How to Manage Under-Voltage Faults in Generator Sets

 
In modern industry and daily life, generator sets are crucial for ensuring a reliable power supply. However, sometimes generator sets experience under-voltage fault alarms and automatically shut down, severely affecting normal power supply. Understanding the potential causes of these faults and implementing effective solutions is essential for maintaining the stable operation of generator sets.
 

Causes of Under-Voltage Fault

 
Several factors can lead to under-voltage fault alarms and shutdowns in generator sets during operation. Below are the primary causes and detailed explanations:
 

1. Faulty Automatic Voltage Regulator (AVR)

The AVR is a critical component of the generator, responsible for regulating output voltage. Several factors can lead to AVR faults:
 
Environmental Factors: Changes in temperature, humidity, and other environmental conditions can affect AVR parameters, necessitating recalibration. Standalone diesel generators typically do not encounter this issue as their AVR parameters are fixed (e.g., at 400V). However, for parallel-connected generators, the AVR adjusts according to the main bus voltage, causing parameter variations. In such cases, the synchronization device's voltage regulation signal should be correctly connected to the AVR. Incorrect connections can cause voltage regulation issues. Additionally, quickly recalibrating voltage using electronic controls (e.g., synchronization devices, AVR) during startup can effectively resolve the problem.
 

2. Diesel Engine Speed Regulation Issues

Diesel engine speed regulation can be managed through electronic or mechanical governors, each potentially causing different issues:
 
Electronic Governor Faults: Malfunctions in the electronic governor can cause unstable speed regulation, affecting voltage output.
Mechanical Governor Faults: For mechanically governed diesel engines, a fuel pump mechanism (such as a common rail fuel pump) controls fuel flow. This mechanism includes a speed regulation rod with limit and regulation pins. If a low voltage alarm occurs 20 seconds after startup, it may be due to an inability to increase speed, affecting voltage and frequency. Adjusting the speed regulation rod may solve this issue.
Typically, diesel generator faults have a primary cause. Addressing the main fault often resolves related secondary faults as well.
 

3. Grounding Faults

Grounding faults are a significant cause of under-voltage in generator sets:
 
Three-Phase Grounding Faults: In cases of three-phase grounding, voltage and current will be extremely low. It's crucial to check if the grounding discharge device (e.g., grounding switch) is engaged.
Varistor Faults: Varistors conduct to reduce voltage during over-voltage conditions. If a varistor is damaged or conducting due to other reasons, voltage will be very low. The rectifier bridge, which consists of six diodes, provides DC power to the AVR and excitation system. Damaged diodes in the rectifier bridge can severely impair the AVR and excitation system, leading to under-voltage faults.
 

Relevant Solutions

 
To ensure the normal operation of generator sets and prevent under-voltage faults, the following measures are recommended.
 

1. Regular Inspection and Maintenance of the AVR

Environmental Adaptation Adjustments: Especially in changing environmental conditions, regularly check and recalibrate AVR parameters. While standalone diesel generators typically do not require this, parallel-connected generators must ensure AVR parameters adapt to main bus voltage variations.
Voltage Regulation Signal Check: Ensure the synchronization device's voltage regulation signal is correctly connected to the AVR. If errors are found, adjust immediately. During startup, quickly recalibrate voltage using electronic controls (e.g., synchronization devices, AVR).
 

2. Speed Regulation System Check and Adjustment

Electronic Governor Maintenance: Regularly inspect the electronic governor's condition to ensure proper speed regulation. If instability is detected, repair or replace as necessary.
Mechanical Governor Maintenance: For mechanically governed diesel engines, periodically check the fuel pump mechanism and speed regulation rod. Ensure the limit and regulation pins function properly. If voltage and frequency issues occur after startup, adjust the speed regulation rod accordingly.
 

3. Grounding System Detection

Grounding Discharge Device Check: Regularly inspect grounding discharge devices (e.g., grounding switches) to ensure they are properly engaged and functioning. Address any grounding faults promptly to restore normal voltage and current.
Varistor Check: Varistors reduce voltage during over-voltage conditions. Regularly inspect varistors for damage and replace them if necessary.
Rectifier Bridge Maintenance: The rectifier bridge diodes supply DC power to the AVR and excitation system. Regularly inspect the rectifier bridge and replace damaged diodes.
 

4. Spare Parts Preparation

Stock Common Spare Parts: To handle unexpected faults, keep common spare parts such as rectifier bridge diodes and varistors on hand. Quick replacement of these components can minimize downtime and impact on normal operations.
By implementing these comprehensive methods, under-voltage faults in generator sets can be effectively prevented and resolved, ensuring stable equipment operation and enhancing system reliability and production efficiency.
 
In conclusion, understanding and addressing the causes of under-voltage fault alarms and shutdowns in generator sets is vital for maintaining their stable operation. Regular inspection and maintenance of AVRs, speed regulation systems, and grounding systems, along with the preparation of spare parts, can significantly improve the reliability of power generation equipment. This not only ensures the continuity of production and daily life but also minimizes the inconvenience and losses caused by power outages.