S7300模拟量转换教程

Relaying technology has advanced dramatically since the Second Edition was issued, most notably for the part some form of computer now plays in the various functions. The uses range from the microprocessors employed in the relays themselves, for measurement or control, to testing by computer for development including power systems simulation, production testing and even site testing.

Although the book is principally concerned with the applications of relays. particular advances in relay design can significantly affect the way they are used. For example, alternative schemes may be selected within some standard designs, simply at the flick of a switch, sometimes involving a closer integration of protection and control functions. So the relay hardware is becoming even more standardized, to the point where versions of a relay may differ only by the software they contain.

his progress has made it both exciting and desirable to tackle the production of a new, Third Edition of this popular book. Several of the chapters have been totally or substantially rewritten, but the changed scene is perhaps best exemplified by the inclusion of a new chapter on the Application of Microprocessors to Substation Control. This sets out to introduce many of the computation terms which may be unfamiliar to some protection engineers of an older generation.

At what some may regard as the simpler end of the application scale, the scope of the book has been widened to include another new chapter. on the protection of industrial power systems. The correct application of protective relays requires not only a knowledge of the relay design parameters but also a good understanding of the behaviour of the power system in which the relay is to be applied. The book attempts to present the practising engineer with sufficient information to assist him in his everyday work, including testing and commissioning, without overstressing the more complex problems. Such problems are, in any case. usually dealt with as a combined effort between the user and the manufacturer, for specific applications.

For the last edition a presentation format was chosen which we believed would be both easy to follow and convenient to use. In response to the many complimentary comments we received, this format has been largely retained for the new edition.

The first part of the book deals with the fundamentals of protective gear practice, basic technology, fault calculations and the circuits and parameters of power system plant. including the transient response and saturation problems that affect the instrument transformers associated with protective relays. The book then goes on to cover the parameters of electromechanical relays, solid state relays and protection signalling and ends with a detailed analysis of the relays systems associated with power system plant. The final chapter is a guide to good relaying practice, with references to the various types of relays manufactured by GEC ALSTHOM T&D Protection & Control. The recommended relays and schemes for the main items of power system plant are listed in the various relay application tables.

Fundamentals of protection practice
  2    Basic technology
  3     Fault calculations
  4     Equivalent circuits and parameters of power system plant
  5     Current and voltage transformers
  6     Electromechanical relays
  7     Static relays
  8     Protection signalling
  9     Overcurrent protection for phase and eanh faults
10     Unit protection of feeders
11     Distance protection
12     Distance protection schemes
13     Protection of parallel and multi-ended feeders
14     Auto-reclosing

自本书第二版出版至今，继电保护技术已取得了长足发展，其中最值得关注的就是计算机的应用越来越广泛，范围从继电器本身采用微处理器来实现测量和控制，到利用计算机进行电力系统仿真开发，产品测试及现场试验。

虽然本书着重讲解继电器应用，但不能不看到快速发展的继电器设计对继电器用途的影响。比如，某些标准设计可以用拨动开关方便地提供多种方案,有时包括保护和控制功能的集成化。因此继电器的硬件部分正日益标准化，继电器种类的不同仅靠其软件部分来区分。

为了适应技术的发展，对本书进行第三次修订就成为当前的迫切需要。书中有几章已全部重写，最好的例子就是新增加了“微处理器在变电所控制中的应用”一章。本书还介绍了许多老一代继电保护工程师所不熟悉的计算术语。

本书不仅仅停留在应用范围，一些新章节已扩展到工业用电系统保护。

正确使用继电器不仅需要了解继电器设计参数，还要对使用继电器的电力系统工况有较深的理解。本书将为从业人员提供足够的资料，帮助其解决日常工作，如试验和调试。但不涉及更复杂的问题，总之这类问题通常涉及用户和制造商的合作成果，用于特殊用途。

