Knowledge of Generator Reverse Power Protection

As we all know, generator sets come in a variety of power ratings. When choosing a generator, the power rating is an important factor to consider. Today, the editor of Dingbo Power will popularize knowledge about generator reverse power protection.

1. What is generator reverse power?

Normally, the power of a generator should flow from the generator to the power system. However, due to certain reasons, if the steam turbine loses its driving force and the generator outlet switch fails to trip, the power flow will reverse, i.e., from the system to the generator. In this case, the generator operates as a motor, drawing active power from the system. This is called reverse power.

2. Hazards of generator reverse power

When the main steam valve of the steam turbine closes due to some reasons and the turbine loses its driving force, the generator operates as a motor, driving the steam turbine to rotate. Under such circumstances, the turbine blades rotate at high - speed without steam, causing windage friction. In particular, the last - stage blades may overheat, leading to damage to the rotor blades. Therefore, reverse power protection is essentially a protection measure for the steam turbine against no - steam operation.

3. Generator programmed reverse power protection

Generator programmed reverse power protection is mainly designed to prevent the situation where, when the generator is operating under a certain load, the generator outlet switch suddenly trips while the main steam valve of the steam turbine fails to close completely. In this case, the steam - turbine generator unit is prone to over - speeding, or even a runaway. To avoid this, for some non - short - circuit fault protections, after the action signal is sent, it first acts to close the main steam valve of the steam turbine. After the reverse power relay of the generator operates, combined with the signal indicating that the main steam valve is closed, a programmed reverse power protection is formed with a short time delay. This protection then acts to shut down the entire unit.

4. Differences between reverse power protection and programmed reverse power protection

Reverse power protection aims to prevent the generator from operating as a motor and driving the steam turbine to rotate after reverse power occurs, which could damage the steam turbine. In essence, it is to prevent the prime mover from having insufficient power and being driven by the system.

Programmed reverse power protection is to prevent the steam turbine from over - speeding when the generator set is suddenly disconnected from the grid and the main steam valve fails to close completely. It uses reverse power as a means to avoid this situation. In essence, it is to prevent the prime mover from having too much power, which could cause the unit to over - speed.

Strictly speaking, reverse power protection is a type of generator relay protection, mainly protecting the steam turbine. Programmed reverse power protection is not a traditional protection but an action process set for programmed tripping, also known as programmed tripping, which is generally applied in the shutdown mode.

The most crucial difference is that reverse power protection trips as soon as the set value is reached, while programmed reverse power protection requires not only the set value to be reached but also the main steam valve of the steam turbine to be closed. Therefore, during the grid - connection moment in the unit startup process, reverse power action must be avoided.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to [email protected] we will pay highly attention on your question.