SCADA — Supervisory Control and Data Acquisition

Definition​

SCADA (Supervisory Control and Data Acquisition) refers to an industrial computer system that provides supervision, control, and data acquisition for an industrial process or distributed infrastructure, in real time and remotely.

A SCADA system allows an operator to monitor the status of an entire facility—such as a factory, water distribution network, power grid, or pipeline—from a centralized interface, collect field measurements, trigger alarms in the event of a malfunction, and remotely control equipment (open a valve, start a pump, adjust a setpoint).

The term SCADA is sometimes mistakenly used as a synonym for monitoring software (HMI). In reality, SCADA refers to the entire architecture: from the field (sensors, RTUs, PLCs) to the control center.

Traditional SCADA Architecture​

A SCADA architecture typically consists of four levels:

Main Components of a SCADA System​

MTU — Master Terminal Unit​

The MTU is the brain of the SCADA system. It is the central server that:

  • Periodically polls the field RTUs and PLCs
  • Receives data in push mode (unsolicited, via DNP3 or IEC 60870)
  • Stores data in a real-time database (historical database)
  • Manages alarms and events
  • Distributes data to operator stations (HMIs)

RTU — Remote Terminal Unit​

RTUs are field devices that acquire data from sensors and actuators and transmit it to the MTU. They are designed for remote sites and long-distance communications. See the full definition: RTU.

HMI — Human-Machine Interface​

The HMI (Human-Machine Interface) is the graphical interface that allows the operator to view the process status, acknowledge alarms, and send commands. Animated process diagrams (screen layouts), real-time trends, and alarm reports are typical features of a SCADA HMI.

SCADA Network​

The communication network between the MTU and the RTUs/PLCs can use different media depending on geographical constraints: fiber optics (for nearby sites), Ethernet/IP over a private network, radio (UHF/VHF, LoRa), 4G/LTE, or satellite for the most remote sites.

Data Historian​

A data historian (OSIsoft PI, Wonderware Historian, InfluxDB) stores time-stamped values over long periods (months, years) for trend analysis, regulatory compliance, and process optimization.

SCADA over 4G/LTE​

In modern installations or migrations of existing systems, SCADA networks are increasingly using industrial 4G LTE as a communication medium, either to replace or supplement proprietary radio or fiber-optic links.

The typical 4G/LTE SCADA architecture works as follows:

  1. At each remote site, an industrial 4G router (or an Eziwan gateway) connects the local RTU or PLC to the cellular network.
  2. An encrypted VPN tunnel (OpenVPN or IPsec) is established between each site and the monitoring center, ensuring the confidentiality and integrity of SCADA communications.
  3. The SCADA server communicates with the remote devices via their native protocol (DNP3, IEC 60870-5-104, Modbus TCP) encapsulated within the VPN tunnel.

4G offers numerous advantages for SCADA systems: rapid deployment, extensive nationwide coverage, lower costs compared to dedicated lines, and sufficient bandwidth for standard monitoring.

The Difference Between SCADA and IIoT​

Although they share common goals (visibility of industrial equipment, data collection), SCADA and IIoT are architecturally different approaches:

CriterionTraditional SCADAIIoT / Industrial Cloud
ArchitectureCentralized, on-premisesDistributed, cloud-native
Real-timeSub-second to a few secondsA few seconds to minutes (acceptable for monitoring)
ProtocolsDNP3, IEC 60870, ModbusMQTT, AMQP, OPC-UA over MQTT, HTTP/REST
SecurityIsolated OT network, DMZZero-trust, end-to-end encryption
ScalabilityLimited (hundreds to thousands of points)Virtually unlimited (millions of sensors)
MaintenanceHeavy (on-premises servers)Light (SaaS)
Initial CostHighLow

SCADA remains essential for mission-critical applications (opening/closing valves, circuit breakers), where latency and availability are crucial. The IIoT complements SCADA for extended monitoring, data analysis, predictive maintenance, and multi-site consolidation.

SCADA + Eziwan Cloud Gateway​

The Eziwan Gateway allows you to extend an existing SCADA system to the cloud without replacing the existing infrastructure:

  • The gateway connects to RTUs and PLCs via their native protocols (Modbus, DNP3).
  • It transmits data simultaneously to the local SCADA server and to the Eziwan cloud platform.
  • Operators access SCADA screens from their usual workstations, while production managers view KPIs on the Eziwan dashboard from any browser.
  • SCADA alerts can be replicated in Eziwan for multi-channel notification (email, SMS, webhook).

