SCADA Systems and Process Control

SCADA, or Supervisory Control and Data Acquisition, is one of the most widely used acronyms in the control panel industry. Having an intricate knowledge of what it is and how it actually works, is integral to the design and manufacture of process control systems. Below, we discuss what makes up a SCADA system, its purpose and how the information they collect is utilised.

What is a SCADA system?

First and foremost, SCADA is a software package, designed to control and monitor equipment in industrial settings. The software element to the system is responsible for gathering and handling data, locating trends and providing diagnostic information on the operation at hand.

Utilised in a wide variety of settings, SCADA systems control most manufacturing, fabrication and production processes, as well as being used in infrastructure for the power, water and the oil & gas industries. The central control system is part software, part hardware – all connected via input/output supply, controller network interfaces and communication equipment.

Simple SCADA system diagram by DualTEC

Together, hardware and software work simultaneously to gather data on whichever process has been assigned for monitoring. Control is then governed either by RTUs (Remote Terminal Units) or PLCs (Programmable Logic Controllers), allowing panel operators to set up logs for analysis, adjust alarm parameters and modify set points.

The hardware in SCADA systems is defined by two layers, the client layer and the data service layer. As the name would suggest, the client layer of hardware takes care of the interaction between man and machine, often consisting of some form of HMI (Human Machine Interface). The data service layer is responsible for all of the data processing within the system – connecting field devices via WAN or LAN networks to RTUs, which convert signals from those field sensors into digital format. That data then determines which control signals will be generated and ultimately sent on to the relays.

These various elements are connected by a combination of wireless and wired technologies and may need to run proprietary protocols, if built by the same manufacturer. For example, Profibus and Conitel’s communication protocols are vendor specific (proprietary), whilst Schneider Electric’s Modbus RTU is open source.

How do SCADA systems work then?

The working procedure of a SCADA system is performed through a combination of software and hardware as mentioned above. Sensors, RTUs and controllers are connected via the comms network to handle data in stages, with aim of executing the primary function of control. The following stages should always be considered during control panel design:

  • Acquisition – quality data acquisition and collection is the keystone to accurate means of control within a given system. Where thousands of sensors or nodes are critical for operational function, the ability to monitor the status of those nodes is essential
  • Communication – SCADA systems are often intended to govern processes in multiple geographical locations, so wireless connectivity is the norm. During the R&D phase, secure internet access via a VPN should be factored into designs for security purposes
  • Presentation – HMIs are an integral part of a SCADA system, enabling the user to view data collected from multiple sources in a format that is easily understood and easily actioned

Acting on the data collected, monitoring and controlling the process intended, is generally an automated process. The user defines specific parameters that are enabled when the right data is fed back into the system from the sensors – though critical tasks are sometimes set to require additional input from the user as an added security measure.

Reach out to the DualTEC team for more info

SCADA systems are easily scalable, making them well suited to a wide variety of businesses, whether in one location or several. If you would like to discuss the adaptability and application of SCADA systems into the design of your control panel, DualTEC’s team of electrical engineers are well placed to do so. For any further information, just call 01535 609314 or email info@dualtec.co.uk.