What are the effects of over-compensation in reactive power compensation?

Capacitor compensation principle: During capacitor compensation, the capacitor and the load are connected in parallel. Just like an electrical reservoir, when the load increases, due to the internal resistance of the power supply, the output voltage of the power supply will decrease. Because the two ends of the capacitor need to maintain the original voltage, that is, the charge in the capacitor needs to release a part, which delays the downward trend of the voltage. This is the capacitor compensation principle.

Adding compensation capacitors can prevent certain impacts on the power supply end and the load end when the capacitance is too large.

1. For the power grid, regardless of whether the load is inductive or capacitive, reactive power will be generated and active power loss will occur; there is no need to use an excessively large compensation capacitor.
2. Additionally, if the compensation capacitor is too large, the power network is capacitive, and since the power supply network is generally inductive, resonance will occur, resulting in resonance overvoltage and overcurrent. In severe cases, it may cause the power grid to separate or damage the electrical equipment. Therefore, over-compensation is not allowed in power supply and consumption.

For ordinary electricity users, a power factor of 0.9 is sufficient. However, at this point, there is still approximately half of the reactive power equivalent to the active power in the power supply network. At this time, the power supply network needs to supply an electric current 1.25 times the active current to enable the load to work normally. This will increase the line loss of the power supply network by 56%. Even if the power factor is compensated to 0.95, the reactive power still accounts for 31% of the active power. Moreover, when compensating, measures such as series reactors are taken, there will be no resonance or amplification of voltage and current phenomena.

Therefore, the so-called reactive power compensation nowadays must be carried out precisely to the right extent.  If the compensation is excessive, it will also lead to a decrease in power factor. If it drops below the standard, a fine will still be imposed. Because over-compensation actually means too much capacitive reactive power. Since it is excessive reactive power (whether capacitive or inductive), it is still reactive power.