In short. Choose automation by requirement, not by product. A single standby set needs an AMF controller. Several sets need sharing and sequencing. Critical or hybrid plants need a PMS and degraded-mode design. Add EMS and analytics only when there is something to optimise.
Requirement to architecture
| Requirement | Typical architecture | See |
|---|---|---|
| One standby generator, automatic start and transfer | AMF controller and ATS | ATS and AMF logic |
| Two or three sets in parallel | Synchronising and load-sharing controllers, paralleling switchgear | synchronising |
| Load shedding and restoration | PLC or PMS with feeder control | load shedding |
| Two utility sources | Main-tie-main logic | main-tie-main |
| UPS plus generator for critical loads | Coordinated ATS, UPS settings and integrated tests | UPS and ATS coordination |
| Battery or solar with generators | PMS with BESS control and microgrid controller | microgrid controller |
| Operator visibility and records | SCADA with events and historian | SCADA |
| Cost, fuel and demand optimisation | EMS above PMS | EMS |
| Existing plant with old controls | Staged modernisation | modernisation |
Questions to ask first
- What is the cost of an outage, and how long can loads wait?
- How many sources and how will they be operated?
- Who operates the plant, and with what skills?
- What must work with no network or no PLC?
- What utility rules apply to paralleling or export?
- What data and records are required?
Cautions
- More automation means more failure modes. Add layers where they pay back.
- Keep protection independent.
- Plan degraded modes before the first line of code. See degraded modes.
- Plan acceptance testing. See FAT and SAT.
Illustrative example
A pharma warehouse with two generators, a UPS and strict records chooses paralleling controllers for sharing, an AMF-based transfer, a small PLC for load shedding and a SCADA for events. It skips an EMS because the load profile is flat. A second site with solar and a battery adds a PMS and EMS because the dispatch choices are real.
From requirement to architecture
| Requirement | Suggested architecture |
|---|---|
| One generator, automatic backup for a building | AMF controller with ATS |
| Two sets, shared load, N+1 | Paralleling controllers with load sharing and a PMS function |
| Three or more sets, load shedding, critical process | PMS with PLC and redundant communications |
| Generator with UPS and sensitive IT | ATS, UPS coordination, walk-in and charge limit control |
| Parallel operation with utility | Synchronising and interconnection protection, utility approval |
| Generator plus battery | Hybrid dispatch controller, EMS as needed |
| Island capability | Microgrid controller |
| Multiple sites, remote management | SCADA with secure remote access |
| Substation with many relays from different makers | IEC 61850 architecture |
Questions to settle first
- How long an interruption can each load tolerate?
- How many sources and what combinations?
- Who operates the plant, and with what skills?
- What are the utility and regulatory rules?
- What is the plan for maintenance and testing?
Principle
Choose the simplest architecture that meets the need. Added complexity must pay for itself in availability or cost saving.
For help selecting, use the application engineering enquiry. See also control architecture overview.
The master engineering question
What is the simplest control architecture that still meets the continuity, safety and record-keeping requirements, including when parts of it fail?
What to send us
Describe your sources, loads and outage tolerance. Send your application details.
Questions engineers ask
Do I need a PLC?
If you must coordinate several sources and loads, usually yes.
Can I start simple and grow?
Yes, if interfaces and hierarchy are planned from the start.
Is SCADA mandatory?
No, but it helps records and visibility at larger sites.
When is EMS worth it?
When multiple sources and tariffs create real optimisation choices.
This guide gives general principles. Architecture must be agreed with the site owner.