外文翻译--变电站与电力系统继电保护

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1、 - 1 - 中文 3826 字 附录 1：外文资料翻译 A1.1 Substation and Power System Protection With the development of undertaking of the electric wire netting , the pattern of national network has already taken shape basically. Scientific and technological level raise, electric environmental protection can strengthen, m

2、ake scientific and technological competence and advanced international standards, Chinese of power industry close day by day. Electric management level and service level are being improved constantly, strategic planning management of electric power development, production operate manage , electric m

3、arket administration and electric information management level , high-quality service level ,etc. general to raise enterprise. The purpose of a substation is to transform the characteristics of the electrical energy supplied to some form suitable for use, as for example, a conversion from alternatio

4、n current to direct current for the use of city railway service, or a change from one voltage to another, or one frequency to another. Their functions include: Tap. TO be economical, transmission of larger amounts of power over long distances must be done at voltages above 110,000 volts. Substations

5、 for supplying small amounts of power from such high-voltage lines are not satisfactory from the standpoint of operation and are also uneconomical. It is, therefore, common practice to install a few substations at advantageous points along the high-tension lines and step down the high-transmission v

6、oltage to a lower secondary-transmission voltage from which numerous small loads may be supplied. Distribution. Any substation that is used to transform electrical energy to a potential that is low enough for general distribution and utilization is a distributing substation. Such a substation will g

7、enerally receive its energy over a few comparatively high-tension lines and distribute it over a large number of low-voltage lines. Industrial. When fairly large blocks of power are required by industrial plants, it often becomes necessary and advisable to install an individual substation to supply

8、such a load directly from the main high-voltage line or secondary line of lower voltage. Its simplest form would comprise only switching equipment, there being no voltage transformation. In most cases a voltage transformation is probably needed； hence transformer equipment is included. Sectionalizin

9、g. In very long high-voltage large capacity lines, particularly when several circuits are run in parallel, it is often necessary to split the lines into sections, in order that proper protection to the line and service can be obtained. Such a substation is , therefore, helpful in sectionalizing dama

10、ged sections of a line, providing continuity of service. Such a substation will generally comprise only switching equipment. In long lines it may also serve to supply power-factor-correcting equipment. Transmission-line Supply. It is becoming more and more common to install the high-tension equipmen

11、t of a - 2 - power plant outdoors, the installation becoming nothing more than a step-up substation receiving its power at generator voltage, then stepping up its voltage and finally sending it out over high-voltage transmission lines. Such a substation is nothing more than an outdoor distributing s

12、ubstation turned around, the voltage being stepped up instead of stepped down. Power-factor Correction. The voltage at the end of long lines tends to increase as the load supplied is decreased, while on the other hand it tends to decrease as the load is increased. Owing to the inductance and capacit

13、y effects, this variation in voltage is accompanied by a wide variation in power factor of a line, it is necessary to use synchronous condensers at the end of the line. To supply such a machine the transmission-line voltage must be stepped down, hence a power-factor-correcting substation will includ

14、e switching equipment, transformers, and all equipment necessary for the operation of synchronous condensers. Railway. Substations supplying railways may be generally classified under two heads, namely, as alternating current and as direct current. In the cases of alternating-current substations the

15、 problem is generally one of voltage transformation and of supplying single-phase power to the trains. It is, however, possible to supply single-phase to three-phase inside the locomotive by the use of a phase converter. In the case of direct-current railways, the substations are generally supplied

16、whit three-phase power and converted to direct current by means of rotary converters, motor-generator sets, or rectifiers. Direct current for Light and Power. There are still a few sections in some of out large cities, which are supplied with direct-current three-wire systems. Such a supply is invar

17、iably obtained from synchronous converters. There are also certain types of motor loads in industrial plants, which require direct current. Because many cities have experience rapid growth, their substations have often reached the limits of their capacity. As a result, downtown distribution systems

