Perfect grounding system Perfect grounding system is one of the important measures for DCS control system to resist electromagnetic interference.There are three types of system grounding methods:floating grounding,direct grounding and capacitive grounding.For the DCS control system,it is a high-speed low-level control device and should be directly grounded.Due to the influence of the distributed capacitance of the signal cable and the filtering of the input device,the signal exchange frequency between the devices is generally lower than 1MHz,so the grounding wire of the DCS control system adopts one point grounding and one point grounding in series.The centrally arranged DCS system is suitable for one-point grounding in parallel,and the central grounding point of the cabinet of each device leads to the grounding electrode with a separate grounding wire.If the distance between the devices is large,the grounding method should be adopted in series.Use a large-section copper busbar(or insulated cable)to connect the center grounding point of the cabinet of each device,and then connect the grounding busbar directly to the grounding electrode.The ground wire adopts copper wire with a cross-section greater than 22mm,and the total busbar uses a copper bar with a cross-section greater than 60mm.The grounding resistance of the grounding electrode is less than 2Ω,and the grounding point of the DCS system must be more than 10m away from the grounding point of the strong electrical equipment.When the signal source is grounded,the shielding layer should be grounded on the signal side;if it is not grounded,it should be grounded on the DCS side;when there is a connector in the middle of the signal line,the shielding layer should be firmly connected and insulated,and multi-point grounding must be avoided;When the shielded twisted pair of the point signal is connected with the multi-core twisted pair total shielded cable,the shielding layers should be well connected to each other,and after insulation treatment,select an appropriate grounding point for single-point grounding.It should be grounded strictly according to the grounding requirements of the DCS manufacturer.
完善接地系统完善的接地系统是DCS控制系统抗电磁干扰的重要措施之一。系统接地方式有:浮地方式、直接接地方式和电容接地三种方式。对DCS控制系统而言,它属高速低电平控制装置,应采用直接接地方式。由于信号电缆分布电容和输人装置滤波等的影响,装置之间的信号交换频率一般都低于1MHz,所以DCS控制系统接地线采用一点接地和串联一点接地方式。集中布置的DCS系统适于并联一点接地方式,各装置的柜体中心接地点以单独的接地线引向接地极。如果装置间距较大,应采用串联一点接地方式。用1根大截面铜母线(或绝缘电缆)连接各装置的柜体中心接地点,然后将接地母线直接连接接地极。接地线采用截面大于22mm的铜导线,总母线使用截面大于60mm的铜排。接地极的接地电阻小于2Ω,而且DCS系统接地点必须与强电设备接地点相距10m以上。信号源接地时,屏蔽层应在信号侧接地;不接地时,应在DCS侧接地;信号线中间有接头时,屏蔽层应牢固连接并进行绝缘处理,一定要避免多点接地;多个测点信号的屏蔽双绞线与多芯对绞总屏电缆连接时,各屏蔽层应相互连接好,并经绝缘处理,选择适当的接地处单点接地。要严格按DCS厂家的接地要求接地。
HFD3020L CUTLER HAMMER
CUTLER HAMMER D520TA2 NSFP D520TA2
CUTLER HAMMER D500PWP10 NSFP D500PWP10
CUTLER HAMMER D520TA3 NSFP D520TA3
CUTLER HAMMER D520TA1 NSFP D520TA1
CUTLER HAMMER D500AOM220 NSFP D500AOM220
Cutler Hammer 400 Amp 3 Pole KDC3400F Takeout