenchman Breguet noted the physical appearance of thin conductors near a telegraph station after a lightning strike. He had observed that the thin conductors had disintegrated after the lightning strike leaving only traces of what had existed beforehand.

His paper, dated the 3rd of May 1847, stated that "...to protect the devices and especially to protect the employees in the station I recommend the use of electricity conductors, 3-4mm in diameter, made of iron and to be located 5-6m from the device." The report continued, "We connect larger diameter wires of equal metallic behavior to the thinner wire conductors. This approach allows only the amount of electricity that can be carried through the thin wire to be conducted to the stations. In the case of a fault discharge the wire fuses and interrupts the current outside the building, not inside."

The Breguet paper is considered the birth of the fusible link.

The Fusible Link

The distribution grids proposed by Edison and his company to supply electric lighting systems used fusible links. In 1880 the fusible links used strips of lead ("Edison Lead Switch").

Another solution discussed a "lever switch whose lever had a reduced diameter which fused at a certain level of current".

In the early days of electric power systems the protection requirement was simply to interrupt the flow of fault current. However selectivity emerged as a growing requirement as electric power systems became more complex with interconnection of transmission lines and the parallel operation of generators.

In 1910 the municipal utility in Hannover was one of the first recorded cases to introduce a color code for fuse identification. The utility had specified the use of fuses on every feeder to achieve selectivity on their system. The utility specified the size of fuses required for all lines and, in an effort to make the specifications more memorable, the authorities in Hannover used a fuse identification color code based on the color of stamps issued by the German postal authority.


In 1904 Kortler proposed the idea of time delayed self reclosing fuses. This technology is widely used today in medium and high voltage grids and is referred to as automatic reclosing or autoreclosing.

The Relay

The word "relay" was established in the time when stage coaches were a means of transportation. A "relay" was a station for the change from tired horses to fresh ones. In the military the term "relay chains" refers to a chain of annunciators for passing on messages and commands. The introduction of protection relays was of course only possible after the creation of suitable switching devices that were capable of extinguishing the fault current arc and could also withstand the onerous short circuit currents generated under fault conditions. Brown proposed an oil circuit-breaker in 1892. With the introduction of direct release (directly initiated by the primary current) and secondary relays (supplied by current transformers or voltage transformers) "oil self switching circuit breakers" were developed.

Figure 2 Oil Circuit-Breaker with Direct Release (Elektra Birsek, CH)

The Birth of the Protection Relay

The first relay for protection purposes was proposed by Stillwell at 1900 although its application was limited since there were no reliable switching devices for the interruption of short-circuit currents at that time.

  

Figure 3 Lewis B. Stillwell (IEEE)
In future articles we will consider the development from simple overcurrent relays through to directional and distance/differential protection devices. We will discuss the different generations of relays as the technology progressed from the initial basic designs towards the current generation of adaptive digital relays.
The aim will be to inform the reader about key aspects of the different technology employed for protection purposes. It is interesting to note at this stage that one of the earliest cases of the application of a line differential relay was in England in 1912 and of a distance protection relay in Germany in 1921. Records show that both types were being used in the United States shortly thereafter.

Figure 4 First Protection Relays
The physical aspects of relays such as the shape, size, dimensions, casing and color have evolved and it can be noted that the physical appearance of relays have changed dramatically.
In the early years they looked like measuring instruments and changed as shown in figure 4.
One of the earliest connection of two separate grids (19th of November 1887), namely two power stations (Mark grafenstrasse and Mauerstrasse in Berlin, Germany), was synchronized using the synchronizing-bright method / synchronizing-dark method or sometimes referred to as dark-lamp synchronizing. An incandescent lamp is used by engineers to estimate the synchronism of the two grids by using to the brightness or otherwise of the light to estimate the voltage difference (magnitude and angle).
The lamp is switched between the same phases of each generator/ system. When the engineer uses the dark method to synchronize the systems the lamp is initially brightly lit and this reflects the fact that there is a voltage from one generator and no voltage from the other. The excitation of the second generator is adjusted and the voltage changes. Consequently the brightness of the lamp changes as the phase angle or the rotation speed of the generator changes. The lamp is completely dark when both generators/systems are in a fully synchronized state and it is safe to switch in. The bright-method works in the opposite way, i.e. the lamp is bright under synchronous conditions.
This synchronizing method was published by Brown Boveri Company (i.e. BBC but now known as ABB) in October 1928. The paper describing this method was published by Stoecklin but it is not clear whether he was the inventor. The author was unable to obtain any further information concerning the patent for this method.
Nowadays almost half the continents are interconnected and operating in parallel using WAMS and GPS systems. Such interconnection would barely have been imagined a hundred years ago. The 220kV grids of France, Germany and Switzerland ("the star of Laufenburg") were interconnected in 1958. The Western-European UCPTE-grid and the East-European CENTREL/VEAG/BEWAG-grid with parts of the Romanian and Ukrainian grid were inadvertently connected one year before the "electrical reunion" of Germany. Obviously consumers remained unaware of this fact. Such interconnection was made possible by the effective operation of synchronizing devices.
Trip times of early PAC equipment were often dubious and dependent on inaccurate timing mechanisms that could only be set to operate in 2 seconds or in the case of generator protection 10 seconds or even up to 30 seconds. The tripping schedule published in 1922 (see figure 5) shows the settings of an overcurrent protection relay (i.e. 12 seconds). The relay operated on lines 5 and 6 of the Zschornewitz - Lichterfelde substation in Berlin and its operating time upon detection of a fault was set at 10 seconds. Such relay time delay settings are unimaginable by today's standards.

  

Figure 5 110-kV-Tripping-Schedule 1922 (Elektrowerke AG, Berlin)

Pioneers of Protection Technology

The upcoming series of articles will mention the devices, techniques and protection philosophies of many pioneers of PAC protection. For example, names synonymous with protection such as Buchholz, Täuber, Pfannkuch, Cleveland, Merz-Price, Bütow, Westinghouse, Kuhlmann, Biermanns and Paul Meyer will be discussed.
We will consider Petersen coil and Bauch's neutral earthing transformer, the paradox of Bauch, Bollinger's switches, Horn's annunciator, Stotz's mini circuit breaker; Scharf's triangle and the Poleck circuit.
There are many other people whose achievements in PAC history and development warrant a mention and indeed those whose achievements should be honored. We look forward to receiving suggestions and contributions from our readers to augment the information that we have collated.

Generations of Protection

Relay technology has evolved from the simple electromechanical or moving-coil relays that were introduced in 1940, to electronic or static relay modules in the 1960s and ultimately towards the more sophisticated microprocessor-based protection devices in the 1980s. Technology was exploited to avoid unwanted tripping and provide more discriminating, stable and reliable performance through the addition of time-delays, fault direction and impedance measurements to the relay's tripping criteria.  
It is incredulous to modern protection engineers that at one time the timing elements on protection relays were running bowls as shown in figure 6. Such devices are perhaps the origin of the phrase "relay run times".

