Compensation Calculation: Reactive Power Balancing Method
Compensation systems are widely used in electrical installations to improve power quality and reduce unnecessary loads on the grid. Compensation calculation is performed to determine the amount of capacitive reactive power required to improve the existing power factor (cosφ₁). Determining the amount of reactive power is very important in terms of identifying capacitor banks.
Why Is Compensation Calculation Done?
Inductive components such as motors, transformers, and ballasts operating in alternating current circuits require reactive power during operation. This reactive power consumption causes a phase shift between current and voltage, leading to a decrease in the power factor. A low power factor both increases energy losses and is reflected on bills by electricity distribution companies as a reactive energy charge. Through the compensation calculation process, the capacitor capacity required by the system is determined and these losses are minimized.
Compensation Calculation Formula
The following expression is used to calculate the required capacitor power (Qc):
Qc = P ⋅ (tanφ1 − taφ2)
Where:
Qc: Required capacitive reactive power (kVAr)
P: Active power of the system (kW)
φ1: Phase angle corresponding to the current power factor
φ2: Phase angle corresponding to the target power factor
The phase angle is found by taking the inverse cosine of the power factor:
φ = cos^-1(φ)
Implementation Stages
1- The system’s active power (P) is measured or obtained from the plant load table.
2 – The current power factor (cosφ₁) and target power factor (cosφ₂) are determined.
3 – The Qc value is calculated using the formula above.
4 – The appropriate capacitor capacitance is determined based on the calculated kVAr value.
5 – The capacitor bank is selected and commissioned according to the voltage level.
Compensation Calculation Example
Let’s assume that in a business:
Active power (P): 100kW
Current power factor: cosφ₁ = 0.80 → φ₁ ≈ 36.87°
Target power factor: cosφ₂ = 0.95 → φ₂ ≈ 18.19°
Now let’s apply the formula:
Qc = 100 ⋅ (tan36.87° − tan18.19°) = 100 ⋅ (0.75 − 0.33) = 42 kVAr
In this case, approximately 42 kVAr of capacitive reactive power is required to increase the power factor from 0.80 to 0.95. This value is included in the system as a capacitor bank.
Benefits of Compensation Calculation
Reactive energy penalties are avoided.
The total current drawn from the grid decreases, and losses are minimized.
Transformer and cable systems are less loaded, and equipment life is extended.
Voltage fluctuations are reduced, and system stability is increased.
Energy costs decrease, and power quality improves.