Understanding Data Flow Inside a Modern Substation to SCADA

As substations evolve toward digitalization, understanding how data flows from field devices to the SCADA control center is crucial. This blog unpacks the real-time data journey—from the high-voltage yard to the SCADA system, including the key devices, protocols, and communication architecture involved.

 1. Substation Yard – Source of Primary Data

At the heart of any substation lie the high-voltage (HV) and low-voltage (LV) sides. Data originates from:

• Incoming lines (33kV / 66kV / 132kV / 220kV)
• Outgoing feeders (1 to 4)
• Primary equipment:
• Lightning Arresters
• Isolators
• Current Transformers (CTs)
• Potential Transformers (PTs)
• Power Transformers (PTRs)

These components provide voltage, current, and status signals used for protection, measurement, and control.

2. Intelligent CRP Panels – Protection & Interface Layer

Each outgoing feeder is connected to a Control and Relay Panel (CRP) which includes:

• Multifunction (MF) Energy Meters
• Protection Relays
• Intelligent Electronic Devices (IEDs)

Each IED communicates over:

• Tx/Rx lines (Transmit/Receive)
• Connected to substation RTU or SCADA Gateway

Purpose:

• Local decision-making (tripping/breaker operation)
• Real-time data capture (amps, volts, breaker status)
• Time-tagged event logs

 3. Communication Network – Digital Backbone

Protocols used:

Networking devices:

• RTU (Remote Terminal Unit)
• Main and Standby CPU
• Router
• Firewall
• Communication Tower (for WAN uplink)
• MPLS Connectivity (for secure Layer-3 IP-based communication)

 4. Control Room – Substation SCADA Interface

Inside the control room:

• FEP (Front-End Processor): Handles protocol translation, typically IEC 104 to/from IEC 61850 or Modbus.
• SCADA Server: Stores and visualizes real-time and historical data.
• Firewall: Ensures cyber-secure communication.
• Redundant Architecture: Main + Standby CPUs for fault tolerance.

5. Data Flow – Step-by-Step

    A[Primary Equipment (CT/PT/CB/PTR)] --> B[CRP Panel (IED, Relay, MF Meter)]

    B --> C[RTU / Protocol Converter]

    C --> D1[FEP Server]

    D1 --> D2[SCADA Server]

    D2 --> E[SLDC / ALDC via IEC 104]

 6. Cybersecurity Considerations

• Firewalls isolate internal OT network from external threats.
• MPLS ensures private WAN communication.
• IEC 62351 standards should be followed to secure IEC 61850/104.

Conclusion