国家电网职称英语题库短文判断.doc

短文判断Passage 1 Feature of power generation The simultaneousness of the electric power generation means that the electric power generation，transmission，transformation，distribution and utilization must be performed at the same instantThe electric power cant be stored .Therefore，the balance must be kept at anytime during the electric power generation，distribution，and utilizationThe electric power system consists of power plants，transmission networks，distribution networks and the consumers electric utilization equipmept The unification of power system equipment means that the generation equipments，transformation equipments，transmission lines，distribution lines and power utilization equipment of a power system form an undivided integerWithout any of them，the power network can not operate normallyThe transmission line connecting two power networks is called link line. Some electric power systems are mutually connected by transmission lines to realize power exchange between these systems. Thus，the inter-connected power system is formed. Electric power network is the general name of the transmission network composed of transmission lines and various connected substations. It is simply called the power network The features of a modem power network frame are：(1)The main network frame is formed by a strong EHV(UHV)system；(2)The networks are connected closely to each other；(3) The voltage classes are simplified.1. The electric power can be stored. A.Right B.Wrong2. The power system is made up of 4 parts. A.Right B. Wrong3. The unification of power system equipment is formed by 4 equipments. A.Right B.Wrong4. A power system is an undivided integerA.Right B. Wrong5. The power network can operate normally without the integration of other 3 equipments A. Right B.Wrong6.A link line is called a transmission line ARight B. Wrong7.A link line is formed by 3 power networksA. Right B .Wrong8 .An electric power network is simply called a power network.A. Right B .Wrong9 .The main network frame is formed by a weak EHV system.A. Right B .Wrong10. The networks are not closely linked with each otherA. Right B .WrongPassage 2 Types of circuit breaker The high voltage circuit breaker is mainly composed of contactors, arc-extinguishing elements，insulation material，operating mechanism. The insulation structure of a high voltage circuit breaker mainly includes the insulation of conductive parts to ground，phase-to-phase and the insulation between breaking contactsAccording to the arc-extinguishing mediums，it can be divided into oil circuit breaker(bulk-oil circuit breaker, oil minimum circuit breaker),air blast circuit breaker,SF6 circuit breaker, vacuum circuit breaker etc. The circuit breaker with 0il as arc-extinguishing and insulation medium are called oil circuit breakerThe circuit breaker whose contactors close and open in high vacuum is called vacuum circuit breaker SF6 circuit breaker is the circuit breaker in which gas SF6 is used as the arc-extinguishing and insulation mediumThe pure SF6 gas is a good arc-extinguishing mediumIts insulation strength is higher than air and vacuum，and it has good heat dissipation capability. Besides，there isnt any danger of burning or explosionNow, the mostly used circuit breakers in the power grid are oil minimum circuit breaker, vacuum circuit breaker and SF6 circuit breaker.1. Contactors，arc-extinguishing elements，insulation material and operating mechanism form the high voltage circuit breakerA. Right B .Wrong2 .The insulation structure is made up of 3 parts.A. Right B .Wrong3.The arc-extinguishing medium can be divided into only 3 parts.A. Right B .Wrong4.An oil circuit breaker means a circuit breaker with oil as arc-extinguishing and insulation medium.A. Right B .Wrong5.A vacuum circuit breaker is not a circuit breaker with close and open contactors in high vacuum.A. Right B .Wrong6 .A pure SF6 gas is not a good arc-extinguishing medium.A. Right B .Wrong7.The insulation strength of SF6 gas is higher than air and vacuum.A. Right B .Wrong8.An oil minimum circuit breaker is very safe in useA. Right B .Wrong9.An oil minimum circuit breaker has bad heat dissipation capability.A. Right B .Wrong10.An oil minimum circuit breaker is one of the mostly used circuit breakers in the power gridA. Right B .WrongPassage 3 Optical fiber communication Optical fiber communication is a kind of information communication by optical fiber. In power system，the composite optical fiber ground wire or OPGW is widely used. The optical fiber main network is mainly responsible for the transmission task of power dispatching telephone，administration telephone of power system，automation information，data network，protective relaying information and so onOptical fiber communication has become the primary