Leading SCADA Software on the Market​

SoftwareVendorKey FeaturesTypical Use
IgnitionInductive AutomationWeb-based architecture, unlimited modules, mobile view, fixed pricingMulti-sector, new installations
WinCC / WinCC OASiemensNative S7 integration, TIA Portal, WinCC Unified HTML5Siemens industries, automotive, chemicals
InTouch / System PlatformAVEVAPetrochemical market, robust track record, integrated MESOil & gas, heavy industry
iFIXGE Digital / EmersonFDA 21 CFR Part 11, pharmaceutical and food & beverage marketsPharma, biotech, food & beverage
Panorama E2CodraFrench SCADA, multilingual, water and environmental sectorFrench utilities
ZenonCopa-DataEnergy industry, substation management, redundancyEnergy, rail transportation
Citect SCADAAVEVAMining and power industries, long-term archivingMining, water, energy

Historian — Process Data Storage​

A historian is a time-series database specialized in the high-density storage of monitoring data: millions of timestamped tags with lossless compression. It serves as the SCADA system's long-term memory.

HistorianVendorKey Feature
OSIsoft PI System (AVEVA PI)AVEVAOil industry standard; Swinging Door compression
Wonderware HistorianAVEVAIntegrated with the InTouch/System Platform suite
InfluxDBInfluxDataOpen-source, cloud-native, Flux query—gaining traction in IIoT
TimescaleDBTimescalePostgreSQL time-series extension — existing SQL integration
Ignition Tag HistorianInductive AutomationIntegrated with Ignition, stored in an SQL database (MySQL, MSSQL, PostgreSQL)

SCADA Cybersecurity — NIS2 Requirements​

SCADA systems are major targets of cyberattacks aimed at critical infrastructure operators (CIOs) and NIS2 essential entities (water, energy, healthcare, transportation). The NotPetya incident (2017), the Triton incident (2017—attack on the Triconex safety system), and the attack on the Oldsmar water system (2021) have demonstrated the very real risks involved.

Minimum measures recommended by ANSSI for SCADA systems connected to 4G/LTE networks or the Internet:

  1. Network segmentation: The SCADA/OT network is isolated from the IT network and the Internet by an industrial firewall or DMZ. No direct Internet access to the SCADA system.
  2. Remote access via VPN only: Maintenance and monitoring exclusively via VPN with strong authentication (X.509 + 2FA), never via direct RDP or exposed access.
  3. Patch management: Keep the SCADA server up to date. Legacy SCADA systems running Windows XP/7 without updates are common vectors for intrusion.
  4. Strong authentication: 2FA for SCADA access; no shared accounts (one account = one identified user).
  5. Audit log: Log connections, configuration changes, and control commands. Recommended minimum retention period: 12 months (NIS2 Article 21).
  6. Offline backups: SCADA configuration (tags, alarms, history) backed up to a medium disconnected from the network. Restores should be tested regularly.

The Eziwan Gateway implements the "zero-inbound-port" principle on the site side: the SCADA system is never directly exposed to the Internet—it communicates via the outbound VPN tunnel from the gateway.

Frequently Asked Questions​

What is SCADA used for?​

To monitor and control an industrial process: collecting field measurements (via RTUs and PLCs), displaying data on process diagrams, managing alarms, logging historical data, and issuing remote commands. It is the central tool in control rooms.

What is the difference between SCADA and an IIoT platform?​

SCADA controls the process in real time within a defined scope; the IIoT platform aggregates data from multiple sites in the cloud for monitoring, analysis, and maintenance. The two complement each other rather than compete.

Can a SCADA system be connected via 4G LTE?​

Yes: With an industrial 4G router, a VPN tunnel, and traffic prioritization, 4G latency (30–60 ms) is well within the range required for SCADA polling cycles. Thousands of remote management sites operate this way.

Cloud-based SCADA or on-premises SCADA?​

On-premises solutions maintain local control over mission-critical real-time operations; the cloud offers multi-site consolidation, remote access, and reduced infrastructure costs. The choice depends on the criticality of the operations and the geographical distribution of the sites.