Detailed answers to questions related to active power and reactive power of generator sets

Search on Baidu Knows, Sosou Ask, Google Q&A, etc.Generator setAt that time, HaixingGenerator setThe employees found that many questions were related to the active and reactive power of the generator, so they answered them in detail for netizens. Below Jiangsu Haixing Power Technology uses a question and answer mode to explain common questions.

Need to understand from basic concepts
Question: What does meritorious service mean? What is reactive work?
Answer: In the process of generating, transmitting, and using alternating current energy, the part of energy used for conversion into non-electric and magnetic forms is called active power; the part of energy used for electrical and magnetic exchange within the circuit is called reactive power.

Question: What is power rate? What's going on with the advance and late phases of Lisu?
Answer: The power factor of an AC motor is also called power factor, which is equal to the ratio of active power to apparent power.
The so-called advancing phase of power rate is the operation state of sending out active power and absorbing reactive power; the late phase of power rate is the operation state of sending out both active power and reactive power.

Secondly, practical problems related to active and reactive power encountered during the adjustment and use of generator sets
Question: What is the physical process of regulating the active power of a generator set? What should we pay attention to when adjusting active load?
Answer: Let’s talk about the process of adjusting the active power based on the power angle of the motor. At this time, it is assumed that the excitation current of the generator set remains unchanged and the voltage of the system does not change.
(1) Load increasing process: When the steam valve is opened, the main torque on the generator rotor shaft increases. At this time, since the electric power has not started to change, that is, the resistance torque has not changed, the rotor must accelerate, so that the rotor and The angle between the stators should be wider. According to the power angle characteristics of the motor itself, as the power angle increases, the output power of the motor will increase. That is, with more loads, will the rotor continue to accelerate? Normally this is not the case, because as the motor carries more load, the resistance torque increases. When the resistance torque is large enough to balance the main torque, the rotor speed stabilizes. At this time, the generator output rises to a new level. numerical value.
(2) Load reduction process: When the steam valve is closed, the main torque on the rotor shaft of the generator unit decreases, so the rotor decelerates and the power angle becomes smaller. When the power angle becomes smaller, the electromagnetic power decreases and the corresponding resistance torque also decreases. When the resistance torque is reduced to the same size as the new main torque, a new balance is reached. At this time, the motor carries less load.
Pay attention to two points when adjusting active load:
(1) The force should be kept within the range specified in the regulations as much as possible, and should not be greater than 0.95 of the late phase, because a high force ratio means that the excitation current corresponding to the active power at that time is small, that is, the magnetic poles between the stator and rotor of the generator are If there are few magnetic lines of force being pulled, it is easy to lose stability. From the perspective of the power angle characteristics, as the active power sent increases, the power angle will be close to 90 degrees, so it is easy to lose stability.
(2) It should be noted that the load should be adjusted slowly. When the unit increases its output, its overload capacity will generally be reduced.

Question: Why does voltage change adjust reactive power?
Answer: Voltage fluctuations are mainly caused by reactive loads. Active loads also have an impact on voltage fluctuations, but their impact is smaller. When there is a shortage of reactive power, that is, when the inductive load is excessive, the inductive load will produce a demagnetizing armature reaction on the generator set, which will weaken the magnetic field in the air gap and reduce the terminal voltage. At this time, to maintain the terminal voltage unchanged, it is necessary to Increase the rotor current, that is, increase the reactive power, to compensate for the demagnetized armature reaction part. On the contrary, when the reactive power is excessive, the terminal voltage will rise. At this time, to maintain the terminal voltage unchanged, it is necessary to reduce the rotor current, that is, reduce the reactive power. . This is the reason why voltage changes adjust reactive power.