communication method of our power communication system. Optical fiber communication has advantages of large capacity of communication，strong ability of anti-jamming，insulation to electrical field，small attenuation and long distance of transmission，etc. The communication capacity of optical fiber is directly proportion to the carrier frequency. Usually the carrier frequency of power line is less than 300kHz，and the carrier frequency of microwave is between 3000MHz and 30000MHz. Carrier frequency of optical fiber is 2.2×107MHz，being 7.42×104 times microwave and 7.42×108 times power line carrierThe main problem of the fiber-optic channel is that the price of fiber-optic equipment and optical fiber cable is comparatively higher.1.Akind of information communication is optical fiber communicationA. Right B .Wrong2.The composite optical fiber ground wire is seldom used in power systemA. Right B .Wrong3.One of the transmission tasks of the optical fiber main network is to transmit administration telephones from power systemA. Right B .Wrong4.Optical fiber communication has been the important communication method in power communication systemA. Right B .Wrong5Large capacity of communication is not one of the advantages of optical fiber communicationA. Right B .Wrong6.The communication capacity of optical fiber is indirectly proportion to the carrier frequencyA. Right B .Wrong7The carrier frequency of power line is more than 300kHzA. Right B .Wrong8.The carrier frequency of microwave is between 3000MHz and 5000MHzA. Right B .Wrong9.The main problem of the fiber-optic channel is the high price of fiber-optic equipmentA. Right B .Wrong10 .The cables made by optical fiber are not expensiveA. Right B .WrongPassage 4 Power plant According to the mode of energy conversion，power plants can be classified into fossil-fired，hydraulic，nuclear, wind，solar, geothermal and tide power plants and so on. A power plant transforms primary energy source into electric power and supplies power to users. A co-generation plant is the power plant that not only generates electricity but also supplies steam to the user Normally, in selecting the site of a new power plant，following factors should be fully considered：power net plan for medium and long term；fuel supply and ash disposal； transportation condition；water sources；local natural condition and environmental protection According to the common stipulation the total capacity in a newly scheduled power plant is in the range of 1200MW to 3600MW, the number of units should not exceed six and the ranks of capacity should not exceed two1. Base on energy conversion，power plants are divided into more than 7 categories.A. Right B .Wrong2. A power plant tries to transform energy source into electric power.A. Right B .Wrong3. The power plant generating electricity and supplying steam is called a co-generation plant.A. Right B .Wrong4. A power net plan for short and medium term is one of factors in selecting a siteA. Right B .Wrong5. Two important factors for a new plant plan are fuel supply and ash disposal.A. Right B .Wrong6. Environmental protection is less considered in building a new power plantA. Right B .Wrong7. Water sources and transportation conditions are not needed to consider in selecting a new siteA. Right B .Wrong8. The total capacity in a newly scheduled plant arranges from 1200MW to 3600MWA. Right B .Wrong9. The number of units exceeds more than sixA. Right B .Wrong10. The ranks of capacity should be limited within two.A. Right B .WrongPassage 5 Selection of metal material for the boiler in units of 1000MW grade Taking a general view of the 1000MW grade high-efficiency supercritical unit designed and made in Chinathe temperature of main steam and reheated steam are basically 5706000C. Further morethis is just medium temperature，the tube wall temperature of superheater and reheater may reach 6006500C. Under this temperature，in addition to good heat resistance，the anti-high temperature steam oxidation performance at tube inner surface and the anti-high temperature flue gas corrosion performance at tube outside surface are also highly demanded. That is to say, heat-resisting steel T91，T92，etc. (their temperature limit for use is 5930C and 6200C respectively)as well as austenite stainless steel super 304H and HR3C，etc. (their temperature for normal use is about 6500C，their temperature limit is near 7000C)must be adopted1. The 1000MW grade high-efficiency supercritical unit is designed and made in China.A. Right B .Wrong2. The temperature of main steam and reheated steam reach basically between 570 to 6500CA. Right B .Wrong3. The tube wall temperature of superheater and reheater can reach more than 600 to 6500CA. Right B .Wrong4. The anti-high temperature steam oxidation performance at tube