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附录1：外文资料翻译
A1.1 Substation and Power S魔兽秘籍大全>神话故事嫦娥奔月ystem 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 rai, electric environmental protection can strengthen, make scientific and technological competence and advanced international 白羊男的特点standards, Chine of power industry clo day by day. Electric management level and rvice level are being improved constantly, strategic planning management of electric power development, production operate manage , electric market administration and electric information management level , high-quality rvice level ,etc. general to rai enterpri.
The purpo of a substation is to transform the characteristics of the electrical energy supplied to some form suitable for u, as for example, a conversion from alternation current to direct current for the u of city railway rvice, or a change from one voltage to another, or one frequency to another. Their functions include:
法律进校园
Tap.─TO be economical, transmission of larger amounts of power over long distances must be done at voltages above 110,000 volts. Substations 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 voltage to a lower condary-transmission voltage from which numerous small loads may be supplied.
Distribution.─Any substation that is ud to transform electrical energy to a potential that is low enough for general distribution and utilization is a distributing substation. Such a substation will generally 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 such a load directly from the main high-voltage line or condary line of lower voltage. Its simple
星星消失st form would compri only switching equipment, there being no voltage transformation. In most cas a voltage transformation is probably needed; hence transformer equipment is included.
Sectionalizing.─In very long high-voltage large capacity lines, particularly when veral circuits are run in parallel, it is often necessary to split the lines into ctions, in order that proper protection to the line and rvice can be obtained. Such a substation is , therefore, helpful in ctionalizing damaged ctions of a line, providing continuity of rvice. Such a substation will generally compri only switching equipment. In long lines it may also rve to supply power-factor-correcting equipment.
Transmission-line Supply.─It is becoming more and more common to install the high-tension equipment of a 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 nding it out over high-voltage transmission lines. Such a substation is nothing more than an outdoor distributing substation turned around, the voltage being stepped up instead of stepped down.
Power-factor Correction.─The voltage at the end of long lines tends to increa as the load supplied is decread, while on the other hand it tends to decrea as the load is incread. Owing to the inductance and capacity effects, this variation in voltage is accompanied by a wide variation in power factor of a line, it is necessary to u synchronous condenrs 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 include switching equipment, transformers, and all equipment necessary for the operation of synchronous condenrs.
Railway.─Substations supplying railways may be generally classified under two heads, namely, as alternating current and as direct current. In the cas of alternating-current substations the problem is generally one of voltage transformation and of supplying single-pha power to the trains. It is, however, possible to supply single-pha to three-pha inside the locomotive by the u of a pha converter. In the ca of direct-current railways, the substations are generally supplied whit three-pha power and converted to direct current by means of rotary converters, motor-generator ts, or rectifiers.
Direct current for Light and Power.─There are still a few ctions in some of out large cities, which最美的教育最简单 are supplied with direct-current three-wire systems. 清炖冬瓜汤Such a supply is invariably obtained from synchronous converters. There are also certain types of motor loads in industrial plants, which require direct current.
