Power factor lag and lead-solutions - Database & Sql Blog Articles

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The lead and lag shown in the power factor table reflect the phase relationship of the voltage and current in the line. Hysteresis is a common situation, indicating that the phase of the current lags behind the phase of the voltage, indicating that the line is inductive and dominates the load of the generator. Advance is a rare case, indicating that the current phase leads the voltage phase, indicating that the line is capacitive, and the capacitance in the load is too large, which generally appears in the capacitor compensation overshoot. Normal loads are less capacitive. The power factor is ahead of time, which often causes instability in the power grid, which is prone to shocks and power grid failures. Therefore, it is necessary to avoid the lead. If there is no capacitive load in the line, the power factor is displayed ahead of time, usually the wiring of the meter has a problem, otherwise the meter is broken.
It can also be said simply that the power factor meter shows that the electrical system is sending reactive current to the power supply grid; the power factor meter shows hysteresis, and the electrical system draws reactive current from the power supply grid.
The power factor of the synchronous generator increases its excitation current, the electromotive force E0 increases, and the synchronous generator operates in the overexcited state.
At this time, the synchronous generator stator current has a front-end voltage (ie, capacitive), and the back-EM-E0 is relatively large. The generator draws capacitive current and capacitive reactive power from the grid, or sends an inductive current and an inductive to the grid. Power. Just to compensate for the nearby inductive load of Yuyao, the power factor of the entire grid has been improved.
2. When the excitation current of the synchronous generator is reduced, -E0 is reduced, and the synchronous generator is operated under the under-excited state.
At this time, the synchronous generator absorbs the inductive current from the grid. For the grid, the inductive load is increased, and the inductive reactive current required by the load is increased, which reduces the power factor of the entire grid.
Therefore, the synchronous generator is generally not operated under the under-excited state and is designed according to the operating conditions of the over-excitation.
The excitation current of the synchronous generator cannot be excessively increased, because the excitation current is too large, the stator current is increased, the stator and rotor losses are increased, and the temperature rise of the motor is increased.
After the synchronous generator is connected to the grid. The grid voltage and frequency are fixed, and the amount of active power absorbed by the synchronous generator from the grid is determined by the amount of load it drives. If the load is constant, adjusting the excitation current of the generator will cause the stator current to also change.
The power factor of a synchronous generator is determined by the field current.