上一版采用了图象格式，我们相信这易于理解和便于使用。根据许多反馈意见，新版本保留了这种格式。

本书首先讲述了保护装置的基本原理、基础技术、故障计算和设备的回路特性，包括暂态响应及磁饱和对继电器的测量变压器的影响；接着是电磁型继电器、静态型继电器和保护信号装置的特性；最后详细分析了电力系统设备保护系统。最后一章以GEC ALSTHOM生产的各种类型的继电器为例，作为继电保护实际应用的指南。继电器使用表列出了电力系统设备主要保护配置推荐的继电器和设计方案。

我们真诚希望该书能继续为世界各地的广大工程师们服务。希望它不仅是一本指导手册，还能作为新一代继电保护工程师的培训教材。

1    保护基本原理
2    基本技术
3    故障计算
4    电力系统设备等值回路及参数
5    电流互感器和电压互感器
6    电磁型继电器
7    静态型继电器
8    保护信号装置
9    相过流保护及接地保护
10    线路单元保护
11    距离保护
12    距离保护设计方案
13    并联及多终点线路的保护
14    自动重合闸
15    母线保护
16    变压器及变压器开关保护
17    发变组保护
18    联跳
19    工业用电系统保护
20    交流马达保护
21    整流装置保护
22    微处理器在变电所控制中的应用

1.1 Introduction.
1.2 Protective gear.
1.3 Reliablity.
1.4 Selectivity.
1.5 Zones of protection.
1.6 Stability.
1.7 Speed.
1.8 Sensitivity.
1.9 Primary and back-up protection.
1.10 Definitions and terminology.
1.11 List of symbols.
1.12 List of device numbers.
1.13 Relay contact systems.
1.14 Operation indicators.
1.15 Relay tripping circuits.
1.16 Supervision of trip circuits.

1.1
INTRODUCTION
The purpose of an electrical power system is to generate and supply electrical energy to consumers. The system should be designed and managed to deliver this energy to the utilization points with both reliability and economy. As these two requirements are largely opposed, it is instructive to look at the reliability of a system and its cost and value to the consumer, which is shown in Figure 1.1.

Figure 1.1 Relationship between reliability of supply,its cost and value to the consumer.

It is important to realize that the system is viable only between the cross-over points A and B. The diagram illustrates the significance of reliability in system design, and the necessity of achieving sufficient reliability. On the other hand, high reliability should not be pursued as an end in itself, regardless of cost, but should rather be balanced against economy, taking all factors into account.

Security of supply can be bettered by improving plant design, increasing the spare capacity margin and arranging alternative circuits to supply loads. Sub-division of the system into zones. each controlled by switchgear in association with protective gear. provides flexibility during normal operation and ensures a minimum of dislocation following a breakdown.

The greatest threat to the security of a supply system is the short circuit,which imposes a sudden and sometimes violent change on system operation. The large current which then flows, accompanied by the localized release of a considerable quantity of energy, can cause fire at the fault location, and mechanical damage throughout the system, particularly to machine and transformer windings. Rapid isolation of the fault by the nearest switchgear will minimize the damage and disruption caused to the system.

A power system represents a very large capital investment. To maximize the return on this outlay. the system must be loaded as much as possible. For this reason it is necessary not only to provide a supply of energy which is attractive to prospective users by operating the system within the range AB (Figure 1.1), but also to keep the system in full operation as far as possible continuously, so that it may give the best service to the consumer, and earn the most revenue for the supply authority. Absolute freedom from failure of the plant and system network cannot be guaran- teed. The risk of a fault occurring, however slight for each item, is multiplied by the number of such items which are closely associated in an extensive system, as any fault produces repercussions throughout the network. When the system is large, the chance of a fault occurring and the disturbance that a fault would bring are both so great that without equipment to remove faults the system will become, in practical terms, inoperable. The object of the system will be defeated if adequate provision for fault clearance is not made. Nor is the installation of switchgear alone sufficient; discriminative protective gear, designed according to the characteristics and requirements of the power system. must be provided to control the switchgear. A system is not properly designed and managed if it is not adequately protected. This is the measure of the importance of protective systems in modern practice and of the responsibility vested in the protection engineer.