Figure 6 Time Relays 1891, DRP 59 192
Protection sensitivity increased with the use of new measuring technologies in instrument transformers and relays. Relay self supervision also led to increased reliability. The development of voltage memory for three-pole close-up faults helped to avoid unwanted relay operations ("dead zone").
Difficulties in detecting faults that had short-circuit values below the relay pick-up levels, for example when large machines are operating at low load times such as on Sunday and at night, caused researchers to develop protection that would operate under such fault criteria. BBC developed the crossed-coil instruments for protection purposes and patented this in 1928.  These electromechanical relays are no longer manufactured but many remain in successful service worldwide demonstrating the effectiveness of the design.
Other developments in technology now mean that engineers no longer have to go to the substations and look for physical indications of faults, e.g. broken pieces of porcelain from power system equipment, fallen lines and towers etc. Modern PAC equipment aids engineers in identifying the nature and location of the fault.

The Wife as an Autorecloser

It may come as a surprise to many to know that in the past many substations contained not only switchyards, transformers and control rooms but also the switching engineer's apartment.
One advantage of such an arrangement was that as the switching engineer worked as the substation operator during normal working conditions, his wife was in a position to supervise the substation (although admittedly she did have a limited license for autoreclosing circuit breakers!).
Although Bollinger patented  a "Self Running On-Break-Switch for Automatic Reclosing" in 1913 it seems that the first published papers concerning autoreclose, and the operational problems associated with autoreclose, did not appear until 1925 in both the United States and Germany.
Autoreclose technology has obviously developed over the years however the author of this article still remembers a station where a circuit breaker operated a three stage autoreclose sequence through the use of weights and levers that moved the breaker.
In the past the switching engineer was able to supervise all feeders in a station through a simple visual check of the ammeter readings against predefined values that were marked on the ammeter faces. With the advent of unmanned stations, faults and irregularities were identified by the transmission of the feeders sum indications. However if it was not possible to transmit information like an earth fault or a Buchholz-warning, an alternative possibility of communicating the occurrence of a fault was when the actual tripping of a line caused the customer suffering the outage to contact the utility to complain about the power cut.

Remote Control

It could be said that the dividing wall was the first "remote control" initiative implemented to protect operators switching potentially explosive oil circuit breakers. Through time mimic boards were introduced to stations - these were the precursors to the modern Human Machine Interface (HMI) now installed with station computers.

Figure 7 Mimic Diagram Symbols EW Amsterdam, 1908 (AEG)
The development of protection and substation automation systems had taken place in parallel however with the introduction of digital technology these two technologies began to converge.

The convergence started with the proprietary exchange of information between protection and substation control systems. The journey from "Interface Number 6" (i.e. the forerunner of today's standard IEC 60870-5-103) and IEC 61850 involved many individuals and significant effort on various international working committees. The latest implementation of PAC technology allows the exchange of power system information across political borders and geographical regions and permits the synchronization of electric power systems to form huge power grids.

Measurement of Power System Values

The conversion of primary power system values to secondary ones are an essential aspect of the protection systems. A measurement technique without iron was proposed by Rogowski and Steinhaus in 1912 however the application of those ideas have only recently been seriously considered and implemented by the power industry.  
In 1926 Arnold proposed a nominal secondary value of 1A however many utilities have continued to use the 5A rating.
Today we speak about the Holmgreen-circuit but in actual fact it was Nicholson who in 1910 proposed and patented a method of measuring zero current.

The Language of Engineers

As the electric industry expanded it soon became essential to establish a common set of terms, standards, rules and regulations to allow effective communication between engineers.
Engineers communicate with drawings - they have done so in the past, are doing so now, and will continue to do so in the future. The first harmonization of symbols took place in 1928 and ten years later the first International Electrotechnical Vocabulary (IEV) was published by the International Electrotechnical Commission (IEC) (The IEC was founded in June 1906, in London, England).

Figure 8 Symbol TOC-Relay 1928

Figure 9 The first IEV 1938
The American Institute of Electrical Engineers (AIEE) (now IEEE) (The AIEE was a United States based organization of electrical engineers that existed between 1884 and 1963. It merged in 1963 with the Institute of Radio Engineers (IRE) to form the Institute of Electrical and Electronics Engineers (IEEE)) introduced codes for the description of protection functionalities in 1928. For many years the use of American National Standards Institute (ANSI) / IEEE codes was limited to the Americas however the codes are now being used all over the world. Some of you, dear readers, might remember the block diagrams from the 30's - you know how to value modern drawings, right?

Practical Tests

Often when there were savings in primary equipment additional funds were made available for more elaborate protection solutions. These solutions were tested using stage faults. There were no grids with isolated or with high resistance grounding on the 30kV grid in Berlin but Kuhlmann obtained the first measurements in 1908 having received special permission to conduct the necessary tests from the director Wilkens.

Examples of stage faults include those in 1925 on the 110-kV-grid of the Bavarian utility "Bayernwerke"; in the 1990's on the 380-kV-grid of Switzerland/ Austria; and in the 750kV interconnection between Hungary and Ukraine.

One of the first cases of a stage fault in the United States and Canada was on the high voltage terminal of transformers in 1924. Stage faults were frequently used in the 1950s in the former Soviet Union on the 30-kV, 110-kV and 220-kV systems. Shorting circuits with spring energy storage were manufactured in Poland and had an operating time of 120 ms on the 110 kV system and 200 ms on the 220 kV system. Shorting circuits with explosive cartridges were manufactured in the former Czechoslovakia and were used in the former German Democratic Republic (GDR) for testing on 110-kV transformers.

The Introduction of Electronics

In 1934 Wiederöe proposed the use of electronics in protection devices. Four years later Maret proposed the use of electronic tubes instead of electromechanical relays for line differential protection. The introduction of analogue measuring techniques began in 1965 and by 1967 Morrison had analyzed the use of computers for grid and network simulation. Two years later Rockefeller published his Masters thesis "Computer Protection" and from hence digital protection technology was to become a reality.

In 1977 the 110-kV/20-kV substation Bad Kissingen substation in Germany became the first substation in Europe that was completely protected by digital protection. This substation had a computer to implement the protection processes and for the real-time logging of events.

As mentioned earlier, the main focus of these articles is to discuss the historical development of protection and substation automation, including distance and differential protection ; generator protection; the evolution of the technology used in protection systems; issues associated with faults and fault location; testing devices; and measurement transformers.

