Friday, April 26, 2013

Basic Breakdown of SCADA Systems

SCADA is the acronym for 'Supervisory Control and Data Acquisition' and the term is generally applied in the context industrial control applications, facility processes or infrastructure management. A SCADA system includes not just a supervisory computing unit for acquiring data and sending commands to a system but also Human Machine Interfaces (HMI's), Remote Terminal Units (RTU's) and Programmable Logic Controllers (PLC's).

It is worth noting that in the past a distinction was made between SCADA and Distributed Control Systems (DCS's) but that the differences between the two systems are becoming less defined. Both technologies have advanced to provide quite similar monitoring and control solutions in more recent times.

Most of the control actions in a SCADA system are automated by RTU's and PLC's based on preset requirements. RTU's connect sensors within the process by sending digital data to the supervisory 'computer' and whilst PLC's fill a similar data acquisition role they offer more versatility and are customisable to perform more specific automation tasks. Newer and increasing applications of 'smart' PLC's and RTU's allow these components to manage non-critical or routine tasks autonomously without drawing on the resources of the master computer.

Operators and system maintenance personnel utilise the HMI (Human Machine Interface) in order to review various portions of data within the system. The Operator will then use this data to control various aspects of the process. In most cases the HMI is linked up to the SCADA system's software and databases and it is set to provide trending data and diagnostic data. Technical information examples include machine or sensor schematics and expert-level troubleshooting guides. Management information examples include logistics data, productivity data and maintenance schedules.

HMI's are often set to display data in graph and diagram formats for ease of interpretation. Such routine 'reports' and schematics are just one aspect of the SCADA HMI. Arguably the most important function of the SCADA system is that of alarm handling. The system monitors all aspects of a process and when certain 'alarm' conditions are met one or more actions occurs such as notifying the operator via email, text or the system itself. It is important to discuss cascading alarm handling with the SCADA engineer or a similar professional to ensure that the initial alarm event is not lost beneath subsequent alarm triggers.

A universal requirement for SCADA systems is that they are built and installed with durability and reliability in mind. Components need to be hardy and able to withstand varying temperature ranges and vibration levels, well as extreme voltages. Systems of critical importance would be setup with built in redundancies (in hardware and communication), multiple servers and disaster recovery sites sometimes to the point of having multiple control centres which are fully equipped to take over failed processes and operations.

All-in-all, SCADA and its related HMI's are a vital part of many aspects of modern production and process control. From space stations to water treatment facilities to refining plants to controlling energy consumption in a building, there is a SCADA based system application available to report on and control its processes.

Article Source:

No comments:

Post a Comment