SCADA: Communication Infrastructure

A SCADA System Component

Communication infrastructure is one of the components of a SCADA system. For meeting requirements of communication, combined radio and direct serial or other modern connections have been used by SCADA systems. Railways and Power Stations which are large sites very often prefer use of Ethernet or IP over Synchronous Optical Networking (SONET). The term Telemetry is used when a SCADA system performs function of remote management and monitoring.

SCADA Communication Protocols

While the earlier low bandwidth protocols are still persisting, customers now mostly want SCADA data to transmit through preset corporate network and sharing of the network with other applications. Protocol designs in SCADA are compact and are so designed as to send information to master station only in case the RTU is surveyed for information by the master station. Modbus, RP570 and Conitel are the traditional vendor specific SCADA communication protocols. Standard communication protocols include IEC61850, DNP3, Profibus and IEC60870-5-101 or 104. All major SCADA vendors recognize these protocols. Communication protocols with extensions can operate in internet protocol TCP/IP. Modbus TCP/IP has now become standard for lot of hardware manufacturers and is a widely accepted communication protocol. Although for safety and security of SCADA system, it is advisable not to connect it to internet and expose it to risk, Ethernet TCP/IP has found its way into industrial automation breaking the barriers in majority of SCADA/HMI markets.

SCADA Control Protocols

Before evolution of standards for interoperability in industry, a lot of automatic control devices like RTU were already developed. This resulted in proliferation of control protocols by various developers. Besides to keep their customers hooked, the vendors made their own protocols. Some communication between devices was originally not designed to be part of industrial network. Now there are solutions gaining wide acceptance for interconnecting diverse hardware and software permitting communication even between devices not part of original network.