电气专业毕业设计外文资料及中文翻译.doc

河南理工大学万方科技学院本科毕业论文外文资料：Intellectual building electric protection and earthSummary : This text pass to several power supply earth systematic generalization introduction, is it suit as intellectual power supply earth system of building to screen, and has done comparatively exhaustive explanation and analysis to all kinds of earth measures should be takenned by it, electric protection that should adopt to the intellectual building and connecting the proper suggestion of local law proposition.Keyword: Load is balanced Electric potential form some earth , TN-S of datum point , defend static earth unify the earth body. Support distribution in the design , earth is it occupy important status to design systematically in building, because it concerns the dependability of the electric power system , the security . No matter how many buildings, include earth design systematically always in supplying power design. And, different with requirements of the building, functions of all kinds of equipment are different, earth systems are corresponding and different too. Especially after entering the 1990s, a large number of intelligent appearance of building design and get a lot of new contents out of systematically earth. In daily several person who connects place, which kind be suit the intelligent building ? We might as well analyse several kinds of earth systems .1.TN-C systemTN-C system call that into three-phase Line four system, systematic neutral line N this protect earth PE unite two into one, generally called PEN line. Although this kind of earth system is high in sensitivity to the earth trouble, circuit economy is simple, but it is only suitable for and used in three-phase load in the more balanced place . In the intelligent building, single-phase load proportion relatively heavy, difficult to realize three-phase to be load balanced, disequilibrium electric current , PEN of line add because fluorescent lamp , brilliant floodgate person who in charge of high times of in harmony wave electric current that equipment cause that exist in the circuit, in it is not the trouble cases , will superpose at the N in neutral line , make the neutral line N voltage fluctuate, and electric current light and extremely unstable when being heavy, cause neutral some electric potential unstable to drift about earth. Not only will electrify equipment outer cover (connects with PEN line ) , cause the rights of the person unsafe, and unable to fetch to a suitable electric potential datum point, the accurate electronic equipment is unable to run accurately reliably. So TN-C earth system cant be regarded as the earth system of the intelligent building .2.TN-C-S systemTN-C-S system is by two earth composition systematically, first part It is TN-C system, second part It is TN-S system, connect with PE line and click on N line the boundary. This system is generally used in the place attracted by regional switchyard of power supply of the building, enter family adopt TN-C system , enter households of place make repeated earth , enter after the family turning into TN-S system. Have already made analysis in front of TN-C system. The characteristic of TN-S system is: Neutral line N protect earth connection PE after grounding together while entering the family , cant have any electric connection. In this system, the neutral line N regular meeting protects the earth connection PE source without electricity with electricity. Equipment outer cover and metal component that PE line connects are in system normal running, will not be with electricity all the time. So TN-S earth system has obviously improved the securities of people and thing . At the same time so long as we adopt the earth lead wire, draw from earth body some each, choose correct earth resistance value make electronic equipment obtain one electric potential datum point ,etc. measure together, then TN-C-S system can be regarded as a kind of earth system of the intelligent building.3.TN-S systemTN-S is a earth system that three-phase Line four added PE line. Building usually is it enter line adopt this system when turning distribution into independently to have. The characteristic of TN-S system is, neutral line N and protecting earth connection PE except in the voltage transformer is grounded neutrally more together a bit, Line two no longer has electric connection of any. Neutral line N belong to electrification, but PE with electricity line. Its time to be grounded the system and totally possessed the safe and reliable basic electric potential. So long as like TN-C-S earth system, takes the same technological measure, TN-S system can be used as the earth system of the intellectual building. If such electronic equipment as the computer ,etc. generally adopt this kind of earth system without special requirement .4.TT systemUsually call TT system the three-phase Line four earth system. This system supplies power to come from the place of the public electric wire netting dailily in the building. Characteristic, TT of system whether neutral line N protect earth connection PE have a bit electric to join, namely neutral some earth separate from that the line earth of PE is. When this system is in normal running, whether three-phase load is balanced, in case of neutral line N electrification, PE line will not be with electricity. Single-phase earth only at the trouble, protect earth to be low in sensitivity, the trouble can be cut off in time, the equipment outer cover is perhaps with electricity. TT system at the time of normal running is similar to TN-S system , can obtain the securities of people and thing and make the qualified basic earth electric potential too. With electric leakage appearance of person who protect of large capacity, should systematic to can regard intelligent earth system of building as more and more too. According to present situation, because the power of the public electric wire netting is of