Why adjust the power factor of a generator?
1. When the generator is running, the power factor is too high, that is, the reactive power is too low, which reduces the reactive power margin of the system and affects the steady-state stability of the generator. Although the economy is improved, in the long run, this is in exchange for an increased probability of accidents. Once an accident occurs, the generator may not be able to withstand small disturbances or shocks and may lose step.
In addition, too low reactive power will cause the generator terminal voltage to drop, affecting the factory motor. The current drawn by the motor increases, causing the voltage to become lower, forming a vicious cycle that may cause the entire system to lose stable operation and collapse. When the generator is running in phase, the end is prone to heat.
2. When the generator is running, the power factor is too low, that is, the reactive power is too high, the excitation current increases, the temperature of the rotor winding increases, and the service life is shortened.
In addition, the power loss during power transmission is increased, and the generator loss is also increased. If the power factor is too low, the terminal voltage of the generator will rise, the magnetic flux density in the iron core will increase, the loss will also increase, and the iron core temperature will rise. When the generator is running under the rated load, if the power factor is too low at this time, the generator output will be Restricted, the efficiency of the generator will be greatly reduced.
Therefore, in normal operation monitoring, operators must reasonably allocate the active and reactive loads of each unit so that the generator can operate under safe and economical conditions.
The rated power factor of the generator actually refers to the power factor value when the generator operates under the operating conditions of rated active power and rated apparent power at the same time (generally in the late phase mode). The same rated active power unit, if its rated power The lower the factor, it means that its ability to carry reactive power during operation is relatively strong, and the rated current of the unit also increases, thus increasing the cost.
When the generator is running, theoretically speaking, under the same terminal voltage and the same active output, the higher the power factor, the less reactive power generated, the lower the generator potential, and the static state of the generator. The operational stability level decreases.
However, under the normal wiring method of the current system network and the normal operation of the generator excitation system, the power factor is allowed to be higher than the rated value until phase-advancing operation within a certain range.
However, when the system encounters stability constraints under certain maintenance methods, the dispatch will impose certain restrictions on the generator output and power due to high limits.
When the generator is running, if the power factor is to be reduced below the rated value, its active output must be reduced so that the stator and rotor currents do not exceed the limit. This operating mode often occurs when an accident occurs in the system and the reactive power shortage is serious, requiring the generator to reduce the amount of active power and increase the amount of reactive power.
How to power factor correction(in 400V)?
1. Capacitor Banks
2. Static Var Generator
