【正文】 oo. 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 . system　TNC system call that into threephase 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 threephase load in the more balanced place . In the intelligent building, singlephase load proportion relatively heavy, difficult to realize threephase 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 TNC earth system can39。河南理工大學(xué)萬(wàn)方科技學(xué)院本科畢業(yè)論文外文資料：Intellectual building electric protection and eartht be regarded as the earth system of the intelligent building . system　TNCS system is by two earth position systematically, first part It is TNC system, second part It is TNS 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 TNC system , enter households of place make repeated earth , enter after the family turning into TNS system. Have already made analysis in front of TNC system. The characteristic of TNS system is: Neutral line N protect earth connection PE after grounding together while entering the family , can39。s time to be grounded the system and totally possessed the safe and reliable basic electric potential. So long as like TNCS earth system, takes the same technological measure, TNS system can be used as the earth system of the intellectual building. If such electronic equipment as the puter ,etc. generally adopt this kind of earth system without special requirement . system　Usually call TT system the threephase Line four earth system. This system supplies power to e 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 threephase load is balanced, in case of neutral line N electrification, PE line will not be with electricity. Singlephase 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 TNS 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. system　IT system threephase 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 shorting can not allot the neutral line N. So it is not suitable for the intelligent building with a large number of singlephase 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 ponent not with electricity, must adopt effective protection earth under some normal situations. If adopt TNC system , use the N line in TNC system as the earth connection at the same time 。 Set up electronic direct current earth lead wire of equipment and then , receive direct current earth on the PE line directly。 If on connecting N line and PE line to receive the equipment outer cover in TNS system, so dangerous and heavy, every receive equipment on the PE line, with electricity outer cover。 Connect together except will take place abovementioned dangers N lin