SCADA

SCADA — Supervisory Control and Data Acquisition — is the operator-facing layer above PLCs and RTUs. It visualizes plant state, issues setpoint commands, records history, and manages alarms across geographically distributed assets.

Overview

SCADA differs from a local HMI by scope: an HMI is one screen on one machine; SCADA covers entire plants, pipelines, water districts, or substations.

Components

• Field devices — PLCs, RTUs, IEDs, smart instruments.
• Communications — Ethernet, fiber, cellular, radio, satellite.
• SCADA server — polls / subscribes, runs scripts, hosts the tag database.
• Historian — long-term time-series storage with compression.
• HMI / operator clients — thick clients or web browsers.
• Engineering workstation — for development & deployment.

HMI Design

• Follow ISA-101 / High-Performance HMI principles.
• Grayscale “at rest”; color only for abnormal conditions.
• Layered displays: Level 1 overview → Level 4 detail.
• Consistent symbol library; trend embedded with the asset.
• Avoid 3-D shading, gradients, and distracting animations.

Alarm Management

• ISA-18.2 / IEC 62682 — alarm philosophy & lifecycle.
• Rationalize: every alarm must have an action and a response time.
• Target rates: <1 alarm/op/10 min steady state; <10 in first 10 min of upset.
• Use priority tiers; suppress redundant chattering alarms.
• Track KPIs: average rate, peak, standing, shelved.

Tags & Historians

• Tags scale from thousands to millions; naming conventions matter.
• Dead-band & rate compression in the historian.
• Time-series stores: PI System, AVEVA Historian (Wonderware), Ignition Tag Historian, Canary, InfluxDB.
• Common interfaces: OPC UA, OPC DA (legacy), MQTT Sparkplug B.

Platforms

• AVEVA System Platform / Plant SCADA (Citect) / InTouch.
• Rockwell FactoryTalk View SE / ME.
• Siemens WinCC, WinCC OA.
• Inductive Automation Ignition.
• GE Cimplicity, iFIX.
• Schneider EcoStruxure / ClearSCADA / Geo SCADA.