System Architecture
General Architecture
A typical SCADA–PLC architecture includes:
- Field Devices/Sensors
- Analog sensors: Pressure, temperature, flow, level
- Digital sensors: Limit switches, status signals
- PLC Controllers
- Core unit performing automation logic, interlocks, sequence control, and real-time processing.
- Communicates to SCADA via industrial protocol.
- SCADA Server
- Central computer hosting SCADA software, database, historian, alarm management, and HMI.
- Operator Workstations
- For visualization, control commands, and system supervision.
- Networking Layer
- Industrial Ethernet, Fiber Optics, Switches, and Firewalls
- Protocols: Modbus TCP/IP, Profinet, EtherNet/IP, IEC 60870-5-104, OPC UA
Applicable Standards
- IEC 61131 – Programmable Controllers
- IEC 60870 / IEC 61850 – Communication Protocols
- ISA 5.1 – Instrumentation Symbols
- ISA 95 – Enterprise-Control Integration
- Modbus, OPC UA, Ethernet/IP or Profinet standards
- IEEE, ISO, and OEM guidelines
PLC Hardware Requirements
1. PLC Controller
- CPU CPU must support:
- Scan time ≤ 10 ms normal load
- Memory program minimal 2 MB
- Non-volatile memory backup
- Real-time clock
- Redundancy (optional as per the project):
- CPU redundancy
- Power supply redundancy
- Hot-swappable I/O modules
2. I/O Modules
- Digital Input: 24 VDC, optically isolated
- Digital Output: 24 VDC or relay type (as the application)
- Analog Input: 4–20 mA / 0–10 V, 12–16 bit resolution
- Analog Output: 4–20 mA / 0–10 V
- Temperature input (RTD/TC) If needed
- I/O harus modular dan hot-swappable (if the system is large)
3. Power Supply
- Input: 230 VAC / 24 VDC
- Redundant PS (if critical system)
- Built-in protection (overvoltage, short circuit)
SCADA System Requirements
1. SCADA Features
- Real-time monitoring & control
- Trending (real-time & historical)
- Alarm management (ISA 18.2 compliant)
- Reporting (daily/weekly/monthly)
- User management & password protection
- Remote access (VPN secure)
- Data logging to historian database
- Dashboard design as per P&ID or SLD
2. SCADA Server & HMI
- Architecture:
- Single Server or Redundant Server
- One or multiple Client/Operator Stations
- Optional Web Client access
- Operating System: Windows 10/11 Industrial or Server OS
- Database: SQL, Historian Database (Wonderware/Aveva, iFix, WinCC, Ignition, etc.)
Communication Network
1. Networking
- Industrial Ethernet (recommended)
- Protocol options:
- Modbus TCP/IP
- Profinet
- Ethernet/IP
- OPC UA
- IEC 61850 (for substation)
- Fiber optic backbone for long distance
- Managed Industrial Ethernet Switch (Layer 2/3)
- Ring topology (RSTP/MRP) for reliability
2. Cybersecurity
- Firewall dan VLAN segmentation
- Role-based access control
- Encrypted communication (SSL/TLS)
- Audit logs dan password policy
- Backup system auto-scheduled
Programming & Software Engineering
- PLC programming languages sesuai IEC 61131:
- Ladder Diagram (LD)
- Function Block Diagram (FBD)
- Structured Text (ST)
- SCADA graphics follow standard ISA HMI (high performance HMI design)
- Tag naming convention clear and consistent
- Alarm class, priority, and color coding according to standards