Protection has evolved from a single phase fuse to the protection of a six phase line or an n-phase transformer. We will attempt to outline the important contributions of the pioneers. The value of their contributions can be appreciated if we consider the influence their developments have had on the ability of modern engineers to provide us with a reliable power supply.

We expect there will be gaps in the information provided. This could be caused by missing manuals, lack of technical records and gaps in the author’s knowledge. I ask for your understanding. Any comments, suggestions and corrections are most welcome. Please send them to walter.schossig@pacw.org

继电保护的历史

简介

这一系列文章的目的是要开始还原与PAC发展有关的真实情况和时间表,并承认先驱者在早期和现代PAC技术上取得的成就。

保护设备的发展和成绩,很少在电力行业引起轰动。当人们考虑到与发电机,变压器和开关设备的物理规模、面积及成本比较起来,黑色的小盒子往往微不足道的时候,就很容易理解为什么会是这样了。事实上,保护主题往往只有在发生干扰或停电后才会被讨论到。
   
现在我们能够获得安全性能高的供电在一定程度上应感谢保护设备、自动化与控制(PAC)设备安全而可靠地表现。事实上,人们把电力的有效供应视为理所当然,并且毫不在意达到这种状态需要的努力。

这就是为什么关注电力供应保护的初步阶段,并勾勒出从早期保险丝保护到技术创新现状中科技的发展是有用的。这种考虑可以对无声的,常常处于幕后的保护和变电站自动化系统的工作的有所了解。这是我们一系列概述PAC装备发展的步骤的文章的第一部分。我们承认文章中的某些信息有可能会受到质疑,尤其关于某些历史事件的准确性,事实上我们并没有看到所有记录。事实上,文章似乎偏向于欧洲开发商,但欧洲中心主义的观点是由我们所能掌握的数据引起的。我们热忱欢迎来自我们的读者,特别是那些熟悉同时在其他地区进行的历史发展,例如来自美国,日本,前苏联等的读者的投稿。

技术的发展通常遵循一定的规则,一般你可以发现有三个发展阶段。最初,可能是比较柔和的或无声的开始,然而紧跟着的往往是一场激烈的发展,最终走向一个伴随着增长的更加稳定的状态。这反映了一个事实,即新的想法常常被怀疑,一旦没有实用价值,都不会被付诸实施,除非存在真正的技术或实际的理由来这样做。需求催生发明,那些满足了人们的需求的想法更容易被成功实践。另一个发明的动力当然是在市场竞争中成为赢家。在这种情况下产生的想法往往可以回收和改进。一项发明取代另一个发明。正如德国保护的先驱汉斯Titze(“康拉德- Matschoß -勋章”),他在1962年获奖的出版物中写道,“新观念有时出现的像雪崩:新的,到现在未知的和新的方法会出现。”这种看法是正确的,甚至在今天人们争相利用新的技术发展开发这种可能性。

100年选择性保护

这些年来,继电保护的发展并不是线性或一致的。一些想法和建议从一开始就被否定(也许市场条件不允许或对解决方案没有明显的需求)。也许在市场条件改变或技术出现难题时,一些被丢弃的想法才能被那些回收、改进和开发它们的人重新回收利用,充分发挥其潜力。

继电器发展的开始可以追溯到19世纪上半叶。法国科学院文件中写道,一个叫Breguet的法国人记录了一个遭雷击后的电报站附近的细导线产生的物理现象。他曾指出,细导线遭雷击后会断裂,只留下之前已经存在过的痕迹。他在1847年5月3日的一篇论文中指出,“...为了保护设备,特别是保护在电站的员工我建议在装置5到6米处安装直径3毫米的铁制电力导线” 该报告接着说,“我们把直径较大导线连接到同等金属性质的更细的导线上。这种方法只允许一定数量的电能通过细导线传输到电站。产生故障电流的情况时,保险丝熔断并中断建筑外的电流,而不是建筑内部的。”

Breguet 的论文被认为是熔断器的起源。

熔断器

由爱迪生和他的公司提出的供给电能照明的配电网使用了熔断器。

1880年,熔断器使用的是导线(爱迪生导线开关)。

另一个解决方案讨论了“杠杆直径较小用于熔断某一特定大小电流的杠杆开关”。在早期,电力系统对保护的要求只是很简单的切断故障电流。然而,随着输电线路的增多,并入电网电机数量的增加,电力系统变得越来越复杂,对于保护的选择性的要求越来越高。

1910年,汉诺威的市政环保部门第一次记录案例引入了一套标志保险丝的颜色编号。该部门将每个馈电线的熔丝进行分类以用于选择不同的系统。该部门对熔断丝的尺寸也进行了分类以用于不同的线路,并努力使此分类更富有纪念意义,汉诺威当局使用的标志保险丝颜色的编号是基于德国邮政部门出版的邮票。

1904年,卡特罗提出了延时自复熔断器。这项技术今天被广泛应用于媒体和高压电网,也就是常常提到的自动重合闸。

继电器

当驿站马车作为一种交通工具的时候,“relay”一词就诞生了。“relay”就是更换疲惫马匹的站点。在军事年代,在军事年代,“relay chain”是指用来传递信息和命令一系列信号器。继电保护器只能在合适的开关设备被发明之后才出现,这种开关设备能熄灭故障电弧和承受故障条件下引起的短路潮流。1892年布朗提出了油断路器。随着一次断路(由一次电流直接组成)和二次继电保护(由电流互感器或电压互感器提供)的引进,“自启动油断路器“诞生了。

继电保护器的诞生

Stillwell在1900年发明了第一个作为保护目的的继电器,尽管它的应用是有限的,但在那之前没有可靠的开关设备作为短路潮流的中断装置。

在下面的文章中我们将讨论从简单的过电流保护到直流和距离差动保护设备的发展。我们将讨论从科技发展的起步阶段到当代数字时代不同时代下的继电保护器。

文章主要目的是为了告诉读者有关应用于保护目的各种技术的关键部分。有趣的是,要注意在这个阶段,线路差动继电器最早的应用案例之一1912年在英国出现,而距离保护继电器在1912年率先在德国投入使用。记录显示,之后不久,这两种类型的继电器均被美国采用。

继电保护器的外形各方面如形状,大小,面积,外盒和颜色被不停改进,可以这么说继电保护器的外形已经发生了戏剧性的演变。

在早期的时候他们看起来像测量仪器,之后发生了改变。如图4显示。

最早的分离电网即两座发电站(柏林的Markgrafenstrasse和德国的Mauerstrasse)的连接(1887年11月19日)使用亮灯法和暗灯法进行同步。工程师运用一个白炽灯的灯光强弱来判别两条电网是否同步,或者用灯光来判别电压差。(光度和角度)