18、are often overworked and many need a major, overhaul, overhaul, or expansion. However, space is scarce. Downtown business owners do not want “ugly” new substation marring the areas appearance, but nor do businesses and residents grid the prospect of grid disturbances. One example of a system capable

19、 of integrating equipment monitoring with substation automation is the GE Harris integrated Substation Control System (ISCS). The system can integrate data from both substation system and equipment online monitoring devices into a common data base. The data can then be processed by an expert system

20、into information on the status and health of monitored equipment using self-diagnostic programs. This information is then sent to a CMMS for automatic generation and tracking of maintenance work orders leads directly to the significant efficiencies found with condition-based maintenance programs. AB

21、B Power and its industry partners have combined to develop the ABB Power System software. The system contains a diagnostic and maintenance system that reports necessary maintenance before failure. It allows utilities and industrial customers to easily expand from a single computer to a full system,

22、without re-engineering. the directional protection basis Early attempts to improve power-service reliability to loads remote from generation led to the dual-line concept. Of course, it is possible to build two lines to a load, and switch the load to whichever line remains energized after a - 3 - dis

23、turbance. But better service continuity will be available if both lines normally feed the load and only the faulted line is tripped when disturbances occur. Fig.14-1 shows a single-generator, two-line, single-load system with breakers properly arranged to supply the load when one line is faulted. Fo

24、r the arrangement to be effective it is necessary to have the proper relay application. Otherwise, the expensive power equipment will not be able to perform as planned. Consider the application of instantaneous and/or time delay relays on the four breakers. Obviously the type of the relay cannot coo

25、rdinate for all line faults. For example, a fault on the line terminals of breaker D. D tripping should be faster than B, however, the condition reverses and B should be faster than D. It is evident that the relay protection engineer must find some characteristic other than time delay if relay coord

26、ination is to be achieved. The magnitude of the fault current through breakers B and D is the same, regardless of the location of the fault on the line terminal of breaker B or D. Therefore relay coordination must be based on characteristics other than a time delay that starts from the time of the f

27、ault. Observe that the direction of current flowing through either breaker B or D is a function of which line the fault is on. Thus for a fault on the line between A and B, the current flows out of the load bus through breaker B toward the fault. At breaker D the current flows toward the load bus th

28、rough breaker D. In this case breaker B should trip, but breaker D should not trip. This can be accomplished by installing directional relays on breakers B and D that are connected in such a way that they will trip only when current flows through them in a direction away from the load bus. Relay coo

29、rdination for the system shown in Fig.14-1 can now be achieved by their - salvations of directional over current time delay relays on breakers B and D. Breakers A and C can have no directional over current time delay relays. They may also now have instantaneous relays applied. The relays would be se

30、t as follows: The directional relays could be set with no intentional time delay. They will have inherent time delay. The time delay over current relays on breakers A and C would have current settings that would permit them to supply backup protection for faults on the load bus and for load equipmen

31、t faults. The instantaneous elements on breakers A and C would have current settings that would not permit them to detect faults on the load bus. Thus the lines between the generator and the load would have high-speed protection over a considerable portion of their length. It should be observed that

32、 faults on the line terminals of breakers A and C can collapse the generator voltage. The instantaneous relays on breakers A and C cannot clear the circuit instantaneously, because it takes time for power equipment to operate. During this period there will be little or no current flow through breake

33、rs B and D. Therefore, B or D cannot operate for this fault condition until the appropriate breaker at the generating station has operated. This is known as sequential tripping. Usually, it is acceptable under such conditions. Direction of current flow on an a. c. system is determined by comparing t

34、he current vector with some other reference vector, such as a voltage vector. In the system of Fig. 14-1 the reference voltage vector would be derived from the voltages on the load bus. Direction of current or power flow cannot be determined instantaneously on a. c. systems whose lines and equipment

35、 contain reactance. This is apparent from the fact that when voltage exists, the lagging current can be plus or minus or zero, depending on the instant sampled in the voltage cycle. Accordingly, the vector quantities must be sampled over a time period. The time period for reasonably accurate sampling may be from