1、现代建筑接地系统如何实现准确可靠运行 智能建筑设备的电器保护极为重要,为了保证智能建筑中电气设备的安全可靠运行。TN-C系统也被称之为三相四线系统,该系统中性线N与保护接地线PE合二为一,通称PEN 线。这种接地系统虽对接地故障灵敏度高,线路经济简单,但它只适合用于三相负荷较平衡的场所。 Electrical protection equipment of intelligent building is very important, in order to ensure the safe and reliable operation of the electrical equipment i2、n intelligent building. The TN-C system is also known as the four phase three wire system, the neutral line of the system of N and protective ground wire become known as the PE, PEN line. The grounding system, grounding fault of high sensitivity, simple circuit economy, but it is only suitable for t3、hree-phase load is balanced place. 智能建筑中,除了部分风机等负荷为三相负荷外,其余设备一般均为单相负荷,在实际运行中难以实现三相负荷平衡,因此在PEN线中存在着不平衡电流;加上建筑内大量采用荧光灯、晶闸管等设备,导致其在供电线路中存在着高次谐波电流,在非故障情况下,谐波电流会在中性线N上叠加,使中性线N电压波动,且电流时大时小极不稳定,造成中性 点接地电位不稳定漂移。 Intelligent building, in addition to some fan load of three-phase load, the other equipment in g4、eneral are single-phase load, difficult to realize three-phase load balance in the actual operation, so in the PEN line unbalance current; with the construction of the fluorescent lamp, such as thyristor devices, leads to the existence harmonic current in the power supply line, under fault condition5、s, the harmonic current will be superimposed on the neutral line N, the neutral line N voltage fluctuation, and the current size is very unstable, resulting in the neutral point grounding potential unstable drift. 不但会使设备外壳带电,对人身造成不安全,而且也无法取到一个合适的电位基准点,精密电子设备无法准确可靠运行。由此可见TN-C系统不适合作为智能建筑的接地系统。 Not onl6、y will make the equipment shell charged, to human body caused by unsafe, but also unable to get to a suitable potential reference point, precision electronic equipment can not be accurate and reliable operation. It is concluded that the TN-C system is not suitable as a grounding system of intelligen7、t building. 为把雷电流迅速导入大地,以防止雷害为目的的接地叫作防雷接地。智能建筑内有大量的电子设备与布线系统,如通信自动化系统,火灾报警及消防联动控制系统,楼宇自动化系统,保安监控系统,办公自动化系统,闭路电视系统等,以及他们相应的布线系统。建筑的各层顶板,底板,侧墙,吊顶内几乎被各种布线布满。 As the lightning current quickly into the earth, for the purpose to prevent lightning grounding called lightning protection and grounding. In the8、 intelligent building electronic equipment and wiring systems, such as communication automation system, fire alarm and fire control systems, building automation systems, security monitoring systems, office automation systems, closed circuit television system, as well as their corresponding wiring sy9、stem. Each layer of building roof, floor, wall, the ceiling was covered with various wiring. 这些电子设备及布线系统一般均属于耐压等级低,防干扰要求高,最怕受到雷击的部分,一旦受到雷击会使电子设备受到不同程度的损坏或严重干扰。因此对智能建筑的防雷接地设计必须严密、可靠。 These electronic equipment and cabling system voltage levels are generally low, for high anti-interference, fear by th10、e lightning part, once struck by lightning can make the electronic equipment are subject to different degrees of damage or serious disturbance. Therefore, lightning protection grounding design of intelligent building must be tight, reliable. 智能建筑的所有功能接地,必须以防雷接地系统为基础,并建立严密、完整的防雷结构。绝大多数情况下智能建筑应按照第二类或第11、三类防雷建筑物的防雷措施设计。 All functional earthing of intelligent building, must be based on the lightning protection and grounding system as the basis, and the establishment of lightning protection of tight structure, complete. Intelligent building in most cases should be in accordance with the design of ligh12、tning protection measures of second or third types of lightning protection of buildings. 电子设备的直流接地有单点接地、多点接地和浮地。单点接地是指整个电路系统中只有一个物理点被定义为接地参考点,其他各个需要接地的点都直接接到这一点上。多点接地是指电子设备中各个接地点都直接接到距它最近的接地平面上。 DC electronic equipment grounding with single-point grounding, multi-point grounding and floating. Single13、 point grounding refers to the whole circuit system is only a physical point is defined as the ground reference point, other all need grounding point directly to this point. Multipoint grounding refers to the electronic device each grounding are directly to the nearest the ground plane. 浮地是指设备地线系统在电14、气上与大地相绝缘,以减少由于地电流引起的电磁干扰。智能建筑的接地系统不宜采用浮地,它必须有稳定的参考电位,若浮接则易受电磁场的杂讯干扰,使系统发生误动作。 Floating refers to equipment grounding system is insulated to ground, so as to reduce the electromagnetic interference current caused by. Intelligent building grounding system should not use floating, it must have a refere15、nce potential stable, if floating is susceptible to noise interference of electromagnetic field, the system malfunction. 频率低于1MHz时,电缆屏蔽层应采用单点接地方式,以防止其他电流流经电缆屏蔽层产生电磁干扰。因此,若采用同轴电缆传输信号时,如要通过屏蔽层提供信号回路,可 在信号源端将信号源与屏蔽层相连接地。也可以将屏蔽电缆穿入金属管内或采用双层屏蔽电缆,将金属管或电缆外屏蔽层在两端接地,而金属管内的电缆屏蔽层或屏蔽电缆的内屏蔽层一端接地。 The frequency i16、s lower than 1MHz, cable shielding layer adopts the way of grounding point, to prevent other current electromagnetic interference through the cable shielding layer. Therefore, if the use of the coaxial cable transmission signal, such as to provide signal loop through the shielding layer, the signal 17、source connects the signal source and the shielding layer. Can also be shielded cable passes through the metal tube or adopts a double-layer shielding cable, metal tube or outside the cable shielding layer at both ends of the ground, and the metal pipe in the cable shield or shield cable shield grou18、nd at one end. 智能化楼宇的供电接地系统宜采用TN-S系统,按规范宜采用一个总的共同接地装置,即统一接地体。统一接地体为接地电位基准点,由此分别引出各种功能接地引线,利用总等电位和辅助等电位的方式组成一个完整的统一接地系统。 Intelligent building power supply grounding system should adopt TN-S system, according to the specification should adopt a common earthing device, namely integrated grounding. Integrated grounding for the grounding potential reference point, which are respectively led out various functional earthing wire, using general equipotential and auxiliary equipotential way to form a complete unity of grounding system.