low quality , difficult to meet the requirement for intelligent equipment, so TT system is seldom adopted by the intelligent building.5.IT systemIT system three-phase the strategic hinterland of China earth system, system this voltage transformer neutral to ground or pass impedance earth a bit, have neutral line N , have only line voltage (380V), is it is it keep to press to have (220V), protect earth connection PE and is grounded independently each. System this advantage to when the earth , can make outer cover have larger trouble electric current as one phase, the system can run as usual . The shortcoming can not allot the neutral line N. So it is not suitable for the intelligent building with a large number of single-phase equipment .In the intelligent building, demand to protect earth equipment very much, there is strong electric equipment , weak electric equipment, and the conductive equipment and component not with electricity, must adopt effective protection earth under some normal situations. If adopt TN-C system , use the N line in TN-C system as the earth connection at the same time ; Is it together , join N line and PE line really stiff to get on to connect among the system in TN-S; Set up electronic direct current earth lead wire of equipment and then , receive direct current earth on the PE line directly; Some clear-cut to is it answer together to mix N line , PE line , direct current earth connection. The above methods do not accord with earth requirement , and wrong. Have analysed , in the intelligent building, there is more single-phase power consuming equipment in in the front, single-phase load is relatively great in specific gravity, three-phase load is usually uneven, so there is random electric current in the neutral line N. In addition, because adopt the fluorescent lamp to light in a large amount, the waves in harmony three times produced by it are superposed on the N line, have strengthened the electric current amount on the N line, if receive N line on the equipment outer cover , will cause shocking by electricity or fire accident ; If on connecting N line and PE line to receive the equipment outer cover in TN-S system, so dangerous and heavy, every receive equipment on the PE line, with electricity outer cover; Will expand the range which will shock by electricity the accident; Connect together except will take place above-mentioned dangers N line , PE line , direct current earth connection, the electronic equipment will be interfered being unable to work. So intelligent building should set up electronic direct current earth of equipment, exchanges earth, safe protection earth, and ordinary dyke thunder that building too should possess protect earth.Now, we continue analysing various kinds of earth measures which should be taken in intelligent building .1 .Whether defend thunders earth: For is it channel earth into rapidly to flow thunder and lightning, taking preventing the thunder from hurting as purpose earth is it defend thunders earth to call.There are a large amount of electronic equipment and wiring system in the intelligent building, such as the communication automated system, the fire reports to the police and fire control link the control system , the automated system of the building , monitoring systems of security personnel, office automated system, the closed-circuit TV system,etc., and their corresponding wiring system. By the look of building built, the roof of every storey in the building, the baseplate, the side wall, hang and is nearly covered with by various kinds of wiring while carrying. These electronic equipment and wiring system generally belong to and able to bear the grade of pressing low , defend and interfere expecting much , is most afraid of the part struck by lightning. No matter attack directly, bunch hit, is it can make electronic equipment the damage in various degree or interfere seriously to strike back. It designs to be must tight , reliable to intelligent dyke thunder earth of building. Intelligent all function earth of building, must in order to avoid thunder based on the system earth, set up tightly , intact dyke thunder structure.The intelligent building is mostly first class load, should design according to the protective measure of first class Fang thunder building , connect person who flash adopt needle is it is it connect person who flash to make up to take , is it is it adopt 25* 4 (mm ) zinc-plated flat-rolled steel make up net of 10* 10 (m ) in roof to take to take shelter from the thunder, this net and metal component of the roofing are joined electrically, make and join with the building column cap reinforcing bar electrically, guide and roll off the production line and utilize the reinforcing bar in the column cap, enclose the reinforcing bar of roof beam , the floor reinforcing bar and defending the thunder system to join , other wall all metal component should with defend thunder system join , column cap reinforcing bar connect with earth body too, make up the shape of enveloping with multi-layer shielding and defend the thunder system. Can is it is it damage floor equipment to strike by lightning , but also still can prevent the outside electromagnetism from interfering to prevent effectively like this. Earth resistance frequently of engineering of all kinds of dyke of thunder earth devices , should according to set thunder reaction terms at confirm generally. Defend if thunder device share one total earth at the network with job earth of electric equipment, earth resistance should accord with its minimum requirement .2.The exchanges is grounded: Some any of power system, direct passing special equipment (such as impedance, resistance ,etc.), make metal join , call work earth with earth.Job earth mean voltage transformer neutral a bit or neutral line (N line ) earth mainly. N line must spend copper core insulating line. There is wiring end son of the electric potential such as