inner surface is highly demandedA. Right B .Wrong 5. The anti-high temperature flue gas corrosion performance at tube outside surface is not highly demandedA. Right B .Wrong6. The temperature limit of T91 for use is about 5930C.A. Right B .Wrong7. The temperature limit of T92 for use is less than 6200C.A. Right B .Wrong8. The temperature of austenite stainless steel for normal use is about 6500CA. Right B .Wrong9. The temperature 1imit of anstenite stainless steel is 1ess than 7000CA. Right B .Wrong10. Only heat-resisting steel can be adopted for useA. Right B .WrongPassage 6 The role of the condenser The condenser is a surface heat exchanger in which cooling water passing through the tubes removes the vaporization heat from the exhaust steam which is passing over the tubes，and condense the exhanst steam into waterIt is important that the water not be sub-cooled below the saturation temperature，which would remove excess energy from the system and reduce the overall efficiency. It is necessary to reduce the steam to water so that it can be effectively pumped back through the systemIn condensing the exhaust steam from the low pressure turbine, the condenser controls the back-pressure at the turbine exhaust The temperature of the cooling water passing through the condenser tubes is the primary factor controlling the turbine backpressure. Typically the temperature of cooling water increases 1520oF as it passes through the condenser and exits at some temperature lower than the turbine exhaust steam temperatureThe temperature difference between the cooling water leaving the condenser and the turbine exhaust steam is called the terminal difference. The temperature increase of the cooling water and the terminal difference depend on the condenser design and performance the steam flow, and the cooling water flowThus with a given set of conditions，the exhaust steam temperature is dependent on the temperature of the cooling water entering the condenser and the back-pressure is dependent on the exhaust steam temperature1. A condenser is a heat exchanger removing the vaporization heat from the exhaust steam and condensing the exhaust steam into waterA. Right B .Wrong2. It is suggested that the water should not be cooled below the saturation temperatureA. Right B .Wrong3. The saturation temperature would not remove excess energy from the system and reduce the overall efficiencyA. Right B .Wrong4. It is unnecessary to reduce the steam to water so that it can be pumped back through the systemA. Right B .Wrong5. The condenser does not control back-pressure at the turbine exhaustA. Right B .Wrong6. The important factor controlling the turbine backpressure is the temperature of the cooling water passing through the condenser tubesA. Right B .Wrong7. The temperature of cooling water will increase its temperature between 15oF and 20oF as it passes through the condenser.A. Right B .Wrong8. The terminal difference means the temperature difference between the cooling water and the turhine exhaust steamA. Right B .Wrong9. The temperature increase of the cooling water and the terminal difference depend on 3 factors.A. Right B .Wrong10. The exhaust steam temperature does not rely on the temperature of the cooling water which enters the condenserA. Right B .WrongPassage 7 Hydraulic structure The selected type of dam of hydraulic power plant depends principally on topographic，geologic，hydrologic，climatic conditions，constructional materials，lay out plan，cost and safety etc. The main effect of the dam safety monitoring and inspecting is to monitor the performance indexes and to inspect equipment inside the dam，to discover the abnormality in time，so as to take emergency measure and keep the dam safe. The main monitoring items of dam are: displacement(horizontal and vertical displacement)，crack，seepage，temperature stress and strain，etc. The monitoring method of dam is that at suitable points on the dam and its foundation，some monitoring devices are embedded for periodical supervisionThe result obtained shall be analyzed and studied1. The type of dam for hydraulic power plant depends on many factors.A. Right B .Wrong2. The main purpose of the dam safety monitoring is to monitor the performance indexes.A. Right B .Wrong3. The equipment installed inside the dam is to discover the normality of dam in timeA. Right B .Wrong4. Horizontal displacement is more important than vertical displacement.A. Right B .Wrong5. Temperature stress and strain are the two main monitoring items of damA. Right B .Wrong6. The monitoring method is the suitable points on the dam and its foundation.A. Right B .Wrong7. Some monitoring devices are movable for periodical supervisionA. Right B .Wrong8. The monitoring result shall be analyzed and studied by computersA. Right