How To Calculate Required Capacitor Bank?

I. Definition: The Reactive Power Solution

A capacitor bank (often called a SVG Active Static Var Generator) is a crucial device for optimizing power supplies and overall electrical system efficiency. Manufactured to the stringent International Electrotechnical Commission standard IEC 62271, it consists of multiple capacitor units, reactors, controllers, and protective devices (fuses, circuit breakers).

Its primary function? Reactive Power Compensation. Capacitor banks store electrical energy in an electrostatic field and release it back into the electrical system as needed. By connecting these units in parallel with the electrical supply, the bank injects "leading" reactive power (kVar). This directly counteracts the "lagging" reactive power inherently drawn by inductive loads (like motors and transformers), thereby:

II. Capacitor Bank Sizing: Core Calculation Methods

1. Method 1: Based on Existing & Target Power Factor (Most Recommended)

NOTICE: Common power factor values are cosφ₁, requiring conversion to tanφ₁

Required Parameters:

   1) P (Maximum Load Active Power):

• Active power at the compensation bus (kW).

• Obtained via: On-site measurements (power analyzer) or Estimation: Transformer Capacity (kVA) × Loading Factor (e.g., 1000kVA × 0.75 = 750kW)

    2) cosφ₁ (Existing Power Factor):

• Measured power factor before compensation.

    3) cosφ₂ (Target Power Factor):

• Desired power factor after compensation.

    4) V (System Voltage):

• Line-to-line voltage at installation point (e.g., 380V, 6kV, 10kV).
  

    5) K (Safety Factor, Optional):

• Recommended 1.1–1.3 to cover: (calculation tolerances, future load growth, capacitance degradation and etc.)
  

• Initial calculations may omit (K = 1).

Capacitor Bank

SVG Active Static Var Generator

2. Method 2: Using Energy Meter Readings (Long-Term Averaging)

Procedure:

    1)  Record over period T (e.g., one month)

• Active energy W_P (kWh)

•  Reactive energy W_q (kvarh)

    2) Calculate Average Power Factor:

    3) Set Target Power Factor (cosφ₂).

    4) Compute Average Active Power:

    5) Apply Method 1 Formula with P=Pavg.

3.Method 3: Transformer-Based Estimation (Empirical, Less Accurate)

NOTICE: Common power factor values are cosφ₁, requiring conversion to sinφ₁

Required Parameters:

    1) S (Power Source Rating):

• Transformer/generator capacity (kVA).

  
  

    2) K_s (Loading Factor):

• Max. load ratio (Actual Load Power / S), typically 0.6–0.9.

    3) cosφ₁ (Existing Power Factor):

• Measured power factor before compensation.

    4) cosφ₂ (Target Power Factor):

• Desired power factor after compensation.

*Simplified Rules of Thumb (if K_s / cosφ₁/ cosφ₂ unknown):*

III. Conclusion

Method 1 provides the highest accuracy for capacitor bank sizing and is strongly recommended where feasible. Methods 2 and 3 offer alternatives for specific scenarios but entail greater uncertainty.

For any inquiries regarding capacitor bank sizing calculations, please contact our engineering team. Our experts will deliver the optimal and most professional compensation solution for your electrical system design.