发电机/电网对应相端点间接入相灯。如果工程人员使用暗灯法来使电网同步,那么开始时相灯将非常明亮,这反映了一台发电机有电压而另外一台没有电压的情况。调整第二台发电机的励磁则其电压发生变化。当相灯完全熄灭,则表明发电机/电网之间完全同步,可以安全投入并联。亮灯法的工作原理与暗灯法相反,即同步条件下相灯是明亮。

这种同步法在1928年十月由Brown Boveri公司(即BBC但通常称为ABB)发布。文章由Stoecklin发表但无法确定他就是这种方法的发现者。该作者无法提供关于这种方法的专利的更进一步的信息。

如今通过使用WAMS
(广域监测系统)和GPS系统,接近一半的大陆得以相互联系并且平行运作。这种联系在一百年前是难以想象的。法国,德国和瑞士(劳芬堡之星)的220KV电网在1958年进行了同步。西欧UCPTE电网和东欧CENTREL/VEAG/BEWAG电网以及罗马尼亚和乌克兰的部分电网无意间在德国“电力再合并”的前一年进行连接。显然用户并不清楚这个事实。类似的连接得以通过同步设施的有效操作实现。

早期继保设备的跳闸时间通常是不明确的,它依赖于动作时间仅仅能设定成2秒甚至高达30秒的计时器。1922年出版的跳闸时间表(图5)说明了过电流保护的整定(即12秒)。该保护工作在柏林的Zschornewitz-Lichterfilde变电所的第5、6线路,其在发现故障后动作时间被整定为10秒。这样的保护延时整定在现代行业标准下是无法想象的。

保护技术的先驱

即将推出的一系列的文章都会提及到许多保护先驱的设备、技术和保护理念。例如,一些名称相像的保护设备,如霍尔兹,塔伯,Pfannkuch,克利夫兰,梅尔茨牌,Bütow,西屋电气,库尔曼,贝南曼和保罗·梅耶将被讨论。

我们会关注消弧线圈和巴赫的中性点接地变压器,巴赫,布林的开关,何恩信号器,斯托茨的小型断路器斯,卡夫三角形和Poleck回路之间的矛盾。

除此之外,还有许多人在PAC的历史和发展中取得的成就值得一提,他们的成就理应受到赞誉。我们期待着收到来自我们的读者的建议和投稿,以增加我们收集的信息.

各代的保护

继保技术已经实现了从1940年引入的简单的机电或动圈式继电器,到20世纪60年代的电子或静态继电器模块和继电器到以更复杂的微处理器为基础的20世纪80年代保护装置的最终演变。技术被利用以避免不必要的跳闸,并通过在继电器的跳闸标准中附加时间延迟故障方向和阻抗测量提供更精确、稳定和可靠的保护。

出乎现代保护工程师意料的是,继电保护中的时间元件曾经是一系列运行的转轴(如图6),这种装置也许是术语“继电器运行时间”的由来。

保护的灵敏度随着新的测量技术,仪器变压器和继电器使用而提高,继电器自检也保障了更高的可靠性。对于三相短路故障的电压记忆也有助于避免继电器误操作(死区)

在检测短路参数低于继电器整定值的故障,例如,当大型机械在低负荷时段如在星期日和夜间的运作时,研究人员遇到的困难促使他们开发可以应对这种故障状况的保护。BBC研发出以保护为目的的交叉线圈公司并在1928年申请了专利。这些机电继电设备已经停产,但许多设备仍然在世界各地成功地运作着,彰显了其高效的设计理念。

如今技术在其他方面的发展意味着工程师再也不需要去电站寻找故障的物理表征,如电力系统设备的瓷器碎片,电线的挂落和电力塔的倒塌等。现代PAC设备帮助工程师查明故障性质和位置。

作为自动重合闸的妻子

许多人会惊讶地发现在过去,许多变电站不仅仅包含开关站、变压器和控制室,而且是工程师的家。

这项安排的优点之一是,作为一个变电站工作的工程师,正常情况下,从某个角度讲,他的妻子就是在监督变电站(尽管无可否认她没有任何操作重合闸断路器的权利!)。

尽管布林在1913年发明了一种“用于自动重合的自动闭合关断开关”,但是首篇关于自动重合及其操作问题的论文直到1925年才在德国和美国出现。

自动重合闸技术数年以来得到了显著发展,然而那种设置了利用权重和杠杆来使断路器动作从而操控一个三阶自动重合序列的回路断路器的电站仍然让笔者记忆犹新。

在过去开关工程师能够通过对标有预定值的电流表的简单目测来监测电站中所有的馈线。随着无人值守站的出现,故障和违规操作的识别由馈线总量传输完成。然而,如果有些信息例如接地故障或赫兹警告信息无法传送,那么供电公司还可以从因断电而蒙受损失的客户的投诉中获知线路跳闸的信息。

遥控

可以说,最早的“遥控”装置是被运用于保护那些有潜在爆炸危险油断路器的操作人员的隔离墙。后来模拟板被引入电站,它就是现在电站微机内置的人机交互界面(HMI)的前身。

保护和变电站自动化系统一直并行发展,然而随着数字技术的出现这两项技术开始有了交集。

这种交集从保护贸易制和变电厂控制系统之间的信息的专有交换开始。从“6号接口”(即今天的标准IEC 60870-5-103的前身)到IEC 61850的发展过程中涉及了许多个人和各种国际工作委员会的重大努力。最新的PAC技术实现允许权力跨越政治边界和地理区域系统的信息交流,并允许电力系统同步,形成巨大的电网。

电力系统参数的测量

一次系统参数转化为二级系统参数是保护系统的一个重要方面。罗氏和施泰因豪斯在1912年提出了无铁测量技术,不过知道最近电力行业才开始认真审议和实施该项技术的应用。

1926年阿诺得建议使用1A辅助标称值,但是许多应用程序仍在使用5A评级。

今天我们讨论的Holmgreen电路实际上是1910年由尼克尔森提出,并获得专利的零电流测量的一种方法。

工程语言

随着电力行业的扩大,建立一套通用的术语、规则以及条例以允许工程师之间的有效沟通是非常必要的。

工程师利用图纸进行交流,在过去这样做,现在和将来也将继续这样做。1928年产生了第一次统一的符号,十年后国际电工委员会出版了第一版国际电工词汇。

1928年美国研究所的电气工程师AIEE(现在IEEE)发明了保护功能的描述代码。很多年来,美国国家标准协会/IEEE代码仅限于美洲使用,但是现在世界各地均在使用。亲爱的读者,你们中的某些人,可能还记得30年代的框图,但你知道如何估计现代绘图的价值吗?

