Generator Load Sharing Problems | Symptoms, Causes, and Fixes

In industrial plants and power stations where multiple generators operate in parallel, generator load sharing is critical to ensure stable power distribution, prevent overloads, and maintain system efficiency. Problems in load sharing are common and can arise from mechanical, electrical, or control system issues.

This article addresses the most frequent generator load sharing problems as encountered by field engineers, providing real-world symptoms, causes, and practical solutions. Understanding these issues is essential to maintain reliable operation, minimize downtime, and extend the life of generator units.

1. Why Is One Generator Carrying More Load Than the Others?

Unequal kW load sharing occurs when one generator consistently handles more active power than its peers. This can lead to overloading on one unit and underutilization on others.
Causes: Incorrect governor setpoints, calibration errors, sensor drift in voltage or current measurements, or mechanical delays in the engine.
Field Solutions: Regularly calibrate governors, inspect and adjust sensors, and verify droop settings to ensure proper load distribution.

Read about: Synchronizing Generators Problems | Common Issues & Field Solutions

2. Why Is Reactive Power Unevenly Distributed Between Generators?

Reactive power (kVAR) imbalance is a frequent issue that causes heating problems and differences in power factor between generators.
Causes: Mismatched AVR settings or incorrectly configured droop characteristics.
Field Solutions: Synchronize AVR settings, adjust reactive power sharing parameters in the paralleling panel, and monitor power factor continuously.

3. Why Do Generators Keep Oscillating or Hunting Between Loads?

Load hunting refers to continuous fluctuations in load sharing between generators, leading to unstable voltage and frequency.
Causes: Poor governor tuning or delayed control loop responses.
Field Solutions: Re-tune governors with proper response rates, ensure control loops are stable and damped, and test load response under varying conditions.

4. Why Does Load Sharing Become Unstable During Sudden Load Changes?

Generators often lose balance when sudden changes in load occur, causing temporary overloads or trips.
Causes: Slow AVR or governor response times or improper droop/feedback loop settings.
Field Solutions: Optimize governor and AVR response times, simulate transient conditions during testing, and ensure load sharing ratios remain consistent.

5. How Do Incorrect Droop Settings Affect Load Distribution?

Incorrect frequency or voltage droop settings can make one generator consistently carry more or less load, resulting in poor active and reactive power distribution.
Field Solutions: Standardize droop percentages across all generators, check control panel configurations, and adjust as needed.

6. What Happens When the Load Sharing Communication Fails?

Communication failures in load sharing systems, whether via CAN, RS485, or Modbus, can lead to uneven load distribution even if all mechanical settings are correct.
Causes: Faulty communication cables, network delays, or data loss.
Field Solutions: Inspect and repair communication lines, test the PLC or load sharing modules, and ensure real-time data exchange is stable.

7. Can CT or PT Calibration Errors Cause Load Sharing Issues?

Yes. Incorrectly calibrated current transformers (CTs) or potential transformers (PTs) can produce inaccurate readings, causing one generator to take more load than it should while others underperform.
Field Solutions: Recalibrate CTs and PTs according to manufacturer standards and cross-check measurements with independent meters to ensure accuracy.

8. Could Poor Governor Tuning Affect Load Sharing?

A malfunctioning or poorly tuned governor leads to slow or overshooting responses during load changes, resulting in imbalanced load sharing.
Field Solutions: Inspect the mechanical governor components, re-tune PID settings, and perform load tests to verify stability under varying conditions.

9. How Does AVR Instability Impact Reactive Power Sharing?

An unstable Automatic Voltage Regulator (AVR) can create uneven reactive power distribution between generators, causing voltage fluctuations and heating problems.
Field Solutions: Stabilize AVR parameters, synchronize reactive load sharing, and monitor generator output for consistency.

10. Can Engine Fuel System Issues Cause Load Sharing Discrepancies?

Problems in the engine fuel system—such as blockages or delayed injection—can prevent a generator from producing the expected power, even if electrical settings are correct.
Field Solutions: Inspect fuel lines and injectors, ensure proper fuel supply, and test engines under full load to confirm consistent output.

11. Could Faulty Temperature or Speed Sensors Affect Load Sharing?

Faulty temperature or speed sensors can trigger incorrect responses in control systems, resulting in uneven load distribution or unnecessary trips.
Field Solutions: Test and replace defective sensors, verify wiring and grounding, and monitor readings for consistency.

12. Can a Synchronization Panel Malfunction Cause Load Imbalance?

The paralleling control panel itself can be the source of load sharing issues if modules fail or parameters drift over time.
Symptoms: Persistent imbalance despite correct generator settings.
Field Solutions: Test panel modules, recalibrate parameters, and replace aging components when necessary.

13. How Does Manual Operation Affect Load Sharing?

Operating generators manually without precise monitoring can create uneven load distribution, especially in complex plants.
Field Solutions: Train operators on proper load sharing procedures and encourage the use of automatic mode for parallel operation.

14. What Are the Effects of Load Shedding or Sudden Disconnections?

Sudden changes in load, whether due to load shedding or network disconnections, can cause temporary overloads or trips in generators, disrupting load sharing.
Field Solutions: Implement soft load shedding strategies, monitor generator connections, and sequence load changes carefully.

15. How Can Power Factor Mismatch Cause Load Sharing Problems?

Different power factor targets across generators can lead to uneven reactive load sharing, overheating, or overcurrent situations.
Field Solutions: Align power factor setpoints, continuously monitor reactive power distribution, and adjust settings in the paralleling panel as needed.

Conclusion

Effective generator load sharing is essential for maintaining stable power distribution, preventing overloads, and ensuring the longevity of generator units in industrial plants and power stations. The problems highlighted in this article—from unequal active or reactive power sharing to governor, AVR, and sensor issues—are all common challenges faced by field engineers.

By understanding the symptoms, causes, and practical solutions for each issue, engineers can troubleshoot efficiently, optimize system performance, and minimize downtime. Regular maintenance, proper calibration, and careful monitoring of all control and synchronization systems are key to achieving reliable parallel generator operation.