Impact of Power Factor on Generator Set Performance

 
The power factor of a generator set is one of the key parameters influencing its operational efficiency, stability, and lifespan. Generally, most generator sets have a rated power factor of 0.8, while some can reach power factors of 0.85 or 0.9. However, despite the power factor varying between its rated value and 1.0, the generator set's output remains constant. To ensure the static stability of the system, the power factor should not exceed 0.95. This implies that the reactive load must be no less than one-third of the active load. When the power factor drops below the rated value, rotor current increases, leading to a rise in rotor temperature. In such cases, it is essential to promptly adjust the load and reduce the generator set's output to avoid exceeding the rotor's safe temperature limit.

Mechanism of Power Factor Influence

 
The power factor directly relates to reactive power and the operational stability of the unit. According to the basic principles of power factor, electrical power can be divided into active and reactive power. Active power is associated with the cosine of the phase difference between current and voltage, while reactive power is related to the sine of that phase difference. It follows that when a generator set outputs more reactive power, the power factor decreases. With the total output power of the generator set remaining unchanged, the terminal voltage rises, the excitation current increases, and both the stator and rotor temperatures rise accordingly. Excessively high temperatures not only threaten the insulation system but may also lead to equipment damage or performance degradation. Conversely, when the power factor is too high, the generator set produces less reactive power, resulting in a drop in terminal voltage, which decreases operational stability and may lead to loss of synchronization or other unstable operating conditions.
To ensure stable operation, the power factor of a generator set is typically required to not exceed 0.95 lagging, or the reactive load should be no less than one-third of the active load. When the generator set's automatic excitation regulation device is operational, it can temporarily operate at a power factor of 1.0 if necessary; however, prolonged operation under these conditions may lead to oscillations and loss of synchronization. Therefore, current high-capacity units generally do not permit leading power factor operation. When conducting leading power factor tests, operators should adjust operating parameters in a timely manner based on the specific operating conditions of the unit.

Dangers of Low Power Factor

 
When the power factor of a generator set falls below the rated value, the generator set's output should be reduced. The lower the power factor, the larger the reactive component in the stator current, which inevitably increases the rotor current. This situation causes the rotor's temperature to rise, potentially exceeding the rated value and leading to winding overheating. Tests have shown that when the power factor drops to 0.7, the generator set's output power will decrease by about 8%. Therefore, during operation, when the power factor is below the rated value, operators must promptly adjust the load to ensure the generator set's output remains within acceptable limits, while also ensuring the rotor current does not exceed its rated value.
A low power factor can also trigger other issues: increased excitation current, rising temperatures in the rotor windings, and reduced equipment lifespan. Additionally, the terminal voltage will increase, leading to greater magnetic flux density in the core, resulting in increased losses and elevated core temperatures, ultimately reducing equipment efficiency. These problems can cause excessive wear on the generator set and premature aging, leading to higher maintenance costs and increased failure probabilities.

Impact of High Power Factor

 
While improving the power factor can enhance the economic performance of a generator set, an excessively high power factor poses potential risks to unit operation. A high power factor indicates that reactive power is too low, reducing the system's reactive margin and compromising generator stability. Although this may temporarily increase power generation efficiency, over the long term, such operational methods increase the likelihood of accidents. In the event of grid faults or disturbances, the generator set may struggle to withstand minor electrical fluctuations or oscillations, ultimately leading to loss of synchronization.
Inadequate reactive power can also cause a decline in terminal voltage, adversely affecting the normal operation of auxiliary motors. When motor current increases while voltage decreases, a vicious cycle ensues. In such cases, the stability of the entire power generation system will be severely threatened, potentially leading to a collapse.
Moreover, a high power factor can increase heat generation at the generator set terminals. Continuous operation under these conditions may cause overheating of the terminal windings, further jeopardizing the safety and stability of the equipment.

Importance of Power Factor Management

 
To ensure the long-term safe and stable operation of generator sets, it is crucial to closely monitor the power factor and ensure it operates within a reasonable range. Generally, the power factor should be maintained between 0.8 and 0.9, adjusted according to the specific operating conditions of the generator set and grid requirements. For example, the operating mode of peak shaving units may differ between day and night, making power factor management especially important.
When the power factor is excessively high or low, operators should adjust the generator set's load and excitation current based on actual conditions to ensure the generator set's output and current remain within safe limits. Both excessively high and low power factors can lead to equipment wear, decreased efficiency, and increased operational failures. Thus, maintaining an appropriate power factor not only improves economic benefits but also effectively extends equipment lifespan, reducing the occurrence of unexpected downtime and failures.

Conclusion

 
The power factor of a generator set plays a critical role in its operational stability and economic viability. Both excessively high and low power factors can affect the generator set's voltage, temperature, and system stability, increasing equipment wear and failure risks. By properly adjusting the generator set's power factor to ensure it operates within a reasonable range, it is possible to effectively enhance power generation efficiency, prolong equipment lifespan, and ensure the long-term stable operation of the power generation system. Operators must closely monitor the power factor during routine operations and take timely adjustment measures to prevent equipment damage or system failures caused by improper power factor management.