实用测试

当一次系统设有备用设备时,往往会有额外的资金被投入到更详尽的保护方案中。这些解决方案使用阶段故障测试。在柏林30kV网络没有网隔离或高电阻接地,但库尔曼在1908年从威尔肯斯主任那儿获得了特殊权限进行了必要的测试。

阶段故障示例包括1925年在巴伐利亚“Bayernwerke”州的110kV电网,1990年瑞士、匈牙利的380kV电网和匈牙利和乌克兰的750kV电网连接。

首例在美国和加拿大的阶段故障之一是1924年发生在变压器高压端子上。在前苏联阶段故障经常用于30kV、110kV和220kV系统上。人为制造的能源储能短路电路在波兰,它在110KV系统上拥有120ms操作时间,在220kV系统有200ms操作时间。爆炸放热导致短路电路则发生在前捷克斯洛伐克,前德国民主共和国在110kV变压器上对其进行了测试。

电子技术的介绍

1934年Wiederöe提出了将电子学用于保护设备。四年后Maret提出在线路差动保护上用电子管替代机电继电器。模拟测量技术的引进始于1965年,到1967年莫里森分析了能在电网和网络使用的计算机仿真。两年后,洛克菲勒发表了他的硕士论文“计算机保护”,从此数字保护成为一个现实。

1977年,110-kV/20-kV德国巴特基辛根变电站成为欧洲第一个完全由数字保护的变电站。该变电站有一台计算机来执行保护流程和实时事件记录。



综述

如前面提到的,这些文章的焦点在于讨论变电站自动化和保护的历史发展,包括距离和差动保护,发电机保护,用于保护系统有关故障和故障位置的问题的技术的进步,测试设备,与测量变压器。

保护已经从单相熔断发展到一个六相线路或N -相变压器保护。我们将试图概述拓荒者的重要贡献。如果我们考虑到他们的研发对现代工程师提供可靠的电力供应的能力的影响,他们所做的贡献将受到赞颂。

由于缺少指导、技术记录加之作者水平有限,文章提供的信息可能与事实有出入,我请求您的谅解。我们热诚欢迎任何意见,建议和指正。请将他们电邮到walter.schossig@pacw.org

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    [LV.6]常住居民II

    发表于 2012-2-11 15:32:55 | 显示全部楼层
    PAC杂志全名?
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    发表于 2012-2-13 20:29:21 | 显示全部楼层
    翻译的不错
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     楼主| 发表于 2012-2-13 21:07:47 | 显示全部楼层
    PAC-------protection and control
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     楼主| 发表于 2012-2-13 22:02:52 | 显示全部楼层

    发电机保护起源,附件为英文(含有精彩图片)。

    Introduction

    In the beginning of electrical power supply (1880-1890) the importance of switching devices was minor. Small units for illumination of a house and commercial building had been put into operation. Knife switches, strip fuses and a simple bulb for supervision of voltage were sufficient for dynamos with a power of 15…25 kW.

    Edison,T.A. started running the first central station and first public electric utility in New York (Pearl Street) on September 4th, 1882. At first he used three and later six 150 kW, 110 VDC, 1200 rpm "Jumbo Generators" (due to their large size). He developed a complicated lighting system with lines, distribution boards, fuses, breakers and metering devices. The first public power station in Germany with six steam machines (150 HP each) and 12 dynamos with a total power of 540 kW (110 VDC with two-wire connection) was put into operation on May10th,1885 (Berlin, Markgrafenstrasse 44).

    The first switching devices were more or less provisional ones due to lack of experience and limited knowledge. They have were in an empirically-manual manner and were suitable for single tasks. Such an example was the "general interrupter" in the Berlin power station which would enable an emergency cutout of the whole grid. Figure 2 shows such a makeshift construction (nominal current approximately 2000 A and 2x110 VDC. Unlocking the four clamps lets the copper ear plate fall down and interrupt the circuit.

    At this time DC was mostly used. Due to this and the inductance of the machines the control and extinguishing of the lightning arc when switch off occurred, was difficult even at low voltages (65…110 VDC). Developing motors and generators was a challenging task anyway- so nobody was really interested in the so called "auxiliary devices" - low voltage circuit breakers. The initial switching devices originated from laboratories (mercury bowls) or from the telegraph industry (switches and push buttons). Because these devices did not meet heavy-current requirements, engineers avoided them or tried to reduce the breaking capacity with de-excitation of generators.

    At the time of introduction of alternating current, oil was estimated as the optimal extinguishing agent. The pioneer of alternating current, Ferranti, was the first at using oil for that purpose. He plunged the agile part of the Ferranti-oil-fuse (1894) into the oil after opening the contact. The first high-voltage device working completely in oil was developed by C.L.E. Brown (one of the founders of Brown, Boveri & Cie) in Baden/Switzerland in 1897. He proposed at the headquarters Porta Volta in Milan to put an air-circuit breaker (5 kV) in a barrel of oil for testing purposes. This was successful, and a new 16-kV-breaker was developed in the same year for Paderno (with an oil hutch made of glass). Later, steel plate hutches were used.

    One could now protect the generator by switching it off with a circuit breaker and de-exciting it in case of a certain smell, electrical arc, or loud noises. Previously, this was not possible due to the long reaction time (Figure 3).

    First Generator Protection Devices

    The first protection devices were fuses in series with knife switches. Before that, there were fuses at the generator only, so in case of a failure the whole grid (very small at this time) was without power. After a short time it became clear that not having a three-phase trip was a disadvantage. That's why from 1885 to1890 the first automatic circuit breakers were developed. One of the first automatic circuit breakers in Germany was made by Hermann Meyer, S & H, 1886 with the "biggest machine circuit breaker at this time" (knife switch) combined with an electromagnetic undercurrent relay (startup at 10% of nominal or reverse current). This was a combination of minimum- and reverse-current-automats (early relays), used for parallel operating DC generators.

    After this the first "triumvirate"-automats were developed: minimum-automat; reverse-current-automat and maximum-automat (Figure 4) as fundamental components of the DC-generation and -distribution at this time together with batteries in power stations. The task of these devices was the switching-off during low currents, wrong direction of currents or overcurrents.

    The tripping was accomplished electromechanically. Several types were created. The first industrial transmission of current in Switzerland took place in 1887 with commissioning of the DC-interconnection Kriegstetten-Solothurn ( 8 km, 2500 V, 50 PS, = 70 %) by Oerlikon. Figure 5 shows the wooden switchboard, above the interface-device ( 3 wires with a diameter of 6 mm, one of them as spare). On the left and on the right the automatic short-circuiters are arranged; they are shorting the field magnets in case of a fault. They were used to replace the lead fuses.

