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影响DCS控制系统的干扰源与一般影响工业控制设备的干扰源一样,大都产生在电流或电压剧烈变化的部位,这些电荷剧烈移动的部位就是噪声源,即干扰源。干扰类型通常按干扰产生的原因、噪声干扰模式和噪声的波形性质的不同划分。其中:按噪声产生的原因不同,分为放电噪声、浪涌噪声、高频振荡噪声等;按噪声的波形、性质不同,分为持续噪声、偶发噪声等;按噪声干扰模式不同,分为共模干扰和差模干扰。共模干扰和差模干扰是一种比较常用的分类方法。共模干扰是信号对地的电位差,主要由电网串入、地电位差及空间电磁辐射在信号线上感应的共态(同方向)电压迭加所形成。共模电压有时较大,特别是采用隔离性能差的配电器供电室,变送器输出信号的共模电压普遍较高,有的可高达130V以上。共模电压通过不对称电路可转换成差模电压,直接影响测控信号,造成元器件损坏(这就是一些系统I/O模件损坏率较高的主要原因),这种共模干扰可为直流、亦可为交流。差模干扰是指作用于信号两极间的干扰电压,主要由空间电磁场在信号间耦合感应及由不平衡电路转换共模干扰所形成的电压,这种直接叠加在信号上,直接影响测量与控制精度。空间的辐射电磁场(EMI)主要是由电力网络、电气设备的暂态过程、雷电、无线电广播、电视、雷达、高频感应加热设备等产生的,通常称为辐射干扰,其分布极为复杂。若DCS系统置于所射频场内,就回收到辐射干扰,其影响主要通过两条路径:一是直接对DCS内部的辐射,由电路感应产生干扰;而是对DCS通信内网络的辐射,由通信线路的感应引入干扰。辐射干扰与现场设备布置及设备所产生的电磁场大小,特别是频率有关,一般通过设置屏蔽电缆和DCS局部屏蔽及高压泄放元件进行保护。实践证明,因电源引入的干扰造成DCS控制系统故障的情况很多,笔者在某工程调试中遇到过,后更换隔离性能更高的DCS电源,问题才得到解决。由于电网覆盖,它将受到所有空间电磁干扰而在线路上感应电压和电路。尤其是电网内部的变化,入开关操作浪涌、大型电力设备起停、交直流传动装置引起的谐波、电网短路暂态冲击等,都通过输电线路传到电源原边。DCS电源通常采用隔离电源,但其机构及制造工艺因素使其隔离性并不理想。实际上,由于分布参数特别是分布电容的存在,隔离是不可能的。与DCS控制系统连接的各类信号传输线,除了传输各类信息之外,总会有外部干扰信号侵入。此干扰主要有两种途径:一是通过变送器供电电源或共用信号仪表的供电电源串入的电网干扰,这往往被忽视;二是信号线受空间电磁辐射感应的干扰,即信号线上的外部感应干扰,这是很严重的。由信号引入干扰会引起I/O信号工作异常和测量精度大大降低,严重时将引起元器件损伤。对于隔离性能差的系统,还将导致信号间互相干扰,引起共地系统总线回流,造成逻辑数据变化、误动和死机。DCS控制系统因信号引入干扰造成I/O模件损坏数相当严重,由此引起系统故障的情况也很多。
型号:
ABB(S800系列)
英维思(3008, 3625, 3508E. 3721, 3700A 4351B)
本特利(3500/42M, 3500/ 22M, 3500/95.3500/05)
黑马(F3330, F3236, F6217, F7126, F8621A)
福克斯波罗(FBM203, FBM204, FBM217, FMB231)
AB: (1746 1747 1756 1770 1771 1785 触摸屏2711系列CPU PLC) .
普罗索芙特PROSOFT MVI46/56/69, AB旗下,跟AB很像,模块
横河YOKOGAWA AAI, ADV, ADI, ANB, AMM, SB, PW(型号开头),卡件模块(CPU,电源,输出,PLC)
摩尔MOORE Q开头, 3开头模块,显示器
Safety control system is a control system specially used for interlocking and emergency shutdown in dangerous places (such as petrochemical plants). The essential difference between it and DCS and PLC of ordinary process control is that its function is to make the device stop safely under accident and fault conditions (including device accident and control system failure), so as to avoid disaster, that is, to avoid injury to device personnel and impact on the environment. Therefore, the safety control system itself must be fail to safe, The reliability of the hardware and software of the system is very high. In the international safety standard IEC61508, there are detailed provisions on the requirements of safety level and safety control system. T ? V is the only safety control system certification body in the world at present.Since hima first launched the t ? V certified fail safe safety control system hima planar system in 1970, the safety control system has a development history of 30 years.
Development history of hima safety control system:
In 1970, hima launched the world's first t ? V certified fail safe control system hima planar system and put it into use.
In 1983, hima launched the world's first fail safe programmable electronic control system (PES) for safety control.
In 1986, hima launched the world's first programmable safety control system H50 certified by t ? V and put it into use. The CPU structure is double redundant fault-tolerant full self diagnosis type, that is, 1oo2d.
In 1991, hima launched the second generation of t ? V certified PES system h51 and H41 series products
In the late 1980s and early 1990s, other manufacturers of safety control systems emerged one after another, and the technology adopted is generally 1oo2d or 2oo3 voting (TMR) technology, which is still used today.
In 1997, hima launched the world's first A-type system product with quad (QMR) CPU structure certified by t ? V, namely 2oo4d.
In 1998, hima launched the third generation of t ? V certified PES systems h41q and H51q, which adopt Quad CPU structure, namely 2oo4d. CPU structure of programmable (PES) safety control systemAt present, the programmable safety control system that conforms to iec-61508 standard and has obtained t ? V ak6/sil3 level certification in the world has the following three mainstream CPU structures:
Double redundant fault-tolerant complete self diagnostic structure, i.e. 1oo2d structure.
power cards (f7130a)
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