What buyers should know first
Some industrial buyers want a industrial generator sets not only for emergency backup but also to run alongside the utility grid, reduce peak-demand charges, or export surplus power. This is technically possible, but it requires synchronising equipment, utility-approved protection, and a control philosophy that goes far beyond a standard automatic transfer switch. The ATS transfer time and pole-count guide guide covers changeover; this guide covers continuous parallel operation.
We do not install grid-interactive systems, but we supply the industrial standby generator sets generator sets that form the power plant. This article explains what a buyer must verify before adding a set to a parallel-with-mains or export-to-grid project.
Three operating modes that are often confused
Suppliers and buyers sometimes use the word ‘parallel’ to mean three very different things. Confusing them causes expensive mistakes.
| Mode | What it does | Key requirements |
|---|---|---|
| Island parallel (multi-set) | Two or more generators run together without the grid. | Standard synchronising panels, load sharing, droop/isochronous governors. |
| Peak lopping / demand management | Generator runs in parallel with the grid but never exports. | Reverse-power relay, import/export meter, utility agreement. |
| Export to grid | Generator supplies power back into the public grid. | Grid-code compliance, export limiters, protective relays, utility approval. |
Peak lopping is usually the easiest to permit because the grid sees the site as a net consumer. Exporting turns the site into a generator connected to the distribution network, which most utilities regulate strictly.
Control and protection checks
A generator running parallel with the grid must match voltage, frequency, phase sequence, and phase angle before closing the breaker. After connection, the governor and AVR keep it stable. Protection relays must disconnect the set safely if the grid fails or the generator develops a fault.
Procurement checklist
- Confirm whether the project needs island, peak-lopping, or export mode.
- Require a synchronising check relay and dead-bus / live-bus logic for the generator breaker.
- Specify reverse-power and under/over-frequency protection for mains-parallel mode.
- Ask for a grid-code compliance statement from the system integrator, not just the genset supplier.
- Verify that the site meter and SCADA can measure import, export, and power factor in real time.
- Request the single-line diagram showing generator, mains, bus coupler, and protection zones.
Where the genset supplier fits in
Our role as a generator set supplier is to provide a machine with the right governor and AVR interfaces for the parallel controller. We can also supply container generator sets enclosures, fuel systems, and acoustic treatment for the power house. The system integrator or EPC normally designs the switchgear, protection, and utility interface. We recommend coordinating both scopes early.
For large schemes, generator sets above 1,000 kW sets with electronic governors are commonly used. Mitsubishi diesel generator sets and MTU diesel generator sets engines are frequent choices where long-run reliability matters; Cummins diesel generator sets and Volvo diesel generator sets are common for mid-size peak-shaving plants.
RFQ wording that gets useful answers
Ask: ‘Confirm whether the quoted generator set is supplied with an AVR and governor suitable for mains-parallel operation via a third-party synchronising controller, and state any interface requirements (4-20 mA, Modbus, droop/isochronous select).’
Questions buyers often ask
Can any diesel generator export to the grid?
Physically yes, but legally and safely only with utility approval, grid-code-compliant protection, and export limiting. Never assume approval is automatic.
What is the difference between droop and isochronous mode?
Droop mode shares load changes proportionally between sets or between generator and grid. Isochronous mode holds a fixed frequency and is used in island operation.
Do I need a special AVR for parallel operation?
You need an AVR that accepts a power-factor or voltage-reactive-power droop signal, and that can interface with the parallel controller. Most modern digital AVRs do this; older analogue units may not.
Who approves a grid-parallel installation?
The local distribution network operator (DNO) or utility. Approval typically requires a protection study, single-line diagrams, and witness testing.
Is peak shaving the same as export?
No. Peak shaving reduces import from the grid but does not feed power back. It usually has simpler metering and faster utility approval.
Parallel-with-mains projects are not an afterthought. The generator set, switchgear, controls, and utility agreement must be designed together. request a quote to confirm which our generator product range can be configured for the interfaces your integrator needs.