    „Switchboards“

    In the first years of high-current technology (1880- 1890) a "switchyard" consisted of a DC-dynamo connected to a switchboard. A board made of planks. Wood was considered a good insulator at this time. In Figure 6 you can see the planks and the attached instruments, main switch and four knife-switches with stripe fuse. The word "board" (in German "Brett") is still used for terminal boxes of generators and motors - “terminal board“ in English. A mock up circuit is sometimes called a "breadboard" ("Brettschaltung").

    Automatic Overcurrent Devices

    In 1885 American engineers equipped the knife switches with overcurrent magnets (Figure 1). A click holds the knife in position "On"; replaceable-devices made of coal took the lightning arc, additional extinguishing possibilities were not prepared. C.E.L. Brown, OERLIKON, built a maximal automat as shown in Figure 7 (open position) in 1888.

    In case of a generator overcurrent condition, the automat starts up and shorts the excitation winding.

    The knife falls down and connects the moving contacts. This approach solves the challenge of interrupting high

    currents in case of high self-induction voltage.

    Later overcurrent automats had more force. The knife closed with a clamped spring (during switching on or with a weight). If the magnet tripping device operated it moved the switch into the Off-position. The smallest starting current possible was 130% of the nominal current, in normal case they have been set with a value of 150%.

    Automatic Undercurrent Devices

    The task of automatic undercurrent devices was to switch off parallel operating generators in case of a decreasing generator current to avoid a feedback current from the battery to the generator. The moment of switching off depends on the prior magnetizing current (magnetization). The higher the preload, the lower the startup value.

    The set point was 15% in 1882, later 5%. An unpleasant –even dangerous- behavior of some automatic undercurrent devices was a malfunction caused by rapidly decreasing currents with fast change of direction of currents due to the magnetic inertia.

    Reverse Current Automatic Devices

    Due to the uncertainty of some automatic undercurrent devices reverse current automats were used instead of them. In 1892 they could start with 20% of the nominal value.

    The tripping magnet was equipped with a current-and a voltage-coil. During normal operation both coils are working against each other ("differential coil"), in case of reverse current

    the switch trips (Figure 9).

    Under Voltage Tripping Device

    Breakdown and recovery of voltage, a daily event in early times, required the usage of devices with under voltage tripping elements. At first "automatic circuit-breakers" (Figure 17) were used.

    Later the devices were combined with other functions for switches. A solution for two-phase short-circuit protection with undervoltage trip was presented by V&H in the 1920's (Figure 8).

    Primary tripping devices, were mounted on the breaker operate mechanism with a lever. The voltage tripping device is supplied by an external voltage transformer (Figure 12). When the voltage transformer operates in the direction of infeed it is guaranteed that the circuit breaker could be switched on only in case of existing voltage.

    The company Dr. Paul Meyer introduced a three phase zero voltage tripping device in 1912


    "Trip Free Mechanism"

    The trip free mechanism, developed in 1900 was the main progress for automatic circuit-breakers. This was a special design of the switch, ensuring that it fully opened before it was enabled to be to closed again. Figure 10 shows such a trip free mechanism. It required a current in coil 1 before the switch could be operated.

    If these devices were not available, the approach was to avoid disabling of the automatic circuit-breakers in case of a trip (e.g. switch onto fault): Then, the automatic circuit-breaker and the lever switch are connected in series.

    When switching, the automatic circuit-breaker was first operated and then the lever switch was opened. This caused some failures due to wrong order of operation, this was reported for instance from the United States. That's why Sharpstein, S.H. required "a trip free mechanism" in 1899, realized by Emmett and Hewlett, GEC.

    Use of Measurement Transformers

    Increase in demand on power and transmission of energy over long distances was the reason to build bigger generators or to operate generators and grids in parallel. This required the use of measuring transformers. It seems that the first voltage transformer had been used in the "Californian Light Company" in San Francisco in 1879. The current transformer was invented by Benischke,G. in 1898. And since 1900 relays were designed to use current transformers.

    Emmet,W.L.R. und Hewlett,H.E., GEC, built in 1901 oil circuit breakers with two tripping coils, directly connected to the current transformers to open the locking mechanism.

    Figure 16 shows an "automatic machine tripping device" with an overcurrent relay supplied by current transformers (used by AEG in power stations in 1905). The figure shows the solution with auxiliary power supply. But this breaker was manufactured with tripping coils supplied by two parallel operating current transformers.

    It was a logical conclusion to change the measuring devices in such a manner that the indicator also operates the contact. Nevertheless this solution was unsatisfying. The breaking capacity was poor (6 VA at 220 V) and the electric arc held the contacts together.

    Since the same measuring principles have been used the first relays have been quite similar to measuring devices (especially the round form Figure 19).

    The Swedish Company ASEA delivered the first induction relay for a water station of the Swedish Rail (16 2/3 Hz) in 1912. To cut one's own path was the decision of Voigt & Haeffner (V&H). Vogelsang, M. developed an overvoltage relay with timing element in 1902. They decided to do it like that because they did not produce current transformers themselves. Additionally Vogelsang developed an "oil circuit breaker with fuse". To change the fuse it was at first necessary to switch off the breaker before opening the cap.

    The history of measuring transformers will be covered in a later issue of PACWorld.

    Overcurrent Protection

    The main element of generator protection was overcurrent protection from the beginning. It protected the generator of inner damages, and was also the backup protection for all further assets such as transformers and lines. Smaller machines were equipped with direct overcurrent release, connected with a lever (Figure 13; Figure 15). The first stand-alone electromechanical relay was designed in1904. Figure 18 shows the first time-overcurrent relay made by ASEA, type TCB, manufactured in 1905. ASEA's (now ABB) first relay of induction type was delivered in 1912 to a hydropower station in the north of Sweden, built to deliver power at 16 2/3 Hz to the railway from Kiruna to Luleå, which was built to transport iron ore. This was the first electrified railway in Sweden.

    Overload Protection

    The use of thermal relays for protection of generators was introduced exclusively by BBC in Europe and was very

    successful.

    German recommendations required generators with a nominal power of more than 5000 kVA to use six resistance the rmometers or thermo elements in the stator to supervise the temperature of winding. Once they were installed it was very difficult to reach them again- that's why they very often were not changed after damage. So it was the decision to supervise the temperature with thermal relays. These devices are equipped with thermo elements (heating relays with current proportional to main current delivered an image of temperature of the machine- Figure 14.

    The outer insulating mat "O", was working as a protection against thermal radiation. It encloses the source of heat, the measuring element and the heat storage "P". The heating element – a band made from a resistive material- heated the measuring column and the heat material storage, consisting of changeable measuring boards. The thermal time constant of the relays could be changed with the numbers of boards in 6 stages between 20 and 110 minutes. The upper scale was a display of the temperature to allow a later estimation of temperature. Additionally the relays were equipped with a tripping device.

    Later single pole overcurrent relays with a setting of 1.1 In and 10 s have been used for indicating overload.

