In short. SCADA lets operators see and command a power system. It collects data from relays, meters and controllers, stores history and presents alarms and mimics. It should be treated as a supervision layer: the plant must run safely if it fails.
Components
- Field devices: protection relays, meters, generator and ATS controllers, UPS, BESS, PLCs.
- Communication: serial and Ethernet links with protocols. See protocols.
- Gateways and RTUs: translate protocols and aggregate data.
- Servers: data acquisition, alarm, historian.
- HMI clients: operator stations and remote views.
Design decisions
| Decision | Consideration |
|---|---|
| Point list | What is measured, status, alarms, commands, with owners |
| Update rate | Fast for events, slower for trends |
| Time stamping | At the source for event analysis. See time synchronisation |
| Redundancy | Servers, networks, and power; match to criticality |
| Command authority | Who can operate what, from where. See control philosophy |
| Security | Segmentation, accounts, patching. See OT network |
| Historian | Retention, resolution and backup |
What SCADA should show for a generator plant
- Source status, breaker positions, bus voltage and frequency.
- kW, kVAr, power factor and loading per set.
- Fuel levels, battery voltage, coolant and oil.
- Mode and readiness: AUTO, not ready, locked out.
- Alarms with priority and first-out.
- Transfer counts, run hours, starts and failures.
Independence from control
SCADA should not be the only place where protection or critical sequences run. If servers or networks fail, the plant continues under local automatic control. See degraded modes.
Illustrative example
A campus has SCADA collecting data from generators, ATS, UPS and meters. A server failure interrupts the display for an hour, but generators and ATS continue to operate. After repair, the historian back-fills data from device buffers, so no event record is lost.
What SCADA contributes
SCADA collects data from field devices, shows it to operators, records history and passes commands back. For power systems it is the window to the plant, not the controller of protection.
| Layer | Elements |
|---|---|
| Field | Relays, meters, generator controllers, ATS, sensors |
| Control | PLC, RTU, gateways |
| Supervision | SCADA servers, HMI clients, historian, alarm server |
| Enterprise and remote | Reports, mobile access, central operations centre |
Architecture decisions
- Single server or redundant pair.
- Polling versus report-by-exception.
- Data retention and historian sizing.
- Command authority and audit trail.
- Local HMI at the site for operation when the central link is down.
Data points that give value
- Breaker position and trip cause.
- Source availability and mode.
- kW, kVA, power factor, current, voltage, frequency.
- Engine data: oil pressure, coolant temperature, fuel level, battery voltage, run hours.
Principle
The plant must be able to run safely with SCADA offline. Protection and local control are independent of it.
Security
Restrict remote commands, use unique accounts, log actions, patch systems and segment networks. See OT network architecture.
See remote electrical monitoring.
The master engineering question
If SCADA disappears during an outage, what do operators lose, what does the plant keep doing and how long until we notice?
What to send us
Send device list and monitoring needs. Send your application details.
Questions engineers ask
Is SCADA needed for one generator?
Not always. Remote monitoring may be enough for simple sites.
How many points should I monitor?
Those that support decisions and diagnosis, not everything available.
Can SCADA be cloud-based?
Parts can; keep local control and local view.
How long to keep data?
Per operational need and regulation; trends help diagnosis over months.
This guide gives general principles. Confirm with a project design.