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PACs are deployed in SCADA systems to provide RTU and PLC functions. In many electrical substation SCADA applications, "distributed RTUs" use information processors or station computers to communicate with digital protective relays, PACs, and other devices for I/O, and communicate with the SCADA master in lieu of a traditional RTU.
Distributed Network Protocol 3 (DNP3) is a set of communications protocols used between components in process automation systems. Its main use is in utilities such as electric and water companies.
DF-1 - used by Allen-Bradley ControlLogix, CompactLogix, PLC-5, SLC-500, and MicroLogix class devices; DNP3 - a protocol used to communicate by industrial control and utility SCADA systems; DirectNet – Koyo / Automation Direct proprietary, yet documented PLC interface; EtherCAT; Ethernet Global Data (EGD) – GE Fanuc PLCs (see also SRTP)
A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis.
A feedback control loop is directly controlled by the RTU or PLC, but the SCADA software monitors the overall performance of the loop. For example, a PLC may control the flow of cooling water through part of an industrial process to a set point level, but the SCADA system software will allow operators to change the set points for the flow.
Direct communication of plant floor equipment data is established by connecting to the PLC. Often, plant floor data is first collected and diagnosed for real-time control in a DCS or SCADA system. In this case, the MES systems connect to these Level 2 systems for exchanging plant floor data.
The first industrial control computer system was built 1959 at the Texaco Port Arthur, Texas, refinery with an RW-300 of the Ramo-Wooldridge Company. [4] In 1975, both Yamatake-Honeywell [5] and Japanese electrical engineering firm Yokogawa introduced their own independently produced DCS's - TDC 2000 and CENTUM systems, respectively. US-based ...
DeviceNet was originally developed by American company Allen-Bradley (now owned by Rockwell Automation). It is an application layer protocol on top of the CAN (Controller Area Network) technology, developed by Bosch. [2] DeviceNet adapts the technology from the Common Industrial Protocol into an open standard. [3]