Explained: Droop vs Isochronous Governing

Summary

The video explains the two basic modes of speed control for diesel generator engines: engine droop and isochronous mode. In isochronous mode, the governor maintains a constant engine speed, typically 1500 RPM, regardless of the load. In contrast, droop mode allows the speed to vary depending on the load, with the speed being higher at no load and decreasing as the load increases. Droop, though originating from mechanical governors, is still widely used for load sharing between multiple generators on a common electrical bus.

Takeaways

• 😀 The script explains two basic modes of speed control for a diesel generator: engine droop and isochronous mode.
• 😀 In isochronous mode, the engine governor tries to keep the engine speed fixed at its normal speed, typically 1500 RPM for 50 Hz power.
• 😀 The engine governor aims to maintain a constant speed at all loads in isochronous mode, keeping the RPM steady at 1500.
• 😀 In droop mode, the governor targets the nominal 1500 RPM speed at full load, but at no load, the speed will be typically 5% higher (around 1575 RPM).
• 😀 As the load increases in droop mode, the speed decreases proportionally back to 1500 RPM.
• 😀 Droop mode originated as a property of old mechanical governors and is still widely used today.
• 😀 Droop mode is commonly used for load sharing among multiple generators connected to a common electrical bus.
• 😀 The graph illustrating droop mode shows a speed decrease from no load to full load, demonstrating how the engine governor operates.
• 😀 The main difference between isochronous and droop mode lies in how the governor adjusts the speed based on load variations.
• 😀 Droop may seem unusual, but it ensures stability and proper load sharing when multiple generators are operating together.

Q & A

What are the two basic modes of speed control for a diesel generator engine?

The two basic modes of speed control for a diesel generator engine are engine droop and isochronous mode.

What happens in isochronous mode?

In isochronous mode, the engine governor attempts to keep the engine speed fixed at its nominal speed, typically 1500 RPM for 50 Hz power, regardless of load variations.

How does the governor behave in droop mode?

In droop mode, the governor targets the nominal 1500 RPM speed only at full load. As the load decreases, the engine speed increases, typically up to 1575 RPM at no load, and decreases proportionally as the load increases.

What is the typical engine speed at no load in droop mode?

The typical engine speed at no load in droop mode is about 1575 RPM, which is approximately 5% higher than the nominal 1500 RPM.

Why might droop mode seem like a strange system?

Droop mode might seem strange because it originated from the properties of old mechanical governors, but it is still widely used today for load sharing across multiple generators on a common electrical bus.

What is the main purpose of using droop mode in diesel generators?

The main purpose of using droop mode in diesel generators is for load sharing when multiple generators are connected to a common electrical bus, ensuring that each generator shares the load proportionally.

How does the engine speed change in droop mode as the load increases?

As the load increases in droop mode, the engine speed decreases proportionally, aiming to maintain the nominal 1500 RPM at full load.

What is the significance of the 1500 RPM speed in this context?

The 1500 RPM speed is the nominal speed for a 50 Hz power system, which is typically maintained in isochronous mode and used as the baseline in droop mode for load control.

Is isochronous mode or droop mode more commonly used in modern generators?

While isochronous mode ensures constant speed regardless of load, droop mode is still more commonly used in modern generators, especially when multiple generators need to share load on a common bus.

Why is droop mode still relevant despite its origins in mechanical governors?

Droop mode is still relevant because it provides a simple and effective method for load sharing between multiple generators, ensuring stability and efficiency in power generation systems.