    Short Circuit Protection

    To use overcurrent relays between generator and busbar in case of failures inside the generator was active only if other machines were able to deliver short circuit currents. The power of another machine had to be as big as the power of the machine to be protected. In case of its own failure the generator delivered a huge short circuit current but this could not be detected with such a setup. That's why overcurrent relays have been installed in the neutral point of the generator. This setup was the only possibility if the generator was the single source in the grid. Figure 21 shows a three-phase overcurrent protection "S", manufactured by SIEMENS in 1936.

    Connecting generators and grids in parallel increased the reliability of power supply but on the other hand created

    unmanageable short-circuit currents in case of failure. Sometimes the unreasonable guaranties for small voltage drops in the machine required the use of coils for the limitation of the current from generators with high short circuit power (hard machines). Later "soft" generators were used, equipped with a huge short-circuit reactance. The Swiss grid reported good experiences with the usage of a cutback of excitation to achieve a limitation of a sustained short-circuit current. All big power stations have been equipped with such devices. The automatic decrease of excitation could limit the steady-state short-circuit current to a certain value (as 1.4*Inom). After switching off the short circuit the voltages recovers. Out of step machines could be "catched". The current level in case of a short circuit sometimes reached the level of overload current.

    Nevertheless, in case of a malfunction of the line protection the generator overcurrent protection should trip. Solowjew,L.E., USSR, proposed in 1932 to use "undervoltage supervision". This allowed a more sensitive setup of the overcurrent startup. An overcurrent relay produced by BBC in the 1960's is shown in Figure 22.

    The overcurrent setting must be over the highest possible operating current. Since these devices started up with a fault in the grid already the operating time must be the biggest in the grid. If several generators are working in parallel all overcurrent relays had the same operating time. In case of terminal short-circuit of a generator there was no selectivity anymore. This was only possible if the faulty generator could be tripped faster than the other ones.

    Further solutions such as reverse power protection, differential protection, interwinding fault protection and earthfault protection will be covered in a later issue of this magazine.


    在电力系统发展初期(18801890年间),开关设备的重要性比较小。为一幢房子或一座商业大楼设计的小型设备当时已经投入运行。对发电容量在15-25kW的发电机来说,闸刀开关、熔断器和一盏用来监控电压的灯泡就已经足够了。

    188294Edison T.A开始在纽约的珍珠街运行第一座中心电站和第一台公共用电设备。一开始他用了三台150kW,额定电压110V,额定转速1200rpm的“巨型发电机”,后来增加到6台用于发电。同时他构造了一个含有线路、配电屏、熔断器、刀闸和测量仪表的复杂照明系统。真正意义上的第一座公用电站于1885510在德国柏林投入运行,装设有6150马力的蒸汽机和12台额定电压110V,总容量540kW的发电机。

    由于知识和经验的缺乏,一开始的开关设备是暂时性的。他们以手动经验为主的方式工作于单任务系统。柏林电站一次普通的电力中断将导致整个电网瘫痪就是一个典型的例子。

    这个时期直流电被广泛应用。正由于这个原因及机器电感的存在,即使是很低的电压(65-110V直流)下,开关断开时产生的电弧也是难以控制和熄灭的。研发电动机和发电机已经是一项相当艰巨的任务以至于没有人对“低电压断路器”这样的所谓的辅助设备真正感兴趣。最初的开关设备起源于实验室里的水银开关或是电报行业的开关按钮。但这些设备不能满足大电流的需求,因此工程师们常常避免使用他们,或是通过降低发电机励磁来减小开关容量。

    当交流电应用的时候,油被认为是最佳的灭弧介质。“交流电先驱”法拉第首先利用油作为灭弧介质。他使熔断器的活动部分再断开电路时浸入油中。第一台完全工作在油中的高压设备由C.L.E Brown1897年在瑞士巴登发明。他向米兰总部提交了将5kV开关放在一桶试验用油中的设想。成功之后,在同一年,一个置于玻璃箱装油中的16kV开关被发明了出来。此后,钢制箱代替了玻璃箱。

    现在人们可以在有异常气味、电弧和异常响声时用断路器切断发电机运行或进行灭磁。由于设备反应时间较长,这在以前是无法实现的。

    第一台发电机保护装置

    第一台保护装置是一些与刀开关相连的熔断器。在这之前,只有发电机上有熔断器,因此一旦发生故障整个电网就将瘫痪。在很短一段时间之后,没有三相脱扣器所带来的缺陷变的很明显。这就是为什么自动断路器在18851890年间被发明了出来。第一台自动断路装置于1886年在德国被Hermann Meyer, S & H发明出来,由一个电磁型低电流继电器组成(当电流减至10%正常值或流过反向电流时动作),是当时体积最大的机械断路器。这是最小电流和反电流自动装置的组合,用于并联运行的直流发电机。

    在这之后,一种三功能合一的自动装置被发明了出来,同时可以进行最小电流、反向电流和最大电流的自动控制,和蓄电池一起成为了当时电站中直流发电和输电的最基本组成部分。这些装置的任务就是在欠电流、反电流和过电流的时候能够切断线路。

    跳闸动作由机电行为完成,许多种类型被发明出来。由Oerlikon创建的第一条直流输电线路于1887年在瑞士试运行,连接了KriegstettenSolothurn两个地方(8公里,2500伏)

    配电板

    在大电流技术的初期(1880年至1890年),由连接到配电板上的一台直流发电机组成了户外配电装置。这种配电板由厚木板制成,木头在当时被认为是一种很好的绝缘体。

    自动过电流保护装置

    1885年,美国的工程师将刀开关和过电流磁铁组合起来。用一个挡板将开关固定在打开的位置上,利用可装配的煤粉来带走电弧,除此以外并没有额外的灭弧措施。一旦发电机处于过流状态,自动装置将会动作,将装置励磁线圈短路,开关就会落下,动静触头闭合。这种办法能够解决由于自感高电压所造成的瞬时大电流带来的威胁。

    以后的过电流自动装置的闭合利用了外力,开关利用夹紧弹簧的弹力闭合。最小的动作电流可以设定在正常值的130%,正常情况下被设定在正常值的150%

    自动欠电流保护装置

    欠电流保护装置的任务是在发电机电流减小时及时将并联运行的发电机组切除,以防止蓄电池向发电机倒送电。切除时机根据超前的磁化电流确定,超前负荷越多,整定值就越低。

    1882年这个值设定在15%正常值,后来降低到5%。一种自动欠电流装置不正确甚至有危险性的动作是由于电流骤减造成的故障,这种电流的骤减是由磁场惯性造成的电流方向瞬变所引起的。