being auxiliary in the distribution , wait for the wiring end son of the electric potential generally in the case cupboard. Must notice , should wire the end son and can expose ; Cant with other earth system, such as direct current earth, shielding earth, defend static earth is it is it connect to mix to wait for; Cant connect with PE line either.In high-pressure system , adopt neutral some person who connects place can make earth relay protection accurate movement and dispel single-phase electric arc earth overvoltage. Can prevent the skew of voltage of zero preface , keep the three-phase voltage in a basic balance in some neutral earth, this is very meaningful to low-voltage system, can be convenient to use the single-phase power.3.Safe protection is grounded: Safe protection earth metal part and earth body with electricity make good metal join electric equipment. Namely power consuming equipment and some metal components near the equipment of building, join with PE thread, but forbid connecting PE line with N line.In the intelligent building, require there is very much earth equipment of safe protection , there is strong electric equipment , weak electric equipment, and some conductive equipment and component with electricity, must take safe protection earth measure. When insulation not doing the earth electric equipment of safe protection is damaged , its outer cover is possible with electricity. If the outer cover that the human body touches this electric equipment may be wounded or caused the life danger by the electricity. Among neutral power system that ground directly a bit, earth short out electric current pass personal, the earth flows back to a bit more neutrally; In a bit more neutrally power system not grounded directly , the earth electric current flows into the earth through the human body, and form thorough fare by electric capacity by circuit to ground, two situation these can lead to the fact the rights of the person get an electric shock.If the insulation which is equipped with the electric equipment of the earth device is damaged while electrifying outer cover , short out in the electric current and flow through two thorough fares of earth body and human body at the same time in earth, I =IL + IP, we know: In a parallel circuit, the electric current value of passing each branch road is in inverse proportion to size of the resistance.In the type: I - Electric current total value in the earth return circuitIL - Electric current flowing through along the earth body IP - Flow through electric current of the human bodyHave type can find out earth resistance little , flow through to little electric current have human body, human resistance usually is it ground than earth resistance through electric current of human body electric current of body have several hundred less flowing through too to have several hundred heavier. When earth resistance is extremely small, the electric current that remakable body flows nearly equals zero. Namely IIL. In fact, because earth resistance very little, earth short out electric current flow out of date produce press and lower very lightly, so equipment outer cover voltage in earth high. People stand while going to touch the outer cover of the equipment on the earth, the voltage that the human body bears is very low, it can not be dangerous.Is it protect earth device and reduce earth resistance of it to install additional , not only ensure the electric security of system of intelligent building, the effective measure operated effectively, it is not the essential means of equipment and personal security in the intelligent building that ensure too.4.Direct current is grounded: In a block of intelligent building , include a large number of computers , communication apparatus and automation equipment of building with computer. Importing to information in these electronic equipment, transmission information, change energy , amplify signal, logic movement, output information a series of course go on through little electric potential or little electric current fast, and will often carry on the work through the internet between the equipment. So in order to make its accuracy high, the stability is good, besides needing to have a steady power supply power, must also possess a steady basic electric potential . Can adopt bigger and sectionaller insulating copper core line as the lead wire , one end is connected with basic electric potential directly, another end support electronic equipment direct current earth. It is unsuitable to connect with PE line to deserve and go between , forbid connecting with N line.5.Whether shielding earth defend static earth: In the intelligent building, it is very important to design electromagnetic and compatibly, in order to avoid the dysfunctions of the equipment used, equipment can appear evenned to prevent from damage, form equipment of wiring system should can prevent inside oneself conduct and extraneous interference from. Or because of the coupling phenomenon between the wire in these production that interfere, or because of the electric capacity effect or inductance effect. Main source its superelevation voltage, high-power pieces of radio magnetic field, strike by lightning naturally and static discharge. Phenomenon these will is it send or receive very high to transmit equipment of frequency produce heavy interference very to used for designing. Is it must take the protective measure to equipment the to connect up , avoid the interference from various kinds of respects. Shielding and correct earth to prevent electromagnetic best protection method that interfere. Can connect the equipment outer cover with PE line ; Require both ends of shielding pipeline and PE line to join reliably in shielding earth of the wire; Indoor shielding should a lot of some is joined with PE thread reliably. It is very important too to defend static interference. In clean, dry room, walking , mobile d