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Basic introduction to reactive power compensation in power distribution rooms and its calculation formula

Time:2024-03-06   Author:As Beam   Browse:

Reactive Power Compensation in Distribution Rooms: Enhancing Efficiency and Stability in Power Systems. Reactive power compensation plays a critical role in the efficiency and stability of power systems. The fundamental principle behind reactive power compensation involves integrating compensating devices within the distribution system to either supply or absorb reactive power. This adjustment improves the power factor of the system, reduces line losses, and enhances voltage stability. Therefore, the application of reactive power compensation technology is vital for optimizing and upgrading power systems. This article provides a basic overview of reactive power compensation and its calculation formulas.



What is Power Factor?

 Power factor is a critical technical parameter in power systems, indicating the efficiency of electrical equipment. A low power factor signifies high reactive power consumption in the circuit for alternating magnetic field conversion, thereby reducing equipment utilization and increasing supply line losses. Generally, the capacity of a capacitor compensation cabinet is calculated as thirty percent of the transformer capacity.

What is Power Factor?.jpg


Why Use Capacitor Compensation?

 Capacitor compensation, also known as power factor compensation or reactive power compensation, addresses the reactive power produced by electrical devices in power systems, which is typically inductive. This inductance reduces the efficiency of the system's capacity utilization. Introducing capacitors into the system can mitigate this issue. Capacitors can store energy, and since reactive power does not consume energy but temporarily stores electrical energy in the form of magnetic (inductive reactive power) or electric fields (capacitive reactive power) during one half-cycle of alternating current, to be returned to the grid in the next half-cycle.


When capacitors absorb reactive power, it coincides with the period when motors release reactive power, and vice versa. Thus, motors and capacitors exchange reactive power, eliminating the need for loads to absorb or release reactive power from the source. In essence, capacitors supply reactive power to motors, compensating for reactive power. This compensation improves load power factor, reduces reactive power, enhances the utilization of useful power, reduces network losses, increases transmission capacity, and improves stability limits.

Why Use Capacitor Compensation?.jpg


What Constitutes a Capacitor Cabinet?

 It refers to circuit breakers and fuse-switch disconnectors. Reactive power compensation controllers issue control signals based on the phase difference between voltage and current in the incoming cabinet, controlling the closure and disconnection of AC contactors, thereby managing the engagement and disengagement of capacitors. Typically, a capacitor compensation cabinet comprises the cabinet shell, busbar, disconnect switch, fuse switch, contactor, thermal relay, capacitor, surge arrester, primary and secondary wiring, terminal blocks, power factor automatic compensation device, panel instruments, etc.



What Role Does Capacitor Compensation Play in Circuits?

 Capacitors can maintain a higher average voltage (close to peak value) in AC circuits, improving and stabilizing circuit voltage.

They provide current compensation for the sudden start-up of large current loads. Power compensation capacitor groups can supply substantial instantaneous current, reducing impact on the grid.

Large inductive loads in circuits can cause phase deviation in the grid (inductive components cause AC current to lag, with voltage phase leading by 90 degrees), while the characteristics of capacitors in circuits are the exact opposite of inductors, thus providing compensation.

How to Calculate Capacitor Compensation?


For an uncompensated load with power factor COSφ1 and current consumption I1:


Load Power (KW) * 1000

I1 = ------------------------------

√3 * 380 * COSφ1


Load Power (KW) * 1000

I2 = ------------------------------

√3 * 380 * COSφ2


To compensate, with a power factor COSφ2 and current consumption I2, the required compensating current is: I = I1 - I2. The required capacitor capacity can be determined as follows: For the desired COSφ2, calculate the capacitor capacity (KVAR) needed per KW of load.




A load of 1500KW with an initial power factor of COSφ1 = 0.60 needs to be improved to COSφ2 = 0.96.


1500 * 1000

I1 = ---------------- = 3802 (Amps)

√3 * 380 * 0.60


1500 * 1000

I2 = ---------------- = 2376 (Amps)

√3 * 380 * 0.96


Before capacitor compensation, with a power factor COSφ1 = 0.60, the load of 1500KW requires a current I1 = 3802 Amps. After capacitor compensation, improving the power factor to COSφ2 = 0.95, the load requires a current I2 = 2376 Amps. Therefore, the required compensating current is I1 - I2 = 1426 Amps. Referring to tables for COSφ1 = 0.60 and COSφ2 = 0.96, the capacitor capacity needed per KW of load is 1.04 KVAR. For a 1500KW load, the required capacitor capacity is 1500 * 1.04 = 1560 KVAR. If each capacitor cabinet has a capacity of 180 KVAR, then 9 cabinets are needed (1500 / 180 = 8.67, rounded to 9).

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TAG:   Capacitor Capacitor Banks