Load Sharing in Multi-Generator Diesel Power Stations

When multiple generators are connected in parallel, the site does not want one set overloaded while another sits lightly loaded. Load sharing balances active and reactive power across available machines so the power station can operate within generator ratings and maintain stable supply.

The exact control method depends on the generator controllers, governors, AVRs, metering, switchgear and site operating philosophy. The supervisory PLC or power management system may also decide when to start another set, when to stop a set, how much reserve to maintain and what happens if a generator trips.

Key control questions

• How many generators should be running for the current site load?
• What minimum spinning reserve is required?
• Which generator has priority when demand increases?
• How are maintenance lockouts and unavailable sets handled?
• What should operators see when load sharing is not behaving as expected?

A useful SCADA display should show total kW, total kVAr, each generator contribution, available capacity, running priority and alarms that explain abnormal behaviour. The screen should help operators make decisions, not simply display numbers.

Common problems

Sites can run into load-sharing problems when controller settings are inconsistent, measurement signals are unreliable, communications are poorly mapped or operating modes are unclear. These issues can appear as hunting, uneven loading, nuisance alarms or uncertainty during plant recovery after a trip.