SCADA — Supervisory Control and Data Acquisition

SCADA is a control system architecture for high-level supervision and data acquisition across industrial processes, often spread over large geographic areas. It combines PLCs or RTUs (Remote Terminal Units) at the field level with a central supervisory system for visualisation, alarming, trending, and data logging.

Why companies use it

·Enables centralised monitoring and control of geographically distributed assets (power grids, pipelines, water treatment)
·Provides historical data logging for process optimisation and regulatory compliance
·Alarm management in SCADA reduces operator overload and enables faster abnormal event response
·Integration with plant information systems (MES, ERP) through OPC-UA or historian databases enables business intelligence

What hiring managers look for

·SCADA system knowledge is essential for automation engineers in process industries, utilities, and building automation
·Experience with major SCADA platforms (Wonderware, Ignition, Siemens WinCC, Aveva) is directly practical
·SCADA cybersecurity is an increasing concern — engineers who understand network segmentation and ICS security show awareness of modern challenges
·Historian database experience (OSIsoft PI, InfluxDB) for process data analytics is highly valued

Typical interview questions

Describe the architecture of a typical SCADA system — what are the layers and what does each do?

What is the difference between a SCADA system and a DCS (Distributed Control System)?

How do you implement effective alarm management in a SCADA system?

What cybersecurity risks are specific to industrial SCADA systems and how do you mitigate them?

Describe a SCADA system you have configured or worked with. What did it monitor and what was the network architecture?

Common mistakes

·Connecting a SCADA system directly to the corporate IT network without a DMZ or firewall — ICS/SCADA networks must be isolated from corporate and internet networks
·Not implementing alarm prioritisation — thousands of alarms with no priority scheme cause operators to ignore them, defeating their purpose
·Storing SCADA data in a proprietary format that cannot be integrated with business intelligence tools
·Not testing failover scenarios — SCADA systems for critical infrastructure must be tested for communication failure, server failure, and network partition
·Using default credentials on SCADA servers and PLCs — ICS systems are increasingly targeted by ransomware

Real engineering example

A water treatment plant upgraded from a proprietary SCADA to Ignition after the original system's vendor withdrew support. The new SCADA was configured with Modbus TCP to the existing PLCs (avoiding PLC replacement cost), a historian database (InfluxDB) with Grafana dashboards for the operations team, and a DMZ architecture that allowed remote monitoring via VPN without exposing the control network to the internet. Alarm rationalisation reduced the daily alarm rate from 800 to 45, improving operator response time to critical alarms by 60%.

Topics covered

SCADAsupervisory controldata acquisitionIgnitionWinCChistorianICSautomation

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