    自动反向电流保护装置

    由于一些自动欠电流装置的不确定性,自动反向电流保护装置逐步取代了它们。1892年的时候,它们可以在正常值的20%就开始动作。电磁部分由一个电流和一个电压线圈组成。正常情况下,两线圈极性是相反的,当流过反向电流时,极性颠倒,装置动作。

    欠电压跳闸装置

    早期经常发生的电压崩溃和电压恢复要求设备具有欠电压跳闸装置。一开始自动断路器被广泛使用。

    后来除了开关电路这种装置又结合了其他的功能。20世纪20年代V&H提出了带欠电压跳闸的两相短路保护方案。

    主要跳闸部分被通过一个连杆安装在断路器的操动机构上。这种电压跳闸装置由一台额外的变压器供能。当变压器运行时保证了断路器只有在电压存在的时候才能合上。

    Dr. Paul Meyer公司在1912年提出了三相零电压跳闸装置。

    自由跳闸机构

    自由跳闸机构的发明是20世纪在自动断路器领域的一大进步。这是一种经过特殊设计的开关,能够确保在动作闭合前可以处于完全打开状态。

    如果装置拒动,那么解决的途径是避免自动断路器由于误跳闸导致失效。这时自动断路器和连杆开关会相串联起来。

    当动作时,自动断路器先动作,然后连杆开关被打开。来自于美国的一些报告称,这样有时由于错误的操作顺序会导致一些故障。这也就是为什么Sharpstein, S.H.要在1899年提出“三相自由跳闸机构”,这一观点后来被美国通用公司的Emmett and Hewlett所意识到。

    测量变压器的使用

    长距离输送更多电能的需求使得我们需要制造更大容量的发电机,或者让多台发电机和电网并联运行。这时就需要用到测量变压器。似乎在1879年旧金山的加利福尼亚照明公司就使用了第一台电压互感器。第一台电流互感器是在1898年由Benischke,G.发明。从二十世纪起继电保护装置就被设计成使用电流互感器。

    美国通用电气公司的Emmet,W.L.R. und Hewlett,H.E.1901年制造出含有两个跳闸线圈的油断路器,直接和电流互感器相连来打开锁定的机构。

    16展示了一个自动跳闸装置,与过电流保护装置相配合,由电流互感器提供测量量。数字显示了辅助电源方案。但是这种断路器由与两路并联运行的电流互感器相连的跳闸线圈制成。

    通过一些操作接触指标来改变测量设备从而改变测量装置是一种合乎逻辑的方法。不过这个解决方案是让人不满意的。因为开关容量太小(6 VA/220v)不足以灭弧。使用相同的测量原理,第一个继电器已经相当类似于一种测量设备形式(特别是图19的圆式)

    瑞典公司ASEA将第一台感应式继电保护装置用于为瑞典一条16 2/3hz电气化铁路供电的水电厂。Voigt &Haeffner (V&H).决定打破自己原有的规划,Vogelsang, M.1902年发明了一个带有时间元件的过电压继电保护装置。他们之所以那样决定是因为他们自己并不生产电流互感器。Vogelsang还额外发明了带有熔断器的油断路器。一开始更换熔断器时必须在打开外盖之前跳开开关。关于测量变压器的历史将在PACWORLD的后续文章中提及。

    过电流保护

    一开始过电流保护是发电机保护的主要组成部分。它主要保护发电机内部的故障,同时作为一些更远端的保护装置,例如输电线路保护和变压器保护的后备。设备由通过杠杆连接在一起的过电流释放装置构成。第一台独立工作的机电型继电器在1904年发明。ASEA的第一台感应式继电装置于1912年交付给瑞典北部的一个水力发电厂使用,这个水电厂当时用于给一条输送铁矿石的铁路提供频率为16 2/3赫兹的交流电。这是瑞典的第一条电气化铁路。

    过负荷保护

    为发电机保护设计的热继电器由欧洲的BBC公司专门引进,并且取得了极大成功。

    德国的电气标准要求额定容量在5000kVA以上的发电机,都必须在定子上安装六个电阻温度计或类似热电装置来监控绕组的温度。但是它们一旦安装上去,就很难再接触到,所以一旦发生故障就无法更换。因此人们决定用热继电器来监控温度。这些装置由许多热元件构成。

    外部的O形绝缘垫,能够对热辐射起到保护作用。它能将封住热源,并且测出热量并锁存。加热元件——一个由电阻性材料做成的小片,为测量部分和热量锁存部分提供热量,共同构成了可变测量元件。继电保护装置的热量时间常数可以有20110分钟六段的调整。上面刻度显示的当前温度可以作为器件温度的估算。这种继电设备同时又额外地装设有跳闸装置。

    此后单级型过电流继电保护装置动作电流整定在1.1倍额定电流,时间延时整定在10秒,用来监控过负荷。

    短路保护

    这种装设于发电机和母线之间的,当发电机内部故障时动作的继电保护装置只有在其他设备能够导通短路电流的时候才能正确动作。其他设备的容量至少要和被保护设备的容量一样大。设备自身故障时会流经发电机一股强大的短路电流,但有可能无法被保护装置监测出来。这也就是为什么过电流保护装置需要安装在发电机的中性点处。当发电机处在单电源网络中时这种装置就是唯一能够起到作用的保护。

    将发电机并网可以增加供电可靠性,但另一方面也在故障时产生了不可控制的短路电流。有时不合理地保证电压小幅降落会用线圈来阻止发电机的电流上升为短路电流(硬装置)。后来投入使用的“柔性”发电机装设有一个很大的短路电抗器。瑞士电网就有这样一个好的应用经验:利用减小励磁来限制持续性的短路电流。所有大型的电站都装设有这样的装置。这种自动减小励磁的装置可以将稳态短路电流限制在一个定值,例如1.4倍的正常电流值。切除短路回路后电压就可以得到恢复。失步运行的设备可以被“拉入同步”。这时短路电流的级别有时很接近于过负荷电流值。

    然而,当输电线路保护装置发生故障的时候,发电机的过电流保护装置也应能动作于跳闸。来自前苏联的Solowjew,L.E.1932年提出利用“欠电压监测装置”。这就允许了过电流装置的启动可以设定得更加灵敏。这样的一台过电流继电保护装置于20世纪60年代由BBC公司生产。

    过电流保护的整定值必须大于可能的最大运行电流。由于这些装置在电网已经发生故障的时候要动作,因此运行时间肯定是电网中最大的。如果几台发电机并联运行,那么所有的过电流继电保护装置拥有相同的动作时限。一旦终端的发电机发生短路故障,那么装置将失去选择性。这只有在故障发电机比其他发电机更快被切除时才是可行的。

    更多解决方案例如功率方向保护,微分保护,内部绕组故障保护和接地保护将在这本杂志的后续文章中提及。

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