The Basic Principle Of Reactive Power Compensation

1. Power factor electricity charge
It refers to the situation where the reactive power consumption of inductive loads of power users is excessive, resulting in a power factor lower than the national standard. 

2. Surge Current and Overvoltage
Surge current refers to the current generated instantaneously when a capacitor is put into service. If the zero-crossing point is not utilized when the contactor is engaged with the capacitor, the instant when the capacitor is engaged is equivalent to a short circuit, resulting in a current that is tens or hundreds of times larger than the rated current of the capacitor. At the same time, many weakly withstand-voltage plates of the capacitor will be broken down, causing the capacitor to be unable to store energy and affecting its service life. Therefore, contactor-type capacitor cabinets cannot be frequently switched on and off.
Overvoltage refers to the voltage generated instantaneously when the capacitor is removed. When the capacitor is removed, due to the superposition of the grid voltage and the terminal voltage of the capacitor, overvoltage is generated.

3. Switching Oscillation
When the capacitor is put into service, overcompensation occurs, and when it is removed, undercompensation occurs. This causes the capacitor to frequently switch on and off, resulting in oscillation.
4. Overcompensation and Undercompensation
Undercompensation means that the inductive reactive power in the power system is greater than the capacitive reactive power.
Overcompensation means that the capacitive reactive power in the power system is greater than the inductive reactive power.
5. Harm of Reverse Supply of Reactive Power
Reverse supply of reactive power is the same as undercompensation of reactive power. It will also cause a potential difference between voltage and current, resulting in a low power factor. If a large amount of reactive power is continuously fed back to the grid, it will cause the grid voltage to rise, resulting in pollution to the grid and, in severe cases, causing the grid to collapse and fail. 
6. Local Compensation
Local compensation refers to compensating for a specific equipment, installed near the equipment, with the characteristics of low investment, small volume, convenient installation, and good compensation effect.
Local compensation is applicable when the capacity of a single equipment is large and the transmission lines of the power user are long. It compensates for the reactive current locally, ensuring voltage quality and reducing line losses.