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1、补 全 短 文Passage 1 Functions of power transmission The function of (1) is to send power from power plants to load center or to exchange power between power networks in order to attain the generation-consumption balance or the supply-demand balance between (2)Power transmission is completed by step-up
2、substations，(3)The transmission line mainly consists of the transmission conductors (cables)，poles or towers，insulators，overhead ground wires，and grounding devices. The (4) can reduce the line loss and the voltage drop，ensure the power quality, raise the economy of (5)The increase of transmission li
3、ne voltage can not only raise the amount of transmitted power, but also reduce the line loss and line voltage drop，and improve the voltage quality A. step-down substations and connected transmission equipment B. power network operation C. power transmission D. transmission at high voltage E. power n
4、etworksPassage 2 Substation misoperation and its preventing The misopemtion that can lead to (1) mainly are：on-load switching of isolating switch；connecting (2)；closing the circuit breaker (isolating switch) with ground lines (ground switch) earthed The“five preventings”for (3) includes：preventing t
5、he wrong opening or closing of circuit breaker；preventing the on load opening and closing of isolating switch；preventing (4)；preventing the closing of circuit breaker with grounding wireconnected；preventing(5) A. preventing the misoperation in substation B. the closing of grounding switch with power
6、 on C. accidents in the electrical operation of the substation D. the persons from illegal entering the lived bay E. the grounding wire (closing the grounding switch) with power onPassage 3 A brief introduction on the development of supercritical boilers and their main advantages In (1) such as U.S.
7、A，Japan and European countries，the supercritical boiler has been developed since the 60s of last centuryIt has been proved by data and experience，the supercritical unit has (2)As for its reliability, because the steam-water flow passages in supercritical boiler is same as that in the (3)，there isnt
8、anything special. But as far as hydraulic characteristic，a symbol of reliability, is concerned，in a supercritical boiler, under supercritical condition，medium is of single phase which has a (4). So that the problem caused by uneven distribution of steam phase and water phase can be avoidedIt is admi
9、tted that, if (5)，both supercritical and subcritical units can get an excellent reliability index. A. good homogenization of distribution B. some advanced countries C. whole process management is strengthened D. great advantages oil economy and environmental protection E. subcritical once-through bo
10、ilerPassage 4 Steam generation and use Steam is one of mans dependable servants More and more in the background，steam is doing more and more work for man. In (1) steam may be seen only at the teakettle, but the electricity used may be generated by burning coal or gas and producing steam to turn the
11、generator rotors in the power plant Even if (2) by nuclear fission，the generation of electricity is still accomplished by (3). In the U.S.A. the demand for electricity doubles every ten years. For the most part water resources suitable for power generation are already in service, except for emergenc
12、y standby and peak-load units; approximately 90% of (4) utilizes steam. The (5) is expanding in most countries of the world except for the countries where available water power resources are greater than power needs. A. first generating steam B. an electrically heated home C. use of steam for electr
13、ic power generation D. the new generating capacity being installed E. the fuel is uranium and the heat is suppliedPassage 5 Circuit breaker Circuit breakers are automatically operated high voltage (or high current) switches. Circuit breakers are required (1) by switching circuits on，by carrying load
14、 and by switching circuits off under manual or automatic supervision. Their duty is as follows：In closed position the circuit breaker must be a good conductor for the normal load current. In open position the gap across the contacts shall have foil insulation level. At opening operating the circuit
15、breaker must be able (2) to many thousands of amperes，and independently of the characteristics from purely inductive to fully capacitive. At closing operation the circuit breaker must close fast and be safe also against full short circuit conditions. They must，therefore，be effective instantaneously
16、when are called upon (3) without movement. As the circuit breaker is the last link in the chain of protective equipment, the circuit breaker reliability is (4) of the total electric power system so the importance (5) cannot be over emphasized. A to perform any switching operation after long periods B. to control electrical power networks C. of the circuit breaker D. t
