RELANCE 0-57406-E 電機(jī)驅(qū)動(dòng)器
DCS整體考慮方案，操作員站都具備工程師站功能，站與站之間在運(yùn)行方案程序下裝后是一種緊密聯(lián)合的關(guān)系，任何站、任何功能、任何被控裝置間都是相互連鎖控制，協(xié)調(diào)控制；而單用PLC互相連接構(gòu)成的系統(tǒng)，其站與站（西門子PLC與西門子PLC）之間的聯(lián)系則是一種松散連接方式，是做不出協(xié)調(diào)控制的功能。
4、DCS在整個(gè)設(shè)計(jì)上就留有大量的可擴(kuò)展性接口，外接系統(tǒng)或擴(kuò)展系統(tǒng)都十分方便，西門子PLC所搭接的整個(gè)系統(tǒng)完成后，想隨意的增加或減少操作員站都是很難實(shí)現(xiàn)的。
5、DCS安全性：為保證DCS控制的設(shè)備的安全可靠，DCS采用了雙冗余的控制單元，當(dāng)重要控制單元出現(xiàn)故障時(shí)，都會(huì)有相關(guān)的冗余單元實(shí)時(shí)無擾的切換為工作單元，保證整個(gè)系統(tǒng)的安全可靠。而西門子PLC所搭接的系統(tǒng)基本沒有冗余的概念，就更談不上冗余控制策略。特別是當(dāng)其某個(gè)西門子PLC單元發(fā)生故障時(shí)，不得不將整個(gè)系統(tǒng)停下來，才能進(jìn)行更換維護(hù)并需重新編程。所以DCS系統(tǒng)要比其安全可靠性上高一個(gè)等級(jí)。
PLC是一種產(chǎn)品，由它可以構(gòu)成SCADA、DCS。DCS是過程控制發(fā)展起來的，PLC是繼電器—邏輯控制系統(tǒng)發(fā)展起來的，PLC是設(shè)備，DCS、SCADA是系統(tǒng)。
DCS與西門子PLC的區(qū)別要點(diǎn)： 1、DCS是一種“分散式控制系統(tǒng)”，而西門子PLC(可編程控制器) 只是一種控制“裝置”，兩者是“系統(tǒng)”與“裝置”的區(qū)別。系統(tǒng)可以實(shí)現(xiàn)任何裝置的功能與協(xié)調(diào)，西門子PLC裝置只實(shí)現(xiàn)本單元所具備的功能。
2、在網(wǎng)絡(luò)方面，DCS網(wǎng)絡(luò)是整個(gè)系統(tǒng)的中樞神經(jīng)，它是安全可靠雙冗余的高速通訊網(wǎng)絡(luò)，系統(tǒng)的拓展性與開放性更好。而西門子PLC因?yàn)榛旧隙紴閭€(gè)體工作，其在與別的西門子PLC或上位機(jī)進(jìn)行通訊時(shí)，所采用的網(wǎng)絡(luò)形式基本都是單網(wǎng)結(jié)構(gòu)，網(wǎng)絡(luò)協(xié)議也經(jīng)常與國(guó)際標(biāo)準(zhǔn)不符。在網(wǎng)絡(luò)安全上，西門子PLC沒有很好的保護(hù)措施。我們采用電源，CPU，網(wǎng)絡(luò)雙冗余。
SCADA system, also known as distributed data acquisition and monitoring system, is a small and medium-sized measurement and control system. It combines the two major advantages of strong on-site measurement and control function of PLC system and network communication ability of DCS system, with high cost-effectiveness.
SCADA and DCS are concepts, while PLC is a product, and the three are not comparable.
PLC is a product that can form SCADA and DCS. DCS has evolved from process control, PLC has evolved from relay logic control systems, PLC is equipment, and DCS and SCADA are systems.
Siemens PLC, which can be programmed as a controller, is suitable for measurement and control in industrial sites. It has strong on-site measurement and control functions, stable performance, high reliability, mature technology, wide use, and reasonable price.
DCS system, also known as distributed control system, belongs to the international advanced level of large-scale control system in the 1990s. It is suitable for industrial sites with multiple measurement and control points, high measurement and control accuracy, and fast measurement and control speed. Its characteristics are decentralized control and centralized monitoring, with network communication capabilities, strong measurement and control functions, reliable operation, easy expansion, convenient configuration, and easy operation and maintenance. However, the system is expensive.
the perspective of computers and networks, they are unified, and the main difference lies in the application requirements. DCS often requires advanced control algorithms. For example, in the refining industry, PLC requires high processing speed because it is often used in interlocking and even in fault safety systems; SCADA also has some special requirements, such as vibration monitoring, flow calculation, peak and valley regulation, etc. SCADA is the dispatch management layer, DCS is the plant management layer, and PLC is the on-site equipment layer.